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Mybatis 数据库物理分页插件 PageHelper

时间：2021-07-01 10:21:17 帮助过：4人阅读

.5</version> </dependency>

2. 配置分页拦截器

PageHelper的原理是基于拦截器实现的。拦截器的配置有两种方法，一种是在mybatis的配置文件中配置，一种是直接在spring的配置文件中进行：

1）在mybatis-config.xml文件中配置：

  1. <plugins>
  2.     <!-- com.github.pagehelper为PageHelper类所在包名 -->
  3.     <plugin interceptor=<span style="color: #800000;">"</span><span style="color: #800000;">com.github.pagehelper.PageHelper</span><span style="color: #800000;">"</span>>
  4.         <property name=<span style="color: #800000;">"</span><span style="color: #800000;">dialect</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">mysql</span><span style="color: #800000;">"</span>/>
  5.         <!-- 该参数默认为false -->
  6.         <!-- 设置为true时，会将RowBounds第一个参数offset当成pageNum页码使用 -->
  7.         <!-- 和startPage中的pageNum效果一样-->
  8.         <property name=<span style="color: #800000;">"</span><span style="color: #800000;">offsetAsPageNum</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">true</span><span style="color: #800000;">"</span>/>
  9.         <!-- 该参数默认为false -->
  10.         <!-- 设置为true时，使用RowBounds分页会进行count查询 -->
  11.         <property name=<span style="color: #800000;">"</span><span style="color: #800000;">rowBoundsWithCount</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">true</span><span style="color: #800000;">"</span>/>
  12.         
  13.         <!-- 设置为true时，如果pageSize=0或者RowBounds.limit = 0就会查询出全部的结果 -->
  14.         <!--<span style="color: #000000;"> （相当于没有执行分页查询，但是返回结果仍然是Page类型）
  15.         </span><property name=<span style="color: #800000;">"</span><span style="color: #800000;">pageSizeZero</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">true</span><span style="color: #800000;">"</span>/>-->
  16.         
  17.         <!-- <span style="color: #800080;">3.3</span>.0版本可用 - 分页参数合理化，默认false禁用 -->
  18.         <!-- 启用合理化时，如果pageNum<1会查询第一页，如果pageNum>pages会查询最后一页 -->
  19.         <!-- 禁用合理化时，如果pageNum<1或pageNum>pages会返回空数据 -->
  20.         <property name=<span style="color: #800000;">"</span><span style="color: #800000;">reasonable</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">true</span><span style="color: #800000;">"</span>/>
  21.         <!-- <span style="color: #800080;">3.5</span>.0版本可用 - 为了支持startPage(Object <span style="color: #0000ff;">params</span>)方法 -->
  22.         <!-- 增加了一个`<span style="color: #0000ff;">params</span>`参数来配置参数映射，用于从Map或ServletRequest中取值 -->
  23.         <!-- 可以配置pageNum,pageSize,count,pageSizeZero,reasonable,不配置映射的用默认值 -->
  24.         <!--<span style="color: #000000;"> 不理解该含义的前提下，不要随便复制该配置 
  25.         </span><property name=<span style="color: #800000;">"</span><span style="color: #800000;">params</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">pageNum=start;pageSize=limit;</span><span style="color: #800000;">"</span>/>    -->
  26.     </plugin>
  27.   </plugins>

这里要注意 <plugins> 在mybatis-config.xml文件中的位置，必须要符合 http://mybatis.org/dtd/mybatis-3-config.dtd 中指定的顺序：

  1. <!ELEMENT configuration (properties?, settings?, typeAliases?, typeHandlers?<span style="color: #000000;">, 
  2.     objectFactory</span>?, objectWrapperFactory?, plugins?, environments?, databaseIdProvider?, mappers?)>

不然会报错。

当然mybatis-config.xml的位置，我们需要在spring的配置文件中进行指定：

  1. <bean id=<span style="color: #800000;">"</span><span style="color: #800000;">sqlSessionFactory</span><span style="color: #800000;">"</span> <span style="color: #0000ff;">class</span>=<span style="color: #800000;">"</span><span style="color: #800000;">org.mybatis.spring.SqlSessionFactoryBean</span><span style="color: #800000;">"</span>>
  2.       <property name=<span style="color: #800000;">"</span><span style="color: #800000;">dataSource</span><span style="color: #800000;">"</span> <span style="color: #0000ff;">ref</span>=<span style="color: #800000;">"</span><span style="color: #800000;">dataSource</span><span style="color: #800000;">"</span> />
  3.       <property name=<span style="color: #800000;">"</span><span style="color: #800000;">configLocation</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">classpath:config/mybatis-config.xml</span><span style="color: #800000;">"</span> />
  4.       <property name=<span style="color: #800000;">"</span><span style="color: #800000;">mapperLocations</span><span style="color: #800000;">"</span> value=<span style="color: #800000;">"</span><span style="color: #800000;">classpath*:config/mappers/**/*.xml</span><span style="color: #800000;">"</span> />
  5.     </bean>

2）如果mybatis没有mybatis-config.xml文件，那么就只能直接在spring的配置文件中配置了：

  1. <bean id=<span style="color: #800000;">"</span><span style="color: #800000;">sqlSessionFactory</span><span style="color: #800000;">"</span> <span style="color: #0000ff;">class</span>=<span style="color: #800000;">"</span><span style="color: #800000;">org.mybatis.spring.SqlSessionFactoryBean</span><span style="color: #800000;">"</span>>
  2.   <property name=<span style="color: #800000;">"</span><span style="color: #800000;">dataSource</span><span style="color: #800000;">"</span> <span style="color: #0000ff;">ref</span>=<span style="color: #800000;">"</span><span style="color: #800000;">dataSource</span><span style="color: #800000;">"</span>/>
  3.   <property name=<span style="color: #800000;">"</span><span style="color: #800000;">mapperLocations</span><span style="color: #800000;">"</span>>
  4.     <array>
  5.       <value>classpath:config/mapper<span style="color: #008000;">/*</span><span style="color: #008000;">.xml</value>
  6.     </array>
  7.   </property>
  8.   <property name="typeAliasesPackage" value="com.test.pojo"/>
  9.   <property name="plugins">
  10.     <array>
  11.       <bean class="com.github.pagehelper.PageHelper">
  12.         <property name="properties">
  13.           <value>
  14.             dialect=mysql
  15.           </value>
  16.         </property>
  17.       </bean>
  18.     </array>
  19.   </property>
  20. </bean></span>

