Allow modification of response from filters

core/src/main/java/com/flipkart/gjex/core/filter/Filter.java

@@ -54,8 +54,11 @@ public void doProcessResponseHeaders(M responseHeaders) {}
  * This method should be viewed almost like a proxy for the Response body.
  *
  * @param response the Response body/message
+ * @return
  */
- public void doProcessResponse(Res response) {}
+ public Res doProcessResponse(Res response) {
+ return response;
+ }
 
  /**
  * Call-back to handle exceptions that occur during the processing of the request or response.

core/src/main/java/com/flipkart/gjex/core/filter/grpc/AccessLogGrpcFilter.java

@@ -109,13 +109,14 @@ public void doProcessResponseHeaders(Metadata responseHeaders) {
  * @param response The outgoing gRPC response message.
  */
  @Override
- public void doProcessResponse(S response) {
+ public S doProcessResponse(S response) {
  accessLogContextBuilder
  .contentLength(response.getSerializedSize())
  .responseTime(System.currentTimeMillis() - startTime)
  .responseStatus(Status.Code.OK.value())
  .build();
  logger.info(accessLogContextBuilder.build().format(format));
+ return response;
  }
 
  /**

core/src/main/java/com/flipkart/gjex/core/filter/grpc/GrpcFilter.java

@@ -26,8 +26,7 @@
  * @param <Res> Proto V3 message
  * @author ajay.jalgaonkar
  */
-public abstract class GrpcFilter<Req extends GeneratedMessageV3, Res extends GeneratedMessageV3>
- extends Filter<Req,Res, Metadata> {
+public abstract class GrpcFilter<Req extends GeneratedMessageV3, Res extends GeneratedMessageV3> extends Filter<Req,Res, Metadata> {
 
  /**
  * Function for creating an instance of this {@link Filter}

core/src/main/java/com/flipkart/gjex/core/filter/http/AccessLogHttpFilter.java

@@ -85,9 +85,10 @@ public void doProcessResponseHeaders(Map<String,String> responseHeaders) {
  * Logs the client IP, requested URI, response status, content length, and the time taken to process the request.
  *
  * @param response The outgoing servlet response.
+ * @return
  */
  @Override
- public void doProcessResponse(ServletResponse response) {
+ public ServletResponse doProcessResponse(ServletResponse response) {
  HttpServletResponse httpServletResponse = (HttpServletResponse) response;
  if (isSuccess(httpServletResponse.getStatus())) {
  // 2xx response
@@ -104,6 +105,7 @@ public void doProcessResponse(ServletResponse response) {
  .responseStatus(httpServletResponse.getStatus())
  .responseTime(System.currentTimeMillis() - startTime);
  logger.info(accessLogContextBuilder.build().format(format));
+ return response;
  }
 
  @Override

examples/src/main/java/com/flipkart/gjex/examples/helloworld/filter/CustomHeaderGRPCFilter.java

@@ -0,0 +1,32 @@
+package com.flipkart.gjex.examples.helloworld.filter;
+
+import com.flipkart.gjex.core.filter.RequestParams;
+import com.flipkart.gjex.core.filter.grpc.GrpcFilter;
+import com.flipkart.gjex.core.logging.Logging;
+import com.google.protobuf.GeneratedMessageV3;
+import io.grpc.Metadata;
+import io.grpc.examples.helloworld.HelloReply;
+
+import javax.inject.Named;
+import java.util.Optional;
+
+@Named("CustomHeaderGRPCFilter")
+public class CustomHeaderGRPCFilter<Req extends GeneratedMessageV3, Res extends GeneratedMessageV3> extends GrpcFilter<Req, Res> implements Logging {
+
+ @Override
+ public void doProcessResponseHeaders(Metadata responseHeaders) {
+ super.doProcessResponseHeaders(responseHeaders);
+ responseHeaders.put(Metadata.Key.of("x-custom-header1", Metadata.ASCII_STRING_MARSHALLER), "value1");
+ }
+
+ @Override
+ public Res doProcessResponse(Res response) {
+ response = (Res) ((HelloReply) response).toBuilder().setMessage("Custom Header GRPC Filter").build();
+ return response;
+ }
+
+ @Override
+ public GrpcFilter<Req, Res> getInstance() {
+ return new CustomHeaderGRPCFilter<>();
+ }
+}

examples/src/main/java/com/flipkart/gjex/examples/helloworld/filter/CustomHeaderHttpFilter.java

@@ -50,12 +50,14 @@ public void doProcessResponseHeaders(Map<String, String> responseHeaders) {
  * Processes the response and also adds a custom header.
  *
  * @param response the servlet response
+ * @return
  */
  @Override
- public void doProcessResponse(ServletResponse response) {
+ public ServletResponse doProcessResponse(ServletResponse response) {
  super.doProcessResponse(response);
  HttpServletResponse httpServletResponse = (HttpServletResponse) response;
  httpServletResponse.addHeader("x-custom-header2", "value2");
+ return response;
  }
 
  @Override

examples/src/main/java/com/flipkart/gjex/examples/helloworld/filter/LoggingFilter.java

@@ -49,8 +49,9 @@ public void doProcessResponseHeaders(Metadata responseHeaders) {
  }
 
