openremoteserviceservlet.java

jetty SERVER連接資料庫用的軟體

/*
 * Copyright 2006 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.net.MalformedURLException;
import java.net.URL;
import java.text.ParseException;
import java.util.HashMap;
import java.util.Map;
import java.util.zip.GZIPOutputStream;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException;
import com.google.gwt.user.client.rpc.SerializationException;

/**
 * RemoteServiceServlet changes to allow extensions required for Jetty Continuatution support.
 *
 * Changes:
 *
 * readPayloadAsUtf8 now protected non-static
 *
 * @author Craig Day ([e-mail])
 *
 */
public class OpenRemoteServiceServlet extends HttpServlet implements SerializationPolicyProvider {
    /*
     * These members are used to get and set the different HttpServletResponse and
     * HttpServletRequest headers.
     */
    private static final String ACCEPT_ENCODING = "Accept-Encoding";
    private static final String CHARSET_UTF8 = "UTF-8";
    private static final String CONTENT_ENCODING = "Content-Encoding";
    private static final String CONTENT_ENCODING_GZIP = "gzip";
    private static final String CONTENT_TYPE_TEXT_PLAIN_UTF8 = "text/plain; 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 EXPECTED_CONTENT_TYPE = "text/x-gwt-rpc";
    private static final String EXPECTED_CHARSET = "charset=utf-8";

    /**
     * Controls the compression threshold at and below which no compression will
     * take place.
     */
    private static final int UNCOMPRESSED_BYTE_SIZE_LIMIT = 256;

    /**
     * Return true if the response object accepts Gzip encoding. This is done by
     * checking that the accept-encoding header specifies gzip as a supported
     * encoding.
     */
    private 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);
    }

    /**
     * This method attempts to estimate the number of bytes that a string will
     * consume when it is sent out as part of an HttpServletResponse. This really
     * a hack since we are assuming that every character will consume two bytes
     * upon transmission. This is definitely not true since some characters
     * actually consume more than two bytes and some consume less. This is even
     * less accurate if the string is converted to UTF8. However, it does save us
     * from converting every string that we plan on sending back to UTF8 just to
     * determine that we should not compress it.
     */
    private static int estimateByteSize(final String buffer) {
        return (buffer.length() * 2);
    }

    /**
     * Read the payload as UTF-8 from the request stream.
     */
    protected String readPayloadAsUtf8(HttpServletRequest request)
            throws IOException, ServletException {
        int contentLength = request.getContentLength();
        if (contentLength == -1) {
            // Content length must be known.
            throw new ServletException("Content-Length must be specified");
        }

        String contentType = request.getContentType();
        boolean contentTypeIsOkay = false;
        // Content-Type must be specified.
        /*if (contentType != null) {
            // The type must be plain text.
            if (contentType.startsWith("text/plain")) {
                // And it must be UTF-8 encoded (or unspecified, in which case we assume
                // that it's either UTF-8 or ASCII).
                if (contentType.indexOf("charset=") == -1) {
                    contentTypeIsOkay = true;
                } else if (contentType.indexOf("charset=utf-8") != -1) {
                    contentTypeIsOkay = true;
                }
            }
        }
        if (!contentTypeIsOkay) {
            throw new ServletException(
                    "Content-Type must be 'text/plain' with 'charset=utf-8' (or unspecified charset)");
        }*/
        if (contentType != null) {
            contentType = contentType.toLowerCase();
            /*
             * The Content-Type must be text/x-gwt-rpc.
             * 
             * NOTE:We use startsWith because some servlet engines, i.e. Tomcat, do
             * not remove the charset component but others do.
             */
            if (contentType.startsWith(EXPECTED_CONTENT_TYPE)) {
                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(CHARSET_UTF8.toLowerCase()) != -1)
                        contentTypeIsOkay = true;                    
                }
            }
        }
        if (!contentTypeIsOkay) {
            throw new ServletException("Content-Type must be '"
                    + EXPECTED_CONTENT_TYPE + "' with '" + EXPECTED_CHARSET + "'.");
        }
        InputStream in = request.getInputStream();
        try {
            byte[] payload = new byte[contentLength];
            int offset = 0;
            int len = contentLength;
            int byteCount;
            while (offset < contentLength) {
                byteCount = in.read(payload, offset, len);
                if (byteCount == -1) {
                    throw new ServletException("Client did not send " + contentLength
                            + " bytes as expected");
                }
                offset += byteCount;
                len -= byteCount;
            }
            return new String(payload, "UTF-8");
        } finally {
            if (in != null) {
                in.close();
            }
        }
    }

    private final ThreadLocal perThreadRequest = new ThreadLocal();

    private final ThreadLocal perThreadResponse = new ThreadLocal();
    
    /**
     * A cache of moduleBaseURL and serialization policy strong name to
     * {@link SerializationPolicy}.
     */
    private final Map<String, SerializationPolicy> serializationPolicyCache = new HashMap<String, SerializationPolicy>();

    /**
     * The default constructor.
     */
    public OpenRemoteServiceServlet() {
    }

    /**
     * Standard HttpServlet method: handle the POST.
     * <p/>
     * This doPost method swallows ALL exceptions, logs them in the
     * ServletContext, and returns a GENERIC_FAILURE_MSG response with status code
     * 500.
     */
    public final void doPost(HttpServletRequest request,
                             HttpServletResponse response) {
        try {
            // Store the request & response objects in thread-local storage.
            //
            perThreadRequest.set(request);
            perThreadResponse.set(response);

            // Read the request fully.
            //
            String requestPayload = readPayloadAsUtf8(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);
            return;
        } catch (Throwable e) {
            // Give a subclass a chance to either handle the exception or rethrow it
            //
            doUnexpectedFailure(e);
        } finally {
            // null the thread-locals to avoid holding request/response
            //
            perThreadRequest.set(null);
            perThreadResponse.set(null);
        }
    }

    /**
     * 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 {
        try {
            RPCRequest rpcRequest = RPC.decodeRequest(payload, this.getClass(), this);
            return RPC.invokeAndEncodeResponse(this, rpcRequest.getMethod(),
                    rpcRequest.getParameters(), rpcRequest.getSerializationPolicy());
        } catch (IncompatibleRemoteServiceException ex) {
            return RPC.encodeResponseForFailure(null, ex);
        }
    }

    /**
     * Override this method to control what should happen when an exception
     * escapes the {@link #processCall(String)} method. The default implementation
     * will log the failure and send a generic failure response to the client.<p/>
     * <p/>
     * An "expected failure" is an exception thrown by a service method that is
     * declared in the signature of the service method. These exceptions are
     * serialized back to the client, and are not passed to this method. This
     * method is called only for exceptions or errors that are not part of the
     * service method's signature, or that result from SecurityExceptions,
     * SerializationExceptions, or other failures within the RPC framework.<p/>
     * <p/>
     * Note that if the desired behavior is to both send the GENERIC_FAILURE_MSG
     * response AND to rethrow the exception, then this method should first send
     * the GENERIC_FAILURE_MSG response itself (using getThreadLocalResponse), and
     * then rethrow the exception. Rethrowing the exception will cause it to
     * escape into the servlet container.
     *
     * @param e the exception which was thrown
     */
    protected void doUnexpectedFailure(Throwable e) {