到这里PageHelper所需要的配置已经完成，下面还需要在serviceImpl类中加入分页参数的代码：

3. 向拦截器传递分页参数

我们首先看下不分页的serviceImpl代码：

  1. <span style="color: #000000;">@Override
  2.     </span><span style="color: #0000ff;">public</span> List<User><span style="color: #000000;"> getUserByNoAndEmail(String no, String email) {
  3.         Map</span><String, Object> map = <span style="color: #0000ff;">new</span> HashMap<><span style="color: #000000;">();
  4.         map.put(</span><span style="color: #800000;">"</span><span style="color: #800000;">no</span><span style="color: #800000;">"</span><span style="color: #000000;">, no);
  5.         map.put(</span><span style="color: #800000;">"</span><span style="color: #800000;">email</span><span style="color: #800000;">"</span><span style="color: #000000;">, email);
  6.         </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">this</span><span style="color: #000000;">.userMapper.getUserByNoAndEmail(map);
  7.     }</span>

然后我们将它改造成使用PageHelper分页：

1）首先我们根据自己项目的情况，定义一个PageBean，来保存分页之后的结果，需要哪些属性，就加入哪些属性，具体可以参考源代码中的PageInfo类的定义，其实PageInfo是插件作者给我们自己定义自己的PageBean，提供的一个参考例子。PageInfo代码如下：

