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/*
* 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 java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.zip.GZIPOutputStream;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Utility class containing helper methods used by servlets that integrate with
* the RPC system.
*/
public class RPCServletUtils {
/**
* Package protected for use in tests.
*/
static final int BUFFER_SIZE = 4096;
private static final String ACCEPT_ENCODING = "Accept-Encoding";
private static final String ATTACHMENT = "attachment";
/**
* Used both as expected request charset and encoded response charset.
*/
private static final String CHARSET_UTF8 = "UTF-8";
private static final String CONTENT_DISPOSITION = "Content-Disposition";
private static final String CONTENT_ENCODING = "Content-Encoding";
private static final String CONTENT_ENCODING_GZIP = "gzip";
private static final String CONTENT_TYPE_APPLICATION_JSON_UTF8 = "application/json; charset=utf-8";
private static final String GENERIC_FAILURE_MSG = "The call failed on the server; see server log for details";
private static final String GWT_RPC_CONTENT_TYPE = "text/x-gwt-rpc";
/**
* Controls the compression threshold at and below which no compression will
* take place.
*/
private static final int UNCOMPRESSED_BYTE_SIZE_LIMIT = 256;
/**
* Returns true if the {@link HttpServletRequest} accepts Gzip
* encoding. This is done by checking that the accept-encoding header
* specifies gzip as a supported encoding.
*
* @param request the request instance to test for gzip encoding acceptance
* @return true if the {@link HttpServletRequest} accepts Gzip
* encoding
*/
public static boolean acceptsGzipEncoding(HttpServletRequest request) {
assert (request != null);
String acceptEncoding = request.getHeader(ACCEPT_ENCODING);
if (null == acceptEncoding) {
return false;
}
return (acceptEncoding.indexOf(CONTENT_ENCODING_GZIP) != -1);
}
/**
* Returns true if the response content's estimated UTF-8 byte
* length exceeds 256 bytes.
*
* @param content the contents of the response
* @return true if the response content's estimated UTF-8 byte
* length exceeds 256 bytes
*/
public static boolean exceedsUncompressedContentLengthLimit(String content) {
return (content.length() * 2) > UNCOMPRESSED_BYTE_SIZE_LIMIT;
}
/**
* Returns true if the {@link java.lang.reflect.Method Method} definition on
* the service is specified to throw the exception contained in the
* InvocationTargetException or false otherwise. NOTE we do not check that the
* type is serializable here. We assume that it must be otherwise the
* application would never have been allowed to run.
*
* @param serviceIntfMethod the method from the RPC request
* @param cause the exception that the method threw
* @return true if the exception's type is in the method's signature
*/
public static boolean isExpectedException(Method serviceIntfMethod,
Throwable cause) {
assert (serviceIntfMethod != null);
assert (cause != null);
Class[] exceptionsThrown = serviceIntfMethod.getExceptionTypes();
if (exceptionsThrown.length <= 0) {
// The method is not specified to throw any exceptions
//
return false;
}
Class causeType = cause.getClass();
for (Class exceptionThrown : exceptionsThrown) {
assert (exceptionThrown != null);
if (exceptionThrown.isAssignableFrom(causeType)) {
return true;
}
}
return false;
}
/**
* Returns the content of an {@link HttpServletRequest} by decoding it using
* expectedCharSet, or UTF-8 if
* expectedCharSet is null.
*
* @param request the servlet request whose content we want to read
* @param expectedContentType the expected content (i.e. 'type/subtype' only)
* in the Content-Type request header, or null if no
* validation is to be performed, and you are willing to allow for
* some types of cross type security attacks
* @param expectedCharSet the expected request charset, or null
* if no charset validation is to be performed and UTF-8
* should be assumed
* @return the content of an {@link HttpServletRequest} by decoding it using
* expectedCharSet, or UTF-8 if
* expectedCharSet is null
* @throws IOException if the request's input stream cannot be accessed, read
* from or closed
* @throws ServletException if the request's content type does not
* equal the supplied expectedContentType or
* expectedCharSet
*/
public static String readContent(HttpServletRequest request,
String expectedContentType, String expectedCharSet)
throws IOException, ServletException {
if (expectedContentType != null) {
checkContentTypeIgnoreCase(request, expectedContentType);
}
if (expectedCharSet != null) {
checkCharacterEncodingIgnoreCase(request, expectedCharSet);
}
/*
* Need to support 'Transfer-Encoding: chunked', so do not rely on
* presence of a 'Content-Length' request header.
*/
InputStream in = request.getInputStream();
byte[] buffer = new byte[BUFFER_SIZE];
ByteArrayOutputStream out = new ByteArrayOutputStream(BUFFER_SIZE);
try {
while (true) {
int byteCount = in.read(buffer);
if (byteCount == -1) {
break;
}
out.write(buffer, 0, byteCount);
}
String contentCharSet = expectedCharSet != null
? expectedCharSet : CHARSET_UTF8;
return out.toString(contentCharSet);
} finally {
if (in != null) {
in.close();
}
}
}
/**
* Returns the content of an {@link HttpServletRequest}, after verifying a
* gwt/x-gwt-rpc; charset=utf-8 content type.
*
* @param request the servlet request whose content we want to read
* @return the content of an {@link HttpServletRequest} by decoding it using
* UTF-8
* @throws IOException if the request's input stream cannot be accessed, read
* from or closed
* @throws ServletException if the request's content type is not
* gwt/x-gwt-rpc; charset=utf-8, ignoring case
*/
public static String readContentAsGwtRpc(HttpServletRequest request)
throws IOException, ServletException {
return readContent(request, GWT_RPC_CONTENT_TYPE, CHARSET_UTF8);
}
/**
* Returns the content of an {@link HttpServletRequest} by decoding it using
* the UTF-8 charset.
*
* @param request the servlet request whose content we want to read
* @return the content of an {@link HttpServletRequest} by decoding it using
* the UTF-8 charset
* @throws IOException if the requests input stream cannot be accessed, read
* from or closed
* @throws ServletException if the content length of the request is not
* specified of if the request's content type is not
* 'text/x-gwt-rpc' and 'charset=utf-8'
* @deprecated Use {@link #readContent} instead.
*/
@Deprecated
public static String readContentAsUtf8(HttpServletRequest request)
throws IOException, ServletException {
return readContent(request, null, null);
}
/**
* Returns the content of an {@link HttpServletRequest} by decoding it using
* the UTF-8 charset.
*
* @param request the servlet request whose content we want to read
* @param checkHeaders Specify 'true' to check the Content-Type header to see
* that it matches the expected value 'text/x-gwt-rpc' and the
* content encoding is UTF-8. Disabling this check may allow some
* types of cross type security attacks.
* @return the content of an {@link HttpServletRequest} by decoding it using
* the UTF-8 charset
* @throws IOException if the requests input stream cannot be accessed, read
* from or closed
* @throws ServletException if the content length of the request is not
* specified of if the request's content type is not
* 'text/x-gwt-rpc' and 'charset=utf-8'
* @deprecated Use {@link #readContent} instead.
*/
@Deprecated
public static String readContentAsUtf8(HttpServletRequest request,
boolean checkHeaders) throws IOException, ServletException {
return readContent(request, GWT_RPC_CONTENT_TYPE, CHARSET_UTF8);
}
/**
* Sets the correct header to indicate that a response is gzipped.
*/
public static void setGzipEncodingHeader(HttpServletResponse response) {
response.setHeader(CONTENT_ENCODING, CONTENT_ENCODING_GZIP);
}
/**
* Returns true if the request accepts gzip encoding and the the
* response content's estimated UTF-8 byte length exceeds 256 bytes.
*
* @param request the request associated with the response content
* @param responseContent a string that will be
* @return true if the request accepts gzip encoding and the the
* response content's estimated UTF-8 byte length exceeds 256 bytes
*/
public static boolean shouldGzipResponseContent(HttpServletRequest request,
String responseContent) {
return acceptsGzipEncoding(request)
&& exceedsUncompressedContentLengthLimit(responseContent);
}
/**
* Write the response content into the {@link HttpServletResponse}. If
* gzipResponse is true, the response content will
* be gzipped prior to being written into the response.
*
* @param servletContext servlet context for this response
* @param response response instance
* @param responseContent a string containing the response content
* @param gzipResponse if true the response content will be gzip
* encoded before being written into the response
* @throws IOException if reading, writing, or closing the response's output
* stream fails
*/
public static void writeResponse(ServletContext servletContext,
HttpServletResponse response, String responseContent, boolean gzipResponse)
throws IOException {
byte[] responseBytes = responseContent.getBytes(CHARSET_UTF8);
if (gzipResponse) {
// Compress the reply and adjust headers.
//
ByteArrayOutputStream output = null;
GZIPOutputStream gzipOutputStream = null;
Throwable caught = null;
try {
output = new ByteArrayOutputStream(responseBytes.length);
gzipOutputStream = new GZIPOutputStream(output);
gzipOutputStream.write(responseBytes);
gzipOutputStream.finish();
gzipOutputStream.flush();
setGzipEncodingHeader(response);
responseBytes = output.toByteArray();
} catch (IOException e) {
caught = e;
} finally {
if (null != gzipOutputStream) {
gzipOutputStream.close();
}
if (null != output) {
output.close();
}
}
if (caught != null) {
servletContext.log("Unable to compress response", caught);
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
return;
}
}
// Send the reply.
//
response.setContentLength(responseBytes.length);
response.setContentType(CONTENT_TYPE_APPLICATION_JSON_UTF8);
response.setStatus(HttpServletResponse.SC_OK);
response.setHeader(CONTENT_DISPOSITION, ATTACHMENT);
response.getOutputStream().write(responseBytes);
}
/**
* Called when the servlet itself has a problem, rather than the invoked
* third-party method. It writes a simple 500 message back to the client.
*
* @param servletContext
* @param response
* @param failure
*/
public static void writeResponseForUnexpectedFailure(
ServletContext servletContext, HttpServletResponse response,
Throwable failure) {
servletContext.log("Exception while dispatching incoming RPC call", failure);
// Send GENERIC_FAILURE_MSG with 500 status.
//
try {
response.setContentType("text/plain");
response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
try {
response.getOutputStream().write(GENERIC_FAILURE_MSG.getBytes("UTF-8"));
} catch (IllegalStateException e) {
// Handle the (unexpected) case where getWriter() was previously used
response.getWriter().write(GENERIC_FAILURE_MSG);
}
} catch (IOException ex) {
servletContext.log(
"respondWithUnexpectedFailure failed while sending the previous failure to the client",
ex);
}
}
/**
* Performs validation of the character encoding, ignoring case.
*
* @param request the incoming request
* @param expectedCharSet the expected charset of the request
* @throws ServletException if requests encoding is not null and
* does not equal, ignoring case, expectedCharSet
*/
private static void checkCharacterEncodingIgnoreCase(
HttpServletRequest request, String expectedCharSet)
throws ServletException {
boolean encodingOkay = false;
String characterEncoding = request.getCharacterEncoding();
if (characterEncoding != null) {
/*
* TODO: It would seem that we should be able to use equalsIgnoreCase here
* instead of indexOf. Need to be sure that servlet engines return a
* properly parsed character encoding string if we decide to make this
* change.
*/
if (characterEncoding.toLowerCase().indexOf(expectedCharSet.toLowerCase())
!= -1) {
encodingOkay = true;
}
}
if (!encodingOkay) {
throw new ServletException("Character Encoding is '"
+ (characterEncoding == null ? "(null)" : characterEncoding)
+ "'. Expected '" + expectedCharSet + "'");
}
}
/**
* Performs Content-Type validation of the incoming request, ignoring case
* and any charset parameter.
*
* @see #checkCharacterEncodingIgnoreCase(HttpServletRequest, String)
* @param request the incoming request
* @param expectedContentType the expected Content-Type for the incoming
* request
* @throws ServletException if the request's content type is not
* null and does not, ignoring case, equal
* expectedContentType,
*/
private static void checkContentTypeIgnoreCase(
HttpServletRequest request, String expectedContentType)
throws ServletException {
String contentType = request.getContentType();
boolean contentTypeIsOkay = false;
if (contentType != null) {
contentType = contentType.toLowerCase();
/*
* NOTE:We use startsWith because some servlet engines, i.e. Tomcat, do
* not remove the charset component but others do.
*/
if (contentType.startsWith(expectedContentType.toLowerCase())) {
contentTypeIsOkay = true;
}
}
if (!contentTypeIsOkay) {
throw new ServletException("Content-Type was '"
+ (contentType == null ? "(null)" : contentType) + "'. Expected '"
+ expectedContentType + "'.");
}
}
private RPCServletUtils() {
// Not instantiable
}
}
