一、MyBatis简介

MyBatis 是支持普通 SQL 查询，存储过程和高级映射的优秀持久层框架。MyBatis 消除了几乎所有的 JDBC 代码和参数的手工设置以及结果集的检索。MyBatis 使用简单的 XML 或注解用于配置和原始映射，将接口和 Java 的 POJOs（Plan Old Java Objects，普通的 Java 对象）映射成数据库中的记录。

orm工具的基本思想

无论是用过的 hibernate,Mybatis,你都可以法相他们有一个共同点：

从配置文件(通常是 XML 配置文件中)得到 sessionfactory.
由 sessionfactory 产生 session
在 session 中完成对数据的增删改查和事务提交等.
在用完之后关闭 session 。
在 Java 对象和数据库之间有做 mapping 的配置文件，也通常是 xml 文件。

二、HelloWorld

创建用户表：

Create TABLE `user` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `userName` varchar(50) DEFAULT NULL,

  `userAge` int(11) DEFAULT NULL,

  `userAddress` varchar(200) DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

Insert INTO `user` VALUES ('', 'summer', '', 'shanghai,pudong');

结构图如下：

Configuration.xml: 这里使用mariadb作为开发环境

<?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>

    <typeAliases>

        <typeAlias alias="User" type="demo.mybatis.helloworld.model.User"/>

    </typeAliases>

    <environments default="development">

        <environment id="development">

            <transactionManager type="JDBC"/>

            <dataSource type="POOLED">

                <property name="driver" value="org.mariadb.jdbc.Driver"/>

                <property name="url" value="jdbc:mariadb://192.168.1.202:3306/demo" />

                <property name="username" value="root"/>

                <property name="password" value="111111"/>

            </dataSource>

        </environment>

    </environments>

    <mappers>

        <mapper resource="mapper/User.xml"/>

    </mappers>

</configuration>

pom.xml:

<?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>demo</groupId>

    <artifactId>mybatis</artifactId>

    <version>1.0-SNAPSHOT</version>

    <dependencies>

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis</artifactId>

            <version>3.2.8</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mariadb.jdbc/mariadb-java-client -->

        <dependency>

            <groupId>org.mariadb.jdbc</groupId>

            <artifactId>mariadb-java-client</artifactId>

            <version>1.4.6</version>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>3.1</version>

                <configuration>

                    <source>1.8</source>

                    <target>1.8</target>

                </configuration>

            </plugin>

        </plugins>

    </build>

</project>

User.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="demo.mybatis.helloworld.mapper.UserMapper">

    <select id="selectUserByID" parameterType="int" resultType="User">

        select * from `user` where id = #{id}

    </select>

</mapper>

User.java：

public class User {

    private int id;

    private String userName;

    private Integer userAge;

    private String userAddress;

    //get and set...

}

UserMapper:

public interface UserMapper {

    User selectUserByID(int id);

}

Test.java:

import java.io.Reader;

import demo.mybatis.helloworld.mapper.UserMapper;

import demo.mybatis.helloworld.model.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;

/**

 * Created by carl.yu on 2016/12/8.

 */

public class Test {

    private static SqlSessionFactory sqlSessionFactory;

    private static Reader reader;

    static {

        try {

            reader = Resources.getResourceAsReader("Configuration.xml");

            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

    public static SqlSessionFactory getSession() {

        return sqlSessionFactory;

    }

    public static void main(String[] args) {

        SqlSession session = sqlSessionFactory.openSession();

        try {

            UserMapper userOperation=session.getMapper(UserMapper.class);

            User user = userOperation.selectUserByID(1);

            System.out.println(user.getUserAddress());

            System.out.println(user.getUserName());

        } finally {

            session.close();

        }

    }

}

三、CRUD

这里直接用接口的方式编程。这种方式，要注意的一个地方就是。在 User.xml 的配置文件中，mapper namespace="demo.mybatis.helloworld.mapper.UserMapper" ，命名空间非常重要，不能有错，必须与我们定义的 package 和接口一致。如果不一致就会出错,这一章主要在上一讲基于接口编程的基础上完成如下事情:

用 mybatis 查询数据，包括列表
用 mybatis 增加数据
用 mybatis 更新数据
用 mybatis 删除数据

1. 查询数据，前面已经讲过简单的，主要看查询出列表的

查询出列表，也就是返回 list, 在我们这个例子中也就是 List , 这种方式返回数据，需要在 User.xml 里面配置返回的类型 resultMap, 注意不是 resultType, 而这个 resultMap 所对应的应该是我们自己配置的

