引言

本文主要从一个基础实例，讲解Mybatis的实现，已经每一步的详细讲解。我会将项目共享在百度云盘，文章最后！

1、项目结构

2、项目配置

 2.1 配置SqlMapConfig.xml

根据Mybatis架构图， 我们第一步应该配置SqlMapConfig，主要涉及到数据源的一些配置。架构请参考教材1

<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!--与spring整个后环境配置将废除--><environments default="development"><environment id="development"><!--使用JDBC事务管理--><transactionManager type="JDBC"></transactionManager><!--数据库连接池--><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/shiro?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertTonull"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><!--加载mapper--><mappers><mapper  resource="mapper/UserMapper.xml"/></mappers>
</configuration>

 2.1 配置sqlsessionFactory.xml

在配置SqlMapConfig中我们看到userMapper.xml,下面详细讲解如果配置sqlsessionFactory、sqlsession、mapperStatement、Executor

2.1.1Orm数据实体映射配置

我们每一个对象映射到关系型数据的一些操作，mybatis也是一种orm模型，自然免不了映射，我们以Mysql的User数据表为例子

数据库：user表

Java对象：User

public class User {private int id;private String username;// 用户姓名private String sex;// 性别private Date birthday;// 生日private String address;// 地址
//自己添加get set方法
}

2.1.1mapperStatement配置

我们的以一个User为例，创建 UserMapper.xml配置文件。把一个sql称为一个statement，这里很多mapperStatement，所以这映射文件里面，把对User的操作的sql都放在里面，即构建了mapperStatement。

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//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="test"><!--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--><select id="getUserById" parameterType="int" resultType="com.ycy.mybatis.module.User">SELECT  * FROM USER WHERE id=#{id}</select><select id="findUserByName" parameterType="java.lang.String" resultType="com.ycy.mybatis.module.User">SELECT * FROM  USER  WHERE  username  LIKE  '%'||#{username}||'%'</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>

2.1.1sqlsessionFactory创建sqlsession

我们必须知道，所有的sql配置都是需要一个sqlsession来执行会话操作，因为session本身意思就是一次会话。需要sqlsession就必须构建一个sqlsessionFactory，下面我们用两种方式来建立会话，进行数据库操作。

2.1.1.1通过junit测试操作会话

我们直接在junit中读取sqlMapConfig.xml，调用会话

 测试类：MybatisFrist

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.Date;
import java.util.List;/*** Created by Administrator on 2015/8/28 0028.*/
public class MybatisFrist {private SqlSessionFactory sqlSessionFactory = null;//创建工厂@Beforepublic void before() throws IOException {//创建会话工厂String resource = "SqlMapConfig.xml";InputStream in = null;in = Resources.getResourceAsStream(resource);sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);}@Testpublic void testGet() {//1通过sqlsessionfactory创建sqlsessionSqlSession sqlSession = sqlSessionFactory.openSession();//2通过sqlsession操作数据库User user = sqlSession.selectOne("test.getUserById", 1);System.out.println(user.getUsername());sqlSession.close();}@Testpublic void testSelect() {//1通过sqlsessionfactory创建sqlsessionSqlSession sqlSession = sqlSessionFactory.openSession();//2通过sqlsession操作数据库List<User> userList = sqlSession.selectList("test.findUserByName", "小");System.out.println(userList.size());for (User user : userList) {System.out.println(user.getUsername());}sqlSession.close();}@Testpublic void testInsert() {User user = new User();user.setUsername("杨长用");user.setAddress("重庆");user.setBirthday(new Date());user.setSex("1");//1通过sqlsessionfactory创建sqlsessionSqlSession sqlSession = sqlSessionFactory.openSession();//2通过sqlsession操作数据库sqlSession.insert("test.insertUser", user);sqlSession.commit();sqlSession.close();System.out.println("--------" + user.getId());}@Testpublic void testDel() {//1通过sqlsessionfactory创建sqlsessionSqlSession sqlSession = sqlSessionFactory.openSession();//2通过sqlsession操作数据库sqlSession.insert("test.deleteUser", 27);sqlSession.commit();sqlSession.close();}@Testpublic void testUpdate() {User user = new User();user.setUsername("杨长用修改");user.setAddress("重庆");user.setBirthday(new Date());user.setSex("1");user.setId(27);//1通过sqlsessionfactory创建sqlsessionSqlSession sqlSession = sqlSessionFactory.openSession();//2通过sqlsession操作数据库sqlSession.insert("test.updateUser", user);sqlSession.commit();sqlSession.close();System.out.println("--------" + user.getId());}
}

2.1.1.2通过接口的方式操作会话

请注意以上直接读取文件的方式，与通过接口方式的区别。我们只是把操作封装了一下，因为实际项目我们不可能写硬编码（直接写死参数值），仍然用junit测试。

Java对象：UserService

public interface UserService {public User getUserById(int id) throws Exception;public List<User> findUserByName(String name) throws Exception;public void  insertUser(User user) throws  Exception;
}

Java对象：UserService

package com.ycy.mybatis.dao.impl;import com.ycy.mybatis.dao.UserService;
import com.ycy.mybatis.module.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;import java.util.List;/*** Created by Administrator on 2015/8/31 0031.*/
public class UserServiceImpl implements UserService {private  SqlSessionFactory sqlSessionFactory;public  UserServiceImpl(SqlSessionFactory sqlSessionFactory){this.sqlSessionFactory=sqlSessionFactory;}@Overridepublic User getUserById(int id) throws Exception {SqlSession sqlSession=sqlSessionFactory.openSession();User user= sqlSession.selectOne("test.getUserById", id);sqlSession.close();return user;}@Overridepublic List<User> findUserByName(String name) throws Exception {SqlSession sqlSession=sqlSessionFactory.openSession();List<User> userList= sqlSession.selectList("test.findUserByName", name);sqlSession.close();return userList;}@Overridepublic void insertUser(User user) throws Exception {SqlSession sqlSession=sqlSessionFactory.openSession();//2通过sqlsession操作数据库sqlSession.insert("test.insertUser", user);sqlSession.commit();sqlSession.close();}
}

测试类：MybatisTest2

由于篇幅关系，我们只做根据Id查询用户

package com.ycy.mybatis.test;import com.ycy.mybatis.dao.impl.UserServiceImpl;
import com.ycy.mybatis.module.User;
import org.apache.ibatis.io.Resources;
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;/*** Created by Administrator on 2015/8/31 0031.*/
public class MybatisTest2 {private SqlSessionFactory sqlSessionFactory = null;@Beforepublic void  before() throws IOException {String resource="SqlMapConfig.xml";InputStream in =Resources.getResourceAsStream(resource);sqlSessionFactory= new  SqlSessionFactoryBuilder().build(in);}@Testpublic void  testGet() throws Exception {UserServiceImpl userService=new UserServiceImpl(sqlSessionFactory);User user= userService.getUserById(1);System.out.println(user.getUsername());}
}

输出结果：