SpringBoot & MyBatis 3 & MySQL

重新整理了一下 *MyBatis* 的使用，以作备忘。

## *Eclipse* vs *IntelliJ IDEA*

作为开发的 IDE 来讲我更喜欢用 *IntelliJ IDEA* ，不过在通过 *Maven* 运行 *MyBatis Generator* 插件时，*java client* 文件（即 *Mapper* 文件）总是会被覆盖。如果在 *Mapper* 中增加了自定义的接口定义，重新生成时就没有了。

根据[官方文档][17]中的说法，*Eclipse* 插件会根据方法备注中的 *@mbg.generated* 标签来识别哪些是自动生成的方法，哪些不是，从而避免自定义的方法被替换掉，但是 *IDEA* 中貌似没有类似的插件。

没有办法，最好还是通过 *Eclipse* 来运行 *MyBatis Generator*。 通过 *Eclipse* 菜单的 *Help* ⇒ *Eclipse Marketplace* 安装 *MyBatis Generator 1.4.0* 插件。另外因为创建的是 *Spring Boot* 项目，所以另外还安装了 *Spring Tools 4 (aka Spring Tool Suite 4)* 插件。

下面是最终使用的配置文件：

### *mybatis-generator.xml*

这里使用了 *MapperAnnotationPlugin* 插件，貌似是 *1.4.0* 版本里才有的，如果运行出错的话可以删掉。其对应的功能可以通过在 *Application* 启动类上添加 `@MapperScan("liujiajia.me.mybatis3sample.mapper")` 注解来实现。

```xml
<?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>
    <properties resource="mybatis-generator.properties" />
    <context id="TestDB" targetRuntime="MyBatis3">
        <property name="javaFileEncoding" value="UTF-8" />
        <plugin
            type="org.mybatis.generator.plugins.MapperAnnotationPlugin"></plugin>
        <commentGenerator>
            <property name="suppressDate" value="true" />
            
            
            <property name="addRemarkComments" value="true" />
        </commentGenerator>
        <jdbcConnection driverClass="${test.driver}"
            connectionURL="${test.url}" userId="${test.username}"
            password="${test.password}">
        </jdbcConnection>
        <javaTypeResolver>
            <property name="forceBigDecimals" value="true" />
        </javaTypeResolver>
        
        <javaModelGenerator
            targetPackage="${javaModelGenerator.targetPackage}"
            targetProject="${javaModelGenerator.targetProject}">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        </javaModelGenerator>
        
        <sqlMapGenerator
            targetPackage="${sqlMapGenerator.targetPackage}"
            targetProject="${sqlMapGenerator.targetProject}">
            <property name="enableSubPackages" value="true" />
        </sqlMapGenerator>
        
        <javaClientGenerator type="XMLMAPPER"
            targetPackage="${javaClientGenerator.targetPackage}"
            targetProject="${javaClientGenerator.targetProject}">
            <property name="enableSubPackages" value="true" />
        </javaClientGenerator>
        <table tableName="country">
        </table>
    </context>
</generatorConfiguration>
```

### *mybatis-generator.properties*

部分配置是放在 *mybatis-generator.properties* 文件中的，示例如下：

```properties
test.driver=com.mysql.cj.jdbc.Driver
test.url=jdbc:mysql://localhost:3306/test?serverTimezone=UTC
test.username=root
test.password=root

javaModelGenerator.targetPackage=liujiajia.me.mybatis3sample.model
javaModelGenerator.targetProject=MyBatisSample/src/main/java
sqlMapGenerator.targetPackage=liujiajia.me.mybatis3sample.mapper
sqlMapGenerator.targetProject=MyBatisSample/src/main/resources
javaClientGenerator.targetPackage=liujiajia.me.mybatis3sample.mapper
javaClientGenerator.targetProject=MyBatisSample/src/main/java
```

