Mybatis-Plus 搭建与使用入门

末蓝、 2022-04-22 16:06 250阅读 0赞

> Mybatis-Plus（简称MP）是一个 Mybatis 的增强工具，在 Mybatis 的基础上只做增强不做改变，为简化开发、提高效率而生。  
> **中文文档 ：[http://baomidou.oschina.io/mybatis-plus-doc/\#/][http_baomidou.oschina.io_mybatis-plus-doc]**

**本文介绍包括**  
1）如何搭建  
2）代码生成（controller、service、mapper、xml）  
3）单表的CRUD、条件查询、分页 基类已经为你做好了

一、如何搭建

1. 首先我们创建一个 springboot 工程 --> [https://start.spring.io/][https_start.spring.io]

![Image 1][]

2. maven 依赖

<dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>2.3</version>
            </dependency>
            
            <dependency>
                <groupId>org.apache.velocity</groupId>
                <artifactId>velocity-engine-core</artifactId>
                <version>2.0</version>
            </dependency>

3. 配置（因为感觉太啰嗦，这里省略了数据源的配置）

application.properties

mybatis-plus.mapper-locations=classpath:/mapper/*Mapper.xml
    mybatis-plus.typeAliasesPackage=com.taven.web.springbootmp.entity
    mybatis-plus.global-config.id-type=3
    mybatis-plus.global-config.field-strategy=2
    mybatis-plus.global-config.db-column-underline=true
    mybatis-plus.global-config.key-generator=com.baomidou.mybatisplus.incrementer.OracleKeyGenerator
    mybatis-plus.global-config.logic-delete-value=1
    mybatis-plus.global-config.logic-not-delete-value=0
    mybatis-plus.global-config.sql-injector=com.baomidou.mybatisplus.mapper.LogicSqlInjector
    #这里需要改成你的类
    mybatis-plus.global-config.meta-object-handler=com.taven.web.springbootmp.MyMetaObjectHandler
    mybatis-plus.configuration.map-underscore-to-camel-case=true
    mybatis-plus.configuration.cache-enabled=false
    mybatis-plus.configuration.jdbc-type-for-null=null

配置类 MybatisPlusConfig

import org.mybatis.spring.annotation.MapperScan;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    import com.baomidou.mybatisplus.incrementer.H2KeyGenerator;
    import com.baomidou.mybatisplus.incrementer.IKeyGenerator;
    import com.baomidou.mybatisplus.mapper.ISqlInjector;
    import com.baomidou.mybatisplus.mapper.LogicSqlInjector;
    import com.baomidou.mybatisplus.mapper.MetaObjectHandler;
    import com.baomidou.mybatisplus.plugins.PaginationInterceptor;
    import com.baomidou.mybatisplus.plugins.PerformanceInterceptor;
    import com.taven.web.springbootmp.MyMetaObjectHandler;
    
    @EnableTransactionManagement
    @Configuration
    @MapperScan("com.taven.web.springbootmp.mapper")
    public class MybatisPlusConfig {
        /**
         * mybatis-plus SQL执行效率插件【生产环境可以关闭】
         */
        @Bean
        public PerformanceInterceptor performanceInterceptor() {
            return new PerformanceInterceptor();
        }
    
        /*
         * 分页插件，自动识别数据库类型 多租户，请参考官网【插件扩展】
         */
        @Bean
        public PaginationInterceptor paginationInterceptor() {
            return new PaginationInterceptor();
        }
    
        @Bean
        public MetaObjectHandler metaObjectHandler() {
            return new MyMetaObjectHandler();
        }
    
        /**
         * 注入主键生成器
         */
        @Bean
        public IKeyGenerator keyGenerator() {
            return new H2KeyGenerator();
        }
    
        /**
         * 注入sql注入器
         */
        @Bean
        public ISqlInjector sqlInjector() {
            return new LogicSqlInjector();
        }
    
    }

import com.baomidou.mybatisplus.mapper.MetaObjectHandler;
    import org.apache.ibatis.reflection.MetaObject;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    /**
     *  注入公共字段自动填充,任选注入方式即可
     */
    //@Component
    public class MyMetaObjectHandler extends MetaObjectHandler {
    
        protected final static Logger logger = LoggerFactory.getLogger(Application.class);
    
        @Override
        public void insertFill(MetaObject metaObject) {
            logger.info("新增的时候干点不可描述的事情");
        }
    
        @Override
        public void updateFill(MetaObject metaObject) {
            logger.info("更新的时候干点不可描述的事情");
        }
    }

二、代码生成

执行 junit 即可生成controller、service接口及实现、mapper及xml

import org.junit.Test;
    
    import com.baomidou.mybatisplus.generator.AutoGenerator;
    import com.baomidou.mybatisplus.generator.config.DataSourceConfig;
    import com.baomidou.mybatisplus.generator.config.GlobalConfig;
    import com.baomidou.mybatisplus.generator.config.PackageConfig;
    import com.baomidou.mybatisplus.generator.config.StrategyConfig;
    import com.baomidou.mybatisplus.generator.config.rules.DbType;
    import com.baomidou.mybatisplus.generator.config.rules.NamingStrategy;
    
    /**
     * <p>
     * 测试生成代码
     * </p>
     *
     * @author K神
     * @date 2017/12/18
     */
    public class GeneratorServiceEntity {
    
