Java Dubbo泛化调用之自定义异常处理
Dubbo 肯定是家常便饭使用了，最近因为项目需要，对一个特定的异常，进行相关处理，并且这个异常不是checked异常，所以就没有在方法上加上异常签名，想通过消费方来直接进行异常捕获。
TODO 接下来是遇到的坑
- 泛化调用和非泛化调用的区别
- Dubbo调用Filter责任链
- 异常包装
泛化调用和非泛化调用在provider上的区别提现，GenericFilter 实现？
问题：Java Dubbo 泛化调用不会返回自定义异常
解决：
自定义两个Filter：
DubboExceptionFilter：替换原生dubbo的Exception，抛出自定义异常，用于常规调用
@Activate(group={ Constants.PROVIDER})
public class DubboExceptionFilter implements Filter {
private static final Logger LOGGER = LoggerFactory.getLogger(DubboExceptionFilter.class);
@Override
public Result invoke(Invoker invoker, Invocation invocation) throws RpcException {
try {
Result result = invoker.invoke(invocation);
if (result.hasException() && GenericService.class != invoker.getInterface()) {
try {
Throwable exception = result.getException();
// directly throw if it's checked exception
if (!(exception instanceof RuntimeException) && (exception instanceof Exception)) {
return result;
}
// directly throw if the exception appears in the signature
try {
Method method = invoker.getInterface().getMethod(invocation.getMethodName(), invocation.getParameterTypes());
Class[] exceptionClassses = method.getExceptionTypes();
for (Class exceptionClass : exceptionClassses) {
if (exception.getClass().equals(exceptionClass)) {
return result;
}
}
} catch (NoSuchMethodException e) {
return result;
}
// 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.getContext().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 result;
}
// directly throw if it's JDK exception
String className = exception.getClass().getName();
if (className.startsWith("java.") || className.startsWith("javax.")) {
return result;
}
// 修改为自定义异常
if (className.startsWith("XXXX") || exception instanceof CustomException) {
return result;
}
// directly throw if it's dubbo exception
if (exception instanceof RpcException) {
return result;
}
// otherwise, wrap with RuntimeException and throw back to the client
return new RpcResult(new RuntimeException(StringUtils.toString(exception)));
} catch (Throwable e) {
return result;
}
} else {
return result;
}
} catch (Exception e) {
throw e;
}
}
}
CustomGenericFilter：替换原生GenericFilter，用于泛化调用
/**
* 这里order的源码是-20000,因为我们要执行在原逻辑之前
* 因此我们这里改成了-25000
**/
@Activate(group = Constants.PROVIDER, order = -25000)
public class CustomGenericFilter implements Filter {
@Override
public Result invoke(Invoker invoker, Invocation inv) throws RpcException {
if (inv.getMethodName().equals(Constants.$INVOKE)
&& inv.getArguments() != null
&& inv.getArguments().length == 3
&& !invoker.getUrl().getParameter(Constants.GENERIC_KEY, false)) {
String name = ((String) inv.getArguments()[0]).trim();
String[] types = (String[]) inv.getArguments()[1];
Object[] args = (Object[]) inv.getArguments()[2];
try {
Method method = ReflectUtils.findMethodByMethodSignature(invoker.getInterface(), name, types);
Class[] params = method.getParameterTypes();
if (args == null) {
args = new Object[params.length];
}
String generic = inv.getAttachment(Constants.GENERIC_KEY);
if (StringUtils.isEmpty(generic)
|| ProtocolUtils.isDefaultGenericSerialization(generic)) {
args = PojoUtils.realize(args, params, method.getGenericParameterTypes());
} else if (ProtocolUtils.isJavaGenericSerialization(generic)) {
for (int i = 0; i < args.length; i++) {
if (byte[].class == args[i].getClass()) {
try {
UnsafeByteArrayInputStream is = new UnsafeByteArrayInputStream((byte[]) args[i]);
args[i] = ExtensionLoader.getExtensionLoader(Serialization.class)
.getExtension(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
.deserialize(null, is).readObject();
} catch (Exception e) {
throw new RpcException("Deserialize argument [" + (i + 1) + "] failed.", e);
}
} else {
throw new RpcException(
new StringBuilder(32).append("Generic serialization [")
.append(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
.append("] only support message type ")
.append(byte[].class)
.append(" and your message type is ")
.append(args[i].getClass()).toString());
}
}
}
Result result = invoker.invoke(new RpcInvocation(method, args, inv.getAttachments()));
if (result.hasException()
&& !(result.getException() instanceof GenericException)) {
/*********************和源码不一样的地方**********************/
if (result.getException() instanceof IllegalImplementsException) {
return new RpcResult(result.getException());
} else {
return new RpcResult(new GenericException(result.getException()));
}
/*********************和源码不一样的地方_结束**********************/
}
if (ProtocolUtils.isJavaGenericSerialization(generic)) {
try {
UnsafeByteArrayOutputStream os = new UnsafeByteArrayOutputStream(512);
ExtensionLoader.getExtensionLoader(Serialization.class)
.getExtension(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
.serialize(null, os).writeObject(result.getValue());
return new RpcResult(os.toByteArray());
} catch (IOException e) {
throw new RpcException("Serialize result failed.", e);
}
} else {
return new RpcResult(PojoUtils.generalize(result.getValue()));
}
} catch (NoSuchMethodException e) {
throw new RpcException(e.getMessage(), e);
} catch (ClassNotFoundException e) {
throw new RpcException(e.getMessage(), e);
}
}
return invoker.invoke(inv);
}
}添加SPI引入文件
META-INF/dubbo/com.alibaba.dubbo.rpc.Filter
dubboExceptionFilter=xxx.DubboExceptionFilter // 完整包
customGenericFilter=xxx.CustomGenericFilter // 完整包添加dubbo配置
重点！！！Attention！！
filter中逗号隔开，代表filter责任链执行顺序，如上执行顺序为：customGenericFilter，原生Filter，dubboExceptionFilter，并去除exception（dubbo自带ExcptionFilter）
It's Over
现在你可以在消费方，使用泛化调用并且捕获自定义异常了。类似
try {
Object ret = genericService.$invoke(method, new String[]{Req.class.getCanonicalName()}, new Object[]{BeanUtil.javabean2map(req)});
logger.info("泛化调用Dubbo服务返回:{}", ret);
return SUCCESS(ret);
} catch (CustomException e) {
return ERROR(e);
} catch (Exception e) {
return ERROR(e);
}
感谢：
泛化调用GenericService自定义Exception变成GenericException的问题
Filter链调用顺序
dubbo filter 扩展 以及 重写 dubbo ExceptionFilter