  1. @SuppressWarnings({<span style="color: #800000;">"</span><span style="color: #800000;">rawtypes</span><span style="color: #800000;">"</span>, <span style="color: #800000;">"</span><span style="color: #800000;">unchecked</span><span style="color: #800000;">"</span><span style="color: #000000;">})
  2. </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">class</span> PageInfo<T><span style="color: #000000;"> implements Serializable {
  3.     </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> final <span style="color: #0000ff;">long</span> serialVersionUID = <span style="color: #800080;">1L</span><span style="color: #000000;">;
  4.     </span><span style="color: #008000;">//</span><span style="color: #008000;">当前页</span>
  5.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> pageNum;
  6.     </span><span style="color: #008000;">//</span><span style="color: #008000;">每页的数量</span>
  7.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> pageSize;
  8.     </span><span style="color: #008000;">//</span><span style="color: #008000;">当前页的数量</span>
  9.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> size;
  10.     </span><span style="color: #008000;">//</span><span style="color: #008000;">由于startRow和endRow不常用，这里说个具体的用法
  11.     </span><span style="color: #008000;">//</span><span style="color: #008000;">可以在页面中"显示startRow到endRow 共size条数据"
  12.     </span><span style="color: #008000;">//</span><span style="color: #008000;">当前页面第一个元素在数据库中的行号</span>
  13.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> startRow;
  14.     </span><span style="color: #008000;">//</span><span style="color: #008000;">当前页面最后一个元素在数据库中的行号</span>
  15.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> endRow;
  16.     </span><span style="color: #008000;">//</span><span style="color: #008000;">总记录数</span>
  17.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">long</span><span style="color: #000000;"> total;
  18.     </span><span style="color: #008000;">//</span><span style="color: #008000;">总页数</span>
  19.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> pages;
  20.     </span><span style="color: #008000;">//</span><span style="color: #008000;">结果集</span>
  21.     <span style="color: #0000ff;">private</span> List<T><span style="color: #000000;"> list;
  22.     </span><span style="color: #008000;">//</span><span style="color: #008000;">第一页</span>
  23.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> firstPage;
  24.     </span><span style="color: #008000;">//</span><span style="color: #008000;">前一页</span>
  25.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> prePage;
  26.     </span><span style="color: #008000;">//</span><span style="color: #008000;">下一页</span>
  27.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> nextPage;
  28.     </span><span style="color: #008000;">//</span><span style="color: #008000;">最后一页</span>
  29.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> lastPage;
  30.     </span><span style="color: #008000;">//</span><span style="color: #008000;">是否为第一页</span>
  31.     <span style="color: #0000ff;">private</span> boolean isFirstPage = <span style="color: #0000ff;">false</span><span style="color: #000000;">;
  32.     </span><span style="color: #008000;">//</span><span style="color: #008000;">是否为最后一页</span>
  33.     <span style="color: #0000ff;">private</span> boolean isLastPage = <span style="color: #0000ff;">false</span><span style="color: #000000;">;
  34.     </span><span style="color: #008000;">//</span><span style="color: #008000;">是否有前一页</span>
  35.     <span style="color: #0000ff;">private</span> boolean hasPreviousPage = <span style="color: #0000ff;">false</span><span style="color: #000000;">;
  36.     </span><span style="color: #008000;">//</span><span style="color: #008000;">是否有下一页</span>
  37.     <span style="color: #0000ff;">private</span> boolean hasNextPage = <span style="color: #0000ff;">false</span><span style="color: #000000;">;
  38.     </span><span style="color: #008000;">//</span><span style="color: #008000;">导航页码数</span>
  39.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> navigatePages;
  40.     </span><span style="color: #008000;">//</span><span style="color: #008000;">所有导航页号</span>
  41.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;">[] navigatepageNums;
  42.     </span><span style="color: #008000;">/*</span><span style="color: #008000;">*
  43.      * 包装Page对象
  44.      *
  45.      * @param list
  46.      </span><span style="color: #008000;">*/</span>
  47.     <span style="color: #0000ff;">public</span> PageInfo(List<T><span style="color: #000000;"> list) {
  48.         </span><span style="color: #0000ff;">this</span>(list, <span style="color: #800080;">8</span><span style="color: #000000;">);
  49.     }
  50.     </span><span style="color: #008000;">/*</span><span style="color: #008000;">*
  51.      * 包装Page对象
  52.      *
  53.      * @param list          page结果
  54.      * @param navigatePages 页码数量
  55.      </span><span style="color: #008000;">*/</span>
  56.     <span style="color: #0000ff;">public</span> PageInfo(List<T> list, <span style="color: #0000ff;">int</span><span style="color: #000000;"> navigatePages) {
  57.         </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (list instanceof Page) {
  58.             Page page </span>=<span style="color: #000000;"> (Page) list;
  59.             </span><span style="color: #0000ff;">this</span>.pageNum =<span style="color: #000000;"> page.getPageNum();
  60.             </span><span style="color: #0000ff;">this</span>.pageSize =<span style="color: #000000;"> page.getPageSize();
  61.             </span><span style="color: #0000ff;">this</span>.total =<span style="color: #000000;"> page.getTotal();
  62.             </span><span style="color: #0000ff;">this</span>.pages =<span style="color: #000000;"> page.getPages();
  63.             </span><span style="color: #0000ff;">this</span>.list =<span style="color: #000000;"> page;
  64.             </span><span style="color: #0000ff;">this</span>.size =<span style="color: #000000;"> page.size();
  65.             </span><span style="color: #008000;">//</span><span style="color: #008000;">由于结果是>startRow的，所以实际的需要+1</span>
  66.             <span style="color: #0000ff;">if</span> (<span style="color: #0000ff;">this</span>.size == <span style="color: #800080;">0</span><span style="color: #000000;">) {
  67.                 </span><span style="color: #0000ff;">this</span>.startRow = <span style="color: #800080;">0</span><span style="color: #000000;">;
  68.                 </span><span style="color: #0000ff;">this</span>.endRow = <span style="color: #800080;">0</span><span style="color: #000000;">;
  69.             } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> {
  70.                 </span><span style="color: #0000ff;">this</span>.startRow = page.getStartRow() + <span style="color: #800080;">1</span><span style="color: #000000;">;
  71.                 </span><span style="color: #008000;">//</span><span style="color: #008000;">计算实际的endRow（最后一页的时候特殊）</span>
  72.                 <span style="color: #0000ff;">this</span>.endRow = <span style="color: #0000ff;">this</span>.startRow - <span style="color: #800080;">1</span> + <span style="color: #0000ff;">this</span><span style="color: #000000;">.size;
  73.             }
  74.             </span><span style="color: #0000ff;">this</span>.navigatePages =<span style="color: #000000;"> navigatePages;
  75.             </span><span style="color: #008000;">//</span><span style="color: #008000;">计算导航页</span>
  76. <span style="color: #000000;">            calcNavigatepageNums();
  77.             </span><span style="color: #008000;">//</span><span style="color: #008000;">计算前后页，第一页，最后一页</span>
  78. <span style="color: #000000;">            calcPage();
  79.             </span><span style="color: #008000;">//</span><span style="color: #008000;">判断页面边界</span>
  80. <span style="color: #000000;">            judgePageBoudary();
  81.         }
  82.     }
  83.     </span><span style="color: #008000;">/*</span><span style="color: #008000;">*
  84.      * 计算导航页
  85.      </span><span style="color: #008000;">*/</span>
  86.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> calcNavigatepageNums() {
  87.         </span><span style="color: #008000;">//</span><span style="color: #008000;">当总页数小于或等于导航页码数时</span>
  88.         <span style="color: #0000ff;">if</span> (pages <=<span style="color: #000000;"> navigatePages) {
  89.             navigatepageNums </span>= <span style="color: #0000ff;">new</span> <span style="color: #0000ff;">int</span><span style="color: #000000;">[pages];
  90.             </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = <span style="color: #800080;">0</span>; i < pages; i++<span style="color: #000000;">) {
  91.                 navigatepageNums[i] </span>= i + <span style="color: #800080;">1</span><span style="color: #000000;">;
  92.             }
  93.         } </span><span style="color: #0000ff;">else</span> { <span style="color: #008000;">//</span><span style="color: #008000;">当总页数大于导航页码数时</span>
  94.             navigatepageNums = <span style="color: #0000ff;">new</span> <span style="color: #0000ff;">int</span><span style="color: #000000;">[navigatePages];
  95.             </span><span style="color: #0000ff;">int</span> startNum = pageNum - navigatePages / <span style="color: #800080;">2</span><span style="color: #000000;">;
  96.             </span><span style="color: #0000ff;">int</span> endNum = pageNum + navigatePages / <span style="color: #800080;">2</span><span style="color: #000000;">;
  97.             </span><span style="color: #0000ff;">if</span> (startNum < <span style="color: #800080;">1</span><span style="color: #000000;">) {
  98.                 startNum </span>= <span style="color: #800080;">1</span><span style="color: #000000;">;
  99.                 </span><span style="color: #008000;">//</span><span style="color: #008000;">(最前navigatePages页</span>
  100.                 <span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = <span style="color: #800080;">0</span>; i < navigatePages; i++<span style="color: #000000;">) {
  101.                     navigatepageNums[i] </span>= startNum++<span style="color: #000000;">;
  102.                 }
