时间：2021-07-01 10:21:17 帮助过：19人阅读
准备工作
1、user实体类
public class User {
private Integer id;
private String username;
private Date birthday;
private String gender;
private String address;
//省略get、set和toString方法
}
2、WorkCard实体类
public class WorkCard {
private User user;
//省略get、set方法
}
3、数据库
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT ‘用户名称‘,
`birthday` datetime DEFAULT NULL COMMENT ‘生日‘,
`gender` char(1) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL COMMENT ‘性别‘,
`address` varchar(256) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL COMMENT ‘地址‘,
PRIMARY KEY (`id`) USING BTREE
)
表结构
接口
public interface UserMapper {
/**
* 查询所有用户
* @return
*/
List<User> findAllUser();
/**
* 保存用户
*/
void saveUser(User user);
/**
* 更新用户
*/
void updateUser(User user);
/**
* 删除用户
*/
void deleteUser(Integer id);
/**
* 根据id查询用户
*/
User findUserById(Integer id);
/**
* like模糊查询，第一种
*/
List<User> findUserByName(String username);
/**
* like模糊查询，第二种
*/
List<User> findUserByName2(String username);
/**
* 查询总用户数（聚合函数count）
*/
int findTotal();
/**
* 根据WorkCard类中User属性的username模糊查询
* WorkCard是user的封装类
* OGNL表达式取值
*/
List<User> findUserByWorkCard(WorkCard workCard);
}
映射文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace填写的是Mapper接口的全限定名-->
<mapper namespace="com.example.mapper.UserMapper">
<!--查询所有-->
<select id="findAllUser" resultType="com.example.pojo.User">
select * FROM user
</select>
<!--添加用户-->
<insert id="saveUser" parameterType="com.example.pojo.User">
<!--配置插入操作后，获取插入数据的id -->
<selectKey keyProperty="id" keyColumn="id" resultType="int" order="AFTER">
SELECT last_insert_id();
</selectKey>
INSERT INTO user(username,birthday,gender,address) VALUES (#{username},#{birthday},#{gender},#{address})
</insert>
<!--更新用户-->
<update id="updateUser" parameterType="com.example.pojo.User">
UPDATE user SET username = #{username}, birthday = #{birthday}, gender = #{gender}, address = #{address} WHERE id = #{id}
</update>
<!--删除用户-->
<delete id="deleteUser" parameterType="Integer">
<!--当参数只用一个并且参数是基本数据类型的包装类是#{占位符}占位符可以随便写 -->
DELETE FROM user WHERE id = #{userid}
</delete>
<!--通过id查询用户-->
<select id="findUserById" parameterType="Integer" resultType="com.example.pojo.User">
select * FROM user where id = #{userId}
</select>
<!--通过名字模糊查询用户-->
<select id="findUserByName" parameterType="java.lang.String" resultType="com.example.pojo.User">
SELECT * FROM user WHERE username LIKE ‘%${username}%‘
</select>
<!--通过名字模糊查询用户-->
<select id="findUserByName2" parameterType="java.lang.String" resultType="com.example.pojo.User">
SELECT * FROM user WHERE username LIKE #{username}
</select>
<!--查询总用户数，聚合函数count（）-->
<select id="findTotal" resultType="int">
SELECT count(*) FROM user
</select>
<!--OGNL表达式
Object Graphic Navigation Language 对象 图 导航 语言
它是通过对象的取值方法来获取数据，在写法上吧get给省略了
比如：获取用户名
通常的写法：user.getUsername();
OGNL表达式写法 user.username
-->
<select id="findUserByWorkCard" parameterType="com.example.pojo.WorkCard" resultType="com.example.pojo.User">
SELECT * FROM user WHERE username LIKE #{user.username}
</select>
</mapper>
public class UserMapperTest {
private UserMapper userMapper;
private SqlSession sqlSession;
private InputStream stream;
@Before
public void init() throws IOException {
stream = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(stream);
sqlSession = sqlSessionFactory.openSession();
userMapper = sqlSession.getMapper(UserMapper.class);
}
@After
public void destory() throws IOException {
// 每次执行完都进行事务提交
sqlSession.commit();
sqlSession.close();
stream.close();
}
/**
* 查询所有
*/
@Test
public void testFindAll(){
List<User> allUser = userMapper.findAllUser();
for (User user: allUser
) {
System.out.println(user);
}
}
/**
* 保存用户
*/
@Test
public void testSaveUser(){
User user = new User();
user.setUsername("小红");
user.setGender("男");
user.setBirthday(new Date());
user.setAddress("汕头市");
userMapper.saveUser(user);
System.out.println(user);
}
/**
* 更新用户
*/
@Test
public void testUpdateUser(){
User user = new User();
user.setUsername("小红");
user.setGender("女");
user.setBirthday(new Date());
user.setAddress("汕头市");
user.setId(52);
userMapper.updateUser(user);
}
/**
* 删除用户
*/
@Test
public void testDeleteUser(){
userMapper.deleteUser(50);
}
/**
* 根据用户id查询用户
*/
@Test
public void testFindUserById(){
User user = userMapper.findUserById(48);
System.out.println(user);
}
/**
* 根据用户姓名模糊查询用户
*/
@Test
public void testFindUserByName(){
/**
* 第一种写法在dao层的sql语句中添加‘%${username}%‘,这种方式的缺点是不能预处理
*/
List<User> users = userMapper.findUserByName("小");
for (User user: users
) {
System.out.println(user);
}
}
/**
* 根据用户姓名模糊查询用户
*/
@Test
public void testFindUserByName2(){
/**
* 第二种写法是在传参是就添加了%
*/
List<User> users = userMapper.findUserByName2("%" + "小" + "%");
for (User user: users
) {
System.out.println(user);
}
}
/**
* 测试聚合函数
*/
@Test
public void testFindTotal(){
int total = userMapper.findTotal();
System.out.println(total);
}
/**
* OGNL取值
*/
/**
* 根据用户姓名模糊查询用户
*/
@Test
public void findUserByWorkCard(){
User user = new User();
user.setUsername("%" + "小" + "%");
WorkCard workCard = new WorkCard();
workCard.setUser(user);
List<User> users = userMapper.findUserByWorkCard(workCard);
for (User u: users
) {
System.out.println(u);
}
}
}
6、MySQL之常见的单表CRUD操作
标签：准备工作 属性 mybatis res date() ring val 保存 datetime