/*
* Copyright 2008 Google Inc.
*
* 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 com.google.gwt.user.server.rpc;
import com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException;
import com.google.gwt.user.client.rpc.RpcTokenException;
import com.google.gwt.user.client.rpc.SerializationException;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.text.ParseException;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* The servlet base class for your RPC service implementations that
* automatically deserializes incoming requests from the client and serializes
* outgoing responses for client/server RPCs.
*/
public class RemoteServiceServlet extends AbstractRemoteServiceServlet
implements SerializationPolicyProvider {
/**
* Used by HybridServiceServlet.
*/
static SerializationPolicy loadSerializationPolicy(HttpServlet servlet,
HttpServletRequest request, String moduleBaseURL, String strongName) {
// The request can tell you the path of the web app relative to the
// container root.
String contextPath = request.getContextPath();
String modulePath = null;
if (moduleBaseURL != null) {
try {
modulePath = new URL(moduleBaseURL).getPath();
} catch (MalformedURLException ex) {
// log the information, we will default
servlet.log("Malformed moduleBaseURL: " + moduleBaseURL, ex);
}
}
SerializationPolicy serializationPolicy = null;
/*
* Check that the module path must be in the same web app as the servlet
* itself. If you need to implement a scheme different than this, override
* this method.
*/
if (modulePath == null || !modulePath.startsWith(contextPath)) {
String message = "ERROR: The module path requested, "
+ modulePath
+ ", is not in the same web application as this servlet, "
+ contextPath
+ ". Your module may not be properly configured or your client and server code maybe out of date.";
servlet.log(message);
} else {
// Strip off the context path from the module base URL. It should be a
// strict prefix.
String contextRelativePath = modulePath.substring(contextPath.length());
String serializationPolicyFilePath = SerializationPolicyLoader.getSerializationPolicyFileName(contextRelativePath
+ strongName);
// Open the RPC resource file and read its contents.
InputStream is = servlet.getServletContext().getResourceAsStream(
serializationPolicyFilePath);
try {
if (is != null) {
try {
serializationPolicy = SerializationPolicyLoader.loadFromStream(is,
null);
} catch (ParseException e) {
servlet.log("ERROR: Failed to parse the policy file '"
+ serializationPolicyFilePath + "'", e);
} catch (IOException e) {
servlet.log("ERROR: Could not read the policy file '"
+ serializationPolicyFilePath + "'", e);
}
} else {
String message = "ERROR: The serialization policy file '"
+ serializationPolicyFilePath
+ "' was not found; did you forget to include it in this deployment?";
servlet.log(message);
}
} finally {
if (is != null) {
try {
is.close();
} catch (IOException e) {
// Ignore this error
}
}
}
}
return serializationPolicy;
}
/**
* A cache of moduleBaseURL and serialization policy strong name to
* {@link SerializationPolicy}.
*/
private final Map<String, SerializationPolicy> serializationPolicyCache = new HashMap<String, SerializationPolicy>();
/**
* The implementation of the service.
*/
private final Object delegate;
/**
* The default constructor used by service implementations that
* extend this class. The servlet will delegate AJAX requests to
* the appropriate method in the subclass.
*/
public RemoteServiceServlet() {
this.delegate = this;
}
/**
* The wrapping constructor used by service implementations that are
* separate from this class. The servlet will delegate AJAX
* requests to the appropriate method in the given object.
*/
public RemoteServiceServlet(Object delegate) {
this.delegate = delegate;
}
public final SerializationPolicy getSerializationPolicy(String moduleBaseURL,
String strongName) {
SerializationPolicy serializationPolicy = getCachedSerializationPolicy(
moduleBaseURL, strongName);
if (serializationPolicy != null) {
return serializationPolicy;
}
serializationPolicy = doGetSerializationPolicy(getThreadLocalRequest(),
moduleBaseURL, strongName);
if (serializationPolicy == null) {
// Failed to get the requested serialization policy; use the default
log(
"WARNING: Failed to get the SerializationPolicy '"
+ strongName
+ "' for module '"
+ moduleBaseURL
+ "'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result.");
serializationPolicy = RPC.getDefaultSerializationPolicy();
}
// This could cache null or an actual instance. Either way we will not
// attempt to lookup the policy again.
putCachedSerializationPolicy(moduleBaseURL, strongName, serializationPolicy);
return serializationPolicy;
}
/**
* Process a call originating from the given request. Uses the
* {@link RPC#invokeAndEncodeResponse(Object, java.lang.reflect.Method, Object[])}
* method to do the actual work.
* <p>
* Subclasses may optionally override this method to handle the payload in any
* way they desire (by routing the request to a framework component, for
* instance). The {@link HttpServletRequest} and {@link HttpServletResponse}
* can be accessed via the {@link #getThreadLocalRequest()} and
* {@link #getThreadLocalResponse()} methods.
* </p>
* This is public so that it can be unit tested easily without HTTP.
*
* @param payload the UTF-8 request payload
* @return a string which encodes either the method's return, a checked
* exception thrown by the method, or an
* {@link IncompatibleRemoteServiceException}
* @throws SerializationException if we cannot serialize the response
* @throws UnexpectedException if the invocation throws a checked exception
* that is not declared in the service method's signature
* @throws RuntimeException if the service method throws an unchecked
* exception (the exception will be the one thrown by the service)
*/
public String processCall(String payload) throws SerializationException {
// First, check for possible XSRF situation
checkPermutationStrongName();
try {
RPCRequest rpcRequest = RPC.decodeRequest(payload, delegate.getClass(), this);
onAfterRequestDeserialized(rpcRequest);
return RPC.invokeAndEncodeResponse(delegate, rpcRequest.getMethod(),
rpcRequest.getParameters(), rpcRequest.getSerializationPolicy(),
rpcRequest.getFlags());
} catch (IncompatibleRemoteServiceException ex) {
log(
"An IncompatibleRemoteServiceException was thrown while processing this call.",
ex);
return RPC.encodeResponseForFailure(null, ex);
} catch (RpcTokenException tokenException) {
log("An RpcTokenException was thrown while processing this call.",
tokenException);
return RPC.encodeResponseForFailure(null, tokenException);
}
}
/**
* Standard HttpServlet method: handle the POST.
*
* This doPost method swallows ALL exceptions, logs them in the
* ServletContext, and returns a GENERIC_FAILURE_MSG response with status code
* 500.
*
* @throws ServletException
* @throws SerializationException
*/
@Override
public final void processPost(HttpServletRequest request,
HttpServletResponse response) throws IOException, ServletException,
SerializationException {
// Read the request fully.
//
String requestPayload = readContent(request);
// Let subclasses see the serialized request.
//
onBeforeRequestDeserialized(requestPayload);
// Invoke the core dispatching logic, which returns the serialized
// result.
//
String responsePayload = processCall(requestPayload);
// Let subclasses see the serialized response.
//
onAfterResponseSerialized(responsePayload);
// Write the response.
//
writeResponse(request, response, responsePayload);
}
/**
* This method is called by {@link #processCall(String)} and will throw a
* SecurityException if {@link #getPermutationStrongName()} returns
* <code>null</code>. This method can be overridden to be a no-op if there are
* clients that are not expected to provide the
* {@value com.google.gwt.user.client.rpc.RpcRequestBuilder#STRONG_NAME_HEADER}
* header.
*
* @throws SecurityException if {@link #getPermutationStrongName()} returns
* <code>null</code>
*/
protected void checkPermutationStrongName() throws SecurityException {
if (getPermutationStrongName() == null) {
throw new SecurityException(
"Blocked request without GWT permutation header (XSRF attack?)");
}
}
/**
* Gets the {@link SerializationPolicy} for given module base URL and strong
* name if there is one.
*
* Override this method to provide a {@link SerializationPolicy} using an
* alternative approach.
*
* @param request the HTTP request being serviced
* @param moduleBaseURL as specified in the incoming payload
* @param strongName a strong name that uniquely identifies a serialization
* policy file
* @return a {@link SerializationPolicy} for the given module base URL and
* strong name, or <code>null</code> if there is none
*/
protected SerializationPolicy doGetSerializationPolicy(
HttpServletRequest request, String moduleBaseURL, String strongName) {
return loadSerializationPolicy(this, request, moduleBaseURL, strongName);
}
/**
* Override this method to examine the serialized response that will be
* returned to the client. The default implementation does nothing and need
* not be called by subclasses.
*
* @param serializedResponse
*/
protected void onAfterResponseSerialized(String serializedResponse) {
}
/**
* Override this method to examine the serialized version of the request
* payload before it is deserialized into objects. The default implementation
* does nothing and need not be called by subclasses.
*
* @param serializedRequest
*/
protected void onBeforeRequestDeserialized(String serializedRequest) {
}
/**
* Determines whether the response to a given servlet request should or should
* not be GZIP compressed. This method is only called in cases where the
* requester accepts GZIP encoding.
* <p>
* This implementation currently returns <code>true</code> if the response
* string's estimated byte length is longer than 256 bytes. Subclasses can
* override this logic.
* </p>
*
* @param request the request being served
* @param response the response that will be written into
* @param responsePayload the payload that is about to be sent to the client
* @return <code>true</code> if responsePayload should be GZIP compressed,
* otherwise <code>false</code>.
*/
protected boolean shouldCompressResponse(HttpServletRequest request,
HttpServletResponse response, String responsePayload) {
return RPCServletUtils.exceedsUncompressedContentLengthLimit(responsePayload);
}
private SerializationPolicy getCachedSerializationPolicy(
String moduleBaseURL, String strongName) {
synchronized (serializationPolicyCache) {
return serializationPolicyCache.get(moduleBaseURL + strongName);
}
}
private void putCachedSerializationPolicy(String moduleBaseURL,
String strongName, SerializationPolicy serializationPolicy) {
synchronized (serializationPolicyCache) {
serializationPolicyCache.put(moduleBaseURL + strongName,
serializationPolicy);
}
}
private void writeResponse(HttpServletRequest request,
HttpServletResponse response, String responsePayload) throws IOException {
boolean gzipEncode = RPCServletUtils.acceptsGzipEncoding(request)
&& shouldCompressResponse(request, response, responsePayload);
RPCServletUtils.writeResponse(getServletContext(), response,
responsePayload, gzipEncode);
}
}