  103.             } </span><span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span> (endNum ><span style="color: #000000;"> pages) {
  104.                 endNum </span>=<span style="color: #000000;"> pages;
  105.                 </span><span style="color: #008000;">//</span><span style="color: #008000;">最后navigatePages页</span>
  106.                 <span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = navigatePages - <span style="color: #800080;">1</span>; i >= <span style="color: #800080;">0</span>; i--<span style="color: #000000;">) {
  107.                     navigatepageNums[i] </span>= endNum--<span style="color: #000000;">;
  108.                 }
  109.             } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> {
  110.                 </span><span style="color: #008000;">//</span><span style="color: #008000;">所有中间页</span>
  111.                 <span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = <span style="color: #800080;">0</span>; i < navigatePages; i++<span style="color: #000000;">) {
  112.                     navigatepageNums[i] </span>= startNum++<span style="color: #000000;">;
  113.                 }
  114.             }
  115.         }
  116.     }
  117.     </span><span style="color: #008000;">/*</span><span style="color: #008000;">*
  118.      * 计算前后页，第一页，最后一页
  119.      </span><span style="color: #008000;">*/</span>
  120.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> calcPage() {
  121.         </span><span style="color: #0000ff;">if</span> (navigatepageNums != <span style="color: #0000ff;">null</span> && navigatepageNums.length > <span style="color: #800080;">0</span><span style="color: #000000;">) {
  122.             firstPage </span>= navigatepageNums[<span style="color: #800080;">0</span><span style="color: #000000;">];
  123.             lastPage </span>= navigatepageNums[navigatepageNums.length - <span style="color: #800080;">1</span><span style="color: #000000;">];
  124.             </span><span style="color: #0000ff;">if</span> (pageNum > <span style="color: #800080;">1</span><span style="color: #000000;">) {
  125.                 prePage </span>= pageNum - <span style="color: #800080;">1</span><span style="color: #000000;">;
  126.             }
  127.             </span><span style="color: #0000ff;">if</span> (pageNum <<span style="color: #000000;"> pages) {
  128.                 nextPage </span>= pageNum + <span style="color: #800080;">1</span><span style="color: #000000;">;
  129.             }
  130.         }
  131.     }
  132.     </span><span style="color: #008000;">/*</span><span style="color: #008000;">*
  133.      * 判定页面边界
  134.      </span><span style="color: #008000;">*/</span>
  135.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> judgePageBoudary() {
  136.         isFirstPage </span>= pageNum == <span style="color: #800080;">1</span><span style="color: #000000;">;
  137.         isLastPage </span>= pageNum ==<span style="color: #000000;"> pages;
  138.         hasPreviousPage </span>= pageNum > <span style="color: #800080;">1</span><span style="color: #000000;">;
  139.         hasNextPage </span>= pageNum <<span style="color: #000000;"> pages;
  140.     }
  141.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setPageNum(<span style="color: #0000ff;">int</span><span style="color: #000000;"> pageNum) {
  142.         </span><span style="color: #0000ff;">this</span>.pageNum =<span style="color: #000000;"> pageNum;
  143.     }
  144.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPageNum() {
  145.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pageNum;
  146.     }
  147.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPageSize() {
  148.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pageSize;
  149.     }
  150.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getSize() {
  151.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> size;
  152.     }
  153.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getStartRow() {
  154.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> startRow;
  155.     }
  156.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getEndRow() {
  157.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> endRow;
  158.     }
  159.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">long</span><span style="color: #000000;"> getTotal() {
  160.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> total;
  161.     }
  162.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPages() {
  163.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pages;
  164.     }
  165.     </span><span style="color: #0000ff;">public</span> List<T><span style="color: #000000;"> getList() {
  166.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> list;
  167.     }
  168.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getFirstPage() {
  169.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> firstPage;
  170.     }
  171.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPrePage() {
  172.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> prePage;
  173.     }
  174.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getNextPage() {
  175.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> nextPage;
  176.     }
  177.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getLastPage() {
  178.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> lastPage;
  179.     }
  180.     </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> boolean isIsFirstPage() {
  181.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> isFirstPage;
  182.     }
  183.     </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> boolean isIsLastPage() {
  184.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> isLastPage;
  185.     }
  186.     </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> boolean isHasPreviousPage() {
  187.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> hasPreviousPage;
  188.     }
  189.     </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> boolean isHasNextPage() {
  190.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> hasNextPage;
  191.     }
  192.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getNavigatePages() {
  193.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> navigatePages;
  194.     }
  195.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;">[] getNavigatepageNums() {
  196.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> navigatepageNums;
  197.     }
  198.     @Override
  199.     </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String toString() {
  200.         final StringBuffer sb </span>= <span style="color: #0000ff;">new</span> StringBuffer(<span style="color: #800000;">"</span><span style="color: #800000;">PageInfo{</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  201.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">pageNum=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(pageNum);
  202.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, pageSize=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(pageSize);
  203.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, size=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(size);
  204.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, startRow=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(startRow);
  205.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, endRow=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(endRow);
  206.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, total=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(total);
  207.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, pages=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(pages);
  208.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, list=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(list);
  209.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, firstPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(firstPage);
  210.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, prePage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(prePage);
  211.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, nextPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(nextPage);
  212.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, lastPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(lastPage);
  213.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, isFirstPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(isFirstPage);
  214.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, isLastPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(isLastPage);
  215.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, hasPreviousPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(hasPreviousPage);
  216.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, hasNextPage=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(hasNextPage);
  217.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, navigatePages=</span><span style="color: #800000;">"</span><span style="color: #000000;">).append(navigatePages);
  218.         sb.append(</span><span style="color: #800000;">"</span><span style="color: #800000;">, navigatepageNums=</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  219.         </span><span style="color: #0000ff;">if</span> (navigatepageNums == <span style="color: #0000ff;">null</span>) sb.append(<span style="color: #800000;">"</span><span style="color: #800000;">null</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  220.         </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> {
  221.             sb.append(‘[‘);
  222.             </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = <span style="color: #800080;">0</span>; i < navigatepageNums.length; ++<span style="color: #000000;">i)
  223.                 sb.append(i </span>== <span style="color: #800080;">0</span> ? <span style="color: #800000;">""</span> : <span style="color: #800000;">"</span><span style="color: #800000;">, </span><span style="color: #800000;">"</span><span style="color: #000000;">).append(navigatepageNums[i]);
  224.             sb.append(‘]‘);
  225.         }
  226.         sb.append(‘}‘);
  227.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> sb.toString();
  228.     }
  229. }</span>
PageInfo.java

