Java连接数据库 #07# MyBatis Generator简单例子
MyBatis Generator是一个可以帮助我们免去手写实体类&接口类以及XML的代码自动生成工具。
下面，通过一个简单的例子介绍MyBatis Generator如何使用。
1、首先用IntelliJ IDEA创建一个最简单的Maven项目。
2、创建一张简单的数据表（我这里用的数据库是MySQL），并插入几条记录，以便之后测试：
CREATE DATABASE jee_ex9; USE jee_ex9; CREATE TABLE student_info ( id BIGINT NOT NULL AUTO_INCREMENT, name VARCHAR(50) NOT NULL, age INT NOT NULL, score INT NOT NULL , PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1000 DEFAULT CHARSET=utf8; -- SET NAMES gbk; INSERT INTO student_info(name, age, score) VALUES ("student1", 12, 82), ("student2", 21, 62);
3、添加Spring Boot-MyBatis相关的依赖：
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.5.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-aop</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>com.jayway.jsonpath</groupId> <artifactId>json-path</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>6.0.6</version> </dependency> <!-- https://mvnrepository.com/artifact/com.alibaba/druid --> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.6</version> </dependency> <!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter --> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>1.3.2</version> </dependency> </dependencies> <properties> <java.version>1.8</java.version> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties>
4、编写MyBatis Generator的配置文件。
我一般这这样布局文件：
mybatis-generator.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> <!-- 可以定义多个context元素以允许从多个数据库中生成对象 --> <context id="DB2Tables" targetRuntime="MyBatis3"> <!-- jdbcConnection元素定义了连接相应数据库所必要的信息 --> <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver" connectionURL="jdbc:mysql://127.0.0.1:3306/jee_ex9?useUnicode=true&characterEncoding=utf8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=Asia/Shanghai" userId="root" password="19971019"> <!-- [WARNING] Cannot obtain primary key information from the database, generated objects may be incomplete --> <property name="nullCatalogMeansCurrent" value="true" /> </jdbcConnection> <!-- javaModelGenerator定义如何生成实体类，例如生成到哪个包下，项目路径等 --> <javaModelGenerator targetPackage="jee_ex9.model" targetProject="src/main/java"> <!-- enableSubPackages属性决定MBG是否会根据自检表(the introspected table)的目录和模式为对象生成不同的Java包 --> <property name="enableSubPackages" value="true" /> <!-- 当设置trimStrings为true时，MBG会增加代码以处理从数据库返回的字符串 --> <property name="trimStrings" value="true" /> </javaModelGenerator> <!-- sqlMapGenerator定义如何生成xml文件 --> <sqlMapGenerator targetPackage="mapping" targetProject="src/main/resources"> <property name="enableSubPackages" value="true" /> </sqlMapGenerator> <!-- javaClientGenerator定义如何生成DAO层的类和接口 --> <javaClientGenerator type="XMLMAPPER" targetPackage="jee_ex9.dao" targetProject="src/main/java"> <!-- XMLMAPPER定义了生成的对象是Java接口，该接口依赖于自动生成的xml文件 --> <property name="enableSubPackages" value="true" /> </javaClientGenerator> <!-- tableName定义表名 domainObjectName定义领域对象名字， enableXxByExample将生成一些复杂的数据操作的示例代码， 但我们实际较少用到，并且即便要用，也是自己去手动写，所以disable掉。--> <table tableName="student_info" domainObjectName="StudentInfo" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false" /> </context> </generatorConfiguration>
对每个元素的详细解释，参考官方文档：http://www.mybatis.org/generator/configreference/xmlconfig.html
5、通过Maven插件来跑MyBatis Generator。
首先需要在pom.xml中添加相应插件，完整的pom.xml如下：
<?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>org.sample</groupId> <artifactId>jee_ex9</artifactId> <version>1.0-SNAPSHOT</version> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.5.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-aop</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>com.jayway.jsonpath</groupId> <artifactId>json-path</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>6.0.6</version> </dependency> <!-- https://mvnrepository.com/artifact/com.alibaba/druid --> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.6</version> </dependency> <!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter --> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>1.3.2</version> </dependency> </dependencies> <properties> <java.version>1.8</java.version> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> <!-- 通过mvn mybatis-generator:generate运行该插件，MBG将根据配置文件自动生成相应文件 --> <!-- 可以添加一些标准命令行参数，例如：mvn -Dmybatis.generator.overwrite=true mybatis-generator:generate --> <!-- mybatis.generator.overwrite覆盖已存在的java文件 --> <plugin> <groupId>org.mybatis.generator</groupId> <artifactId>mybatis-generator-maven-plugin</artifactId> <version>1.3.7</version> <dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>6.0.6</version> </dependency> </dependencies> <configuration> <configurationFile>src/main/resources/mybatis-generator.xml</configurationFile> <verbose>true</verbose> </configuration> </plugin> </plugins> </build> </project>
执行该插件：
mvn mybatis-generator:generate
运行成功长这个样：
自动生成的文件：
6、测试一下。
编写Spring Boot应用的程序入口：
package jee_ex9; import org.mybatis.spring.annotation.MapperScan; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication @MapperScan("jee_ex9.dao") // 省得在每个DAO接口上写@Mapper注解 public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
编写Spring Boot配置文件（直接拷贝之前写的）：
server.port=8090 mybatis.mapper-locations=classpath:mapping/*.xml spring.datasource.name=jee_ex9_datasource spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver spring.datasource.url=jdbc:mysql://127.0.0.1:3306/jee_ex9?useUnicode=true&characterEncoding=utf8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=Asia/Shanghai spring.datasource.username=root spring.datasource.password=********* spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
编写测试类：
package jee_ex9.dao; import jee_ex9.model.StudentInfo; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.test.context.junit4.SpringRunner; import static org.junit.Assert.*; @RunWith(SpringRunner.class) @SpringBootTest public class StudentInfoMapperTest { @Autowired private StudentInfoMapper mapper; @Test public void selectByPrimaryKey() throws Exception { StudentInfo info = mapper.selectByPrimaryKey(1000L); assertEquals("student1", info.getName()); } }
最后运行测试，能通过应该就没问题了。
