起因
发现这个问题的起因是前端联调接口的时候发现统一的异常处理没有发挥作用,我们定义的处理的异常类型为AppException(国际惯例继承于RuntimeException),但是Dubbo服务端实际返回的异常变成了RuntimeException,我们自定义的异常处理没有发生作用，导致前端报500异常而不是正常的错误提示.
深入研究Dubbo的异常处理
针对发现的问题,查阅了相关的代码和源码发现Dubbo有一个自带的过滤器接口声明了,并且实现了一个异常过滤器,当服务端抛出异常给消费端时异常都会被该异常过滤器处理(其实可以转换思维理解一下,rpc无非就是通过特定的网络协议进行数据传输,既然是网络传输,和我们的接口调用就应该类似,就应该存在一个过滤器之类的东西)
接口类名: com.alibaba.dubbo.rpc.Filter ,
异常过滤器代码
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
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package com.mr.common.filter;
import com.mr.common.exception.BizException;
import org.apache.dubbo.common.constants.CommonConstants;
import org.apache.dubbo.common.extension.Activate;
import org.apache.dubbo.common.logger.Logger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.utils.ReflectUtils;
import org.apache.dubbo.common.utils.StringUtils;
import org.apache.dubbo.rpc.Filter;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Result;
import org.apache.dubbo.rpc.RpcContext;
import org.apache.dubbo.rpc.RpcException;
import org.apache.dubbo.rpc.service.GenericService;
import java.lang.reflect.Method;
/**
* 自定义dubbo异常过滤器
* ExceptionInvokerFilter
* <p>
* Functions:
* <ol>
* <li>unexpected exception will be logged in ERROR level on provider side. Unexpected exception are unchecked
* exception not declared on the interface</li>
* <li>Wrap the exception not introduced in API package into RuntimeException. Framework will serialize the outer exception but stringnize its cause in order to avoid of possible serialization problem on client side</li>
* </ol>
*/
@Activate(group = CommonConstants.PROVIDER)
public class DubboExceptionFilter implements Filter, Filter.Listener {
private Logger logger = LoggerFactory.getLogger(DubboExceptionFilter.class);
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
return invoker.invoke(invocation);
}
@Override
public void onResponse(Result appResponse, Invoker<?> invoker, Invocation invocation) {
if (appResponse.hasException() && GenericService.class != invoker.getInterface()) {
try {
Throwable exception = appResponse.getException();
//如果是自定义异常，直接返回
if (exception instanceof BizException) {
return;
}
// directly throw if it's checked exception
if (!(exception instanceof RuntimeException) && (exception instanceof Exception)) {
return;
}
// directly throw if the exception appears in the signature
try {
Method method = invoker.getInterface().getMethod(invocation.getMethodName(), invocation.getParameterTypes());
Class<?>[] exceptionClasses = method.getExceptionTypes();
for (Class<?> exceptionClass : exceptionClasses) {
if (exception.getClass().equals(exceptionClass)) {
return;
}
}
} catch (NoSuchMethodException e) {
return;
}
// for the exception not found in method's signature, print ERROR message in server's log.
logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getServiceContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + exception.getClass().getName() + ": " + exception.getMessage(), exception);
// directly throw if exception class and interface class are in the same jar file.
String serviceFile = ReflectUtils.getCodeBase(invoker.getInterface());
String exceptionFile = ReflectUtils.getCodeBase(exception.getClass());
if (serviceFile == null || exceptionFile == null || serviceFile.equals(exceptionFile)) {
return;
}
// directly throw if it's JDK exception
String className = exception.getClass().getName();
if (className.startsWith("java.") || className.startsWith("javax.")) {
return;
}
// directly throw if it's dubbo exception
if (exception instanceof RpcException) {
return;
}
// otherwise, wrap with RuntimeException and throw back to the client
appResponse.setException(new RuntimeException(StringUtils.toString(exception)));
} catch (Throwable e) {
logger.warn("Fail to ExceptionFilter when called by " + RpcContext.getServiceContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
}
}
}
@Override
public void onError(Throwable e, Invoker<?> invoker, Invocation invocation) {
logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getServiceContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
}
// For test purpose
public void setLogger(Logger logger) {
this.logger = logger;
}
}
上面代码最重要的是这句话：
//如果是自定义异常，直接返回
if (exception instanceof BizException) {
return;
}
然后在resources目录下创建文件：META-INF/dubbo/org.apache.dubbo.rpc.Filter
中间的META-INF目录和dubbo目录也需要自己创建
文件org.apache.dubbo.rpc.Filter内容为（注意：文件名就叫org.apache.dubbo.rpc.Filter，必须是这样）：
dubboExceptionFilter=com.provider.service.filter.DubboExceptionFilter
dubboExceptionFilter：随便取，不能和原有的重复，原有的不知道有些啥，取得长一点应该就不会重复
com.provider.service.filter.DubboExceptionFilter：我们刚刚创建的自定义异常过滤器全类名
要把原有的异常过滤器去掉，不然会有两个异常过滤器执行：
在application.yml中添加配置：
dubbo:
provider:
#去除dubbo默认异常处理过滤器，改用自己的
filter: -exception
这样就搞定了，抛出异常就不会是RuntimeException，而是自己自定义的BizException了