因为PageInfo.java只是一个示例，所以他定义得有点重量级，属性有点多，我们可以参考它，定义适合我们自己的PageBean, 比如如下定义：

  1. <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">class</span> PageBean<T><span style="color: #000000;"> implements Serializable {
  2.     </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> final <span style="color: #0000ff;">long</span> serialVersionUID = <span style="color: #800080;">8656597559014685635L</span><span style="color: #000000;">;
  3.     </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">long</span> total;        <span style="color: #008000;">//</span><span style="color: #008000;">总记录数</span>
  4.     <span style="color: #0000ff;">private</span> List<T> list;    <span style="color: #008000;">//</span><span style="color: #008000;">结果集</span>
  5.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span> pageNum;    <span style="color: #008000;">//</span><span style="color: #008000;"> 第几页</span>
  6.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span> pageSize;    <span style="color: #008000;">//</span><span style="color: #008000;"> 每页记录数</span>
  7.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span> pages;        <span style="color: #008000;">//</span><span style="color: #008000;"> 总页数</span>
  8.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span> size;        <span style="color: #008000;">//</span><span style="color: #008000;"> 当前页的数量 <= pageSize，该属性来自ArrayList的size属性</span>
  9.     
  10.     <span style="color: #008000;">/*</span><span style="color: #008000;">*
  11.      * 包装Page对象，因为直接返回Page对象，在JSON处理以及其他情况下会被当成List来处理，
  12.      * 而出现一些问题。
  13.      * @param list          page结果
  14.      * @param navigatePages 页码数量
  15.      </span><span style="color: #008000;">*/</span>
  16.     <span style="color: #0000ff;">public</span> PageBean(List<T><span style="color: #000000;"> list) {
  17.         </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (list instanceof Page) {
  18.             Page</span><T> page = (Page<T><span style="color: #000000;">) list;
  19.             </span><span style="color: #0000ff;">this</span>.pageNum =<span style="color: #000000;"> page.getPageNum();
  20.             </span><span style="color: #0000ff;">this</span>.pageSize =<span style="color: #000000;"> page.getPageSize();
  21.             </span><span style="color: #0000ff;">this</span>.total =<span style="color: #000000;"> page.getTotal();
  22.             </span><span style="color: #0000ff;">this</span>.pages =<span style="color: #000000;"> page.getPages();
  23.             </span><span style="color: #0000ff;">this</span>.list =<span style="color: #000000;"> page;
  24.             </span><span style="color: #0000ff;">this</span>.size =<span style="color: #000000;"> page.size();
  25.         }
  26.     }
  27.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">long</span><span style="color: #000000;"> getTotal() {
  28.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> total;
  29.     }
  30.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setTotal(<span style="color: #0000ff;">long</span><span style="color: #000000;"> total) {
  31.         </span><span style="color: #0000ff;">this</span>.total =<span style="color: #000000;"> total;
  32.     }
  33.     </span><span style="color: #0000ff;">public</span> List<T><span style="color: #000000;"> getList() {
  34.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> list;
  35.     }
  36.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setList(List<T><span style="color: #000000;"> list) {
  37.         </span><span style="color: #0000ff;">this</span>.list =<span style="color: #000000;"> list;
  38.     }
  39.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPageNum() {
  40.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pageNum;
  41.     }
  42.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setPageNum(<span style="color: #0000ff;">int</span><span style="color: #000000;"> pageNum) {
  43.         </span><span style="color: #0000ff;">this</span>.pageNum =<span style="color: #000000;"> pageNum;
  44.     }
  45.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPageSize() {
  46.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pageSize;
  47.     }
  48.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setPageSize(<span style="color: #0000ff;">int</span><span style="color: #000000;"> pageSize) {
  49.         </span><span style="color: #0000ff;">this</span>.pageSize =<span style="color: #000000;"> pageSize;
  50.     }
  51.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPages() {
  52.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pages;
  53.     }
  54.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setPages(<span style="color: #0000ff;">int</span><span style="color: #000000;"> pages) {
  55.         </span><span style="color: #0000ff;">this</span>.pages =<span style="color: #000000;"> pages;
  56.     }
  57.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getSize() {
  58.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> size;
  59.     }
  60.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> setSize(<span style="color: #0000ff;">int</span><span style="color: #000000;"> size) {
  61.         </span><span style="color: #0000ff;">this</span>.size =<span style="color: #000000;"> size;
  62.     }
  63.     
  64. }</span>
PageBean.java

因为分页查询结果返回的是一个 Page 对象，而 Page 对象继承自ArrayList，但是如果我们直接返回ArrayList的话，在一些场景下回遇到问题，比如在JSON处理Page类型的结果时，会被当成List来JSON格式化，会丢弃 Page 对象的所有扩展属性，所以这里我们要将分页的结果 Page 类型转换成我们自己定义的 PageBean. 我们自己定义的PageBean没有继承ArrayList，而是包含一个List属性来保存分页结果。所以避免前面的问题。

2）修改 serviceImpl中的代码：

  1. <span style="color: #000000;">  @Override
  2.     </span><span style="color: #0000ff;">public</span> PageBean<User><span style="color: #000000;"> getUserByNoAndEmail(String no, String email) {
  3.         Map</span><String, Object> map = <span style="color: #0000ff;">new</span> HashMap<><span style="color: #000000;">();
  4.         map.put(</span><span style="color: #800000;">"</span><span style="color: #800000;">no</span><span style="color: #800000;">"</span><span style="color: #000000;">, no);
  5.         map.put(</span><span style="color: #800000;">"</span><span style="color: #800000;">email</span><span style="color: #800000;">"</span><span style="color: #000000;">, email);
  6.         
  7.         PageHelper.startPage(PaginationContext.getPageNum(), PaginationContext.getPageSize());
  8.         List</span><User> list = <span style="color: #0000ff;">this</span><span style="color: #000000;">.userMapper.getUserByNoAndEmail(map);
  9.         </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span> PageBean<User><span style="color: #000000;">(list);
  10.     }</span>

