mybatis学习教程（三）mybatis映射开发规范

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1、前言

前面一讲讲到讲到初级的Mybatis开发，现在晋级将一些他的规范开发，规范的东西更便于维护和阅读。

2、为Mybatis开发规范

1、mapper.xml中namespace指定为mapper接口的全限定名

此步骤目的：通过mapper.xml和mapper.java进行关联。

2、mapper.xml中statement的id就是mapper.java中方法名

3、mapper.xml中statement的parameterType和mapper.java中方法输入参数类型一致

4、mapper.xml中statement的resultType和mapper.java中方法返回值类型一致.

现在只需要一个mapper.java(UserMapper.java)接口文件与一个mapper.xml(UserMapper.xml),注意一点无论是返回li大st集合还是单个对象，返回参数都只需要单个对象的类型，这个是不是萌萌哒！以为他判断了你的java文件里面是集合类型

java对象:UserMapper依旧

import com.ycy.mybatis.module.User;import java.util.List;/** * Created by Administrator on 2015/8/31 0031. */public interface UserMapper {    public User getUserById(int id) throws Exception;    public List<User> findUserByName(String username) throws Exception;    public void  insertUser(User user) throws  Exception;}

xml对象：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"><!--命名空间：分类管理sql隔离，方便管理--><mapper namespace="com.ycy.mybatis.dao.UserMapper">    <!--id标示一个sql语句，一个Statement，封装为一个MapperStatement-->    <!--parameterType:传入参数类型;resultType:输出结果类型，指定映射的pojo-->    <!--#{}标示一个占位符，-->    <!--查询用户-->    <!--oracle-->    <!--   SELECT * FROM  USER  WHERE  username  LIKE  '%'||#{_parameter}||'%'-->    <!-- mysql-->    <select id="getUserById" parameterType="int" resultType="com.ycy.mybatis.module.User">         SELECT  * FROM USER WHERE id=#{id}        </select>    <select id="findUserByName" parameterType="String" resultType="com.ycy.mybatis.module.User">      SELECT * FROM  USER  WHERE  username  LIKE  '%${_parameter}%'    </select>    <!--新增用户-->    <insert id="insertUser" parameterType="com.ycy.mybatis.module.User" >        <!--插入值之后返回主键值-->        <selectKey resultType="int" order="AFTER" keyProperty="id">            SELECT LAST_INSERT_ID()        </selectKey>        INSERT  INTO USER  (username,birthday,sex,address) VALUES (#{username},#{birthday},#{sex},#{address})    </insert>    <!--删除用户-->    <delete id="deleteUser" parameterType="int">    DELETE  FROM USER  WHERE  id=#{id}    </delete>    <!--更新用户-->    <update id="updateUser" parameterType="com.ycy.mybatis.module.User">        UPDATE USER  SET username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} WHERE id=#{id}    </update></mapper>

测试结果：MybatisTest3

package com.ycy.mybatis.test;import com.ycy.mybatis.dao.UserMapper;import com.ycy.mybatis.module.User;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 java.io.IOException;import java.io.InputStream;import java.util.List;/** * Created by Administrator on 2015/8/31 0031. */public class MybatisTest3 {    private SqlSessionFactory sqlSessionFactory = null;    @Before    public void  before() throws IOException {        String resource="SqlMapConfig.xml";        InputStream in = Resources.getResourceAsStream(resource);        sqlSessionFactory= new SqlSessionFactoryBuilder().build(in);    }    @Test    public  void testGet() throws Exception {        SqlSession sqlSession=sqlSessionFactory.openSession();        UserMapper userService=  sqlSession.getMapper(UserMapper.class);        User user=  userService.getUserById(1);        System.out.println(user.getUsername());    }    @Test    public  void testFindByname() throws Exception {        SqlSession sqlSession=sqlSessionFactory.openSession();        UserMapper userMapper=  sqlSession.getMapper(UserMapper.class);        List<User> userList=  userMapper.findUserByName("陈小明");        for (User user : userList) {            System.out.println(user.getUsername());        }    }}

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