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DAO设计模式实现数据库的增删改查（进一步封装JDBC工具类）

时间：2021-07-01 10:21:17 帮助过：3人阅读

技术分享 
  1. <span style="color: #008080;"> 1 <span style="color: #0000ff;">package<span style="color: #000000;"> com.util.db;
  2. <span style="color: #008080;"> 2 
  3. <span style="color: #008080;"> 3 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.Connection;
  4. <span style="color: #008080;"> 4 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.DriverManager;
  5. <span style="color: #008080;"> 5 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.ResultSet;
  6. <span style="color: #008080;"> 6 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.SQLException;
  7. <span style="color: #008080;"> 7 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.Statement;
  8. <span style="color: #008080;"> 8 <span style="color: #0000ff;">import<span style="color: #000000;"> java.util.ResourceBundle;
  9. <span style="color: #008080;"> 9 
  10. <span style="color: #008080;">10 <span style="color: #008000;">/**
  11. <span style="color: #008080;">11 <span style="color: #008000;"> * 数据库操作工具类
  12. <span style="color: #008080;">12 <span style="color: #008000;"> * <span style="color: #808080;">@author<span style="color: #008000;"> lamp
  13. <span style="color: #008080;">13 <span style="color: #008000;"> *
  14. <span style="color: #008080;">14  <span style="color: #008000;">*/
  15. <span style="color: #008080;">15 <span style="color: #0000ff;">public <span style="color: #0000ff;">class<span style="color: #000000;"> DBUtils {
  16. <span style="color: #008080;">16     
  17. <span style="color: #008080;">17     <span style="color: #008000;">//<span style="color: #008000;">数据库连接地址
  18. <span style="color: #008080;">18     <span style="color: #0000ff;">public <span style="color: #0000ff;">static<span style="color: #000000;"> String URL;
  19. <span style="color: #008080;">19     <span style="color: #008000;">//<span style="color: #008000;">用户名
  20. <span style="color: #008080;">20     <span style="color: #0000ff;">public <span style="color: #0000ff;">static<span style="color: #000000;"> String USERNAME;
  21. <span style="color: #008080;">21     <span style="color: #008000;">//<span style="color: #008000;">密码
  22. <span style="color: #008080;">22     <span style="color: #0000ff;">public <span style="color: #0000ff;">static<span style="color: #000000;"> String PASSWORD;
  23. <span style="color: #008080;">23     <span style="color: #008000;">//<span style="color: #008000;">mysql的驱动类
  24. <span style="color: #008080;">24     <span style="color: #0000ff;">public <span style="color: #0000ff;">static<span style="color: #000000;"> String DRIVER;
  25. <span style="color: #008080;">25     
  26. <span style="color: #008080;">26     <span style="color: #0000ff;">private <span style="color: #0000ff;">static ResourceBundle rb = ResourceBundle.getBundle("com.util.db.db-config"<span style="color: #000000;">);
  27. <span style="color: #008080;">27     
  28. <span style="color: #008080;">28     <span style="color: #0000ff;">private<span style="color: #000000;"> DBUtils(){}
  29. <span style="color: #008080;">29     
  30. <span style="color: #008080;">30     <span style="color: #008000;">//<span style="color: #008000;">使用静态块加载驱动程序
  31. <span style="color: #008080;">31     <span style="color: #0000ff;">static<span style="color: #000000;">{
  32. <span style="color: #008080;">32         URL = rb.getString("jdbc.url"<span style="color: #000000;">);
  33. <span style="color: #008080;">33         USERNAME = rb.getString("jdbc.username"<span style="color: #000000;">);
  34. <span style="color: #008080;">34         PASSWORD = rb.getString("jdbc.password"<span style="color: #000000;">);
  35. <span style="color: #008080;">35         DRIVER = rb.getString("jdbc.driver"<span style="color: #000000;">);
  36. <span style="color: #008080;">36         <span style="color: #0000ff;">try<span style="color: #000000;"> {