我们只需要使用 PageHelper.startPage(pageNum, pageSize); 函数来指定 pageNum(第几页) 和 pageSize(每页显示几条记录) 两个参数。然后调用原来的查询，就进行了分页。最后将返回的List，转换成 PageBean类型的结果即可。前台页面就可以根据PageBean中包括的属性来进行分页显示了。

上面的 PaginationContext 是基于 ThreadLocal 来传递分页参数的一个工具类，其实现如下：

  1. <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> PaginationContext {
  2.     </span><span style="color: #008000;">//</span><span style="color: #008000;"> 定义两个threadLocal变量：pageNum和pageSize</span>
  3.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> ThreadLocal<Integer> pageNum = <span style="color: #0000ff;">new</span> ThreadLocal<Integer>();    <span style="color: #008000;">//</span><span style="color: #008000;"> 保存第几页</span>
  4.     <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> ThreadLocal<Integer> pageSize = <span style="color: #0000ff;">new</span> ThreadLocal<Integer>();    <span style="color: #008000;">//</span><span style="color: #008000;"> 保存每页记录条数</span>
  5.     <span style="color: #008000;">/*</span><span style="color: #008000;">
  6.      * pageNum ：get、set、remove
  7.      </span><span style="color: #008000;">*/</span>
  8.     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPageNum() {
  9.         Integer pn </span>= pageNum.<span style="color: #0000ff;">get</span><span style="color: #000000;">();
  10.         </span><span style="color: #0000ff;">if</span> (pn == <span style="color: #0000ff;">null</span><span style="color: #000000;">) {
  11.             </span><span style="color: #0000ff;">return</span> <span style="color: #800080;">0</span><span style="color: #000000;">;
  12.         }
  13.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pn;
  14.     }
  15.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> setPageNum(<span style="color: #0000ff;">int</span><span style="color: #000000;"> pageNumValue) {
  16.         pageNum.</span><span style="color: #0000ff;">set</span><span style="color: #000000;">(pageNumValue);
  17.     }
  18.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> removePageNum() {
  19.         pageNum.remove();
  20.     }
  21.     </span><span style="color: #008000;">/*</span><span style="color: #008000;">
  22.      * pageSize ：get、set、remove
  23.      </span><span style="color: #008000;">*/</span>
  24.     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> getPageSize() {
  25.         Integer ps </span>= pageSize.<span style="color: #0000ff;">get</span><span style="color: #000000;">();
  26.         </span><span style="color: #0000ff;">if</span> (ps == <span style="color: #0000ff;">null</span><span style="color: #000000;">) {
  27.             </span><span style="color: #0000ff;">return</span> <span style="color: #800080;">0</span><span style="color: #000000;">;
  28.         }
  29.         </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ps;
  30.     }
  31.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> setPageSize(<span style="color: #0000ff;">int</span><span style="color: #000000;"> pageSizeValue) {
  32.         pageSize.</span><span style="color: #0000ff;">set</span><span style="color: #000000;">(pageSizeValue);
  33.     }
  34.     </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> removePageSize() {
  35.         pageSize.remove();
  36.     }
  37. }</span>
PaginationContext.java

实现了前台页面向ServiceImpl中传递分页参数： pageNum 和 pageSize.

OK，到此，PageHelper的使用方法，基本结束。

PageHelper 项目地址：http://git.oschina.net/free/Mybatis_PageHelper

文档地址：http://git.oschina.net/free/Mybatis_PageHelper/blob/master/wikis/HowToUse.markdown

 

 

