一、SpringBoot中统一全局返回格式

package com.gzgs.study01.common.utils.results;

import lombok.Data;
import lombok.experimental.Accessors;

@Data
@Accessors(chain = true)
public class Result<T> {
    public static final String SUCCESS_CODE = "OK";
    private String code;
    private String message;
    private T data;
    private long timestamp;
}

package com.gzgs.study01.common.utils.results;


public class ResultHelper {

    public static <T> Result<T> success(T data) {
        return new Result<T>()
                .setCode("200")
                .setData(data)
                .setTimestamp(System.currentTimeMillis());

    }

    public static <T> Result<T> fail(String message) {
        return new Result<T>()
                .setCode("500")
                .setMessage(message)
                .setTimestamp(System.currentTimeMillis());

    }

}

二、数据层-mapper

1、UserMapper类

package com.gzgs.study01.web.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.gzgs.study01.web.entity.User;
import com.gzgs.study01.web.param.UserParam;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;

import java.util.List;


//我们使用的@Mapper和@MapperScan并不是spring框架的注解，未在spring容器中注册为bean;
//@Repository标签可加可不加，不加的话@Autowired的时候会爆红而已，因为@MapperScan不是spring框架的注解
public interface UserMapper extends BaseMapper<User> {


    //通过用户名查询，为什么会加limit 1，因为我这里的返回类是User,如果查询到多条数据会报错
    @Select({"select * from t_user where user_name = #{userName} limit 1"})
    User getUserByName(String userName);


    //模糊查询
    @Select({"select * from t_user where user_name like concat('%',#{userName},'%') "})
    List<User> selectUserByName(String userName);


    /**
     * 复杂查询:自己搜索mapper@Select复杂查询
     * @param param
     * @return
     */
    @Select({"<script>"+
            " select t.* from t_user t"+
            " <where>"+
            " <if test='param.userName!= null and param.userName !=\"\" '>"+
            " and t.user_name like concat('%',#{param.userName},'%')"+
            " </if>"+
            " <if test='param.age!=null'>"+
            " and t.age = #{param.age} "+
            " </if>"+
            " </where>"+
            "</script>"
    })
    List<User> selectUserByParam(@Param("param") UserParam param);

}

三、业务层-service

1、UserService类

package com.gzgs.study01.web.service;

import com.gzgs.study01.web.param.UserParam;
import com.gzgs.study01.web.vo.UserVo;

import java.util.List;

public interface UserService {

    List<UserVo> selectUserByParam(UserParam param);

    UserVo getUserByName(String userName);
}

2、UserServiceImpl类

package com.gzgs.study01.web.service.impl;


import com.gzgs.study01.common.utils.MyBeanUtils;
import com.gzgs.study01.web.entity.User;
import com.gzgs.study01.web.mapper.UserMapper;
import com.gzgs.study01.web.param.UserParam;
import com.gzgs.study01.web.service.UserService;
import com.gzgs.study01.web.vo.UserVo;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Objects;


@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;


    @Override
    public List<UserVo> selectUserByParam(UserParam param) {

        List<User> list = userMapper.selectUserByParam(param);

        //entity转vo
        List<UserVo> voList = MyBeanUtils.listCopy(UserVo.class, list);

        return voList;
    }

    @Override
    public UserVo getUserByName(String userName) {

        User user = userMapper.getUserByName(userName);
        //entity转vo
        UserVo userVo = new UserVo();
        if(Objects.nonNull(user)){//判空处理，如果不判空会报异常
            BeanUtils.copyProperties(user,userVo);
        }
        return userVo;
    }


}

四、控制层-Controller

1、UserController类

package com.gzgs.study01.web.controller;

import com.gzgs.study01.common.utils.results.Result;
import com.gzgs.study01.common.utils.results.ResultHelper;
import com.gzgs.study01.web.param.UserParam;
import com.gzgs.study01.web.service.UserService;
import com.gzgs.study01.web.vo.UserVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/v1/user")
public class UserController {

    @Autowired
    private UserService userService;

    @PostMapping("/selectUserByParam")
    public Result<List<UserVo>> selectUserByParam(@RequestBody UserParam param){

        List<UserVo> voList = userService.selectUserByParam(param);

        return ResultHelper.success(voList);

    }

}

五、Postman请求

六、其他

1、一般来说，返回给前端的是vo数据

2、list的entity转vo需要自己封装

package com.gzgs.study01.common.utils;

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

import java.util.ArrayList;
import java.util.List;

public class MyBeanUtils {

    public static <T,F> List<F> listCopy(Class<F> target,List<T> sourceList){

        if(!CollectionUtils.isEmpty(sourceList)){
            List<F> targetList = new ArrayList<>();
            for (T t : sourceList){
                try {
                    F f = target.newInstance();
                    BeanUtils.copyProperties(t,f);
                    targetList.add(f);
                }catch (Exception e){

                }
            }
            return targetList;
        }else {
            return null;
        }

    }

}

3、项目结构