  37. <span style="color: #008080;">37 <span style="color: #000000;">            Class.forName(DRIVER);
  38. <span style="color: #008080;">38         } <span style="color: #0000ff;">catch<span style="color: #000000;"> (ClassNotFoundException e) {
  39. <span style="color: #008080;">39 <span style="color: #000000;">            e.printStackTrace();
  40. <span style="color: #008080;">40 <span style="color: #000000;">        }
  41. <span style="color: #008080;">41 <span style="color: #000000;">    }
  42. <span style="color: #008080;">42     <span style="color: #008000;">//<span style="color: #008000;">定义一个获取数据库连接的方法
  43. <span style="color: #008080;">43     <span style="color: #0000ff;">public <span style="color: #0000ff;">static<span style="color: #000000;"> Connection getConnection(){
  44. <span style="color: #008080;">44         Connection conn = <span style="color: #0000ff;">null<span style="color: #000000;">;
  45. <span style="color: #008080;">45         <span style="color: #0000ff;">try<span style="color: #000000;"> {
  46. <span style="color: #008080;">46             conn =<span style="color: #000000;"> DriverManager.getConnection(URL, USERNAME, PASSWORD);
  47. <span style="color: #008080;">47         } <span style="color: #0000ff;">catch<span style="color: #000000;"> (SQLException e) {
  48. <span style="color: #008080;">48 <span style="color: #000000;">            e.printStackTrace();
  49. <span style="color: #008080;">49             System.out.println("获取连接失败"<span style="color: #000000;">);
  50. <span style="color: #008080;">50 <span style="color: #000000;">        }
  51. <span style="color: #008080;">51         <span style="color: #0000ff;">return<span style="color: #000000;"> conn;
  52. <span style="color: #008080;">52 <span style="color: #000000;">    }
  53. <span style="color: #008080;">53     
  54. <span style="color: #008080;">54     <span style="color: #008000;">/**
  55. <span style="color: #008080;">55 <span style="color: #008000;">     * 关闭数据库连接
  56. <span style="color: #008080;">56 <span style="color: #008000;">     * <span style="color: #808080;">@param<span style="color: #008000;"> rs
  57. <span style="color: #008080;">57 <span style="color: #008000;">     * <span style="color: #808080;">@param<span style="color: #008000;"> stat
  58. <span style="color: #008080;">58 <span style="color: #008000;">     * <span style="color: #808080;">@param<span style="color: #008000;"> conn
  59. <span style="color: #008080;">59      <span style="color: #008000;">*/
  60. <span style="color: #008080;">60     <span style="color: #0000ff;">public <span style="color: #0000ff;">static <span style="color: #0000ff;">void<span style="color: #000000;"> close(ResultSet rs,Statement stat,Connection conn){
  61. <span style="color: #008080;">61             <span style="color: #0000ff;">try<span style="color: #000000;"> {
  62. <span style="color: #008080;">62                 <span style="color: #0000ff;">if(rs!=<span style="color: #0000ff;">null<span style="color: #000000;">)rs.close();
  63. <span style="color: #008080;">63                 <span style="color: #0000ff;">if(stat!=<span style="color: #0000ff;">null<span style="color: #000000;">)stat.close();
  64. <span style="color: #008080;">64                 <span style="color: #0000ff;">if(conn!=<span style="color: #0000ff;">null<span style="color: #000000;">)conn.close();
  65. <span style="color: #008080;">65             } <span style="color: #0000ff;">catch<span style="color: #000000;"> (SQLException e) {
  66. <span style="color: #008080;">66 <span style="color: #000000;">                e.printStackTrace();
  67. <span style="color: #008080;">67 <span style="color: #000000;">            }
  68. <span style="color: #008080;">68 <span style="color: #000000;">    }
  69. <span style="color: #008080;">69     
  70. <span style="color: #008080;">70 }</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
技术分享