  @Override
- public void doProcessResponse(Res response) {
+ public Res doProcessResponse(Res response) {
  info("Logging from filter. Response payload is : " + response.toString());
+ return response;
  }
 
 

examples/src/main/java/com/flipkart/gjex/examples/helloworld/guice/HelloWorldModule.java

@@ -20,6 +20,7 @@
 import com.flipkart.gjex.core.filter.http.JavaxFilterParams;
 import com.flipkart.gjex.core.tracing.TracingSampler;
 import com.flipkart.gjex.examples.helloworld.filter.AuthFilter;
+import com.flipkart.gjex.examples.helloworld.filter.CustomHeaderGRPCFilter;
 import com.flipkart.gjex.examples.helloworld.filter.CustomHeaderHttpFilter;
 import com.flipkart.gjex.examples.helloworld.filter.LoggingFilter;
 import com.flipkart.gjex.examples.helloworld.service.GreeterService;
@@ -52,7 +53,8 @@ protected void configure() {
  bind(GreeterGrpc.GreeterBlockingStub.class).toInstance(GreeterGrpc.newBlockingStub(channel));
  bind(BindableService.class).annotatedWith(Names.named("GreeterService")).to(GreeterService.class);
  bind(GrpcFilter.class).annotatedWith(Names.named("LoggingFilter")).to(LoggingFilter.class);
- bind(GrpcFilter.class).annotatedWith(Names.named("AuthFilter")).to(AuthFilter.class);
+ bind(GrpcFilter.class).annotatedWith(Names.named("AuthFilter")).to(AuthFilter.class);
+ bind(GrpcFilter.class).annotatedWith(Names.named("CustomHeaderGRPCFilter")).to(CustomHeaderGRPCFilter.class);
  bind(TracingSampler.class).to(AllWhitelistTracingSampler.class);
  bind(ResourceConfig.class).annotatedWith(Names.named("HelloWorldResourceConfig")).to(HelloWorldResourceConfig.class);
  bind(JavaxFilterParams.class).annotatedWith(Names.named("ExampleJavaxFilter")).toInstance(JavaxFilterParams.builder().filter(new ExampleJavaxFilter()).pathSpec("/*").build());

examples/src/main/java/com/flipkart/gjex/examples/helloworld/service/GreeterService.java

@@ -20,6 +20,7 @@
 
 import com.flipkart.gjex.core.context.GJEXContext;
 import com.flipkart.gjex.examples.helloworld.filter.AuthFilter;
+import com.flipkart.gjex.examples.helloworld.filter.CustomHeaderGRPCFilter;
 import io.dropwizard.metrics5.annotation.Timed;
 import com.flipkart.gjex.core.filter.grpc.ApplicationHeaders;
 import com.flipkart.gjex.core.filter.grpc.MethodFilters;
@@ -68,7 +69,8 @@ public GreeterService(@Named("hw.greeting") String greeting, HelloBeanService he
  @Override
  @Api(deadlineConfig = "apiProperties.sayhello.deadline") // specify an API level Deadline that will cascade to all @ConcurrentTask invoked in serving this API
  @Timed // the Timed annotation for publishing JMX metrics via MBean
- @MethodFilters({LoggingFilter.class, AuthFilter.class}) // Method level filters
+
+ @MethodFilters({LoggingFilter.class, AuthFilter.class, CustomHeaderGRPCFilter.class}) // Method level filters
  @Traced(withSamplingRate=0.5f) // Start a new Trace or participate in a Client-initiated distributed trace
  public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
 

grpc-jexpress-template/src/main/java/com/flipkart/grpc/jexpress/filter/CreateLoggingFilter.java

@@ -44,8 +44,9 @@ public void doProcessRequest(CreateRequest request, RequestParams<Metadata> requ
  public void doProcessResponseHeaders(Metadata responseHeaders) {}
 
  @Override
- public void doProcessResponse(CreateResponse response) {
+ public CreateResponse doProcessResponse(CreateResponse response) {
  info("Response: " + response);
+ return response;
  }
 
 }

grpc-jexpress-template/src/main/java/com/flipkart/grpc/jexpress/filter/GetLoggingFilter.java

@@ -46,8 +46,9 @@ public void doProcessResponseHeaders(Metadata reponseHeaders) {
  }
 
  @Override
- public void doProcessResponse(GetResponse response) {
+ public GetResponse doProcessResponse(GetResponse response) {
  info("Response: " + response);
+ return response;
  }
 
 }

guice/src/main/java/com/flipkart/gjex/grpc/interceptor/FilterInterceptor.java

@@ -121,10 +121,12 @@ public <Req, Res> Listener<Req> interceptCall(ServerCall<Req, Res> call, Metadat
 
  ServerCall.Listener<Req> listener = next.startCall(new SimpleForwardingServerCall<Req, Res>(call) {
  @Override
- public void sendMessage(final Res response) {
+ public void sendMessage(Res response) {
  Context previous = attachContext(contextWithHeaders); // attaching headers to gRPC context
  try {
- grpcFilters.forEach(filter -> filter.doProcessResponse(response));
+ for (GrpcFilter f : grpcFilters) {
+ response = (Res) f.doProcessResponse(response);
+ }
  super.sendMessage(response);
  } finally {
  detachContext(contextWithHeaders, previous); // detach headers from gRPC context