<!-- 为了返回list 类型而定义的returnMap -->

    <resultMap type="User" id="resultListUser">

        <id column="id" property="id" />

        <result column="userName" property="userName" />

        <result column="userAge" property="userAge" />

        <result column="userAddress" property="userAddress" />

    </resultMap>

查询列表的语句在 User.xml 中

<!-- 返回list 的select 语句，注意 resultMap 的值是指向前面定义好的 -->

    <select id="selectUsers" parameterType="string" resultMap="resultListUser">

        select * from user where userName like #{userName}

    </select>

在 UserMapper接口中增加方法：public List selectUsers(String userName);

现在在 Test 类中做测试

public void getUserList(String userName){

        SqlSession session = sqlSessionFactory.openSession();

        try {

            UserMapper userOperation=session.getMapper(UserMapper.class);

            List<User> users = userOperation.selectUsers(userName);

            for(User user:users){

                System.out.println(user.getId()+":"+user.getUserName()+":"+user.getUserAddress());

            }

        } finally {

            session.close();

        }

    }

现在在 main 方法中可以测试：

public static void main(String[] args) {

        Test testUser=new Test();

        testUser.getUserList("%");

    }

可以看到，结果成功查询出来。如果是查询单个数据的话，用第二讲用过的方法就可以了。

2. 用 mybatis 增加数据

在 UseMapper接口中增加方法：

public void addUser(User user);

在 User.xml 中配置

<!--执行增加操作的SQL语句。id和parameterType

       分别与UserMapper接口中的addUser方法的名字和

       参数类型一致。以#{name}的形式引用Student参数

       的name属性，MyBatis将使用反射读取Student参数

       的此属性。#{name}中name大小写敏感。引用其他

       的gender等属性与此一致。seGeneratedKeys设置

       为"true"表明要MyBatis获取由数据库自动生成的主

       键；keyProperty="id"指定把获取到的主键值注入

       到Student的id属性-->

    <insert id="addUser" parameterType="User"

        useGeneratedKeys="true" keyProperty="id">

        insert into user(userName,userAge,userAddress)

             values(#{userName},#{userAge},#{userAddress})

    </insert>

然后在 Test 中写测试方法:

/**

     * 测试增加,增加后，必须提交事务，否则不会写入到数据库.

     */

    public void addUser(){

        User user=new User();

        user.setUserAddress("人民广场");

        user.setUserName("飞鸟");

        user.setUserAge(80);

        SqlSession session = sqlSessionFactory.openSession();

        try {

            UserMapper userOperation=session.getMapper(UserMapper.class);

            userOperation.addUser(user);

            session.commit();

            System.out.println("当前增加的用户 id为:"+user.getId());

        } finally {

            session.close();

        }

    }

3. 用 mybatis 更新数据

方法类似，先在 UserMapper中增加方法：

public void updateUser(User user);

然后配置 User.xml

<update id="updateUser" parameterType="User" >

        update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}

   </update>

Test 类总的测试方法如下：

public void updateUser(){

        //先得到用户,然后修改，提交。

        SqlSession session = sqlSessionFactory.openSession();

        try {

            UserMapper userOperation=session.getMapper(UserMapper.class);

            User user = userOperation.selectUserByID(4);

            user.setUserAddress("原来是魔都的浦东创新园区");

            userOperation.updateUser(user);

            session.commit();

        } finally {

            session.close();

        }

    }

4. 用 mybatis 删除数据

同理，UserMapper增加方法：public void deleteUser(int id);

配置 User.xml

<delete id="deleteUser" parameterType="int">

        delete from user where id=#{id}

    </delete>

然后在 Test 类中写测试方法:

 /**

     * 删除数据，删除一定要 commit.

     * @param id

     */

    public void deleteUser(int id){

        SqlSession session = sqlSessionFactory.openSession();

        try {

            IUserOperation userOperation=session.getMapper(IUserOperation.class);

            userOperation.deleteUser(id);

            session.commit();

        } finally {

            session.close();

        }

    }

这样，所有增删改查都完成了，注意在增加，更改，删除的时候要调用 session.commit()，这样才会真正对数据库进行操作，否则是没有提交的。

到此为止，简单的单表操作，应该都会了，接下来的时间了，我会讲多表联合查询，以及结果集的选取。

四、spring boot 配置mybatis

参考文章：http://www.mybatis.org/spring-boot-starter/mybatis-spring-boot-autoconfigure/

MyBatis-Spring-Boot-Starter will:

自动探测 DataSource.
自动根据探测到的DataSource创建SqlSessionFactoryBean .
Will create and register an instance of a SqlSessionTemplate got out of the SqlSessionFactoryBean.
Autoscan your mappers, link them to the SqlSessionTemplate and register them to Spring context so they can be injected into your beans.