注意：26行中，注意获取属性文件的包名是否正确。稍后会定义这个属性文件。

28行：既然是工具类，一般不要实例化，此时可以采用单例设计模式，或者将构造方法私有化。

26行：很明显可以看到，我们是将连接数据库的URL、用户名，密码等信息编写在一个属性文件（jdbc.properties）中，稍后再来定义这个属性文件。

31行：为避免重复代码，使用静态代码块：只会在类加载的时候执行一次。

42行：定义一个获取数据库连接的方法

60行：关闭数据库连接

（2）接下来新建一个属性文件，new-->file，命名为：db-config.properties，代码如下：

  1. jdbc.url=jdbc:mysql:<span style="color: #008000;">//<span style="color: #008000;">localhost:3306/jdbcdb
  2. jdbc.username=<span style="color: #000000;">root
  3. jdbc.password=<span style="color: #000000;">smyh
  4. jdbc.driver=com.mysql.jdbc.Driver</span></span></span></span>

以后如果需要修改配置信息，只需要在这里改就行了。注意在上面的DBUtils类中是怎么来调用这个配置信息的。

紧接着新建文件，定义好Person类：(package com.vae.domain)

技术分享 
  1. <span style="color: #008080;"> 1 <span style="color: #0000ff;">package<span style="color: #000000;"> com.vae.domain;
  2. <span style="color: #008080;"> 2 
  3. <span style="color: #008080;"> 3 <span style="color: #0000ff;">public <span style="color: #0000ff;">class<span style="color: #000000;"> Person {
  4. <span style="color: #008080;"> 4     <span style="color: #0000ff;">private <span style="color: #0000ff;">int<span style="color: #000000;"> id;
  5. <span style="color: #008080;"> 5     <span style="color: #0000ff;">private<span style="color: #000000;"> String name;
  6. <span style="color: #008080;"> 6     <span style="color: #0000ff;">private <span style="color: #0000ff;">int<span style="color: #000000;"> age;
  7. <span style="color: #008080;"> 7     <span style="color: #0000ff;">private<span style="color: #000000;"> String description;
  8. <span style="color: #008080;"> 8     <span style="color: #0000ff;">public <span style="color: #0000ff;">int<span style="color: #000000;"> getId() {
  9. <span style="color: #008080;"> 9         <span style="color: #0000ff;">return<span style="color: #000000;"> id;
  10. <span style="color: #008080;">10 <span style="color: #000000;">    }
  11. <span style="color: #008080;">11     <span style="color: #0000ff;">public <span style="color: #0000ff;">void setId(<span style="color: #0000ff;">int<span style="color: #000000;"> id) {
  12. <span style="color: #008080;">12         <span style="color: #0000ff;">this.id =<span style="color: #000000;"> id;
  13. <span style="color: #008080;">13 <span style="color: #000000;">    }
  14. <span style="color: #008080;">14     <span style="color: #0000ff;">public<span style="color: #000000;"> String getName() {
  15. <span style="color: #008080;">15         <span style="color: #0000ff;">return<span style="color: #000000;"> name;
  16. <span style="color: #008080;">16 <span style="color: #000000;">    }
  17. <span style="color: #008080;">17     <span style="color: #0000ff;">public <span style="color: #0000ff;">void<span style="color: #000000;"> setName(String name) {
  18. <span style="color: #008080;">18         <span style="color: #0000ff;">this.name =<span style="color: #000000;"> name;
  19. <span style="color: #008080;">19 <span style="color: #000000;">    }
  20. <span style="color: #008080;">20     <span style="color: #0000ff;">public <span style="color: #0000ff;">int<span style="color: #000000;"> getAge() {
  21. <span style="color: #008080;">21         <span style="color: #0000ff;">return<span style="color: #000000;"> age;
  22. <span style="color: #008080;">22 <span style="color: #000000;">    }
  23. <span style="color: #008080;">23     <span style="color: #0000ff;">public <span style="color: #0000ff;">void setAge(<span style="color: #0000ff;">int<span style="color: #000000;"> age) {
  24. <span style="color: #008080;">24         <span style="color: #0000ff;">this.age =<span style="color: #000000;"> age;
  25. <span style="color: #008080;">25 <span style="color: #000000;">    }
  26. <span style="color: #008080;">26     <span style="color: #0000ff;">public<span style="color: #000000;"> String getDescription() {
  27. <span style="color: #008080;">27         <span style="color: #0000ff;">return<span style="color: #000000;"> description;
  28. <span style="color: #008080;">28 <span style="color: #000000;">    }
  29. <span style="color: #008080;">29     <span style="color: #0000ff;">public <span style="color: #0000ff;">void<span style="color: #000000;"> setDescription(String description) {
  30. <span style="color: #008080;">30         <span style="color: #0000ff;">this.description =<span style="color: #000000;"> description;
  31. <span style="color: #008080;">31 <span style="color: #000000;">    }
  32. <span style="color: #008080;">32     <span style="color: #0000ff;">public Person(<span style="color: #0000ff;">int id, String name, <span style="color: #0000ff;">int<span style="color: #000000;"> age, String description) {
  33. <span style="color: #008080;">33         <span style="color: #0000ff;">super<span style="color: #000000;">();
  34. <span style="color: #008080;">34         <span style="color: #0000ff;">this.id =<span style="color: #000000;"> id;
  35. <span style="color: #008080;">35         <span style="color: #0000ff;">this.name =<span style="color: #000000;"> name;
  36. <span style="color: #008080;">36         <span style="color: #0000ff;">this.age =<span style="color: #000000;"> age;
  37. <span style="color: #008080;">37         <span style="color: #0000ff;">this.description =<span style="color: #000000;"> description;
  38. <span style="color: #008080;">38 <span style="color: #000000;">    }
  39. <span style="color: #008080;">39     <span style="color: #0000ff;">public Person(String name, <span style="color: #0000ff;">int<span style="color: #000000;"> age, String description) {
  40. <span style="color: #008080;">40         <span style="color: #0000ff;">super<span style="color: #000000;">();
  41. <span style="color: #008080;">41         <span style="color: #0000ff;">this.name =<span style="color: #000000;"> name;
  42. <span style="color: #008080;">42         <span style="color: #0000ff;">this.age =<span style="color: #000000;"> age;
  43. <span style="color: #008080;">43         <span style="color: #0000ff;">this.description =<span style="color: #000000;"> description;
  44. <span style="color: #008080;">44 <span style="color: #000000;">    }
  45. <span style="color: #008080;">45     <span style="color: #0000ff;">public<span style="color: #000000;"> Person() {
  46. <span style="color: #008080;">46         <span style="color: #0000ff;">super<span style="color: #000000;">();
  47. <span style="color: #008080;">47         <span style="color: #008000;">//<span style="color: #008000;"> TODO Auto-generated constructor stub
  48. <span style="color: #008080;">48 <span style="color: #000000;">    }
  49. <span style="color: #008080;">49 <span style="color: #000000;">    @Override
  50. <span style="color: #008080;">50     <span style="color: #0000ff;">public<span style="color: #000000;"> String toString() {
  51. <span style="color: #008080;">51         <span style="color: #0000ff;">return "Person [id=" + id + ", name=" + name + ", age=" +<span style="color: #000000;"> age
  52. <span style="color: #008080;">52                 + ", description=" + description + "]"<span style="color: #000000;">;
  53. <span style="color: #008080;">53 <span style="color: #000000;">    }
  54. <span style="color: #008080;">54     
  55. <span style="color: #008080;">55     
  56. <span style="color: #008080;">56 }</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
技术分享

