springBoot学习笔记（2.4）—— 整合PageHelper分页组件

一、构建项目步骤

1.引入pageHelper的jar包

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

2.完整pom.xml内容

<?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>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springBoot-pageHelp</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.1</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
        </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>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </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>
        </plugins>
    </build>
</project>

3.application.yml的内容

spring:
  datasource:
    #   数据源基本配置
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://101.34.49.127:3306/springBootAll?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8&useSSL=false
  main:
    allow-circular-references: true #解决升级 Spring Boot 2.6后，因循环引用导致启动时报错的问题
mybatis:
  mapper-locations: classpath:mybatis/mapper/*.xml
server:
  port: 8083 # 配置项目启动端口
pagehelper:
  helper-dialect: mysql #设置pageHelper的语言
  reasonable: true

4.controller中查询分页数据

  /****
     * description: 查询分页数据
     * version: 1.0 ->
     * date: 2022/1/7 18:09
     * author: xiaYZ
     * iteration: 迭代说明
     * @param commodityName
     * @param pageSize 每页数据大小
     * @param pageNum 页码
     * @return java.lang.Object
     */
    @GetMapping("findAllCommodity")
    public Object findAllCommodity(String commodityName, int pageSize,int pageNum){
        List<Commodity> allCommodity;
        try{
                PageHelper.startPage(pageNum, pageSize);
            allCommodity = commodityService.findAllCommodity(commodityName);
        }catch (Exception e){
            e.printStackTrace();
            return "查询分页数据错误";
        }
        PageInfo<Commodity> pageInfo = new PageInfo<>(allCommodity);
        return pageInfo;
    }

5.service层中调用dao接口

 public List<Commodity> findAllCommodity(String  commodityName){
        return commodityDao.findAllCommodity(commodityName);
    }

6.dao中的接口

/**
     * description: 查询所有商品数据
     * version: 1.0
     * date: 2022/1/7 18:01
     * author: xiaYZ
     * iteration: 迭代说明
     * @param commodityName 商品类
     * @return
     */
    List<Commodity> findAllCommodity(String commodityName);

7.mapper文件内容

    <select id="findAllCommodity" resultType="com.example.demo.entity.Commodity">
        select id, commodity_name commodityName, create_time createTime
        from commodity
        <where>
            <if test="commodityName != null and commodityName != ''">
                commodity_name = #{commodityName}
            </if>
        </where>
    </select>

pageHelper生效后查询语句后面会自动添加limit语句限制

8.运行截图

总结

1. 引入pagehelper的jar包

2. 设置pageHelper的语言种类

   pagehelper:
   helper-dialect: mysql #设置pageHelper的语言
   reasonable: true

1. java语言中使用PageHelper

   PageHelper.startPage(pageNum, pageSize);

注意 PageHelper.startPage(pageNum, pageSize);这句要紧跟查询数据的语句,否则会失效

项目源码