springboot 自定义异常，并捕获异常返给前端

在开发中，如果用try catch的方式，每个方法都需要单独实现，为了方便分类异常，返回给前端，采用了@ControllerAdvice注解和继承了RuntimeException的方式来实现。

捕获了三类异常
1.业务异常

          BusinessException

2.系统异常 

        SystemException

3.其他异常

        利用@ExceptionHandler(RuntimeException.class)去捕获

ExceptionAdvice类捕获以上三类异常，并返回自定义类型格式数据

业务异常BusinessException类实现方式，继承RuntimeException

public class BusinessException extends  RuntimeException {
	
	private String code;

	public BusinessException() {
		super();
	}

	public BusinessException(String message) {
		super(message);
	}

	public BusinessException(String code, String message) {
		super(message);
		this.code = code;
	}

	public BusinessException(Throwable cause) {
		super(cause);
	}

	public BusinessException(String message, Throwable cause) {
		super(message, cause);
	}

	public BusinessException(String message, Throwable cause,
							 boolean enableSuppression, boolean writableStackTrace) {
		super(message, cause, enableSuppression, writableStackTrace);
	}

	public String getCode() {
		return code;
	}

	public void setCode(String code) {
		this.code = code;
	}

	@Override
	public String getMessage() {
		return super.getMessage();
	}

	@Override
	public String toString() {
		return this.code + ":" + this.getMessage();
	}
}

系统异常SystemException类实现方式，继承RuntimeException，同业务异常类的实现方式一样

public class SystemException extends  RuntimeException {
	
	private String code;

	public SystemException() {
		super();
	}

	public SystemException(String message) {
		super(message);
	}

	public SystemException(String code, String message) {
		super(message);
		this.code = code;
	}

	public SystemException(Throwable cause) {
		super(cause);
	}

	public SystemException(String message, Throwable cause) {
		super(message, cause);
	}

	public SystemException(String message, Throwable cause,
                           boolean enableSuppression, boolean writableStackTrace) {
		super(message, cause, enableSuppression, writableStackTrace);
	}

	public String getCode() {
		return code;
	}

	public void setCode(String code) {
		this.code = code;
	}

	@Override
	public String getMessage() {
		return super.getMessage();
	}

	@Override
	public String toString() {
		return this.code + ":" + this.getMessage();
	}
}

ExceptionAdvice类，采用增强Controller注解 @ControllerAdvice的方式来实现

1.方法名称和返回类型都可以根据自己需要定义；

2.采用注解@ExceptionHandler，就是捕获的异常类型，我们只需要把需要捕获异常类型写进来就好

 ExceptionAdvice 具体代码实现如下：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

@ControllerAdvice
public class ExceptionAdvice {
    public static Logger logger = LoggerFactory.getLogger(ExceptionAdvice.class);

    @ResponseBody
    @ExceptionHandler(SystemException.class)
    public Result handleException(Exception e) {
        logger.error("系统异常信息：", e);
        Result result = new Result();
        if (e instanceof BusinessException) {
            e = (BusinessException) e;
            result.setCode(((BusinessException) e).getCode());
        }
        result.setFailed(e.getMessage());
        return result;
    }

    @ExceptionHandler(RuntimeException.class)
    @ResponseBody
    public Result handleException(RuntimeException e) {
        logger.error("异常信息：", e.getMessage());
        Result result = new Result();
        result.setStatus(500);
        result.setMessage(e.getMessage());
        return result;
    }

    @ExceptionHandler(BusinessException.class)
    @ResponseBody
    public AjaxJson doBusinessException(Exception e) {
        AjaxJson ajaxJson = new AjaxJson();
        logger.error("业务异常消息：", e.getMessage());
        ajaxJson.setRet(-1);
        ajaxJson.setMsg(e.getMessage());
        return ajaxJson;
    }

}

1.我们捕获一个业务异常BusinessException，输出aaa

2.捕获系统异常

throw new SystemException("aaaa");

3.其他的try catch的异常，这个就可以捕获了