可以配置的信息有：

Property	Description
config-location	MyBatis xml config file (optional)
mapper-locations	Mapper xml config files (optional)
type-aliases-package	Package to search for type aliases (optional)
type-handlers-package	Package to search for type aliases (optional)
executor-type	Executor type: SIMPLE, REUSE, BATCH (optional)

文件图：

pom.xml:

<?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>demo</groupId>

    <artifactId>demo.mybatis</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <packaging>jar</packaging>

    <name>demo</name>

    <description>mybatis spring boot demo</description>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>1.4.2.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <java.version>1.8</java.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.mybatis.spring.boot</groupId>

            <artifactId>mybatis-spring-boot-starter</artifactId>

            <version>1.1.1</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <!-- https://mvnrepository.com/artifact/com.alibaba/druid -->

        <dependency>

            <groupId>com.alibaba</groupId>

            <artifactId>druid</artifactId>

            <version>1.0.18</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mariadb.jdbc/mariadb-java-client -->

        <dependency>

            <groupId>org.mariadb.jdbc</groupId>

            <artifactId>mariadb-java-client</artifactId>

            <version>1.4.6</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

application.properties：

jdbc.driverClassName=org.mariadb.jdbc.Driver

jdbc.url=jdbc:mariadb://192.168.1.202:3306/demo

jdbc.username=root

jdbc.password=111111

mybatis.config-location=classpath:mybatis-config.xml

logging.level.root=WARN

logging.level.sample.mybatis.mapper=TRACE

mybatis-config.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>

    <typeAliases>

        <!--<package name="sample.mybatis.domain"/>-->

        <typeAlias alias="User" type="demo.domain.User"/>

    </typeAliases>

    <mappers>

        <mapper resource="mapper/User.xml"/>

    </mappers>

</configuration>

MyBatisConfig: 配置数据源

package demo;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.core.env.Environment;

import javax.sql.DataSource;

import java.util.Properties;

/**

 * Created by carl.yu on 2016/12/8.

 */

@Configuration

public class MyBatisConfig {

    @Autowired

    private Environment env;

    /**

     * 创建数据源

     *

     * @Primary 该注解表示在同一个接口有多个实现类可以注入的时候，默认选择哪一个，而不是让@autowire注解报错

     */

    @Bean

    //@Primary

    public DataSource getDataSource() throws Exception {

        Properties props = new Properties();

        props.put("driverClassName", env.getProperty("jdbc.driverClassName"));

        props.put("url", env.getProperty("jdbc.url"));

        props.put("username", env.getProperty("jdbc.username"));

        props.put("password", env.getProperty("jdbc.password"));

        props.put("testWhileIdle", "false");

        return DruidDataSourceFactory.createDataSource(props);

    }

}

配置User.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="demo.dao.UserMapper">

    <select id="selectUserByID" parameterType="int" resultType="User">

        select * from `user` where id = #{id}

    </select>

    <resultMap type="User" id="resultListUser">

        <id column="id" property="id"/>

        <result column="userName" property="userName"/>

        <result column="userAge" property="userAge"/>

        <result column="userAddress" property="userAddress"/>

    </resultMap>

    <!-- 返回list 的select 语句，注意 resultMap 的值是指向前面定义好的 -->

    <select id="selectUsers" parameterType="string" resultMap="resultListUser">

        select * from user where userName like #{userName}

    </select>

    <!--执行增加操作的SQL语句。id和parameterType

       分别与UserMapper接口中的addUser方法的名字和

       参数类型一致。以#{name}的形式引用Student参数

       的name属性，MyBatis将使用反射读取Student参数

       的此属性。#{name}中name大小写敏感。引用其他

       的gender等属性与此一致。seGeneratedKeys设置

       为"true"表明要MyBatis获取由数据库自动生成的主

       键；keyProperty="id"指定把获取到的主键值注入

       到Student的id属性-->

    <insert id="addUser" parameterType="User"

            useGeneratedKeys="true" keyProperty="id">

        insert into user(userName,userAge,userAddress)

        values(#{userName},#{userAge},#{userAddress})

    </insert>

    <update id="updateUser" parameterType="User">

        update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}

    </update>

    <delete id="deleteUser" parameterType="int">

        delete from user where id=#{id}

    </delete>

</mapper>

配置UserMapper：

package demo.dao;

import demo.domain.User;

import org.apache.ibatis.annotations.Mapper;

import java.util.List;

/**

 * Created by carl.yu on 2016/12/8.

 */

@Mapper

public interface UserMapper {

    User selectUserByID(int id);

    public List selectUsers(String userName);

    public void addUser(User user);

    public void updateUser(User user);

}

可以直接使用了: UserService

package demo.service;

import demo.dao.UserMapper;

import demo.domain.User;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import org.springframework.transaction.annotation.Transactional;

import java.util.List;

/**

 * Created by carl.yu on 2016/12/8.

 */

@Service

public class UserService {

    @Autowired

    private UserMapper userMapper;

    @Transactional(readOnly = true)

    public List<User> findAll() {

        return userMapper.selectUsers("%");

    }

}

巴特西

mybatis(1)