SpringBoot使用Mybatis-plus及分页功能的细节部分

pom.xml

<?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.example</groupId>
    <artifactId>other</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <!--数据库相关-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.22</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!-- SQL 执行过程 分析打印-->
        <dependency>
            <groupId>p6spy</groupId>
            <artifactId>p6spy</artifactId>
            <version>3.9.0</version>
        </dependency>

        <!--数据库相关 over-->

        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.3.7</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

application.yml

spring:
  datasource:
#    url: jdbc:mysql://localhost:33006/tt?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai&allowMultiQueries=true
#    driver-class-name: com.mysql.cj.jdbc.Driver

    # url和driver-class-name 改成p6spy的,就可以查看sql执行信息
    url: jdbc:p6spy:mysql://localhost:33006/tt?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai&allowMultiQueries=true
    driver-class-name: com.p6spy.engine.spy.P6SpyDriver
    type: com.alibaba.druid.pool.DruidDataSource
    username: root
    password: liuyalong

logging:
  level:
    root: error

#mybatis-plus配置控制台SQL语句
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

spy.properties

sql语句执行分析p6spy的匹配文件

# sql语句执行分析p6spy匹配文件
modulelist=com.baomidou.mybatisplus.extension.p6spy.MybatisPlusLogFactory,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,commit,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

MybatisPlusConfig.java

必须配置这个分页插件才是物理分页

package com.yalong.config;

import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import com.baomidou.mybatisplus.extension.plugins.pagination.optimize.JsqlParserCountOptimize;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @author liuyalong
 * 分页插件
 */
@Configuration
public class MybatisPlusConfig {
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
        // 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求  默认false
        // paginationInterceptor.setOverflow(false);
        // 设置最大单页限制数量，默认 500 条，-1 不受限制
        paginationInterceptor.setLimit(100);
        // 开启 count 的 join 优化,只针对部分 left join
        paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true));
        return paginationInterceptor;
    }
}

pojo

package com.yalong.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

import java.io.Serializable;

/**
 * @author liuyalong
 * 注解@TableName("t_metas"):设置表名字t_metas
 * 注解@TableId(value = "mid",type = IdType.AUTO):表示此字段为表的主键,value属性可以指定表中字段,
 * 注解@TableId(value = "mid",type = IdType.ASSIGN_ID):默认使用雪花算法生成id
 * 当此字段为自增(IdType.AUTO)时,如果给它设设置指定值会不起作用
 * 注解@TableField(value = "sort") 表明这是一个表中的字段,value指定表中的列名
 * 注解@TableField(exist = false) 表示这个字段不是表中的字段
 */
@Data
@TableName("t_metas")
public class Metas implements Serializable {
    @TableId(value = "mid",type = IdType.ASSIGN_ID)
    private Long mid;

    //@TableId(value = "mid",type = IdType.AUTO)
    //private Integer mid;

    @TableField(value = "sort")
    private Integer sort;
    private Integer parent;
    private String name;
    private String slug;
    private String type;
    private String description;
    @TableField(exist = false)
    private String fuck;

}

mapper

package com.yalong.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.yalong.pojo.Metas;

/**
 * @author liuyalong
 */
public interface MetasMapper extends BaseMapper<Metas> {
}

启动类

@MapperScan("com.yalong.mapper")
@SpringBootApplication
public class MyApplication {

    public static void main(String[] args) {

        SpringApplication.run(MyApplication.class, args);
    }
}

Test

  @Test
    public void mybatisPlus() {
//        HashMap<String, Object> hashMap = new HashMap<>();
//        hashMap.put("mid",1);
//        metasMapper.deleteByMap(hashMap);
//
//        System.out.println("------查询id 6--------");
//        Metas metas = metasMapper.selectById(6);
//        System.out.println(metas);
//        System.out.println("------插入数据--------");
//        Metas metas1 = new Metas();
//        metas1.setMid(998);
//        metas1.setFuck("wulala1");
//        metas1.setName("我叫刘亚龙11");
//        metas1.setParent(5);
//        metas1.setSort(0);
//        int insert = metasMapper.insert(metas1);
//        System.out.println("插入结果:"+insert);

        //查询mid列,值大于100的
        QueryWrapper<Metas> metasQueryWrapper = new QueryWrapper<>();
        metasQueryWrapper.gt("mid", 100);
//        System.out.println("-----条件查询1-----");

//        List<Metas> metas2 = metasMapper.selectList(metasQueryWrapper);
//        List<Metas> userList = metasMapper.selectList(null);
//        metas2.forEach(System.out::println);
        System.out.println("-----条件查询2-----");

        // 注意这里的metasPage 和 metasPage1 是同一个对象,
        // 即selectPage传入的对象和返回的对象是同一个
        //这里需要去配置分页插件才是真正的物理分页,否则是内存分页,即查询全表,然后分页
        Page<Metas> metasPage = new Page<>(100, 10);
        Page<Metas> metasPage1 = metasMapper.selectPage(metasPage, metasQueryWrapper);

        //不进行 count sql 优化，解决 MP 无法自动优化 SQL 问题，这时候你需要自己查询 count 部分
//        metasPage.setOptimizeCountSql(false);
        //设置setSearchCount(false),分页查询不会执行count(1)
//        metasPage.setSearchCount(false);

       /* System.out.println(metasPage==metasPage1);
        System.out.println(metasPage.equals(metasPage1));*/
        System.out.println("================= 相关的分页信息 ==================");
        System.out.println("总条数:" + metasPage1.getTotal());
        System.out.println("当前页码:" + metasPage1.getCurrent());
        System.out.println("总页数:" + metasPage1.getPages());
        System.out.println("每页显示条数:" + metasPage1.getSize());
        System.out.println("是否有上一页:" + metasPage1.hasPrevious());
        System.out.println("是否有下一页:" + metasPage1.hasNext());

        //获取当页数据
        List<Metas> records = metasPage1.getRecords();
        records.forEach(System.out::println);

    }