这个Person类就是领域模型，表示是对它进行增删改查。

（3）定义PersonDao接口：专门对Person类进行操作（例如增删改查）的接口(package com.vae.dao)

技术分享 
  1. <span style="color: #0000ff;">package<span style="color: #000000;"> com.vae.dao;
  2. <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.SQLException;
  3. <span style="color: #0000ff;">import<span style="color: #000000;"> java.util.List;
  4. <span style="color: #0000ff;">import<span style="color: #000000;"> com.vae.domain.Person;
  5. <span style="color: #0000ff;">public <span style="color: #0000ff;">interface<span style="color: #000000;"> PersonDao {
  6.     <span style="color: #008000;">//<span style="color: #008000;">添加方法
  7.     <span style="color: #0000ff;">public <span style="color: #0000ff;">void add(Person p)<span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException;
  8.     
  9.     <span style="color: #008000;">//<span style="color: #008000;">更新方法
  10.     <span style="color: #0000ff;">public <span style="color: #0000ff;">void update(Person p)<span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException;
  11.     
  12.     <span style="color: #008000;">//<span style="color: #008000;">删除方法
  13.     <span style="color: #0000ff;">public <span style="color: #0000ff;">void delete(<span style="color: #0000ff;">int id)<span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException;
  14.     
  15.     <span style="color: #008000;">//<span style="color: #008000;">查找方法
  16.     <span style="color: #0000ff;">public Person findById(<span style="color: #0000ff;">int id)<span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException;
  17.     
  18.     <span style="color: #008000;">//<span style="color: #008000;">查找所有
  19.     <span style="color: #0000ff;">public List<Person> findAll()<span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException;
  20.     
  21. }<span style="font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; line-height: 1.5;"> </span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
技术分享

