Spring Boot新手指南018：打造接口 - 文章列表实现分页功能

1.1 分页查询

1.1.1 创建pageBean封装分页的数据

package com.geji.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.List;

//分页返回结果对象
@Data
@NoArgsConstructor
@AllArgsConstructor
public class PageBean <T>{
    private Long total;//总条数
    private List<T> items;//当前页数据集合
}

1.1.2 引入pagehelper坐标

    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper-spring-boot-starter</artifactId>
      <version>1.4.6</version>
    </dependency>

1.2 Controller

package com.geji.controller;

import com.geji.pojo.Article;
import com.geji.pojo.PageBean;
import com.geji.pojo.Result;
import com.geji.service.ArticleService;
import com.geji.utils.JwtUtil;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;


@RestController
@RequestMapping("/article")
public class ArticleController {

    @Autowired
    private ArticleService articleService;

    @PostMapping
    public Result add(@RequestBody @Validated Article article) {
        articleService.add(article);
        return Result.success();
    }

    @GetMapping
    public Result<PageBean<Article>> list(
            Integer pageNum,
            Integer pageSize,
            @RequestParam(required = false) Integer categoryId, //不是必须得参数
            @RequestParam(required = false) String state
    ) {
        PageBean<Article> pb =  articleService.list(pageNum,pageSize,categoryId,state);
        return Result.success(pb);
    }
}

1.3 Service

package com.geji.service;

import com.geji.pojo.Article;
import com.geji.pojo.PageBean;

public interface ArticleService {
    void add(Article article);

    PageBean<Article> list(Integer pageNum, Integer pageSize, Integer categoryId, String state);
}

1.4 ServiceImpl

package com.geji.service.impl;

import com.geji.mapper.ArticleMapper;
import com.geji.pojo.Article;
import com.geji.pojo.PageBean;
import com.geji.service.ArticleService;
import com.geji.utils.ThreadLocalUtil;
import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.time.LocalDateTime;
import java.util.List;
import java.util.Map;

@Service
public class ArticleServiceImpl implements ArticleService {

    @Autowired
    private ArticleMapper articleMapper;

    @Override
    public void add(Article article) {
        //补充属性值
        article.setCreateTime(LocalDateTime.now());
        article.setUpdateTime(LocalDateTime.now());

        Map<String,Object> map = ThreadLocalUtil.get();
        Integer userId = (Integer) map.get("id");
        article.setCreateUser(userId);

        articleMapper.add(article);
    }

    @Override
    public PageBean<Article> list(Integer pageNum, Integer pageSize, Integer categoryId, String state) {
        //1.创建PageBean对象
        PageBean<Article> pb = new PageBean<>();

        //2.开启分页查询 PageHelper
        PageHelper.startPage(pageNum,pageSize);

        //3.调用mapper
        Map<String,Object> map = ThreadLocalUtil.get();
        Integer userId = (Integer) map.get("id");
        List<Article> as = articleMapper.list(userId,categoryId,state);

        //Page中提供了方法,可以获取PageHelper分页查询后 得到的总记录条数和当前页数据
        Page<Article> p = (Page<Article>) as;

        //把数据填充到PageBean对象中
        pb.setTotal(p.getTotal());
        pb.setItems(p.getResult());
        return pb;
    }
}

1.5 Mapper中写动态sql比较麻烦，使用映射配置文件，注意xml路径要保持一致

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.geji.mapper.ArticleMapper">
    <!--动态sql-->
    <select id="list" resultType="com.geji.pojo.Article">
        select * from article
        <where>
            <if test="categoryId!=null">
                category_id=#{categoryId}
            </if>

            <if test="state!=null">
                and state=#{state}
            </if>

            and create_user=#{userId}
        </where>
    </select>
</mapper>

1.6 Postman测试