使用Mybatis Generator自动生成代码

看过前几篇关于Mybatis的文章可以发现，在DAO层做数据库交互时，存在两中方式。一种为使用注解手写mapper.xml，这种方式比较复杂，手写xml文件相当麻烦。另一种较手写mapper.xml文件简单一些，就是使用注解(@Select、@Update、@Insert、@Delete)的方式，但是手写sql也经常会带来一些隐式错误，并切也要手写sql，而Mybatis Generator的出现很好解决了这个痛点，Mybatis Generator可以自动生成dao层接口、pojo以及mapper.xml。DAO层可以使用Mybatis Generator自动生成的接口的现有功能，来完成具体业务需求。本篇文章将讲述一下Mybatis Generator插件的配置，及具体使用方法。

1. 项目结构

|   pom.xml
|   springboot-07-mybatis-generator.iml
|
+---src
|   +---main
|   |   +---java
|   |   |   \---com
|   |   |       \---zhuoli
|   |   |           \---service
|   |   |               \---springboot
|   |   |                   \---mybatis
|   |   |                       \---generator
|   |   |                           |   SpringBootMybatisGeneratorApplicationContext.java
|   |   |                           |
|   |   |                           +---controller
|   |   |                           |       UserController.java
|   |   |                           |
|   |   |                           +---repository
|   |   |                           |   +---conf
|   |   |                           |   |       DataSourceConfig.java
|   |   |                           |   |
|   |   |                           |   +---mapper
|   |   |                           |   |       UserMapper.java
|   |   |                           |   |
|   |   |                           |   +---model
|   |   |                           |   |       User.java
|   |   |                           |   |       UserExample.java
|   |   |                           |   |
|   |   |                           |   \---service
|   |   |                           |       |   UserRepository.java
|   |   |                           |       |
|   |   |                           |       \---impl
|   |   |                           |               UserRepositoryImpl.java
|   |   |                           |
|   |   |                           \---service
|   |   |                               |   UserControllerService.java
|   |   |                               |
|   |   |                               \---impl
|   |   |                                       UserControllerServiceImpl.java
|   |   |
|   |   \---resources
|   |       |   application.properties
|   |       |
|   |       +---autogen
|   |       |       generatorConfig_zhuoli.xml
|   |       |
|   |       \---base
|   |           \---com
|   |               \---zhuoli
|   |                   \---service
|   |                       \---springboot
|   |                           \---mybatis
|   |                               \---generator
|   |                                   \---repository
|   |                                       \---mapper
|   |                                               UserMapper.xml
|   |
|   \---test
|       \---java

其中generatorConfig_zhuoli.xml文件就是Mybatis Generator的配置文件。

2. 新建user表

CREATE TABLE `user` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '用户编号',
  `user_name` varchar(25) DEFAULT NULL COMMENT '用户名称',
  `description` varchar(25) DEFAULT NULL COMMENT '描述',
  `is_deleted` tinyint(3) DEFAULT NULL COMMENT '是否删除',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

3. pom.xml添加Mybatis-Generator插件依赖

<?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.zhuoli.service</groupId>
    <artifactId>springboot-07-mybatis-generator</artifactId>
    <version>1.0-SNAPSHOT</version>

    <!-- Spring Boot 启动父依赖 -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
    </parent>

    <build>
        <plugins>
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.5</version>
                <!--如果不配置configuration节点，Mybatis Generator配置文件名字必须为generatorConfig.xml-->
                <configuration>
                    <!--可以自定义generatorConfig文件名-->
                    <configurationFile>src/main/resources/autogen/generatorConfig_zhuoli.xml</configurationFile>
                    <verbose>true</verbose>
                    <overwrite>true</overwrite>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <!-- Exclude Spring Boot's Default Logging -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.2</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>

</project>

4. application.properties配置

本文示例，数据源采用上篇文章介绍的Java Config配置数据源，application.properties文件中定义数据库信息，用于在Java Config中使用，如下：

##数据源配置
test.datasource.url=jdbc:mysql://115.47.149.48:3306/zhuoli_test?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true&useSSL=false
test.datasource.username=zhuoli
test.datasource.password=zhuoli
test.datasource.driverClassName=com.mysql.jdbc.Driver

5. 数据源配置

@Configuration
@MapperScan(basePackages = "com.zhuoli.service.springboot.mybatis.generator.repository.mapper", sqlSessionFactoryRef = "sqlSessionFactory")
public class DataSourceConfig {
    @Value("${test.datasource.url}")
    private String url;

    @Value("${test.datasource.username}")
    private String user;

    @Value("${test.datasource.password}")
    private String password;

    @Value("${test.datasource.driverClassName}")
    private String driverClass;

    @Bean(name = "dataSource")
    public DataSource dataSource() {
        PooledDataSource dataSource = new PooledDataSource();
        dataSource.setDriver(driverClass);
        dataSource.setUrl(url);
        dataSource.setUsername(user);
        dataSource.setPassword(password);
        return dataSource;
    }

    @Bean(name = "transactionManager")
    public DataSourceTransactionManager dataSourceTransactionManager() {
        return new DataSourceTransactionManager(dataSource());
    }