  1. @SuppressWarnings({"rawtypes", "unchecked"<span style="padding: 0px; color: #000000;">})
  2. </span><span style="padding: 0px; color: #0000ff;">public</span> <span style="padding: 0px; color: #0000ff;">class</span> PageInfo<T> <span style="padding: 0px; color: #0000ff;">implements</span><span style="padding: 0px; color: #000000;"> Serializable {
  3.     </span><span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">static</span> <span style="padding: 0px; color: #0000ff;">final</span> <span style="padding: 0px; color: #0000ff;">long</span> serialVersionUID = 1L<span style="padding: 0px; color: #000000;">;
  4.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">当前页</span>
  5.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> pageNum;
  6.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">每页的数量</span>
  7.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> pageSize;
  8.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">当前页的数量</span>
  9.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> size;
  10.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">由于startRow和endRow不常用，这里说个具体的用法
  11.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">可以在页面中"显示startRow到endRow 共size条数据"
  12.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">当前页面第一个元素在数据库中的行号</span>
  13.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> startRow;
  14.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">当前页面最后一个元素在数据库中的行号</span>
  15.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> endRow;
  16.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">总记录数</span>
  17.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">long</span><span style="padding: 0px; color: #000000;"> total;
  18.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">总页数</span>
  19.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> pages;
  20.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">结果集</span>
  21.     <span style="padding: 0px; color: #0000ff;">private</span> List<T><span style="padding: 0px; color: #000000;"> list;
  22.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">第一页</span>
  23.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> firstPage;
  24.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">前一页</span>
  25.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> prePage;
  26.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">下一页</span>
  27.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> nextPage;
  28.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">最后一页</span>
  29.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> lastPage;
  30.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">是否为第一页</span>
  31.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">boolean</span> isFirstPage = <span style="padding: 0px; color: #0000ff;">false</span><span style="padding: 0px; color: #000000;">;
  32.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">是否为最后一页</span>
  33.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">boolean</span> isLastPage = <span style="padding: 0px; color: #0000ff;">false</span><span style="padding: 0px; color: #000000;">;
  34.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">是否有前一页</span>
  35.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">boolean</span> hasPreviousPage = <span style="padding: 0px; color: #0000ff;">false</span><span style="padding: 0px; color: #000000;">;
  36.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">是否有下一页</span>
  37.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">boolean</span> hasNextPage = <span style="padding: 0px; color: #0000ff;">false</span><span style="padding: 0px; color: #000000;">;
  38.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">导航页码数</span>
  39.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> navigatePages;
  40.     </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">所有导航页号</span>
  41.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;">[] navigatepageNums;
  42.     </span><span style="padding: 0px; color: #008000;">/**</span><span style="padding: 0px; color: #008000;">
  43.      * 包装Page对象
  44.      *
  45.      * </span><span style="padding: 0px; color: #808080;">@param</span><span style="padding: 0px; color: #008000;"> list
  46.      </span><span style="padding: 0px; color: #008000;">*/</span>
  47.     <span style="padding: 0px; color: #0000ff;">public</span> PageInfo(List<T><span style="padding: 0px; color: #000000;"> list) {
  48.         </span><span style="padding: 0px; color: #0000ff;">this</span>(list, 8<span style="padding: 0px; color: #000000;">);
  49.     }
  50.     </span><span style="padding: 0px; color: #008000;">/**</span><span style="padding: 0px; color: #008000;">
  51.      * 包装Page对象
  52.      *
  53.      * </span><span style="padding: 0px; color: #808080;">@param</span><span style="padding: 0px; color: #008000;"> list          page结果
  54.      * </span><span style="padding: 0px; color: #808080;">@param</span><span style="padding: 0px; color: #008000;"> navigatePages 页码数量
  55.      </span><span style="padding: 0px; color: #008000;">*/</span>
  56.     <span style="padding: 0px; color: #0000ff;">public</span> PageInfo(List<T> list, <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> navigatePages) {
  57.         </span><span style="padding: 0px; color: #0000ff;">if</span> (list <span style="padding: 0px; color: #0000ff;">instanceof</span><span style="padding: 0px; color: #000000;"> Page) {
  58.             Page page </span>=<span style="padding: 0px; color: #000000;"> (Page) list;
  59.             </span><span style="padding: 0px; color: #0000ff;">this</span>.pageNum =<span style="padding: 0px; color: #000000;"> page.getPageNum();
  60.             </span><span style="padding: 0px; color: #0000ff;">this</span>.pageSize =<span style="padding: 0px; color: #000000;"> page.getPageSize();
  61.             </span><span style="padding: 0px; color: #0000ff;">this</span>.total =<span style="padding: 0px; color: #000000;"> page.getTotal();
  62.             </span><span style="padding: 0px; color: #0000ff;">this</span>.pages =<span style="padding: 0px; color: #000000;"> page.getPages();
  63.             </span><span style="padding: 0px; color: #0000ff;">this</span>.list =<span style="padding: 0px; color: #000000;"> page;
  64.             </span><span style="padding: 0px; color: #0000ff;">this</span>.size =<span style="padding: 0px; color: #000000;"> page.size();
  65.             </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">由于结果是>startRow的，所以实际的需要+1</span>
  66.             <span style="padding: 0px; color: #0000ff;">if</span> (<span style="padding: 0px; color: #0000ff;">this</span>.size == 0<span style="padding: 0px; color: #000000;">) {
  67.                 </span><span style="padding: 0px; color: #0000ff;">this</span>.startRow = 0<span style="padding: 0px; color: #000000;">;
  68.                 </span><span style="padding: 0px; color: #0000ff;">this</span>.endRow = 0<span style="padding: 0px; color: #000000;">;
  69.             } </span><span style="padding: 0px; color: #0000ff;">else</span><span style="padding: 0px; color: #000000;"> {
  70.                 </span><span style="padding: 0px; color: #0000ff;">this</span>.startRow = page.getStartRow() + 1<span style="padding: 0px; color: #000000;">;
  71.                 </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">计算实际的endRow（最后一页的时候特殊）</span>
  72.                 <span style="padding: 0px; color: #0000ff;">this</span>.endRow = <span style="padding: 0px; color: #0000ff;">this</span>.startRow - 1 + <span style="padding: 0px; color: #0000ff;">this</span><span style="padding: 0px; color: #000000;">.size;
