MyBatis笔记——Mapper动态代理

前提概要

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

下面是实例介绍。

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1.环境配置

工程目录结构如下 

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> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/db_pwc" /> <property name="username" value="pwc" /> <property name="password" value="123456" /> </dataSource> </environment> </environments> <mappers> <mapper resource="com/pwc/dao/mapper/UserMapper.xml" /> </mappers> </configuration>

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2.Mapper映射接口（UserMapper.java)和Mapper映射表(UserMapper.xml)

UserMapper.java

package com.pwc.dao.mapper; import java.util.List; import com.pwc.pojo.User; public interface UserMapper { public User findById(int id); public void deleteById(int id); public void insert(User user); public List<User> findByAge(int age); }

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"> <mapper namespace="com.pwc.dao.mapper.UserMapper"> <select id="findById" parameterType="int" resultType="com.pwc.pojo.User"> SELECT * FROM User WHERE id = #{id} </select> <insert id="insert" parameterType="com.pwc.pojo.User"> INSERT INTO User(name,age) VALUES(#{name},#{age}) </insert> <delete id="deleteById" parameterType="int"> DELETE * FROM User WHERE id=#{id} </delete> <select id="findByAge" parameterType="int" resultType="com.pwc.pojo.User"> SELECT * FROM User WHERE age=#{age} </select> </mapper>

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3.测试

测试类

package com.pwc.test; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import com.pwc.dao.mapper.UserMapper; import com.pwc.pojo.User; public class Test { public static void main(String[] args) { SqlSessionFactoryBuilder builder=new SqlSessionFactoryBuilder(); SqlSessionFactory factory=builder.build(Test.class.getClassLoader().getResourceAsStream("SqlMapConfig.xml")); SqlSession session = factory.openSession(); UserMapper mapper = session.getMapper(UserMapper.class); User user = mapper.findById(1); session.close(); System.out.println(user); } }

测试结果如下 User [id=1, name=pwc, age=18]

转载于:https://www.cnblogs.com/haw2106/p/6951996.html

相关资源：数据结构—成绩单生成器