电子书列表查询接口开发、通用返回类、封装请求参数和返回参数

1.表结构设计

# 电子书表
drop table if exists `ebook`;
create table `ebook` (
  `id` bigint not null comment 'id',
  `name` varchar(50) comment '名称',
  `category1_id` bigint comment '分类1',
  `category2_id` bigint comment '分类2',
  `description` varchar(200) comment '描述',
  `cover` varchar(200) comment '封面',
  `doc_count` int comment '文档数',
  `view_count` int comment '阅读数',
  `vote_count` int comment '点赞数',
  primary key (`id`)
) engine=innodb default charset=utf8mb4 comment='电子书';

insert into `ebook` (id, name, description) values (1, 'Spring Boot 入门教程', '零基础入门 Java 开发，企业级应用开发最佳首选框架');
insert into `ebook` (id, name, description) values (2, 'Vue 入门教程', '零基础入门 Vue 开发，企业级应用开发最佳首选框架');
insert into `ebook` (id, name, description) values (3, 'Python 入门教程', '零基础入门 Python 开发，企业级应用开发最佳首选框架');
insert into `ebook` (id, name, description) values (4, 'Mysql 入门教程', '零基础入门 Mysql 开发，企业级应用开发最佳首选框架');
insert into `ebook` (id, name, description) values (5, 'Oracle 入门教程', '零基础入门 Oracle 开发，企业级应用开发最佳首选框架');

2.生成持久层

（1）修改generator-config.xml对象
电子书列表对应数据库表ebook，因此持久层的对象应指定为ebook。

（2）mybatis-generator生成对象

3.生成服务层service

@Service
public class EbookService {
    //注入EbookMapper
    @Resource//JDK自带
    //@Autowired//spring自带
    private EbookMapper ebookMapper;

    public List<Ebook> list(){
//        查询所有数据
        return ebookMapper.selectByExample(null);
    }
}

4.生成接口控制层controller

@RestController
@RequestMapping("/ebook")
public class EbookController {
    @Resource
    private EbookService ebookService;
    @RequestMapping("/list")
    public List<Ebook> list(){
        return ebookService.list();
    }
}

5.生成测试接口http

GET http://localhost:8880/ebook/list
接口测试结果：

6.通用返回类resp

package com.dengfei.wiki.resp;
//通用返回类
public class CommonResp<T> {

    /**
     * 业务上的成功或失败
     */
    private boolean success = true;

    /**
     * 返回信息
     */
    private String message;

    /**
     * 返回泛型数据，自定义类型
     */
    private T content;

    public boolean getSuccess() {
        return success;
    }

    public void setSuccess(boolean success) {
        this.success = success;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public T getContent() {
        return content;
    }

    public void setContent(T content) {
        this.content = content;
    }

    @Override
    public String toString() {
        final StringBuffer sb = new StringBuffer("ResponseDto{");
        sb.append("success=").append(success);
        sb.append(", message='").append(message).append('\'');
        sb.append(", content=").append(content);
        sb.append('}');
        return sb.toString();
    }
}

7.改造controller层

改造前：

@RestController
@RequestMapping("/ebook")
public class EbookController {
    @Resource
    private EbookService ebookService;
    @RequestMapping("/list")
    public List<Ebook> list(){
        return ebookService.list();
    }
}

改造后：

@RestController
@RequestMapping("/ebook")
public class EbookController {
    @Resource
    private EbookService ebookService;
    @RequestMapping("/list")
    public CommonResp list(){
        CommonResp<List<Ebook>> resp = new CommonResp<>();
        List<Ebook> list=ebookService.list();
        //将list放入content当中
        resp.setContent(list);
        resp.setMessage("测试");
        return resp;
    }
}

改造结果：

8.封装请求参数和返回参数

使用请求类封装请求参数，有利于根据类中参数进行数据查询，而不需要函数中添加String name,Int id等参数（因为这些全部体现在类中）：

package com.dengfei.wiki.req;

public class EbookReq {
    private Long id;

    private String name;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(getClass().getSimpleName());
        sb.append(" [");
        sb.append("Hash = ").append(hashCode());
        sb.append(", id=").append(id);
        sb.append(", name=").append(name);
        sb.append("]");
        return sb.toString();
    }
}