（4）定义PeronDaoImpl实现类 ，实现上面的PeronDao接口（package com.vae.dao.impl）

技术分享 
  1. <span style="color: #008080;">  1 <span style="color: #0000ff;">package<span style="color: #000000;"> com.vae.dao.impl;
  2. <span style="color: #008080;">  2 
  3. <span style="color: #008080;">  3 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.Connection;
  4. <span style="color: #008080;">  4 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.PreparedStatement;
  5. <span style="color: #008080;">  5 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.ResultSet;
  6. <span style="color: #008080;">  6 <span style="color: #0000ff;">import<span style="color: #000000;"> java.sql.SQLException;
  7. <span style="color: #008080;">  7 <span style="color: #0000ff;">import<span style="color: #000000;"> java.util.ArrayList;
  8. <span style="color: #008080;">  8 <span style="color: #0000ff;">import<span style="color: #000000;"> java.util.List;
  9. <span style="color: #008080;">  9 
  10. <span style="color: #008080;"> 10 <span style="color: #0000ff;">import<span style="color: #000000;"> com.util.db.DBUtils;
  11. <span style="color: #008080;"> 11 <span style="color: #0000ff;">import<span style="color: #000000;"> com.vae.dao.PersonDao;
  12. <span style="color: #008080;"> 12 <span style="color: #0000ff;">import<span style="color: #000000;"> com.vae.domain.Person;
  13. <span style="color: #008080;"> 13 
  14. <span style="color: #008080;"> 14 <span style="color: #008000;">/**
  15. <span style="color: #008080;"> 15 <span style="color: #008000;"> * PersonDao的具体实现类
  16. <span style="color: #008080;"> 16 <span style="color: #008000;"> * <span style="color: #808080;">@author<span style="color: #008000;"> lamp
  17. <span style="color: #008080;"> 17 <span style="color: #008000;"> *
  18. <span style="color: #008080;"> 18  <span style="color: #008000;">*/
  19. <span style="color: #008080;"> 19 <span style="color: #0000ff;">public <span style="color: #0000ff;">class PersonDaoImpl <span style="color: #0000ff;">implements<span style="color: #000000;"> PersonDao{
  20. <span style="color: #008080;"> 20 
  21. <span style="color: #008080;"> 21     <span style="color: #008000;">/**
  22. <span style="color: #008080;"> 22 <span style="color: #008000;">     * 实现添加方法
  23. <span style="color: #008080;"> 23      <span style="color: #008000;">*/
  24. <span style="color: #008080;"> 24 <span style="color: #000000;">    @Override
  25. <span style="color: #008080;"> 25     <span style="color: #0000ff;">public <span style="color: #0000ff;">void add(Person p) <span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException {
  26. <span style="color: #008080;"> 26         Connection conn = <span style="color: #0000ff;">null<span style="color: #000000;">;
  27. <span style="color: #008080;"> 27         PreparedStatement ps = <span style="color: #0000ff;">null<span style="color: #000000;">;
  28. <span style="color: #008080;"> 28         String sql = "insert into person(name,age,description)values(?,?,?)"<span style="color: #000000;">;
  29. <span style="color: #008080;"> 29         <span style="color: #0000ff;">try<span style="color: #000000;">{
  30. <span style="color: #008080;"> 30             conn =<span style="color: #000000;"> DBUtils.getConnection();
  31. <span style="color: #008080;"> 31             ps =<span style="color: #000000;"> conn.prepareStatement(sql);
  32. <span style="color: #008080;"> 32             ps.setString(1<span style="color: #000000;">, p.getName());
  33. <span style="color: #008080;"> 33             ps.setInt(2<span style="color: #000000;">, p.getAge());
  34. <span style="color: #008080;"> 34             ps.setString(3<span style="color: #000000;">, p.getDescription());
  35. <span style="color: #008080;"> 35 <span style="color: #000000;">            ps.executeUpdate();
  36. <span style="color: #008080;"> 36         }<span style="color: #0000ff;">catch<span style="color: #000000;">(SQLException e){
