2. MyBatis-Plus 的使用

2.1 代码生成器

  • 项目依赖：mybatis-plus-boot-starter、mysql-connector-java、mybatis-plus-generator、druid-spring-boot-starter、spring-boot-starter-freemarker
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    <dependencies>
        <!--SpringMVC-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!--mp、druid、mysql、mp-generator（MyBatis-Plus 从 3.0.3后移除了代码生成器与模板引擎的默认依赖）、MP支持的SQL分析器-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.2.0</version>
        </dependency>
    <!--        <dependency>-->
    <!--            <groupId>com.alibaba</groupId>-->
    <!--            <artifactId>druid-spring-boot-starter</artifactId>-->
    <!--            <version>1.1.10</version>-->
    <!--        </dependency>-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-generator</artifactId>
            <version>3.2.0</version>
        </dependency>
        <dependency>
            <groupId>p6spy</groupId>
            <artifactId>p6spy</artifactId>
            <version>3.8.6</version>
        </dependency>

        <!--Freemarker-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-freemarker</artifactId>
        </dependency>
    </dependencies>

2.2 分页插件

  • 配置类，SpringBoot 的使用方式
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    @Configuration
    @EnableTransactionManagement
    @MapperScan("org.myslayers.mapper")
    public class MyBatisPlusConfig {

        /**
         * 分页插件
         */
        @Bean
        public PaginationInterceptor paginationInterceptor() {
            PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
            return paginationInterceptor;
        }
    }

2.3 执行 SQL 分析打印

  • 该功能依赖 p6spy 组件，其中 datasource、freemarker、mybatis-plus 的配置如下：
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    spring:
      datasource:
        #    driver-class-name: com.mysql.cj.jdbc.Driver
        driver-class-name: com.p6spy.engine.spy.P6SpyDriver
        url: jdbc:p6spy:mysql://127.0.0.1:3306/xblog?useUnicode=true&useSSL=false&characterEncoding=utf8&serverTimezone=UTC
        username: root
        password: 4023615
      freemarker:
        settings:
          classic_compatible: true
          datetime_format: yyyy-MM-dd HH:mm
          number_format: 0.##

    mybatis-plus:
      mapper-locations: classpath*:/mapper/**Mapper.xml
  • p6spy 组件对应的 spy.properties 配置如下：
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    #3.2.1以下使用或者不配置
    module.log=com.p6spy.engine.logging.P6LogFactory,com.p6spy.engine.outage.P6OutageFactory
    # 自定义日志打印
    logMessageFormat=com.baomidou.mybatisplus.extension.p6spy.P6SpyLogger
    #日志输出到控制台
    appender=com.baomidou.mybatisplus.extension.p6spy.StdoutLogger
    # 使用日志系统记录 sql
    #appender=com.p6spy.engine.spy.appender.Slf4JLogger
    # 设置 p6spy driver 代理
    deregisterdrivers=true
    # 取消JDBC URL前缀
    useprefix=true
    # 配置记录 Log 例外,可去掉的结果集有error,info,batch,debug,statement,commit,rollback,result,resultset.
    excludecategories=info,debug,result,batch,resultset
    # 日期格式
    dateformat=yyyy-MM-dd HH:mm:ss
    # 实际驱动可多个
    #driverlist=org.h2.Driver
    # 是否开启慢SQL记录
    outagedetection=true
    # 慢SQL记录标准 2 秒
    outagedetectioninterval=2

2.4 条件构造器

  • AbstractWrapper、QueryWrapper、UpdateWrapper
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    @Service
    public class PostServiceImpl extends ServiceImpl<PostMapper, Post> implements PostService {
        @Autowired
        PostMapper postMapper;

        @Override
        public IPage<PostVo> selectPosts(Page page, Long categoryId, Long userId, Integer level, Boolean recommend, String order) {
            if (level == null) level = -1;
            QueryWrapper wrapper = new QueryWrapper<Post>()
                    .eq(categoryId != null, "category_id", categoryId)
                    .eq(userId != null, "user_id", userId)
                    .eq(level == 0, "level", 0)
                    .gt(level > 0, "level", 0)
                    .orderByDesc(order != null, order);
            return postMapper.selectPosts(page, wrapper);
        }

        @Override
        public PostVo selectOnePost(QueryWrapper<Post> warapper) {
            return postMapper.selectOnePost(warapper);
        }
    }