spring boot 使用通用 mapper 简化开发

2024-12-15 技术教程

在使用 mybaits 时虽然有 mybatis generator 代码自动生成工具但是还是有很多需要我们自己写的 sql 所以就有了通用 mapper tk.mapper 简化我们的开发但是它也同样不支持表联合查询，联合查询也需要我们自己编写 sql

通用mapper 使用方法：

1 引入依赖：

<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>2.0.1</version></dependency><dependency> <groupId>tk.mybatis</groupId> <artifactId>mapper-spring-boot-starter</artifactId> <version>2.1.5</version></dependency><dependency> <groupId>com.github.pagehelper</groupId> <artifactId>pagehelper-spring-boot-starter</artifactId> <version>1.2.12</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></dependency>

2.配置数据库和 mybaits 相关信息

spring: datasource: url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC+8 username: root password: root driver-class-name: com.mysql.jdbc.Drivermapper: notEmpty: true identity: MYSQLmybatis: mapperLocations: classpath:**/mapper/*.xml

3 指定mapper需要扫面的包路劲

@MapperScan(basePackages = "com.example.tkmapper.mapper")@SpringBootApplicationpublic class TkMapperApplication { public static void main(String[] args) { SpringApplication.run(TkMapperApplication.class, args); }}

注意： MapperScan 是通用mapper的 tk.mybatis.spring.annotation.MapperScan

4.书写mapper类

public interface UserMapper extends tk.mybatis.mapper.common.Mapper<User> {}很多查询方法我们都可以直接使用了----------------------------------------------------------------------同样我们也可以使用工具自动生成 mapper 和 entity文件1.首先配置maven插件<plugin> <groupId>org.mybatis.generator</groupId> <artifactId>mybatis-generator-maven-plugin</artifactId> <version>1.3.7</version> <configuration> <configurationFile> ${basedir}/src/main/resources/generator/generatorConfig.xml </configurationFile> <overwrite>true</overwrite> <verbose>true</verbose> </configuration> <dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.16</version> </dependency> <dependency> <groupId>tk.mybatis</groupId> <artifactId>mapper</artifactId> <version>4.0.0</version> </dependency> </dependencies></plugin>

2 在resource 下配置数据库信息 generator.properties

#Mybatis Generator configuration
#dao类和实体类的位置
project =src/main/java
#mapper文件的位置
resources=src/main/resources
#根据数据库中的表生成对应的pojo类、dao、mapper
jdbc_driver =com.mysql.jdbc.Driver
jdbc_url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
jdbc_user=root
jdbc_password=root

3 在resource下配置 generatorConfig.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="generator/generator.properties"/>     <context id="MysqlTables" targetRuntime="MyBatis3Simple" defaultModelType="flat">  <property name="autoDelimitKeywords" value="true" />  <property name="javaFileEncoding" value="utf-8" />  <property name="beginningDelimiter" value="`" /> <property name="endingDelimiter" value="`" />  <property name="javaFormatter" value="org.mybatis.generator.api.dom.DefaultJavaFormatter"/>  <property name="xmlFormatter" value="org.mybatis.generator.api.dom.DefaultXmlFormatter"/> <plugin type="org.mybatis.generator.plugins.SerializablePlugin" /> <plugin type="org.mybatis.generator.plugins.ToStringPlugin" /> <plugin type="tk.mybatis.mapper.generator.MapperPlugin"> <property name="mappers" value="tk.mybatis.mapper.common.Mapper"/> <property name="caseSensitive" value="true"/> </plugin>  <commentGenerator > <property name="suppressAllComments" value="false"/> <property name="suppressDate" value="true" />  </commentGenerator>  <jdbcConnection driverClass="${jdbc_driver}" connectionURL="${jdbc_url}" userId="${jdbc_user}" password="${jdbc_password}" >  <property name="serverTimezone" value="UTC"/>   <property name="nullCatalogMeansCurrent" value="true"/>  <property name="useSSL" value="false"/> </jdbcConnection>  <javaTypeResolver>  <property name="forceBigDecimals" value="false"/> </javaTypeResolver>  <javaModelGenerator targetPackage="com.example.tkmapper.entity" targetProject="${project}" > <property name="enableSubPackages" value="false"/> <property name="trimStrings" value="true"/> </javaModelGenerator>  <sqlMapGenerator targetPackage="mapper" targetProject="${resources}" > <property name="enableSubPackages" value="false" /> </sqlMapGenerator>  <javaClientGenerator targetPackage="com.example.tkmapper.mapper" targetProject="${project}" type="XMLMAPPER" > <property name="enableSubPackages" value="false" /> </javaClientGenerator>  <table tableName="user" enableCountByExample="true" enableUpdateByExample="true" enableDeleteByExample="true" enableSelectByExample="true" selectByExampleQueryId="true">  <generatedKey column="id" sqlStatement="Mysql" identity="true" /> </table> </context></generatorConfiguration>

最后执行命令代码生成

mvn mybatis-generator:generate

表联合查询就需要自己写 sql 了同样在xml 文件里面写和普通的用法相同

<select id = "findUserById" resultMap = "BaseResult"> SELECT * FROM user where id = #{id}</select>