mybatis PageHelper 分页

Spring Boot 结合mybatis 分页插件 PageHelper实现分页

引入依赖

跟分页相关的是 pagehelper-spring-boot-starter

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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.lagou</groupId>
    <artifactId>mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatis</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.0</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- !!!分页starter -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Spring boot 配置文件

application.yml

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/springboot?serverTimezone=UTC&characterEncoding=UTF-8
    username: root
    password: root

mybatis:
  configuration:
    map-underscore-to-camel-case: true
  type-aliases-package: com.lagou.mybatis.entitiy
  #配置MyBatis的xml配置文件路径
  mapper-locations: classpath:mapper/*.xml

# 分页配置
pagehelper:
  helper-dialect: mysql
  reasonable: true
  support-methods-arguments: true
  params: count=countSql

com/lagou/mybatis/MybatisApplication.java

package com.lagou.mybatis;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
// 配置 mappper扫描，省去每个mapper写 @Mapper注解
@MapperScan("com.lagou.mybatis.mapper")
public class MybatisApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisApplication.class, args);
    }

}

创建实体类

com/lagou/mybatis/entity/User.java

package com.lagou.mybatis.entity;

import lombok.Data;

import java.util.Date;

@Data
public class User {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;
}

创建mapper接口

com/lagou/mybatis/mapper/UserMapper.java

package com.lagou.mybatis.mapper;

import com.lagou.mybatis.entity.User;

import java.util.List;

public interface UserMapper {
    List<User> findAll();
}

resource/mapper/UserMapper.xml

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.lagou.mybatis.mapper.UserMapper">
    <!--查询所有-->
    <select id="findAll" resultType="com.lagou.mybatis.entity.User">
        select * from user
    </select>
</mapper>

测试分页

com/lagou/mybatis/MybatisApplicationTests.java

package com.lagou.mybatis;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.lagou.mybatis.entity.User;
import com.lagou.mybatis.mapper.UserMapper;
import org.junit.jupiter.api.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 java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest
class MybatisApplicationTests {
    @Autowired
    private UserMapper userMapper;

    @Test
    public void testPageHelper() {
        PageHelper.startPage(1,1);
        List<User> users = userMapper.findAll();
        PageInfo<User> pageInfo = new PageInfo<>(users);
        System.out.println("total:"+pageInfo.getTotal());
        System.out.println("page num:"+pageInfo.getPageNum());
        System.out.println("page size:"+pageInfo.getPageSize());
        users.stream().forEach(System.out::println);
    }
}

总结

1. 依赖中引入 pagehelper-spring-boot-starter
2. 查询之前使用 PageHelper.startPage(1,1);