Java連接數據庫 #07# MyBatis Generator簡單例子
阿新 • • 發佈：2019-05-15
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MyBatis Generator是一個可以幫助我們免去手寫實體類&接口類的代碼自動生成工具。
下面，通過一個簡單的例子介紹MyBatis Generator如何使用。
大體流程如下：
- 創建項目
- 創建數據表
- 添加依賴
- 編寫MyBatis Generator的配置文件
- 通過Maven插件來跑MyBatis Generator
- 測試一下
1、首先用IntelliJ IDEA創建一個最簡單的Maven項目。
2、創建一張簡單的數據表（我這裏用的數據庫是MySQL），並插入幾條記錄，以便之後測試：
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相關的依賴：
<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、編寫MyBatis Generator的配置文件。
我一般這這樣布局文件：
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> <!-- 可以定義多個context元素以允許從多個數據庫中生成對象 --> <context id="DB2Tables" targetRuntime="MyBatis3"> <!-- jdbcConnection元素定義了連接相應數據庫所必要的信息 --> <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定義如何生成實體類，例如生成到哪個包下，項目路徑等 --> <javaModelGenerator targetPackage="jee_ex9.model" targetProject="src/main/java"> <!-- enableSubPackages屬性決定MBG是否會根據自檢表(the introspected table)的目錄和模式為對象生成不同的Java包 --> <property name="enableSubPackages" value="true" /> <!-- 當設置trimStrings為true時，MBG會增加代碼以處理從數據庫返回的字符串 --> <property name="trimStrings" value="true" /> </javaModelGenerator> <!-- sqlMapGenerator定義如何生成xml文件 --> <sqlMapGenerator targetPackage="mapping" targetProject="src/main/resources"> <property name="enableSubPackages" value="true" /> </sqlMapGenerator> <!-- javaClientGenerator定義如何生成DAO層的類和接口 --> <javaClientGenerator type="XMLMAPPER" targetPackage="jee_ex9.dao" targetProject="src/main/java"> <!-- XMLMAPPER定義了生成的對象是Java接口，該接口依賴於自動生成的xml文件 --> <property name="enableSubPackages" value="true" /> </javaClientGenerator> <!-- tableName定義表名 domainObjectName定義領域對象名字， enableXxByExample將生成一些復雜的數據操作的示例代碼， 但我們實際較少用到，並且即便要用，也是自己去手動寫，所以disable掉。--> <table tableName="student_info" domainObjectName="StudentInfo" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false" /> </context> </generatorConfiguration>
對每個元素的詳細解釋，參考官方文檔：http://www.mybatis.org/generator/configreference/xmlconfig.html
5、通過Maven插件來跑MyBatis Generator。
首先需要在pom.xml中添加相應插件，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> <!-- 通過mvn mybatis-generator:generate運行該插件，MBG將根據配置文件自動生成相應文件 --> <!-- 可以添加一些標準命令行參數，例如：mvn -Dmybatis.generator.overwrite=true mybatis-generator:generate --> <!-- mybatis.generator.overwrite覆蓋已存在的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>View Code
執行該插件：
mvn mybatis-generator:generate
運行成功長這個樣：
自動生成的文件：
6、測試一下。
編寫Spring Boot應用的程序入口：
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") // 省得在每個DAO接口上寫@Mapper註解 public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
編寫Spring Boot配置文件（直接拷貝之前寫的）：
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=19971019 spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
編寫測試類：
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()); } }
最後運行測試，能通過應該就沒問題了。
Java連接數據庫 #07# MyBatis Generator簡單例子