从原始JDBC代码中我们能看出,只有数据库操作语言是变化的，其他基本保持不变，大量代码模板化 ，所以我们可以进行优化

MyBatise的快速入门

添加MyBatis的坐标

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.itheima</groupId>
  <artifactId>itheima_mybatis_quick</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.32</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>


</project>

创建User数据表

 
编写User实体类

package com.itheima.domain;

public class User {

    private int id;
    private String username;
    private String password;

    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 getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

编写映射文件Usermapper.xml(在内部写映射关系和sql语句)

<?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="userMapper">

    <!--删除操作 Sql语句中使用#{任意字符串}方式引用传递的单个参数-->
    <delete id="delete" parameterType="int">
        delete from user where id=#{abc}
    </delete>

    <!--修改操作 -->
    <update id="update" parameterType="com.itheima.domain.User">
        update user set username=#{username},password=#{password} where id=#{id}
    </update>

    <!--插入操作 插入的是一个个参数，所以用parameterType，是一个user对象 -->
    <insert id="save" parameterType="com.itheima.domain.User">
        insert into user values(#{id},#{username},#{password})
    </insert>

    <!--查询操作 resultType 查询结果对应的实体类型-->
    <select id="findAll" resultType="user">
        select * from user
    </select>

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

</mapper>

编写核心文件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>

    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>

    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <!--数据源环境 因为是开发环境，所以命名为developement-->
    <!-- mybatis会自动连接配置的数据库 -->
    <environments default="developement">
        <environment id="developement">
            <transactionManager type="JDBC"></transactionManager>
            <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>
    

    <!--加载映射文件-->
    <mappers>
        <mapper resource="com/itheima/mapper/UserMapper.xml"></mapper>
    </mappers>


</configuration>

编写测试类

package com.itheima.test;

import com.itheima.domain.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.Test;

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

public class MyBatisTest {


    @Test
    //删除操作
    public void test4() throws IOException {

        //获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得session回话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行操作  参数：namespace+id
        sqlSession.delete("userMapper.delete",8);

        //mybatis执行更新操作  提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

    @Test
    //修改操作
    public void test3() throws IOException {

        //模拟user对象
        User user = new User();
        user.setId(7);
        user.setUsername("lucy");
        user.setPassword("123");

        //获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得session回话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行操作  参数：namespace+id
        sqlSession.update("userMapper.update",user);

        //mybatis执行更新操作  提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

    @Test
    //插入操作
    public void test2() throws IOException {

        //模拟user对象
        User user = new User();
        user.setUsername("xxx");
        user.setPassword("abc");

        //获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得session回话对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //执行操作  参数：namespace+id
        sqlSession.insert("userMapper.save",user);

        //mybatis执行更新操作  提交事务
        //sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

    @Test
    //查询操作
    public void test1() throws IOException {
        //获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得session回话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行操作  参数：namespace+id
        List<User> userList = sqlSession.selectList("userMapper.findAll");
        //打印数据
        System.out.println(userList);
        //释放资源
        sqlSession.close();
    }

    @Test
    //查询一个对象
    public void test5() throws IOException {
        //获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得session回话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行操作  参数：namespace+id
        User user = sqlSession.selectOne("userMapper.findById", 1);
        //打印数据
        System.out.println(user);
        //释放资源
        sqlSession.close();
    }

}

MyBatise的映射文件概述

MyBatise的增删改查操作

 插入操作涉及数据库数据变化,所以要使用sqlSessioni对象显示的提交事务即sqlSession.commit()

//mybatis执行更新操作  提交事务
sqlSession.commit();

MyBatise的核心配置文件概述

<?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>

    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>

    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <!--数据源环境 因为是开发环境，所以命名为developement-->
    <!-- mybatis会自动连接配置的数据库 -->
    <environments default="developement">
        <environment id="developement">
            <transactionManager type="JDBC"></transactionManager>
            <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>
    

    <!--加载映射文件-->
    <mappers>
        <mapper resource="com/itheima/mapper/UserMapper.xml"></mapper>
    </mappers>


</configuration>

MyBatise的相应API  

    @Test
    //查询操作
    public void test1() throws IOException {
        //获得核心配置文件
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获得session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得session会话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行操作  参数：namespace+id
        List<User> userList = sqlSession.selectList("userMapper.findAll");
        //打印数据
        System.out.println(userList);
        //释放资源
        sqlSession.close();
    }

 一个需要手动提交事务，一个是自动提交事务 

sqlsession会话对象（最重要）