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rmichelarmichela
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Implement TransmitUnexpectedExceptionInterceptor
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‎contrib/grpc-contrib/src/main/java/com/salesforce/grpc/contrib/interceptor/TransmitUnexpectedExceptionInterceptor.java

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/*
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* Copyright (c) 2019, Salesforce.com, Inc.
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* All rights reserved.
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* Licensed under the BSD 3-Clause license.
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* For full license text, see LICENSE.txt file in the repo root or https://opensource.org/licenses/BSD-3-Clause
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*/
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package com.salesforce.grpc.contrib.interceptor;
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import io.grpc.*;
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import java.io.PrintWriter;
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import java.io.StringWriter;
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import java.util.Collection;
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import java.util.HashSet;
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import java.util.Set;
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/**
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* A class that intercepts uncaught exceptions of all types and handles them by closing the {@link ServerCall}, and
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* transmitting the exception's description and stack trace to the client. This class is a complement to gRPC's
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* {@code TransmitStatusRuntimeExceptionInterceptor}.
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*
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* <p>Without this interceptor, gRPC will strip all details and close the {@link ServerCall} with
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* a generic {@link Status#UNKNOWN} code.
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*
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* <p>Security warning: the exception description and stack trace may contain sensitive server-side
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* state information, and generally should not be sent to clients. Only install this interceptor
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* if all clients are trusted.
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*/
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// Heavily inspired by https://github.com/saturnism/grpc-java-by-example/blob/master/error-handling-example/error-server/src/main/java/com/example/grpc/server/UnknownStatusDescriptionInterceptor.java
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public class TransmitUnexpectedExceptionInterceptor implements ServerInterceptor {
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private final Set<Class<? extends Throwable>> exactTypes = new HashSet<>();
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private final Set<Class<? extends Throwable>> parentTypes = new HashSet<>();
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/**
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* Allows this interceptor to match on an exact exception type.
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* @param exactType The exact type to match on.
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* @return this
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*/
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public TransmitUnexpectedExceptionInterceptor forExactType(Class<? extends Throwable> exactType) {
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this.exactTypes.add(exactType);
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return this;
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}
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/**
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* Allows this interceptor to match on a set of exact exception type.
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* @param exactTypes The set of exact types to match on.
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* @return this
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*/
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public TransmitUnexpectedExceptionInterceptor forExactTypes(Collection<Class<? extends Throwable>> exactTypes) {
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this.exactTypes.addAll(exactTypes);
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return this;
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}
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/**
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* Allows this interceptor to match on any exception type deriving from {@code parentType}.
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* @param parentType The parent type to match on.
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* @return this
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*/
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public TransmitUnexpectedExceptionInterceptor forParentType(Class<? extends Throwable> parentType) {
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this.parentTypes.add(parentType);
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return this;
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}
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/**
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* Allows this interceptor to match on any exception type deriving from any element of {@code parentTypes}.
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* @param parentTypes The set of parent types to match on.
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* @return this
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*/
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public TransmitUnexpectedExceptionInterceptor forParentTypes(Collection<Class<? extends Throwable>> parentTypes) {
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this.parentTypes.addAll(parentTypes);
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return this;
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}
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/**
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* Allows this interceptor to match all exceptions. Use with caution!
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* @return this
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*/
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public TransmitUnexpectedExceptionInterceptor forAllExceptions() {
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return forParentType(Throwable.class);
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}
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@Override
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public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
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ServerCall<ReqT, RespT> wrappedCall = new ForwardingServerCall.SimpleForwardingServerCall<ReqT, RespT>(call) {
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@Override
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public void sendMessage(RespT message) {
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super.sendMessage(message);
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}
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@Override
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public void close(Status status, Metadata trailers) {
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if (status.getCode() == Status.Code.UNKNOWN &&
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status.getDescription() == null &&
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status.getCause() != null &&
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exceptionTypeIsAllowed(status.getCause().getClass())) {
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Throwable e = status.getCause();
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status = Status.INTERNAL
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.withDescription(e.getMessage())
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.augmentDescription(stacktraceToString(e));
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}
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super.close(status, trailers);
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}
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};
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return new ForwardingServerCallListener.SimpleForwardingServerCallListener<ReqT>(next.startCall(wrappedCall, headers)) {
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@Override
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public void onHalfClose() {
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try {
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super.onHalfClose();
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} catch (Throwable e) {
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if (exceptionTypeIsAllowed(e.getClass())) {
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call.close(Status.INTERNAL
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.withDescription(e.getMessage())
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.augmentDescription(stacktraceToString(e)), new Metadata());
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} else {
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throw e;
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}
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}
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}
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};
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}
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private boolean exceptionTypeIsAllowed(Class<? extends Throwable> exceptionClass) {
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// exact matches
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for (Class<? extends Throwable> clazz : exactTypes) {
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if (clazz.equals(exceptionClass)) {
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return true;
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}
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}
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// parent type matches
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for (Class<? extends Throwable> clazz : parentTypes) {
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if (clazz.isAssignableFrom(exceptionClass)) {
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return true;
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}
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}
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// no match
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return false;
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}
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private String stacktraceToString(Throwable e) {
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StringWriter stringWriter = new StringWriter();
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PrintWriter printWriter = new PrintWriter(stringWriter);
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e.printStackTrace(printWriter);
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return stringWriter.toString();
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}
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}

