mabatis--使用mapper代理开发dao

1、编写mapper.xml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">

<!-- 命名空间:其作用是对sql进行分类管理,使用mapper代理开发dao时，namespace需要设置为mapper接口的全类名 -->
<mapper namespace="com.tt.mybatis.mapper.CustomerMapper">

    <!-- 
        配置sql语句
        通过select执行数据库查询：
            id标识映射文件中的sql
            parameterType为输入参数的类型；
            resultType为输出参数的Java对象类型 
    -->
    <select id="findCustomerById" parameterType="int" resultType="com.tt.po.Customer">
        <!-- #{value}表示一个占位符，其中的value可以为任何名称 -->
        select * from customers where id=#{id}
    </select>
    
    <select id="findCustomerByName" parameterType="java.lang.String" resultType="com.tt.po.Customer">
        <!-- ${value}表示字符串拼接，{}中的变量只能为value，存在sql注入风险，不建议使用 -->
        select * from customers where name like '%${value}%';
    </select>
    
    <!-- 添加用户 -->
    <insert id="insertCustomer" parameterType="com.tt.po.Customer">
        <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
            select LAST_INSERT_ID()
        </selectKey>
        insert into customers(name, email, address) values(#{name}, #{email}, #{address})
    </insert>
    
    <!-- 删除用户 -->
    <delete id="deleteCustomer" parameterType="java.lang.Integer">
        delete from customers where id=#{id}
    </delete>
    
    <!-- 更新用户 -->
    <update id="updateCustomer" parameterType="java.util.HashMap">
        update customers set name=#{name}, email=#{email},address=#{address} where id=#{id}
    </update>
</mapper>

--注意：需要在全局配置文件(SqlMapConfig.xml)中加载该映射文件。

2、编写 mapper 接口，需要遵循一些开发规范，mybatis可以自动生成mybatis接口实现类对象:

--1) 在mapper.xml中的 namespace 等于mapper接口地址（全类名）；

--2) mapper.java 接口中的方法和mapper.xml中 statement 的id一致；

--3) mapper.java 接口中的方法的输入参数类型和mapper.xml中的 statement 的 parameterType 指定的类型一致；

--4) mapper.java 接口中的方法的返回值类型和 mapper.xml 中的 statement 的resultType 指定的类型一致；

package com.tt.mybatis.mapper;

import java.util.List;

import com.tt.po.Customer;

public interface CustomerMapper {
    
    public Customer findCustomerById(int id) throws Exception;
    public List<Customer> findCustomerByName(String name) throws Exception;
    public void insertCustomer(Customer customer) throws Exception;
    public void deleteCustomer(int id) throws Exception;
}

3、测试：

public class CustomerMapperTest {

    private SqlSessionFactory sqlSessionFactory = null;
    @Before
    public void setUp() throws Exception {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    @Test
    public void testFindCustomerById() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        CustomerMapper customerMapper = sqlSession.getMapper(CustomerMapper.class);
        
        Customer customer = customerMapper.findCustomerById(4);
        sqlSession.close();
        System.out.println(customer);
    }

    @Test
    public void testFindCustomerByName() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        CustomerMapper customerMapper = sqlSession.getMapper(CustomerMapper.class);
        
        List<Customer> customers = customerMapper.findCustomerByName("TT");
        sqlSession.close();
        System.out.println(customers);
    }

    @Test
    public void testInsertCustomer() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        CustomerMapper customerMapper = sqlSession.getMapper(CustomerMapper.class);
        
        Customer customer = new Customer("TestUser", "test@gmail.com", "China");
        customerMapper.insertCustomer(customer);
        sqlSession.commit();
        sqlSession.close();
        System.out.println(customer.getId());
    }

    @Test
    public void testDeleteCustomer() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        CustomerMapper customerMapper = sqlSession.getMapper(CustomerMapper.class);
        
        customerMapper.deleteCustomer(9);
        sqlSession.commit();
        sqlSession.close();
    }

}