  37. <span style="color: #008080;"> 37 <span style="color: #000000;">            e.printStackTrace();
  38. <span style="color: #008080;"> 38             <span style="color: #0000ff;">throw <span style="color: #0000ff;">new SQLException("添加数据失败"<span style="color: #000000;">);
  39. <span style="color: #008080;"> 39         }<span style="color: #0000ff;">finally<span style="color: #000000;">{
  40. <span style="color: #008080;"> 40             DBUtils.close(<span style="color: #0000ff;">null<span style="color: #000000;">, ps, conn);
  41. <span style="color: #008080;"> 41 <span style="color: #000000;">        }
  42. <span style="color: #008080;"> 42 <span style="color: #000000;">    }
  43. <span style="color: #008080;"> 43 
  44. <span style="color: #008080;"> 44     <span style="color: #008000;">/**
  45. <span style="color: #008080;"> 45 <span style="color: #008000;">     * 更新方法
  46. <span style="color: #008080;"> 46      <span style="color: #008000;">*/
  47. <span style="color: #008080;"> 47 <span style="color: #000000;">    @Override
  48. <span style="color: #008080;"> 48     <span style="color: #0000ff;">public <span style="color: #0000ff;">void update(Person p) <span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException {
  49. <span style="color: #008080;"> 49         Connection conn = <span style="color: #0000ff;">null<span style="color: #000000;">;
  50. <span style="color: #008080;"> 50         PreparedStatement ps = <span style="color: #0000ff;">null<span style="color: #000000;">;
  51. <span style="color: #008080;"> 51         String sql = "update person set name=?,age=?,description=? where id=?"<span style="color: #000000;">;
  52. <span style="color: #008080;"> 52         <span style="color: #0000ff;">try<span style="color: #000000;">{
  53. <span style="color: #008080;"> 53             conn =<span style="color: #000000;"> DBUtils.getConnection();
  54. <span style="color: #008080;"> 54             ps =<span style="color: #000000;"> conn.prepareStatement(sql);
  55. <span style="color: #008080;"> 55             ps.setString(1<span style="color: #000000;">, p.getName());
  56. <span style="color: #008080;"> 56             ps.setInt(2<span style="color: #000000;">, p.getAge());
  57. <span style="color: #008080;"> 57             ps.setString(3<span style="color: #000000;">, p.getDescription());
  58. <span style="color: #008080;"> 58             ps.setInt(4<span style="color: #000000;">, p.getId());
  59. <span style="color: #008080;"> 59 <span style="color: #000000;">            ps.executeUpdate();
  60. <span style="color: #008080;"> 60         }<span style="color: #0000ff;">catch<span style="color: #000000;">(SQLException e){
  61. <span style="color: #008080;"> 61 <span style="color: #000000;">            e.printStackTrace();
  62. <span style="color: #008080;"> 62             <span style="color: #0000ff;">throw <span style="color: #0000ff;">new SQLException("更新数据失败"<span style="color: #000000;">);
  63. <span style="color: #008080;"> 63         }<span style="color: #0000ff;">finally<span style="color: #000000;">{
  64. <span style="color: #008080;"> 64             DBUtils.close(<span style="color: #0000ff;">null<span style="color: #000000;">, ps, conn);
  65. <span style="color: #008080;"> 65 <span style="color: #000000;">        }        
  66. <span style="color: #008080;"> 66 <span style="color: #000000;">    }
  67. <span style="color: #008080;"> 67 
  68. <span style="color: #008080;"> 68     <span style="color: #008000;">/**
  69. <span style="color: #008080;"> 69 <span style="color: #008000;">     * 删除方法
  70. <span style="color: #008080;"> 70      <span style="color: #008000;">*/
  71. <span style="color: #008080;"> 71 <span style="color: #000000;">    @Override
  72. <span style="color: #008080;"> 72     <span style="color: #0000ff;">public <span style="color: #0000ff;">void delete(<span style="color: #0000ff;">int id) <span style="color: #0000ff;">throws<span style="color: #000000;"> SQLException {