        @Test
        public void generateCode() {
            String packageName = "com.taven.web.springbootmp";
            boolean serviceNameStartWithI = false;//user -> UserService, 设置成true: user -> IUserService
            generateByTables(serviceNameStartWithI, packageName, "cable", "station");//修改为你的表名
        }
    
        private void generateByTables(boolean serviceNameStartWithI, String packageName, String... tableNames) {
            GlobalConfig config = new GlobalConfig();
            String dbUrl = "jdbc:mysql://localhost:3306/communicate";
            DataSourceConfig dataSourceConfig = new DataSourceConfig();
            dataSourceConfig.setDbType(DbType.MYSQL)
                    .setUrl(dbUrl)
                    .setUsername("root")
                    .setPassword("root")
                    .setDriverName("com.mysql.jdbc.Driver");
            StrategyConfig strategyConfig = new StrategyConfig();
            strategyConfig
                    .setCapitalMode(true)
                    .setEntityLombokModel(false)
                    .setDbColumnUnderline(true)
                    .setNaming(NamingStrategy.underline_to_camel)
                    .setInclude(tableNames);//修改替换成你需要的表名，多个表名传数组
            config.setActiveRecord(false)
                    .setEnableCache(false)
                    .setAuthor("殷天文")
                    .setOutputDir("E:\\dev\\stsdev\\spring-boot-mp\\src\\main\\java")
                    .setFileOverride(true);
            if (!serviceNameStartWithI) {
                config.setServiceName("%sService");
            }
            new AutoGenerator().setGlobalConfig(config)
                    .setDataSource(dataSourceConfig)
                    .setStrategy(strategyConfig)
                    .setPackageInfo(
                            new PackageConfig()
                                    .setParent(packageName)
                                    .setController("controller")
                                    .setEntity("entity")
                    ).execute();
        }
    
    //    private void generateByTables(String packageName, String... tableNames) {
    //        generateByTables(true, packageName, tableNames);
    //    }
    }

到这一步搭建已经基本完成了，下面就可以开始使用了！

三、使用 Mybatis-Plus

首先我们执行 上面的 `generateCode()` 会为我们基于 **表结构** 生成以下代码（xml是我手动移到下面的），service 和 mapper 已经继承了基类，为我们封装了很多方法，下面看几个简单的例子。

![Image 1][]

/**
     * <p>
     *  前端控制器
     * </p>
     *
     * @author 殷天文
     * @since 2018-05-31
     */
    @Controller
    @RequestMapping("/cable")
    public class CableController {
        
        @Autowired private CableService cableService;
        
        /**
         * list 查询测试
         * 
         */
        @RequestMapping("/1")
        @ResponseBody
        public Object test1() {
            // 构造实体对应的 EntityWrapper 对象，进行过滤查询
            EntityWrapper<Cable> ew = new EntityWrapper<>();
            ew.where("type={0}", 1)
                    .like("name", "王")
                    .and("core_number={0}", 24)
                    .and("is_delete=0");
            List<Cable> list = cableService.selectList(ew);
            List<Map<String, Object>> maps = cableService.selectMaps(ew);
            System.out.println(list);
            System.out.println(maps);
            return "ok";
        }
        
        /**
         * 分页 查询测试
         */
        @RequestMapping("/2")
        @ResponseBody
        public Object test2() {
            // 构造实体对应的 EntityWrapper 对象，进行过滤查询
            EntityWrapper<Cable> ew = new EntityWrapper<>();
            ew.where("type={0}", 1)
    //              .like("name", "王")
                    .and("core_number={0}", 24)
                    .and("is_delete=0");
            Page<Cable> page = new Page<>(1,10);
            Page<Cable> pageRst = cableService.selectPage(page, ew);
            return pageRst;
        }
        
        /**
         * 自定义查询字段
         */
        @RequestMapping("/3")
        @ResponseBody
        public Object test3() {
            Object vl = null;
            // 构造实体对应的 EntityWrapper 对象，进行过滤查询
            EntityWrapper<Cable> ew = new EntityWrapper<>();
            ew.setSqlSelect("id, `name`, "
                    + "case type\n" + 
                    "when 1 then '220kv'\n" + 
                    "end typeName")
                    .where("type={0}", 1)
    //              .like("name", "王")
                    .where(false, "voltage_level=#{0}", vl);//当vl 为空时，不拼接
            Page<Cable> page = new Page<>(1,10);
            Page<Cable> pageRst = cableService.selectPage(page, ew);
            return pageRst;
        }
        
        /**
         * insert
         */
        @RequestMapping("/4")
        @ResponseBody
        public Object test4() {
            Cable c = new Cable();
            c.setName("测试光缆");
            cableService.insert(c);
            return "ok";
        }
        
        /**
         * update
         */
        @RequestMapping("/5")
        @ResponseBody
        public Object test5() {
            Cable c = cableService.selectById(22284l);
            c.setName("测试光缆2222");
            c.setType(1);
            cableService.updateById(c);
            return "ok";
        }
        
    }

作者：殷天文  
链接：https://www.jianshu.com/p/8fbd22c3e981

[http_baomidou.oschina.io_mybatis-plus-doc]: http://baomidou.oschina.io/mybatis-plus-doc/#/
[https_start.spring.io]: https://start.spring.io/
[Image 1]: