feat(ServletAdapter): Ability remove context path when get method name

servlet/src/main/java/io/grpc/servlet/GrpcServlet.java

@@ -20,6 +20,7 @@
 import io.grpc.ExperimentalApi;
 import java.io.IOException;
 import java.util.List;
+import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -36,11 +37,20 @@
 @ExperimentalApi("https://github.com/grpc/grpc-java/issues/5066")
 public class GrpcServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;
+  public static final String REMOVE_CONTEXT_PATH = "REMOVE_CONTEXT_PATH";
 
   private final ServletAdapter servletAdapter;
+  private boolean removeContextPath;
 
   GrpcServlet(ServletAdapter servletAdapter) {
     this.servletAdapter = servletAdapter;
+    removeContextPath = false; // default value
+  }
+
+  @Override
+  public void init() throws ServletException {
+    super.init();
+    removeContextPath = Boolean.parseBoolean(getInitParameter(REMOVE_CONTEXT_PATH));
   }
 
   /**
@@ -58,6 +68,15 @@ private static ServletAdapter loadServices(List<? extends BindableService> binda
     return serverBuilder.buildServletAdapter();
   }
 
+  protected String getMethod(HttpServletRequest req) {
+    String method = req.getRequestURI();
+    if (removeContextPath) {
+      // remove context path used in application server
+      method = method.substring(req.getContextPath().length());
+    }
+    return method.substring(1); // remove the leading "/"
+  }
+
   @Override
   protected final void doGet(HttpServletRequest request, HttpServletResponse response)
       throws IOException {
@@ -67,7 +86,7 @@ protected final void doGet(HttpServletRequest request, HttpServletResponse respo
   @Override
   protected final void doPost(HttpServletRequest request, HttpServletResponse response)
       throws IOException {
-    servletAdapter.doPost(request, response);
+    servletAdapter.doPost(getMethod(request), request, response);
   }
 
   @Override

servlet/src/main/java/io/grpc/servlet/ServletAdapter.java

@@ -59,10 +59,11 @@
  * process it, and transforms the gRPC response into {@link HttpServletResponse}. An adapter can be
  * instantiated by {@link ServletServerBuilder#buildServletAdapter()}.
  *
- * <p>In a servlet, calling {@link #doPost(HttpServletRequest, HttpServletResponse)} inside {@link
- * javax.servlet.http.HttpServlet#doPost(HttpServletRequest, HttpServletResponse)} makes the servlet
- * backed by the gRPC server associated with the adapter. The servlet must support Asynchronous
- * Processing and must be deployed to a container that supports servlet 4.0 and enables HTTP/2.
+ * <p>In a servlet, calling {@link #doPost(String, HttpServletRequest, HttpServletResponse)} inside 
+ * {@link javax.servlet.http.HttpServlet#doPost(HttpServletRequest, HttpServletResponse)} makes
+ * the servlet backed by the gRPC server associated with the adapter. The servlet must support 
+ * Asynchronous Processing and must be deployed to a container that supports servlet 4.0
+ * and enables HTTP/2.
  *
  * <p>The API is experimental. The authors would like to know more about the real usecases. Users
  * are welcome to provide feedback by commenting on
@@ -103,14 +104,19 @@ public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOExc
     resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "GET method not supported");
   }
 
+  public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    doPost(req.getRequestURI().substring(1), req, resp);
+  }
+
   /**
    * Call this method inside {@link javax.servlet.http.HttpServlet#doPost(HttpServletRequest,
    * HttpServletResponse)} to serve gRPC POST request.
    *
    * <p>Do not modify {@code req} and {@code resp} before or after calling this method. However,
    * calling {@code resp.setBufferSize()} before invocation is allowed.
    */
-  public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+  public void doPost(String method, HttpServletRequest req, HttpServletResponse resp)
+      throws IOException {
     checkArgument(req.isAsyncSupported(), "servlet does not support asynchronous operation");
     checkArgument(ServletAdapter.isGrpc(req), "the request is not a gRPC request");
 
@@ -119,7 +125,6 @@ public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOEx
 
     AsyncContext asyncCtx = req.startAsync(req, resp);
 
-    String method = req.getRequestURI().substring(1); // remove the leading "/"
     Metadata headers = getHeaders(req);
 
     if (logger.isLoggable(FINEST)) {

servlet/src/test/java/io/grpc/servlet/GrpcServletTest.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2025 The gRPC Authors
+ *
+ * Licensed 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
+ * limitations under the License.
+ */
+
+package io.grpc.servlet;
+
+import static io.grpc.servlet.GrpcServlet.REMOVE_CONTEXT_PATH;
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.doCallRealMethod;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class GrpcServletTest {
+  private static final String EXPECTED_METHOD = "hello/world";
+  private static final String CONTEXT_PATH = "/grpc";
+  private static final String REQUEST_URI = "/hello/world";
+
+  @Test
+  public void defaultMethodTest() throws ServletException {
+    HttpServletRequest request = mock(HttpServletRequest.class);
+    GrpcServlet grpcServlet = mock(GrpcServlet.class);
+
+    doCallRealMethod().when(grpcServlet).init();
+    grpcServlet.init();
+
+    doReturn(REQUEST_URI).when(request).getRequestURI();
+    when(grpcServlet.getMethod(request)).thenCallRealMethod();
+
+    assertEquals(EXPECTED_METHOD, grpcServlet.getMethod(request));
+  }
+
+  @Test
+  public void removeContextPathMethodTest() throws ServletException {
+    HttpServletRequest request = mock(HttpServletRequest.class);
+    GrpcServlet grpcServlet = mock(GrpcServlet.class);
+
+    doReturn("true").when(grpcServlet).getInitParameter(REMOVE_CONTEXT_PATH);
+    doCallRealMethod().when(grpcServlet).init();
+    grpcServlet.init();
+
+    doReturn(CONTEXT_PATH + REQUEST_URI).when(request).getRequestURI();
+    doReturn(CONTEXT_PATH).when(request).getContextPath();
+    when(grpcServlet.getMethod(request)).thenCallRealMethod();
+
+    assertEquals(EXPECTED_METHOD, grpcServlet.getMethod(request));
+  }
+}