1、系统常量接口

package com.echo.blog.api;

/**
 * @className SystemConstant
 * @author Echo
 * @description 系统常量接口
 * @updateTime 2021/12/11 22:31
 * @version 1.0
 */
public interface SystemConstant {

    int SYSTEM_SUCCESS = 0000; //返回成功
    int SYSTEM_ERROR = 9999;  //返回错误
    int LOGIN_FAIL = 9991; //登录失败
    int NO_LOGIN = 9992; //未登录
    int NO_PERMISSION = 9993; //无权限
    int PARAM_ERROR = 9994; //参数异常
    int REPEAT_LOGIN = 9995; // 重复登录

}

2、系统返回枚举值

package com.echo.blog.api;

import lombok.Getter;

/**
 * @className SystemEnum
 * @author Echo
 * @description 系统返回枚举值
 * @updateTime 2021/12/11 22:28
 * @version 1.0
 */
@Getter
public enum SystemEnum {

    LOGIN_FAIL(SystemConstant.LOGIN_FAIL,"用户名或密码错误"),
    NO_LOGIN(SystemConstant.NO_LOGIN,"请先登录"),
    LOGIN_EXPIRE(SystemConstant.NO_LOGIN,"登录超时请重新登录"),
    USERNAME_REPEAT(SystemConstant.SYSTEM_ERROR,"用户名已经存在"),
    REQUEST_FAIL(SystemConstant.SYSTEM_ERROR,"请求失败"),
    REQUEST_SUCCESS(SystemConstant.SYSTEM_SUCCESS,"请求成功"),
    NO_PERMISSION(SystemConstant.NO_PERMISSION,"没有操作权限,请联系管理员"),
    PARAM_ERROR(SystemConstant.PARAM_ERROR,"参数校验失败"),
    NO_DATA_FOR_ID(SystemConstant.SYSTEM_ERROR,"当前id没有对应的数据"),
    PARAM_EMPTY_ERROR(SystemConstant.SYSTEM_ERROR,"请求参数不能为空"),
    REPEAT_LOGIN(SystemConstant.REPEAT_LOGIN,"您的账号重复登录"),
    CHECKED(SystemConstant.SYSTEM_ERROR,"该项目已经被处理"),
    JWT_EXPIRE(SystemConstant.SYSTEM_ERROR,"凭证过期");

    private int code;
    private String msg;

    SystemEnum(int code,String msg){
        this.code = code;
        this.msg = msg;
    }

}

3、系统统一返回类

package com.echo.blog.api;

import lombok.Data;

import static com.echo.blog.api.SystemEnum.*;

/**
 * @className SystemResult
 * @author Echo
 * @description 系统统一返回类
 * @updateTime 2021/12/11 22:44
 * @version 1.0
 */

@Data
public class SystemResult<T> {

    private int code;

    private String msg;

    private T data;

    // 构造方法
    private SystemResult(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    private SystemResult(int code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }

    /**
     * @methodName success
     * @author Echo
     * @version 1.0
     * @description 返回系统默认的状态码
     * @updateTime 2021/12/11 22:50
     * @return: com.echo.blog.api.SystemResult
     * @throws
     */
    public static SystemResult success(){
        return new SystemResult(REQUEST_SUCCESS.getCode(),REQUEST_SUCCESS.getMsg());
    }

    /**
     * @methodName success
     * @author Echo
     * @param: msg
     * @version 1.0
     * @description 返回自定义状态信息
     * @updateTime 2021/12/11 22:51
     * @return: com.echo.blog.api.SystemResult
     * @throws
     */
    public static SystemResult success(String msg){
        return new SystemResult(REQUEST_SUCCESS.getCode(),msg);
    }

    /**
     * @methodName success
     * @author Echo
     * @param: data
     * @version 1.0
     * @description 返回系统默认状态码以及自定义数据
     * @updateTime 2021/12/11 22:52
     * @return: com.echo.blog.api.SystemResult
     * @throws
     */
    public static <T>SystemResult success(T data){
        return new SystemResult(REQUEST_SUCCESS.getCode(),REQUEST_SUCCESS.getMsg(),data);
    }


    /**
     * @methodName fail
     * @author Echo
     * @version 1.0
     * @description 返回系统默认失败状态值及信息
     * @updateTime 2021/12/11 22:54
     * @return: com.echo.blog.api.SystemResult
     * @throws
     */
    public static SystemResult fail(){
        return new SystemResult(REQUEST_FAIL.getCode(),REQUEST_FAIL.getMsg());
    }

    /**
     * @methodName fail
     * @author Echo
     * @param: msg
     * @version 1.0
     * @description 返回系统默认失败状态值以及自定义信息
     * @updateTime 2021/12/11 22:55
     * @return: com.echo.blog.api.SystemResult
     * @throws
     */
    public static SystemResult fail(String msg){
        return new SystemResult(REQUEST_FAIL.getCode(),msg);
    }

    /**
     * @methodName fail
     * @author Echo
     * @param: code
     * @param: msg
     * @version 1.0
     * @description 返回系统自定义失败状态值以及信息
     * @updateTime 2021/12/11 22:56
     * @return: com.echo.blog.api.SystemResult
     * @throws
     */
    public static SystemResult fail(int code, String msg){
        return new SystemResult(code,msg);
    }

}

现项目目录如下: