在前后端分离开发中，我们经常需要统一返回结果对象
1、首先创建一个接口(也可以用枚举和普通类调用final静态变量)统一返回状态码

public interface ResultCode {
    public static final Integer SUCCESS = 200;
    public static final Integer ERROR = 201;
}

2、创建统一返回结果对象(导入lombok依赖)

import java.util.HashMap;
import java.util.Map;

@Data
public class R {
    private Boolean success; //是否成功
    private Integer code; //状态码
    private String message; //返回消息
    private Map<String,Object> data = new HashMap<>(); //返回数据

    private R(){}

    public static R ok(){
        R r = new R();
        r.setSuccess(true);
        r.setCode(ResultCode.SUCCESS);
        r.setMessage("成功");
        return r;
    }

    public static R error(){
        R r = new R();
        r.setSuccess(false);
        r.setCode(ResultCode.ERROR);
        r.setMessage("失败");
        return r;
    }

    public R success(Boolean bool){
        this.setSuccess(bool);
        return this;
    }
    public R code(Integer code){
        this.setCode(code);
        return this;
    }
    public R message(String message){
        this.setMessage(message);
        return this;
    }

    public R data(String key,Object value){
        this.data.put(key, value);
        return this;
    }
    public R data(Map<String,Object> map){
        this.setData(map);
        return this;
    }

3、创建实体类Student

public class Student {
}

4、开始测试，2步骤的铺垫使得4步骤可以使用链式编程

import java.util.HashMap;
import java.util.Map;

public class MyTest {
    public static void main(String[] args) {
        Student student = new Student();
        //成功返回不带数据
        System.out.println(R.ok());
        //成功返回带数据
        System.out.println(R.ok().data("total", 1).data("items", student));
        //成功返回带数据
        Map<String,Object> map = new HashMap<>();
        map.put("total",1);
        map.put("items",student);
        System.out.println(R.ok().data(map));

        //失败返回
        System.out.println(R.error());
        System.out.println(R.error().message("返回失败"));
    }
}

返回结果