‎contrib/grpc-contrib/src/test/java/com/salesforce/grpc/contrib/interceptor/TransmitUnexpectedExceptionInterceptorTest.java

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/*
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* Copyright (c) 2019, Salesforce.com, Inc.
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* All rights reserved.
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* Licensed under the BSD 3-Clause license.
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* For full license text, see LICENSE.txt file in the repo root or https://opensource.org/licenses/BSD-3-Clause
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*/
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package com.salesforce.grpc.contrib.interceptor;
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import com.salesforce.grpc.contrib.GreeterGrpc;
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import com.salesforce.grpc.contrib.HelloRequest;
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import com.salesforce.grpc.contrib.HelloResponse;
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import io.grpc.ServerInterceptor;
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import io.grpc.ServerInterceptors;
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import io.grpc.Status;
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import io.grpc.StatusRuntimeException;
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import io.grpc.stub.StreamObserver;
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import io.grpc.testing.GrpcServerRule;
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import org.junit.Rule;
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import org.junit.Test;
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import java.util.Iterator;
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import static org.assertj.core.api.Assertions.assertThatThrownBy;
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public class TransmitUnexpectedExceptionInterceptorTest {
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@Rule
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public final GrpcServerRule serverRule = new GrpcServerRule();
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@Test
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public void noExceptionDoesNotInterfere() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onNext(HelloResponse.newBuilder().setMessage("Hello " + request.getName()).build());
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responseObserver.onCompleted();
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor();
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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stub.sayHello(HelloRequest.newBuilder().setName("World").build());
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}
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@Test
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public void exactTypeMatches() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onError(new ArithmeticException("Divide by zero"));
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forExactType(ArithmeticException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.INTERNAL.getCode()), "is Status.INTERNAL")
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.hasMessageContaining("Divide by zero");
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}
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@Test
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public void parentTypeMatches() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onError(new ArithmeticException("Divide by zero"));
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forParentType(RuntimeException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.INTERNAL.getCode()), "is Status.INTERNAL")
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.hasMessageContaining("Divide by zero");
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}
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@Test
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public void parentTypeMatchesExactly() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onError(new RuntimeException("Divide by zero"));
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forParentType(RuntimeException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.INTERNAL.getCode()), "is Status.INTERNAL")
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.hasMessageContaining("Divide by zero");
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}
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@Test
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public void alleMatches() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onError(new ArithmeticException("Divide by zero"));
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forAllExceptions();
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.INTERNAL.getCode()), "is Status.INTERNAL")
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.hasMessageContaining("Divide by zero");
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}
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@Test
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public void unknownTypeDoesNotMatch() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onError(new NullPointerException("Bananas!"));
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forExactType(ArithmeticException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.UNKNOWN.getCode()), "is Status.UNKNOWN")
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.hasMessageContaining("UNKNOWN");
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}
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@Test
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public void unexpectedExceptionCanMatch() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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throw new ArithmeticException("Divide by zero");
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forExactType(ArithmeticException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.INTERNAL.getCode()), "is Status.INTERNAL")
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.hasMessageContaining("Divide by zero");
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}
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@Test
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public void unexpectedExceptionCanNotMatch() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHello(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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throw new ArithmeticException("Divide by zero");
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forExactType(NullPointerException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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assertThatThrownBy(() -> stub.sayHello(HelloRequest.newBuilder().setName("World").build()))
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.UNKNOWN.getCode()), "is Status.UNKNOWN")
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.hasMessageContaining("UNKNOWN");
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}
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@Test
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public void unexpectedExceptionCanMatchStreaming() {
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GreeterGrpc.GreeterImplBase svc = new GreeterGrpc.GreeterImplBase() {
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@Override
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public void sayHelloStream(HelloRequest request, StreamObserver<HelloResponse> responseObserver) {
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responseObserver.onNext(HelloResponse.getDefaultInstance());
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responseObserver.onNext(HelloResponse.getDefaultInstance());
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throw new ArithmeticException("Divide by zero");
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}
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};
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ServerInterceptor interceptor = new TransmitUnexpectedExceptionInterceptor().forExactType(ArithmeticException.class);
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serverRule.getServiceRegistry().addService(ServerInterceptors.intercept(svc, interceptor));
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GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(serverRule.getChannel());
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Iterator<HelloResponse> it = stub.sayHelloStream(HelloRequest.newBuilder().setName("World").build());
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it.next();
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it.next();
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assertThatThrownBy(it::next)
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.isInstanceOf(StatusRuntimeException.class)
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.matches(sre -> ((StatusRuntimeException) sre).getStatus().getCode().equals(Status.INTERNAL.getCode()), "is Status.INTERNAL")
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.hasMessageContaining("Divide by zero");
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}
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}

‎contrib/grpc-contrib/src/test/proto/helloworld.proto

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// Sends a greeting
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rpc SayHello (HelloRequest) returns (HelloResponse) {}
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// Sends many greetings
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rpc SayHelloStream (HelloRequest) returns (stream HelloResponse) {}
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// Sends the current time
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rpc SayTime (google.protobuf.Empty) returns (TimeResponse) {}
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}

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