  73.             }
  74.             </span><span style="padding: 0px; color: #0000ff;">this</span>.navigatePages =<span style="padding: 0px; color: #000000;"> navigatePages;
  75.             </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">计算导航页</span>
  76. <span style="padding: 0px; color: #000000;">            calcNavigatepageNums();
  77.             </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">计算前后页，第一页，最后一页</span>
  78. <span style="padding: 0px; color: #000000;">            calcPage();
  79.             </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">判断页面边界</span>
  80. <span style="padding: 0px; color: #000000;">            judgePageBoudary();
  81.         }
  82.     }
  83.     </span><span style="padding: 0px; color: #008000;">/**</span><span style="padding: 0px; color: #008000;">
  84.      * 计算导航页
  85.      </span><span style="padding: 0px; color: #008000;">*/</span>
  86.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">void</span><span style="padding: 0px; color: #000000;"> calcNavigatepageNums() {
  87.         </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">当总页数小于或等于导航页码数时</span>
  88.         <span style="padding: 0px; color: #0000ff;">if</span> (pages <=<span style="padding: 0px; color: #000000;"> navigatePages) {
  89.             navigatepageNums </span>= <span style="padding: 0px; color: #0000ff;">new</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;">[pages];
  90.             </span><span style="padding: 0px; color: #0000ff;">for</span> (<span style="padding: 0px; color: #0000ff;">int</span> i = 0; i < pages; i++<span style="padding: 0px; color: #000000;">) {
  91.                 navigatepageNums[i] </span>= i + 1<span style="padding: 0px; color: #000000;">;
  92.             }
  93.         } </span><span style="padding: 0px; color: #0000ff;">else</span> { <span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">当总页数大于导航页码数时</span>
  94.             navigatepageNums = <span style="padding: 0px; color: #0000ff;">new</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;">[navigatePages];
  95.             </span><span style="padding: 0px; color: #0000ff;">int</span> startNum = pageNum - navigatePages / 2<span style="padding: 0px; color: #000000;">;
  96.             </span><span style="padding: 0px; color: #0000ff;">int</span> endNum = pageNum + navigatePages / 2<span style="padding: 0px; color: #000000;">;
  97.             </span><span style="padding: 0px; color: #0000ff;">if</span> (startNum < 1<span style="padding: 0px; color: #000000;">) {
  98.                 startNum </span>= 1<span style="padding: 0px; color: #000000;">;
  99.                 </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">(最前navigatePages页</span>
  100.                 <span style="padding: 0px; color: #0000ff;">for</span> (<span style="padding: 0px; color: #0000ff;">int</span> i = 0; i < navigatePages; i++<span style="padding: 0px; color: #000000;">) {
  101.                     navigatepageNums[i] </span>= startNum++<span style="padding: 0px; color: #000000;">;
  102.                 }
  103.             } </span><span style="padding: 0px; color: #0000ff;">else</span> <span style="padding: 0px; color: #0000ff;">if</span> (endNum ><span style="padding: 0px; color: #000000;"> pages) {
  104.                 endNum </span>=<span style="padding: 0px; color: #000000;"> pages;
  105.                 </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">最后navigatePages页</span>
  106.                 <span style="padding: 0px; color: #0000ff;">for</span> (<span style="padding: 0px; color: #0000ff;">int</span> i = navigatePages - 1; i >= 0; i--<span style="padding: 0px; color: #000000;">) {
  107.                     navigatepageNums[i] </span>= endNum--<span style="padding: 0px; color: #000000;">;
  108.                 }
  109.             } </span><span style="padding: 0px; color: #0000ff;">else</span><span style="padding: 0px; color: #000000;"> {
  110.                 </span><span style="padding: 0px; color: #008000;">//</span><span style="padding: 0px; color: #008000;">所有中间页</span>
  111.                 <span style="padding: 0px; color: #0000ff;">for</span> (<span style="padding: 0px; color: #0000ff;">int</span> i = 0; i < navigatePages; i++<span style="padding: 0px; color: #000000;">) {
  112.                     navigatepageNums[i] </span>= startNum++<span style="padding: 0px; color: #000000;">;
  113.                 }
  114.             }
  115.         }
  116.     }
  117.     </span><span style="padding: 0px; color: #008000;">/**</span><span style="padding: 0px; color: #008000;">
  118.      * 计算前后页，第一页，最后一页
  119.      </span><span style="padding: 0px; color: #008000;">*/</span>
  120.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">void</span><span style="padding: 0px; color: #000000;"> calcPage() {
  121.         </span><span style="padding: 0px; color: #0000ff;">if</span> (navigatepageNums != <span style="padding: 0px; color: #0000ff;">null</span> && navigatepageNums.length > 0<span style="padding: 0px; color: #000000;">) {
  122.             firstPage </span>= navigatepageNums[0<span style="padding: 0px; color: #000000;">];
  123.             lastPage </span>= navigatepageNums[navigatepageNums.length - 1<span style="padding: 0px; color: #000000;">];
  124.             </span><span style="padding: 0px; color: #0000ff;">if</span> (pageNum > 1<span style="padding: 0px; color: #000000;">) {
  125.                 prePage </span>= pageNum - 1<span style="padding: 0px; color: #000000;">;
  126.             }
  127.             </span><span style="padding: 0px; color: #0000ff;">if</span> (pageNum <<span style="padding: 0px; color: #000000;"> pages) {
  128.                 nextPage </span>= pageNum + 1<span style="padding: 0px; color: #000000;">;
  129.             }
  130.         }
  131.     }
  132.     </span><span style="padding: 0px; color: #008000;">/**</span><span style="padding: 0px; color: #008000;">
  133.      * 判定页面边界
  134.      </span><span style="padding: 0px; color: #008000;">*/</span>
  135.     <span style="padding: 0px; color: #0000ff;">private</span> <span style="padding: 0px; color: #0000ff;">void</span><span style="padding: 0px; color: #000000;"> judgePageBoudary() {
  136.         isFirstPage </span>= pageNum == 1<span style="padding: 0px; color: #000000;">;
  137.         isLastPage </span>= pageNum ==<span style="padding: 0px; color: #000000;"> pages;
  138.         hasPreviousPage </span>= pageNum > 1<span style="padding: 0px; color: #000000;">;
  139.         hasNextPage </span>= pageNum <<span style="padding: 0px; color: #000000;"> pages;
  140.     }
  141.     </span><span style="padding: 0px; color: #0000ff;">public</span> <span style="padding: 0px; color: #0000ff;">void</span> setPageNum(<span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> pageNum) {
  142.         </span><span style="padding: 0px; color: #0000ff;">this</span>.pageNum =<span style="padding: 0px; color: #000000;"> pageNum;
  143.     }
  144.     </span><span style="padding: 0px; color: #0000ff;">public</span> <span style="padding: 0px; color: #0000ff;">int</span><span style="padding: 0px; color: #000000;"> getPageNum() {
  145.         </span><span style="padding: 0px; color: #0000ff;">return</span><span style="padding: 0px; color: #000000;"> pageNum;
  146.     }
  147.     </span><span style="padding: 0px; color: #0000ff;                    </div>
  148.                   
  149.  
  150.                     <div class=" "="">
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