SpringBoot2.0学习(四)-MyBatis

MyBatis是一款优秀的持久层构架，它支持定制化SQL语句、存储过程以及高级映射，可以通过简单的XML或注解配置和映射原生信息，将POJOs映射成数据库中的记录，从而方便进行增删改查的操作(官网)。本文会分别介绍通过XML、自动生成、注解三种传统使用MyBatis的方式以及在SpringBoot中使用MyBatis。

GitHub源码地址

1. XML配置方式使用MyBatis

1.1 引入依赖(jdbc,mysql,mybatis)

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

1.2 配置数据库连接信息

resources:mybatis/mybatis.properties

jdbc.driver-class=com.mysql.jdbc.Driver
jdbc.user=root
jdbc.password=123456
jdbc.url=jdbc:mysql://localhost:3306/test

1.3 配置Mybatis

resources:mybatis/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>
    <properties resource="mybatis/mybatis.properties" />

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver-class}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mybatis/mappers/UserMapper.xml"/>
    </mappers>
</configuration>

1.4 配置映射信息

resources:mybatis/mappers/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.hebaohua.springbootmybatis.mappers.UserMapper">
    <select id="selectUser" resultType="com.hebaohua.springbootmybatis.entity.User">
    select * from user where id = #{id}
  </select>
</mapper>

1.5运行测试

public class XmlConfigDemo {
    public static void main(String[] args) throws IOException {
        ResourceLoader resourceLoader = new DefaultResourceLoader();
        Resource resource = resourceLoader.getResource("classpath:/mybatis/mybatis-config.xml");
        InputStream inputStream = resource.getInputStream();
        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        try {
            User user = session.selectOne("com.hebaohua.springbootmybatis.mappers.UserMapper.selectUser", 4);
            System.out.println(user);
        } finally {
            session.close();
        }
    }
}

运行效果:

2. 使用MyBatis配置生成器

此处只讲解在idea中使用maven连接Mysql的配置方式, 其它可以查看网址.

2.1 首先添加Maven插件

           <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.5</version>
                <dependencies>
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>5.1.46</version>
                    </dependency>
                </dependencies>
            </plugin>

注意: 不要忘了下面的mysql驱动依赖

2.2 编写生成配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">

<generatorConfiguration>
    <context id="TestTables" targetRuntime="MyBatis3">
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/test"
                        userId="root"
                        password="123456">
        </jdbcConnection>

        <javaTypeResolver >
            <property name="forceBigDecimals" value="false" />
        </javaTypeResolver>

        <!-- Java 模型对象生成器 -->
        <javaModelGenerator targetPackage="com.hebaohua.springbootmybatisgenerator.entity"
                            targetProject="${user.dir}/src/main/java"/>

        <!-- SQL Mapper XML 生成器 -->
        <sqlMapGenerator  targetPackage="mybatis.mappers" targetProject="${user.dir}/src/main/resources"/>

        <!-- SQL Mapper Java 接口 -->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.hebaohua.springbootmybatisgenerator.mappers"
                             targetProject="${user.dir}/src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>

        <table tableName="user" domainObjectName="User" >
            <property name="useActualColumnNames" value="true"/>
            <generatedKey column="id" sqlStatement="MySQL" identity="true" />
            <columnOverride column="name"/>
            <columnOverride column="age"/>
        </table>

    </context>
</generatorConfiguration>

注意命名为generatorConfig.xml，并且直接放在resources下面

2.3 执行生成命令

在项目根目录打开命令窗口并执行mvn mybatis-generator:generate下图中的四个文件，然后其添加如XML方式中的配置信息。

2.4 运行测试

上一步中产生的文件提供了关于数据库user表中丰富的增删改查接口，使我们在使用起来非常的方便。

public class Demo {
    public static void main(String[] args) throws IOException {
        ResourceLoader resourceLoader = new DefaultResourceLoader();
        Resource resource = resourceLoader.getResource("classpath:/mybatis/mybatis-config.xml");
        InputStream inputStream = resource.getInputStream();
        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = session.getMapper(UserMapper.class);
            List<User> users = userMapper.selectByExample(null);

            System.out.println(users);
        } finally {
            session.close();
        }
    }
}

运行效果:

3. 使用注解

注解的方式总是能减少繁琐的配置文件。

3.1 编写注解Mapper

@Mapper
public interface UserMapper {

    @Results(value = {
            @Result(property = "id", column = "id", id = true),
            @Result(property = "name", column = "name"),
            @Result(property = "age", column = "age")
    })
    @Select("SELECT id,name,age FROM user WHERE id = #{id}")
    User selectUser(int id);
}

3.2 运行测试

同样需要引入全局配置文件，并注意要增加以下内容:

    <mappers>
        <mapper class="com.hebaohua.springbootmybatisannotation.mappers.UserMapper"/>
    </mappers>

测试代码:

public class Demo {
    public static void main(String[] args) throws IOException {
        ResourceLoader resourceLoader = new DefaultResourceLoader();
        Resource resource = resourceLoader.getResource("classpath:/mybatis/mybatis-config.xml");
        InputStream inputStream = resource.getInputStream();
        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = session.getMapper(UserMapper.class);
            User user= userMapper.selectUser(4);

            System.out.println(user);
        } finally {
            session.close();
        }
    }
}

运行效果:

4.SpringBoot中使用MyBatis

通过查看 MybatisAutoConfiguration以及MybatisProperties源码可知，在SpringBoot的配置文件中配置好datasource以及以“mybatis”开头的相关配置就会自动装配SqlSessionFactory，SqlSessionTemplate对象，因此在Contorller中就可以直接使用。

@org.springframework.context.annotation.Configuration
@ConditionalOnClass({ SqlSessionFactory.class, SqlSessionFactoryBean.class })
@ConditionalOnBean(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class MybatisAutoConfiguration 

@ConfigurationProperties(prefix = MybatisProperties.MYBATIS_PREFIX)
public class MybatisProperties {

  public static final String MYBATIS_PREFIX = "mybatis";

  /**
   * Location of MyBatis xml config file.
   */
  private String configLocation;

SpringBoot配置文件：

spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/test

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

Controller类:

@RestController
public class MyBatisController {
    @Autowired
    private SqlSessionTemplate sqlSessionTemplate;

    @GetMapping("/user/{id}")
    public User getUser(@PathVariable int id){
        User user = sqlSessionTemplate.selectOne("com.hebaohua.springbootmybatisannotation.mappers.UserMapper.selectUser",id);
        return user;
    }
}

运行效果: