mybaits的Mapper动态代理的简单例子（定义类型别名，ResultMap类型的使用）

 实现原理

Mapper接口开发方法只需要程序员编写Mapper接口（相当于Dao接口），由Mybatis框架根据接口定义创建接口的动态代理对象，代理对象的方法体同上边Dao接口实现类方法。

Mapper接口开发需要遵循以下规范：

1、 Mapper.xml文件中的namespace与mapper接口的类路径相同。

2、  Mapper接口方法名和Mapper.xml中定义的每个statement的id相同

3、 Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql的parameterType的类型相同

4、 Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同

步骤：

1、导入相应的jar包

2、添加mybaits的核心文件和创建javaBean

3、创建Mapper代理对象和相关的配置文件（建议放在同一个文件夹下面）

4、运行测试

相关代码

Mybaits的数据库管理文件和核心配置文件

数据库管理文件  db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybaits
jdbc.username=root
jdbc.password=1921

核心配置文件SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

<!-- 加载数据库管理文件 -->
<properties resource="db.properties"/>

<!-- 配置别名 -->
<typeAliases>
<!-- 单个配置 -->
<typeAlias type="com.caokaiyuan.domain.User" alias="user"/>

<!-- 多个配置 -->
<!-- <package name="com.caokaiyuan.domain"/> -->
</typeAliases>

<!-- 和spring整合后 environments配置将废除-->
<environments default="development">
<environment id="development">
<!-- 使用jdbc事务管理-->
<transactionManager type="JDBC" />
<!-- 数据库连接池-->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>


</environment>
</environments>

<!-- 添加映射文件 -->
<mappers>
<!-- 加载单个映射文件 --> 
<!-- <mapper resource="com/caokaiyuan/mapper/UserMapper.xml"/> -->
<!-- 通过自动扫描包的方式来加载多个映射文件,要求配置文件和代理文件同在一个文件夹 -->
<package name="com.caokaiyuan.mapper"/>
</mappers>
</configuration>

JavaBean类

package com.caokaiyuan.domain;


public class User
{
private int id;
private String username;
private String sex;
private String address;

public int getId() 
{
return id;
}
public void setId(int id) 
{
this.id = id;
}
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
public String getSex()
{
return sex;
}
public void setSex(String sex)
{
this.sex = sex;
}
public String getAddress()
{
return address;
}
public void setAddress(String address)
{
this.address = address;
}

}

创建Mapper代理对象和相关的映射文件

UserMapper.java

package com.caokaiyuan.mapper;


import java.util.List;


import com.caokaiyuan.domain.User;


public interface UserMapper 
{
public User findById(int id);
public List<User> findByName(String usrname);
public void save(User user);
public void delete(User user);
public void update(User user);
}

接口定义有如下特点：

1、 Mapper接口方法名和Mapper.xml中定义的statement的id相同

2、 Mapper接口方法的输入参数类型和mapper.xml中定义的statement的parameterType的类型相同

3、 Mapper接口方法的输出参数类型和mapper.xml中定义的statement的resultType的类型相同

UserMapper.xml文件

定义mapper映射文件UserMapper.xml，需要修改namespace的值为UserMapper接口路径。将UserMapper.xml放在classpath下mapper目录 下。

<?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">


<mapper namespace="com.caokaiyuan.mapper.UserMapper"> 

<!-- 定义resultMap  column定义别名名称，property要定义别名的属性 -->

<resultMap type="user" id="query_user_sql">
<id column="id_" property="id"/>
<result column="user_" property="username"/>
<result column="sex_" property="sex"/>
<result column="add_" property="address"/>
</resultMap>

<!-- 通过Id查询 -->
<select id="findById" parameterType="int" resultType="user">
select *from user where id=#{id}
</select>

<!-- 通过姓名查询 -->
<select id="findByName" parameterType="String" resultMap="query_user_sql"> 
<!-- 运用定义的resultMap -->
select id id_,username user_,address add_, sex sex_ from user where username like '%${value}%'
</select>

<!-- 添加数据 -->
<insert id="save" parameterType="com.caokaiyuan.domain.User"> 
insert into user(username,sex,address) values(#{username},#{sex},#{address})
</insert>

<!-- 删除数据 -->
<delete id="delete" parameterType="com.caokaiyuan.domain.User">
delete from user where id=#{id}
</delete>

<!-- 修改数据 -->
<update id="update" parameterType="com.caokaiyuan.domain.User">
update user set username=#{username},sex=#{sex},address=#{address} where id=#{id}
</update>
</mapper>

测试类

package com.caokaiyuan.test;


import java.io.IOException;
import java.util.List;


import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;


import com.caokaiyuan.domain.User;
import com.caokaiyuan.mapper.UserMapper;


public class UserTest 
{
private SqlSessionFactory sqlSessionFactory;

@Before
public void before()
{
try 
{
sqlSessionFactory = new SqlSessionFactoryBuilder().
build(Resources.getResourceAsStream("SqlMapConfig.xml"));
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}

@Test
public void testFindById()
{
SqlSession session = sqlSessionFactory.openSession();
//获得Mapper代理对象
UserMapper userMapper = session.getMapper(UserMapper.class);
User user = userMapper.findById(1);
System.out.println(user.getAddress() + "   " + user.getSex() + "   " + user.getUsername());
}

@Test
public void testFindByName()
{
SqlSession session = sqlSessionFactory.openSession();
UserMapper userMapper = session.getMapper(UserMapper.class);
List<User> lists = userMapper.findByName("a");

for (User user : lists)
{
System.out.println(user.getUsername() + "\t" + user.getAddress() + "\t" + user.getSex());
}
}

@Test
public void testAdd()
{
SqlSession session = sqlSessionFactory.openSession();
User user = new User();
user.setAddress("桂平");
user.setSex("男");
user.setUsername("老曹");
UserMapper userMapper = session.getMapper(UserMapper.class);
userMapper.save(user);
session.commit();
}

@Test
public void testDelete()
{
SqlSession session = sqlSessionFactory.openSession();
UserMapper userMapper = session.getMapper(UserMapper.class);
User user = userMapper.findById(16);
userMapper.delete(user);
session.commit();
}

@Test
public void testUpdate()
{
SqlSession session = sqlSessionFactory.openSession();
UserMapper userMapper = session.getMapper(UserMapper.class);
User user = userMapper.findById(12);
user.setUsername("嘉宁1");
userMapper.update(user);
session.commit();
}
}