> 关于 *targetProject* 的值，在 IDEA 中是不需要带上项目名（*MyBatisSample*）的，在 *Eclipse* 中需要加上去，否则会报找不到 *src* 项目的错误（Eclipse 用的少，不确定是不是哪边配置不对导致的）。
> 另外 *sqlMapGenerator* 和 *javaClientGenerator* 的 *targetPackage* 貌似一定要一致，否则运行时会报错。

### 运行 *MyBatis Generator* 插件

右键 *mybatis-generator.xml* 然后选择 *Run As* ⇒ *Run MyBatis Generator*。生成的代码根据 *targetRuntime* 的不同会有很大的不同，这里就不贴了。

## 项目代码

这部分是项目中使用到的 *Maven* 配置文件等。

### *pom.xml*

因为用到了 *Swagger-UI* ，所以添加了 *springfox-swagger-ui* 和 *springfox-swagger2* 包。

数据库是 *MySQL*，需要添加 *mysql-connector-java* 包。

*plugins* 中还配置了 *mybatis-generator-maven-plugin* 插件，不过如果只通过 *Eclipse* 中的插件来生成的话，这段配置就用不到了。

```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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.RELEASE</version>
        <relativePath/> 
    </parent>
    <groupId>liujiajia.me</groupId>
    <artifactId>mybatis3sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatis3sample</name>
    <description>Demo project for MyBatis3</description>

<dependencies>
        <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>2.1.2</version>
        </dependency>
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>${swagger.version}</version>
        </dependency>
        
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>${swagger.version}</version>
        </dependency>
        
        <dependency>
            <groupId>org.mybatis.generator</groupId>
            <artifactId>mybatis-generator-core</artifactId>
            <version>1.3.5</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.4.0</version>
                <dependencies>
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>8.0.20</version>
                    </dependency>
                    <dependency>
                        <groupId>org.mybatis.generator</groupId>
                        <artifactId>mybatis-generator-core</artifactId>
                        <version>1.4.0</version>
                    </dependency>
                    <dependency>
                        <groupId>org.mybatis</groupId>
                        <artifactId>mybatis</artifactId>
                        <version>3.2.4</version>
                    </dependency>
                </dependencies>
                <configuration>
                    
                    <verbose>true</verbose>
                    
                    <overwrite>true</overwrite>
                    
                    <configurationFile>src/main/resources/mybatis-generator.xml</configurationFile>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>
```

### *applicationContext.xml*

这里是代码中需要用到的配置文件，在启动文件中指定。

```xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
    
    <bean id="dataSource"
          class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://127.0.0.1:3306/test?serverTimezone=UTC"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    </bean>
    
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
    </bean>
    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>
</beans>
```

### *Mybatis3sampleApplication.java*

上面提到过如果 *MapperAnnotationPlugin* 插件找不到的话，可以在这里通过添加 `@MapperScan("liujiajia.me.mybatis3sample.mapper")` 注解的方式来实现相同的功能。

```java
package liujiajia.me.mybatis3sample;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ImportResource;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@SpringBootApplication
@ImportResource("classpath:applicationContext.xml")
@EnableSwagger2
public class Mybatis3sampleApplication {

public static void main(String[] args) {
        SpringApplication.run(Mybatis3sampleApplication.class, args);
    }
}
```

### *CountryController.java*

这是一个默认的示例，可以用来做参考。

```java
package liujiajia.me.mybatis3sample.controller;

import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import liujiajia.me.mybatis3sample.mapper.CountryMapper;
import liujiajia.me.mybatis3sample.model.Country;
import liujiajia.me.mybatis3sample.model.CountryExample;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import java.util.List;

@Api(tags = { "国家操作接口" })
@RestController
@RequestMapping("api/country")
public class CountryController {
    @Resource
    private CountryMapper mapper;

@ApiOperation(value = "根据主键获取国家信息", notes = "接口备注信息")
    @RequestMapping(value = "pk/{id}", method = RequestMethod.GET)
    public Country findByPrimaryKey(@PathVariable("id") int id) {
        return mapper.selectByPrimaryKey(id);
    }

@ApiOperation(value = "根据主键获取国家信息（自定义Mapper方法）", notes = "接口备注信息（自定义Mapper方法）")
    @RequestMapping(value = "customize/{id}", method = RequestMethod.GET)
    public Country findById(@PathVariable("id") int id) {
        return mapper.findById(id);
    }

@ApiOperation(value = "根据主键获取国家信息（Example）", notes = "接口备注信息（Example）")
    @RequestMapping(value = "example/{id}", method = RequestMethod.GET)
    public List<Country> findByExample(@PathVariable("id") int id) {
        CountryExample example = new CountryExample();
        example.createCriteria().andIdEqualTo(id);
        return mapper.selectByExample(example);
    }
}
```