服务层如下：

@Service
public class EbookService {
    //注入EbookMapper
    @Resource//JDK自带
    //@Autowired//spring自带
    private EbookMapper ebookMapper;
    //无条件查询，即查询全部数据
    public List<Ebook> list(){
//        查询所有数据
        return ebookMapper.selectByExample(null);
    }
    //单条件查询，一次查询只能输入name；若要增加查询条件，需要增加请求参数
    public List<Ebook> list(String name){
        EbookExample ebookExample=new EbookExample();
        //创建where条件
        EbookExample.Criteria criteria= ebookExample.createCriteria();
        //查询条件为包含name的数据项
        criteria.andNameLike("%"+name+"%");
//        查询name数据
        return ebookMapper.selectByExample(ebookExample);
    }
    //不定条件查询，即请求参数是一个请求类，具体传入参数看传入类
    public List<EbookResp> list(EbookReq req){
        EbookExample ebookExample=new EbookExample();
        //创建where条件
        EbookExample.Criteria criteria= ebookExample.createCriteria();
        //查询条件为包含name的数据项
        criteria.andNameLike("%"+req.getName()+"%");
        List<Ebook>ebookList=ebookMapper.selectByExample(ebookExample);
        List<EbookResp>respList=new ArrayList<>();
        //实体类复制
        for(Ebook ebook:ebookList){
            EbookResp ebookResp=new EbookResp();
            BeanUtils.copyProperties(ebook,ebookResp);
            respList.add(ebookResp);
        }
        return respList;
    }
}

使用返回类封装返回结果：

package com.dengfei.wiki.resp;

public class EbookResp {
    private Long id;

    private String name;

    private Long category1Id;

    private Long category2Id;

    private String description;

    private String cover;

    private Integer docCount;

    private Integer viewCount;

    private Integer voteCount;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Long getCategory1Id() {
        return category1Id;
    }

    public void setCategory1Id(Long category1Id) {
        this.category1Id = category1Id;
    }

    public Long getCategory2Id() {
        return category2Id;
    }

    public void setCategory2Id(Long category2Id) {
        this.category2Id = category2Id;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getCover() {
        return cover;
    }

    public void setCover(String cover) {
        this.cover = cover;
    }

    public Integer getDocCount() {
        return docCount;
    }

    public void setDocCount(Integer docCount) {
        this.docCount = docCount;
    }

    public Integer getViewCount() {
        return viewCount;
    }

    public void setViewCount(Integer viewCount) {
        this.viewCount = viewCount;
    }

    public Integer getVoteCount() {
        return voteCount;
    }

    public void setVoteCount(Integer voteCount) {
        this.voteCount = voteCount;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(getClass().getSimpleName());
        sb.append(" [");
        sb.append("Hash = ").append(hashCode());
        sb.append(", id=").append(id);
        sb.append(", name=").append(name);
        sb.append(", category1Id=").append(category1Id);
        sb.append(", category2Id=").append(category2Id);
        sb.append(", description=").append(description);
        sb.append(", cover=").append(cover);
        sb.append(", docCount=").append(docCount);
        sb.append(", viewCount=").append(viewCount);
        sb.append(", voteCount=").append(voteCount);
        sb.append("]");
        return sb.toString();
    }
}

9.封装实体对象复制工具

封装前（将ebookList复制到respList当中）：

//实体类复制
        List<EbookResp>respList=new ArrayList<>();
        for(Ebook ebook:ebookList){
            EbookResp ebookResp=new EbookResp();
            //单个实体复制
            BeanUtils.copyProperties(ebook,ebookResp);
            respList.add(ebookResp);
        }

封装后（整个列表对象进行复制）：

List<EbookResp>respList= CopyUtil.copyList(ebookList,EbookResp.class);

或者单个对象逐一进行复制：

List<EbookResp>respList=new ArrayList<>();
        for(Ebook ebook:ebookList){
            //单个实体复制
            EbookResp ebookResp=CopyUtil.copy(ebook,EbookResp.class);
            respList.add(ebookResp);
        }

封装的对象复制工具：

package com.dengfei.wiki.util;

import org.springframework.beans.BeanUtils;
import org.springframework.util.CollectionUtils;

import java.util.ArrayList;
import java.util.List;
/**
 * @ClassName CopyUtil
 * @Description 实体复制
 * @Author dengfei
 * @Date 2022/10/4 22:13
 * @Version 1.0
 **/

public class CopyUtil {

    /**
     * 单体复制
     * 输入：Object source-源对象；Class clazz-目标类（不是目标对象）
     */
    public static <T> T copy(Object source, Class<T> clazz) {
        if (source == null) {
            return null;
        }
        T obj = null;
        try {
            //new 目标对象
            obj = clazz.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
        BeanUtils.copyProperties(source, obj);
        return obj;
    }

    /**
     * 列表复制
     */
    public static <T> List<T> copyList(List source, Class<T> clazz) {
        List<T> target = new ArrayList<>();
        if (!CollectionUtils.isEmpty(source)){
            for (Object c: source) {
                T obj = copy(c, clazz);
                target.add(obj);
            }
        }
        return target;
    }
}