  73. <span style="color: #008080;"> 73         Connection conn = <span style="color: #0000ff;">null<span style="color: #000000;">;
  74. <span style="color: #008080;"> 74         PreparedStatement ps = <span style="color: #0000ff;">null<span style="color: #000000;">;
  75. <span style="color: #008080;"> 75         String sql = "delete from person where id=?"<span style="color: #000000;">;
  76. <span style="color: #008080;"> 76         <span style="color: #0000ff;">try<span style="color: #000000;">{
  77. <span style="color: #008080;"> 77             conn =<span style="color: #000000;"> DBUtils.getConnection();
  78. <span style="color: #008080;"> 78             ps =<span style="color: #000000;"> conn.prepareStatement(sql);
  79. <span style="color: #008080;"> 79             ps.setInt(1<span style="color: #000000;">,id);
  80.  80             ps.executeUpdate();
  81.  81         }catch(SQLException e){
  82.  82             e.printStackTrace();
  83.  83             throw new SQLException(" 删除数据失败");
  84.  84         }finally{
  85.  85             DBUtils.close(null, ps, conn);
  86.  86         }        
  87.  87     }
  88.  88 
  89.  89     /**
  90.  90      * 根据ID查询一个对象
  91.  91      */
  92.  92     @Override
  93.  93     public Person findById(int id) throws SQLException {
  94.  94         Connection conn = null;
  95.  95         PreparedStatement ps = null;
  96.  96         ResultSet rs = null;
  97.  97         Person p = null;
  98.  98         String sql = "select name,age,description from person where id=?";
  99.  99         try{
  100. 100             conn = DBUtils.getConnection();
  101. 101             ps = conn.prepareStatement(sql);
  102. 102             ps.setInt(1, id);
  103. 103             rs = ps.executeQuery();
  104. 104             if(rs.next()){
  105. 105                 p = new Person();
  106. 106                 p.setId(id);
  107. 107                 p.setName(rs.getString(1));
  108. 108                 p.setAge(rs.getInt(2));
  109. 109                 p.setDescription(rs.getString(3));
  110. 110             }
  111. 111         }catch(SQLException e){
  112. 112             e.printStackTrace();
  113. 113             throw new SQLException("根据ID查询数据失败");
  114. 114         }finally{
  115. 115             DBUtils.close(rs, ps, conn);
  116. 116         }
  117. 117         return p;
  118. 118     }
  119. 119 
  120. 120     /**
  121. 121      * 查询所有数据
  122. 122      */
  123. 123     @Override
  124. 124     public List<Person> findAll() throws SQLException {
  125. 125         Connection conn = null;
  126. 126         PreparedStatement ps = null;
  127. 127         ResultSet rs = null;
  128. 128         Person p = null;
  129. 129         List<Person> persons = new ArrayList<Person>();
  130. 130         String sql = "select id,name,age,description from person";
  131. 131         try{
  132. 132             conn = DBUtils.getConnection();
  133. 133             ps = conn.prepareStatement(sql);
  134. 134             rs = ps.executeQuery();
  135. 135             while(rs.next()){
  136. 136                 p = new Person();
  137. 137                 p.setId(rs.getInt(1));
  138. 138                 p.setName(rs.getString(2));
  139. 139                 p.setAge(rs.getInt(3));
  140. 140                 p.setDescription(rs.getString(4));
  141. 141                 persons.add(p);
  142. 142             }
  143. 143         }catch(SQLException e){
  144. 144             e.printStackTrace();
  145. 145             throw new SQLException("查询所有数据失败");
  146. 146         }finally{
  147. 147             DBUtils.close(rs, ps, conn);
  148. 148         }
  149. 149         return persons;
  150. 150     }
  151. 151 
  152. 152 }</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>

DAO设计模式实现数据库的增删改查（进一步封装JDBC工具类）

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