[官方示例][17] 是通过 *sqlSession.getMapper* 方法来获取 *Mapper* 实例的，不过我感觉通过 `@Resource` 注解的方式也挺方便的。

```java
SqlSession sqlSession = sqlSessionFactory.openSession();

try {
    MyTableMapper mapper = sqlSession.getMapper(MyTableMapper.class);
    List<MyTable> allRecords = mapper.selectByExample(null);
} finally {
    sqlSession.close();
}
```

## 附

### time zone 错误

连接 *MySQL* 数据库时报如下错误：

> Failed to execute goal org.mybatis.generator:mybatis-generator-maven-plugin:1.3.5:generate (default-cli) on project mybatis3sample: The server time zone value '�й���׼ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
>
> Description:
>
> Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.
>
> Reason: Failed to determine a suitable driver class

把 *url* 从 *jdbc:mysql://localhost:3306/test* 后面添加 *?serverTimezone=UTC* 就好了。

## 参考

1. [MyBatis-Spring SqlSession][1]：之前写的一篇博客
2. [Spring Initializr][2]：可以很方便的初始化一个 *Spring* 项目代码
3. [Mvn Repository][3]：查询 *Maven* 依赖的网站
4. [MySQL的driverClassName、url][4]
5. [github/gitignore][5]：包含常用的开发语言、IDE对应的 *.gitignore* 文件的常规写法
6. [Mybatis Generator 生成代码重复][6]
7. [eclipse集成MybatisGenerator及使用][11]
8. [MyBatis Generator Generated Java Client Objects][17]

[1]: /2019/1/25/mybatis-spring-sql-session (MyBatis-Spring SqlSession)
[2]: https://start.spring.io/ (Spring Initializr)
[3]: https://mvnrepository.com/ (Mvn Repository)
[4]: https://blog.csdn.net/qq_37960603/article/details/83415215 (MySQL的driverClassName、url)
[5]: https://github.com/github/gitignore (github/gitignore)
[6]: https://my.oschina.net/u/2289161/blog/1589644 (Mybatis Generator 生成代码重复)
[7]: https://stackoverflow.com/questions/4278601/what-of-eclipse-project-metadata-can-i-safely-ignore-in-git-mercurial (What of Eclipse project .metadata can I safely ignore in Git/Mercurial?)
[8]: https://maven.aliyun.com/mvn/view (AliRepo)
[9]: https://www.cnblogs.com/tangshengwei/p/6341462.html (Eclipse上Maven环境配置使用 (全))
[10]: https://blog.csdn.net/weixin_42267411/article/details/80899895 (Eclipse搭建简单的Spring boot项目)
[11]: https://blog.csdn.net/shuang3281/article/details/85248680 (eclipse集成MybatisGenerator及使用)
[12]: https://blog.csdn.net/zdb1314/article/details/79256128 (解决mybatis-generator 生成的mapper.xml覆盖自定义sql的问题)
[13]: https://blog.csdn.net/u014231523/article/details/76522486 (swagger2常用注解说明)
[14]: https://blog.csdn.net/isea533/article/details/83045335 (MyBatis 为什么需要通用 Mapper ?)
[15]: https://github.com/abel533/Mapper (abel533/Mapper)
[16]: https://www.jetbrains.com/idea/ (IntelliJ IDEA)
[17]: https://mybatis.org/generator/generatedobjects/javaclient.html (MyBatis Generator Generated Java Client Objects)

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