为什么要统一 API 响应结果 ​

package com.aea.cbb.core.tool.api;

import lombok.NoArgsConstructor;
import org.springframework.lang.Nullable;

import javax.servlet.http.HttpServletResponse;
import java.io.Serializable;
import java.util.Map;
import java.util.Optional;

/**
 * 统一API响应结果封装
 *
 * @author tanminglin
 */
@NoArgsConstructor
public class R<T> implements Serializable {

	private static final long serialVersionUID = 1L;

	private int code;

	private boolean success;

	private T data;

	private String msg;

	public R(IResultCode resultCode) {
		this(resultCode, null, resultCode.getMessage());
	}

	public R(IResultCode resultCode, String msg) {
		this(resultCode, null, msg);
	}

	public R(IResultCode resultCode, T data) {
		this(resultCode, data, resultCode.getMessage());
	}

	public R(IResultCode resultCode, T data, String msg) {
		this(resultCode.getCode(), data, msg);
	}

	public R(int code, T data, String msg) {
		this.code = code;
		this.data = data;
		this.msg = msg;
		this.success = ResultCode.SUCCESS.code == code;
	}

	/**
	 * 根据 Map 快速构建
	 * @param map /
	 */
	public R(Map<String, Object> map) {
		for (String key : map.keySet()) {
			if (key == "code") {
				this.setCode(Integer.valueOf(map.get(key).toString()));
			}
			else if (key == "msg") {
				this.setMsg(String.valueOf(map.get(key)));
			}
			else if (key == "data") {
				this.setData((T) map.get(key));
			}
			else if (key == "success") {
				this.setSuccess(Boolean.valueOf(map.get(key).toString()));
			}
		}
	}

	/**
	 * 判断返回是否为成功
	 * @param result Result
	 * @return 是否成功
	 */
	public static boolean isSuccess(@Nullable R<?> result) {
		return Optional.ofNullable(result).map(x -> ResultCode.SUCCESS.code == x.code).orElse(Boolean.FALSE);
	}

	/**
	 * 判断返回是否为成功
	 * @param result Result
	 * @return 是否成功
	 */
	public static boolean isNotSuccess(@Nullable R<?> result) {
		return !R.isSuccess(result);
	}

	/**
	 * 返回R
	 * @param data 数据
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> data(T data) {
		return data(data, "操作成功");
	}

	/**
	 * 返回R
	 * @param data 数据
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> data(T data, String msg) {
		return data(HttpServletResponse.SC_OK, data, msg);
	}

	/**
	 * 返回R
	 * @param code 状态码
	 * @param data 数据
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> data(int code, T data, String msg) {
		return new R<>(code, data, data == null ? "暂无承载数据" : msg);
	}

	/**
	 * 返回R
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> success(String msg) {
		return new R<>(ResultCode.SUCCESS, msg);
	}

	/**
	 * 返回R
	 * @param data 数据
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> success(T data, String msg) {
		return data(HttpServletResponse.SC_OK, data, msg);
	}

	/**
	 * 返回R
	 * @param resultCode 业务代码
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> success(IResultCode resultCode) {
		return new R<>(resultCode);
	}

	/**
	 * 返回R
	 * @param resultCode 业务代码
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> success(IResultCode resultCode, String msg) {
		return new R<>(resultCode, msg);
	}

	/**
	 * 返回R
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> fail(String msg) {
		return new R<>(ResultCode.FAILURE, msg);
	}

	/**
	 * 返回R
	 * @param data 数据
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> fail(T data, String msg) {
		return data(ResultCode.FAILURE.code, data, msg);
	}

	/**
	 * 返回R
	 * @param code 状态码
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> fail(int code, String msg) {
		return new R<>(code, null, msg);
	}

	/**
	 * 返回R
	 * @param resultCode 业务代码
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> fail(IResultCode resultCode) {
		return new R<>(resultCode);
	}

	/**
	 * 返回R
	 * @param resultCode 业务代码
	 * @param msg 消息
	 * @param <T> T 泛型标记
	 * @return R
	 */
	public static <T> R<T> fail(IResultCode resultCode, String msg) {
		return new R<>(resultCode, msg);
	}

	/**
	 * 返回R
	 * @param flag 成功状态
	 * @return R
	 */
	public static <T> R<T> status(boolean flag) {
		return flag ? success("操作成功") : fail("操作失败");
	}

	/**
	 * 返回R
	 * @param flag 成功状态
	 * @return R
	 */
	public static <T> R<T> status(boolean flag, String successMsg, String failMsg) {
		return flag ? success(successMsg) : fail(failMsg);
	}

	/**
	 * 字符串
	 * @return {@link String }
	 * @author tanminglin
	 * @date 2023/02/21 17:37:43
	 */
	@Override
	public String toString() {
		boolean flag = ResultCode.SUCCESS.code == code;
		return "{" + "\"code\": " + this.getCode() + ", \"msg\": \"" + this.getMsg() + "\"" + ", \"data\": \""
				+ this.getData() + "\"" + ", \"success\": \"" + flag + "\"" + "}";
	}

	public int getCode() {
		return code;
	}

	public R<T> setCode(int code) {
		this.code = code;
		return this;
	}

	public boolean isSuccess() {
		return success;
	}

	public R<T> setSuccess(boolean success) {
		this.success = success;
		return this;
	}

	public T getData() {
		return data;
	}

	public R<T> setData(T data) {
		this.data = data;
		return this;
	}

	public String getMsg() {
		return msg;
	}

	public R<T> setMsg(String msg) {
		this.msg = msg;
		return this;
	}

}

@RequestMapping("/responseData")
public R responseData(String info){
  return R.success("Hello，Response success：" + info);
}