    @Bean(name = "sqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(@Qualifier("dataSource") DataSource dataSource) throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(dataSource);

        /*设置mapper文件位置*/
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources("classpath:base/com/zhuoli/service/springboot/mybatis/generator/repository/mapper/*.xml"));
        return sessionFactory.getObject();
    }
}

注意一定要添加@MapperScan注解，否则因为Mybatis Generator生成的Mapper类并没有@Mapper注解，在Repository层无法Autowired。

6. Mybatis Generator插件配置文件

<?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>

    <!--注意:本地需要有mysql-connector-java-5.1.45-bin.jar-->
    <classPathEntry location="D:\\mysql-connector-java-5.1.45-bin.jar"/>
    <context id="DB2Tables" targetRuntime="MyBatis3">

        <property name="javaFileEncoding" value="UTF-8"/>
        <property name="javaFormatter" value="org.mybatis.generator.api.dom.DefaultJavaFormatter"/>
        <property name="xmlFormatter" value="org.mybatis.generator.api.dom.DefaultXmlFormatter"/>
        <property name="beginningDelimiter" value="`"/>
        <property name="endingDelimiter" value="`"/>

        <plugin type="org.mybatis.generator.plugins.RowBoundsPlugin"/>
        <plugin type="org.mybatis.generator.plugins.SerializablePlugin"/>

        <commentGenerator>
            <property name="suppressDate" value="true"/>
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>

        <!--数据源-->
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://115.47.149.48:3306/zhuoli_test?zeroDateTimeBehavior=convertToNull&amp;useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8"
                        userId="zhuoli"
                        password="zhuoli">
        </jdbcConnection>

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

        <!--Model & Example文件-->
        <javaModelGenerator targetPackage="com.zhuoli.service.springboot.mybatis.generator.repository.model"
                            targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>

        <!--Mapper.xml文件-->
        <sqlMapGenerator targetPackage="com.zhuoli.service.springboot.mybatis.generator.repository.mapper"
                         targetProject="src/main/resources/base">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>

        <!--Mapper文件-->
        <javaClientGenerator type="XMLMAPPER"
                             targetPackage="com.zhuoli.service.springboot.mybatis.generator.repository.mapper"
                             targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>

        <!--表映射-->
        <table tableName="user" domainObjectName="User">
            <generatedKey column="id" sqlStatement="JDBC" identity="true"/>
            <columnOverride column="id" javaType="Long"/>
            <columnOverride column="is_deleted" javaType="Integer"/>
        </table>

    </context>
</generatorConfiguration>

7. Mybatis Generator插件使用

对于Idea用户，可以使用Ide集成的Maven插件运行Mybatis Generator，操作方法为：Maven Projects -> Plugins->mybatis-generator->mybatis-generator:generate->右键 Run Maven Build

看到console提示SUCCESS的时候，就表明Mybatis Generator已经运行成功，代码已经自动生成了。如果本地装了maven，还可以使用命令行方式运行，在Terminal运行命令”mvn mybatis-generator:generate”。

不知道是Mybatis Generator的bug还是其他原因，如果之前运行过Mybatis Generator插件并且已经生成POJO、Mapper、Mapper.xml文件，如果再次执行时，第二次生成的Mapper.xml文件并不会替换之前生成的文件，而是会去追加，POJO和Mapper类都是替换的。所以重新运行Mybatis Generator时，要先删除之前生成的Mapper.xml文件。

8. Mybatis Generator自动生成的代码介绍

对于一张表，Mybatis Generator生成的文件有四个，以本文的user表为例，我再配置文件中generatorConfig_zhuoli.xml中配置了user表的映射，所以生成的文件有以下四个：

8.1 POJO实体类

public class User implements Serializable {
    private Long id;

    private String userName;

    private String description;

    private Integer isDeleted;

    private static final long serialVersionUID = 1L;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName == null ? null : userName.trim();
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description == null ? null : description.trim();
    }

    public Integer getIsDeleted() {
        return isDeleted;
    }

    public void setIsDeleted(Integer isDeleted) {
        this.isDeleted = isDeleted;
    }
}

8.2 Example类

Example类主要用做查询、更新、删除时的条件定义，通俗的讲就是用来定义where后面的条件，底层通过一个Criteria静态内部类实现条件定义的，对于这个自动生成的类不用太多研究，结合使用场景，就能很好理解了，篇幅原因这里也不粘代码了，建议具体去操作一下。使用方法如下：

xxxExample example = new xxxExample(); 
UserExample.Criteria criteria = example.createCriteria();

8.3 DAO接口Mapper

其实这个Mapper跟之前我手写的mapper类是一个概念，都是定义接口，底层依赖mapper.xml文件实现具体sql操作。Mybatis Generator对生成的Mapper做了抽象，即每一张表生成的mapper类方法名都是一样的，使用这些方法，可以满足绝大多数简单sql操作，省去了我们手写sql的麻烦。

public interface UserMapper {
    long countByExample(UserExample example);

    int deleteByExample(UserExample example);

    int deleteByPrimaryKey(Long id);

    int insert(User record);

    int insertSelective(User record);

    List<User> selectByExampleWithRowbounds(UserExample example, RowBounds rowBounds);

    List<User> selectByExample(UserExample example);

    User selectByPrimaryKey(Long id);

    int updateByExampleSelective(@Param("record") User record, @Param("example") UserExample example);

    int updateByExample(@Param("record") User record, @Param("example") UserExample example);

    int updateByPrimaryKeySelective(User record);

    int updateByPrimaryKey(User record);
}

方法说明：

8.4 Mapper.xml文件

与之前文章手写的mapper.xml文件一样，Mybatis Generator插件生成的mapper.xml文件同样用来定义sql语句(支持动态查询)。

9. 使用生成的DAO接口实特定功能

代码中我定义了一个UserRepository接口，用于给Service层调用。

public interface UserRepository {
    List<User> getAllUsers();

    List<User> getUserByCondition(String userName, String description);

    User getUserById(Long id);

    int delUserById(Long id);

    int createUser(User user);

    int updateUser(User user);
}

实现类如下：

@Repository
@AllArgsConstructor
public class UserRepositoryImpl implements UserRepository {

    private UserMapper userMapper;

    @Override
    public List<User> getAllUsers() {
        UserExample example = new UserExample();
        return userMapper.selectByExample(example);
    }

    @Override
    public List<User> getUserByCondition(String userName, String description) {
        UserExample example = new UserExample();
        /*动态sql，userName和description不为null，则作为查询条件查询*/
        UserExample.Criteria criteria = example.createCriteria();
        if (!StringUtils.isNullOrEmpty(userName)) {
            criteria.andUserNameEqualTo(userName);
        }
        if (!StringUtils.isNullOrEmpty(description)) {
            criteria.andDescriptionEqualTo(description);
        }
        return userMapper.selectByExample(example);
    }

    @Override
    public User getUserById(Long id) {
        return userMapper.selectByPrimaryKey(id);
    }

    @Override
    public int delUserById(Long id) {
        UserExample example = new UserExample();
        example.createCriteria().andIdEqualTo(id);
        return userMapper.deleteByExample(example);
        /*等价于
        return userMapper.deleteByPrimaryKey(id);
        */
    }

    @Override
    public int createUser(User user) {
        return userMapper.insertSelective(user);
    }

    @Override
    public int updateUser(User user) {
        return userMapper.updateByPrimaryKey(user);
    }
}

10. Service层定义

public interface UserControllerService {
    List<User> getAllUsers();

    List<User> getByCondition(String userName, String description);

    User getUserById(Long id);

    int delUserById(Long id);

    int createUser(User user);

    int updateUser(User user);
}

实现这里不粘了，就是调用UserRepository交互数据库。

11. Controller层定义

@RestController
@AllArgsConstructor
@RequestMapping(value = "/user")
@Slf4j
public class UserController {

    private UserControllerService userControllerService;

    @RequestMapping(value = "/get_all", method = RequestMethod.POST)
    public ResponseEntity getAllUser() {
        return ResponseEntity.status(HttpStatus.OK).body(userControllerService.getAllUsers());
    }

    @RequestMapping(value = "/get_by_condition", method = RequestMethod.POST)
    public ResponseEntity getUserByCondition(@RequestParam(value = "userName") String userName,
                                             @RequestParam(value = "description") String description) {
        return ResponseEntity.status(HttpStatus.OK).body(userControllerService.getByCondition(userName, description));
    }

    @RequestMapping(value = "/create", method = RequestMethod.POST)
    public ResponseEntity createUser(@RequestParam(value = "userName") String userName,
                                     @RequestParam(value = "description") String description) {
        User user = new User();
        user.setUserName(userName);
        user.setDescription(description);

        userControllerService.createUser(user);
        return ResponseEntity.status(HttpStatus.OK).body("create user success");
    }

    @RequestMapping(value = "/query_user", method = RequestMethod.POST)
    public ResponseEntity queryUserById(@RequestParam(value = "id") Long id) {
        return ResponseEntity.status(HttpStatus.OK).body(userControllerService.getUserById(id));
    }

    @RequestMapping(value = "/update_user", method = RequestMethod.POST)
    public ResponseEntity updateUserById(@RequestParam(value = "id") Long id,
                                         @RequestParam(value = "userName") String userName,
                                         @RequestParam(value = "description") String description) {
        User user = new User();
        user.setId(id);
        user.setUserName(userName);
        user.setDescription(description);
        userControllerService.updateUser(user);
        return ResponseEntity.status(HttpStatus.OK).body("update user success");
    }

    @RequestMapping(value = "/del_user", method = RequestMethod.POST)
    public ResponseEntity deleteUserById(@RequestParam(value = "id") Long id) {
        userControllerService.delUserById(id);
        return ResponseEntity.status(HttpStatus.OK).body("del user success");
    }
}

12. 测试

使用postman进行接口测试，由于controller方法参数使用的是@RequestParam接收的，所以测试时，请求头要设置为x-www-form-urlencoded，否则会报“HTTP Status 400 – Required String parameter ‘xx’ is not present”错，具体请查看

示例代码：码云 – 卓立 – Mybatis Generator使用示例