详解SpringBoot如何优雅的进行全局异常处理

@Log4j2  
@RestControllerAdvice  
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {  
    /**  
     * 定义要捕获的异常 可以多个 @ExceptionHandler({})     *  
     * @param request  request  
     * @param e        exception  
     * @param response response  
     * @return 响应结果  
     */  
    @ExceptionHandler(AuroraRuntimeException.class)  
    public GenericResponse customExceptionHandler(HttpServletRequest request, final Exception e, HttpServletResponse response) {  
        AuroraRuntimeException exception = (AuroraRuntimeException) e;  
       if (exception.getCode() == ResponseCode.USER_INPUT_ERROR) {  
           response.setStatus(HttpStatus.BAD_REQUEST.value());  
       } else if (exception.getCode() == ResponseCode.FORBIDDEN) {  
           response.setStatus(HttpStatus.FORBIDDEN.value());  
       } else {  
           response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());  
       }  
        return new GenericResponse(exception.getCode(), null, exception.getMessage());  
    }  
    @ExceptionHandler(NotLoginException.class)  
    public GenericResponse tokenExceptionHandler(HttpServletRequest request, final Exception e, HttpServletResponse response) {  
        log.error("token exception", e);  
        response.setStatus(HttpStatus.FORBIDDEN.value());  
        return new GenericResponse(ResponseCode.AUTHENTICATION_NEEDED);  
    }  
}

@Getter  
public enum ResponseCode {  
    SUCCESS(0, "Success"),  
    INTERNAL_ERROR(1, "服务器内部错误"),  
    USER_INPUT_ERROR(2, "用户输入错误"),  
    AUTHENTICATION_NEEDED(3, "Token过期或无效"),  
    FORBIDDEN(4, "禁止访问"),  
    TOO_FREQUENT_VISIT(5, "访问太频繁，请休息一会儿");  
    private final int code;  
    private final String message;  
    private final Response.Status status;  
    ResponseCode(int code, String message, Response.Status status) {  
        this.code = code;  
        this.message = message;  
        this.status = status;  
    }  
    ResponseCode(int code, String message) {  
        this(code, message, Response.Status.INTERNAL_SERVER_ERROR);  
    }  
}

@Getter  
public class AuroraRuntimeException extends RuntimeException {  
    private final ResponseCode code;  
    public AuroraRuntimeException() {  
        super(String.format("%s", ResponseCode.INTERNAL_ERROR.getMessage()));  
        this.code = ResponseCode.INTERNAL_ERROR;  
    }  
    public AuroraRuntimeException(Throwable e) {  
        super(e);  
        this.code = ResponseCode.INTERNAL_ERROR;  
    }  
    public AuroraRuntimeException(String msg) {  
        this(ResponseCode.INTERNAL_ERROR, msg);  
    }  
    public AuroraRuntimeException(ResponseCode code) {  
        super(String.format("%s", code.getMessage()));  
        this.code = code;  
    }  
    public AuroraRuntimeException(ResponseCode code, String msg) {  
        super(msg);  
        this.code = code;  
    }  
}

@Getter  
@Setter  
public class GenericResponse<T> {  
    private int code;  
    private T data;  
    private String message;  
    public GenericResponse() {};  
    public GenericResponse(int code, T data) {  
        this.code = code;  
        this.data = data;  
    }  
    public GenericResponse(int code, T data, String message) {  
        this(code, data);  
        this.message = message;  
    }  
    public GenericResponse(ResponseCode responseCode) {  
        this.code = responseCode.getCode();  
        this.data = null;  
        this.message = responseCode.getMessage();  
    }  
    public GenericResponse(ResponseCode responseCode, T data) {  
        this(responseCode);  
        this.data = data;  
    }  
    public GenericResponse(ResponseCode responseCode, T data, String message) {  
        this(responseCode, data);  
        this.message = message;  
    }  
}

public User getUserInfo(Long userId) {  
	// some logic
    User user = daoFactory.getExtendedUserMapper().selectByPrimaryKey(userId);  
    if (user == null) {  
        throw new AuroraRuntimeException(ResponseCode.USER_INPUT_ERROR, "用户id不存在");  
    }
    // some logic
	....
}

public class DispatcherServlet extends FrameworkServlet {
    // ......
	protected void initStrategies(ApplicationContext context) {
		initMultipartResolver(context);
		initLocaleResolver(context);
		initThemeResolver(context);
		initHandlerMappings(context);
		initHandlerAdapters(context);
		// 重点关注
		initHandlerExceptionResolvers(context);
		initRequestToViewNameTranslator(context);
		initViewResolvers(context);
		initFlashMapManager(context);
	}
    // ......
}

public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExceptionResolver
		implements ApplicationContextAware, InitializingBean {
    // ......
	private void initExceptionHandlerAdviceCache() {
		// ......
		List<ControllerAdviceBean> adviceBeans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
		AnnotationAwareOrderComparator.sort(adviceBeans);
		for (ControllerAdviceBean adviceBean : adviceBeans) {
			ExceptionHandlerMethodResolver resolver = new ExceptionHandlerMethodResolver(adviceBean.getBeanType());
			if (resolver.hasExceptionMappings()) {
			    // 找到所有ExceptionHandler标注的方法并保存成一个ExceptionHandlerMethodResolver类型的对象缓存起来
				this.exceptionHandlerAdviceCache.put(adviceBean, resolver);
				if (logger.isInfoEnabled()) {
					logger.info("Detected @ExceptionHandler methods in " + adviceBean);
				}
			}
			// ......
		}
	}
    // ......
}

public class ExceptionHandlerMethodResolver {
	// ......
	private Method getMappedMethod(Class<? extends Throwable> exceptionType) {
		List<Class<? extends Throwable>> matches = new ArrayList<Class<? extends Throwable>>();
		// 找到所有适用于Controller抛出异常的处理方法,例如Controller抛出的异常
		// 是AuroraRuntimeException(继承自RuntimeException),那么@ExceptionHandler(AuroraRuntimeException.class)和
		// @ExceptionHandler(Exception.class)标注的方法都适用此异常
		for (Class<? extends Throwable> mappedException : this.mappedMethods.keySet()) {
			if (mappedException.isAssignableFrom(exceptionType)) {
				matches.add(mappedException);
			}
		}
		if (!matches.isEmpty()) {
		/* 这里通过排序找到最适用的方法,排序的规则依据抛出异常相对于声明异常的深度,例如
	Controller抛出的异常是是AuroraRuntimeException(继承自RuntimeException),那么AuroraRuntimeException
	相对于@ExceptionHandler(AuroraRuntimeException.class)声明的AuroraRuntimeException.class其深度是0,
	相对于@ExceptionHandler(Exception.class)声明的Exception.class其深度是2,所以
	@ExceptionHandler(BizException.class)标注的方法会排在前面 */
			Collections.sort(matches, new ExceptionDepthComparator(exceptionType));
			return this.mappedMethods.get(matches.get(0));
		}
		else {
			return null;
		}
	}
    // ......
}