[Java知识库]mybatis增删改查实现

测试顺序：

在接口中编写方法→在与该接口绑定的mapper中写对应操作→junit测试
在这里我用的接口类为UserMapper，对应绑定的xml为UserMapper.xml，代码如下

UserMapper：

public interface UserMapper {
    //获取用户列表方法
    List<User> getAlluser();

    //通过用户id获取用户
    User getUserById(int id);

    //插入一个用户
    int insertUser(User user);

    //通过id修改用户
    int updateUser(User user);

    //通过id删除用户
    int deleteUser(int id);
}

UserMapper.xml：

<?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命名空间，对应一个dao层接口-->
<mapper namespace="com.chong.dao.UserMapper">
    <!--注意，增删改操作都需要用sqlsession.commit来提交事务-->
    <!--id对应方法名,返回一般用resultType，注意这里面要写返回类型的完全限定名-->
   <select id="getAlluser" resultType="com.chong.pojo.User">
    select * from mybatis.user
   </select>

    <!--通过id获取用户-->
    <select id="getUserById" parameterType="int" resultType="com.chong.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>

    <!--插入用户-->
    <insert id="insertUser" parameterType="com.chong.pojo.User" >
        insert into mybatis.user (id, name, pwd) values (#{id},#{name},#{pwd});
    </insert>

    <!--修改用户-->
    <update id="updateUser" parameterType="com.chong.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id};
    </update>

    <!--通过id删除用户-->
    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id = #{id};
    </delete>
</mapper>

junit测试类：

public class UserMapperTest {
    //测试获取所有用户
    @Test
    public void test(){
        //获取到工厂
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //获取到userDao对象
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        //执行方法得到返回值
        List<User> alluser = userMapper.getAlluser();
        //遍历
        for (User user: alluser) {
            System.out.println(user.toString());
        }
        //关闭sqlsession
        sqlSession.close();
    }

    //测试通过id获取用户
    @Test
    public void testgetUserById(){
        //官网建议使用trycatch 为了保证最后关闭了sqlsession，实际中不太使用
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        try{
            // 你的应用逻辑代码
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            User userById = userMapper.getUserById(2);
            System.out.println(userById.toString());
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            sqlSession.close();     //关闭数据库资源
        }
    }

    @Test
    //测试插入用户
    public void  testinsertUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper insertuser = sqlSession.getMapper(UserMapper.class);
        int i = insertuser.insertUser(new User(6, "东皇太一", "123456"));
        if (i > 0) {
            System.out.println("用户插入成功");
        }else {
            System.out.println("用户插入失败");
        }
        //增删改操作必须要提交事务，不然修改是无效的
        sqlSession.commit();
        sqlSession.close();     //关闭数据库资源
    }

    @Test
    //测试修改用户
    public void testupdateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.updateUser(new User(4,"姚","11111111"));
        //提交事务
        sqlSession.commit();
        //关闭资源
        sqlSession.close();
    }

    @Test
    //测试通过id删除用户
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.deleteUser(5);
        sqlSession.commit();
        sqlSession.close();
    }
}