利用自定义异常，可以让我们做一些自定义操作，比如实现一个不需要写 return ，就能在我们设定好的逻辑处发生错误，就自动 return 出去，从而不需要写 if 判断，再 return 的写法，从而让代码看起来更加简洁，下面简单举个列子：

利用自定义异常，判断请求参数非空，若是空，就自动 return 出去：

1、定义一个自定义异常类，继承想继承的异常，

package cn.wmadmin.co2.config;

import cn.wmadmin.co2.util.Result;


public class MyCustomException  extends RuntimeException{

    private ErrorEnum errorEnum;

    public  MyCustomException(ErrorEnum errorEnum,String msg) {

        errorEnum.setCode(200);
        errorEnum.setMsg(msg);
        this.errorEnum=errorEnum;
    }

    public ErrorEnum getResponseStatusEnum() {
        return errorEnum;
    }

    public void setResponseStatusEnum(ErrorEnum responseStatusEnum) {
        this.errorEnum = responseStatusEnum;
    }

}

2, 配置异常,添加自定义异常

package cn.wmadmin.co2.config;

import cn.wmadmin.co2.util.Result;
import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
@Slf4j
public class GraceExceptionHandler {
    /**
     * 全局异常捕获
     * @param e
     * @return
     */
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public Object returnException(Exception e) {
        log.error("error",e);
        System.out.println("异常为：666");

        return Result.build(500,"全局异常啦啦啦"+e.getMessage());
    }

    /**
     * 自定义异常
     * @param e
     * @return
     */
    @ExceptionHandler(value = MyCustomException.class)
    @ResponseBody
    public Object returnMyCustomException(MyCustomException e) {
        log.info("异常为："+e.getResponseStatusEnum());
        System.out.println("异常为：777"+ErrorEnum.PARAM_IS_NOT_NULL.getMsg());
        return Result.exception(e.getResponseStatusEnum());
    }
}

重点是：这个配置类上的注解：@RestControllerAdvice ，方法上的注解 @ExceptionHandler(Exception.class)

之后程序里面，一旦发生了任何异常，都会走这里的异常方法，即可达到全局异常捕获！

==============

3, Result 统一返回格式工具类

package cn.wmadmin.co2.util;

import cn.wmadmin.co2.config.ErrorEnum;
import com.fasterxml.jackson.annotation.JsonIgnore;

import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.Data;


import java.io.Serializable;

/**
 *   接口返回数据格式
 * @author scott
 * @date  2019年1月19日
 */
@Data
@ApiModel(value="接口返回对象", description="接口返回对象")
public class Result implements Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * 成功标志
     */
    @ApiModelProperty(value = "成功标志")
    private boolean success = true;

    /**
     * 返回处理消息
     */
    @ApiModelProperty(value = "返回处理消息")
    private String message = "";

    /**
     * 返回代码
     */
    @ApiModelProperty(value = "返回代码")
    private Integer code = 0;

    /**
     * 返回数据对象 data
     */
    @ApiModelProperty(value = "返回数据对象")
    private T result;

    /**
     * 时间戳
     */
    @ApiModelProperty(value = "时间戳")
    private long timestamp = System.currentTimeMillis();

    public Result() {
    }

    /**
     * @param code
     * @param message
     */
    public Result(Integer code,String message) {
        this.code = code;
        this.message = message;
    }

    public Result<T> success(String message) {
        this.message = message;
        this.code = 200;
        this.success = true;
        return this;
    }


    public static<T> Result<T> OK() {
        Result<T> r = new Result();
        r.setSuccess(true);
        r.setCode(200);
        return r;
    }

    public static<T> Result<T> OK(String msg) {
        Result<T> r = new Result<T>();
        r.setSuccess(true);
        r.setCode(200);
        r.setMessage(msg);
        //Result OK(String msg)方法会造成兼容性问题 issues/I4IP3D
        r.setResult((T) msg);
        return r;
    }

    public static<T> Result<T> OK(T data) {
        Result<T> r = new Result<T>();
        r.setSuccess(true);
        r.setCode(200);
        r.setResult(data);
        return r;
    }

    public static<T> Result<T> OK(String msg, T data) {
        Result<T> r = new Result<T>();
        r.setSuccess(true);
        r.setCode(200);
        r.setMessage(msg);
        r.setResult(data);
        return r;
    }

    public static<T> Result<T> error(String msg, T data) {
        Result<T> r = new Result<T>();
        r.setSuccess(false);
        r.setCode(500);
        r.setMessage(msg);
        r.setResult(data);
        return r;
    }

    public static Result<Object> error(String msg) {

        return error(500, msg);
    }

    public static Result<Object> error(int code, String msg) {
        Result