gdataresponse.java

一套java版本的搜索引擎源码

/** 
 * Copyright 2004 The Apache Software Foundation 
 * 
 * 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 org.apache.lucene.gdata.server;

import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Date;

import javax.servlet.http.HttpServletResponse;
import javax.xml.transform.Source;
import javax.xml.transform.Templates;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.lucene.gdata.server.GDataRequest.OutputFormat;
import org.apache.lucene.gdata.server.registry.ProvidedService;
import org.apache.lucene.gdata.utils.DateFormater;

import com.google.gdata.data.BaseEntry;
import com.google.gdata.data.BaseFeed;
import com.google.gdata.data.DateTime;
import com.google.gdata.data.ExtensionProfile;
import com.google.gdata.util.common.xml.XmlWriter;
import com.google.gdata.util.common.xml.XmlWriter.Namespace;

/**
 * The FeedRequest Class wraps the current HttpServletResponse. Any action on the
 * HttpServletRequest will be executed via this class. This represents an
 * abstraction on the plain {@link HttpServletResponse}. Any action which has
 * to be performed on the underlying {@link HttpServletResponse} will be
 * executed within this class.
 * <p>
 * The GData basically writes two different kinds of response to the output
 * stream.
 * <ol>
 * <li>update, delete or insert requests will respond with a status code and if
 * successful the feed entry modified or created</li>
 * <li>get requests will respond with a status code and if successful the
 * requested feed</li>
 * </ol>
 * 
 * For this purpose the {@link GDataResponse} class provides the overloaded
 * method
 * {@link org.apache.lucene.gdata.server.GDataResponse#sendResponse(BaseEntry, ExtensionProfile)}
 * which sends the entry e.g feed to the output stream.
 * </p>
 * <p>
 * This class will set the HTTP <tt>Last-Modified</tt> Header to enable
 * clients to send <tt>If-Modified-Since</tt> request header to avoid
 * retrieving the content again if it hasn't changed. If the content hasn't
 * changed since the If-Modified-Since time, then the GData service returns a
 * 304 (Not Modified) HTTP response.
 * </p>
 * 
 * 
 * 
 * 
 * @author Simon Willnauer
 * 
 */
public class GDataResponse {
    /**
     * Response code bad request
     */
    public static final int BAD_REQUEST = HttpServletResponse.SC_BAD_REQUEST;
    /**
     * Response code version conflict
     */
    public static final int CONFLICT = HttpServletResponse.SC_CONFLICT;
    /**
     * Response code forbidden access
     */
    public static final int FORBIDDEN = HttpServletResponse.SC_FORBIDDEN;
    /**
     * Response code internal server error
     */
    public static final int SERVER_ERROR = HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
    /**
     * Response code not found
     */
    public static final int NOT_FOUND = HttpServletResponse.SC_NOT_FOUND;
    /**
     * Response code not modified since
     */
    public static final int NOT_MODIFIED = HttpServletResponse.SC_NOT_MODIFIED;
    /**
     * Response code created
     */
    public static final int CREATED = HttpServletResponse.SC_CREATED;
    /**
     * Response code unauthorized access
     */
    public static final int UNAUTHORIZED = HttpServletResponse.SC_UNAUTHORIZED;
    
    
    static final Log LOG = LogFactory.getLog(GDataResponse.class);
    private int error;

    private boolean isError = false;

    private String encoding;

    private OutputFormat outputFormat;

    private final HttpServletResponse response;

    protected static final String XMLMIME_ATOM = "text/xml";

    protected static final String XMLMIME_RSS = "text/xml";

    private static final String HEADER_LASTMODIFIED = "Last-Modified";

    /**
     * Creates a new GDataResponse
     * 
     * @param response -
     *            The underlying {@link HttpServletResponse}
     */
    public GDataResponse(HttpServletResponse response) {
        if (response == null)
            throw new IllegalArgumentException("response must not be null");
        this.response = response;

    }

    /**
     * Sets an error code to this FeedResponse.
     * 
     * @param errorCode -
     *            {@link HttpServletResponse} error code
     */
    public void setError(int errorCode) {
        this.isError = true;
        this.error = errorCode;
    }

    /**
     * Sets the status of the underlying response
     * 
     * @see HttpServletResponse
     * @param responseCode -
     *            the status of the response
     */
    public void setResponseCode(int responseCode) {
        this.response.setStatus(responseCode);
    }

    /**
     * This method sends the specified error to the user if set
     * 
     * @throws IOException -
     *             if an I/O Exception occurs
     */
    public void sendError() throws IOException {
        if (this.isError)
            this.response.sendError(this.error);
        
    }

    /**
     * @return - the {@link HttpServletResponse} writer
     * @throws IOException -
     *             If an I/O exception occurs
     */
    public Writer getWriter() throws IOException {
        return this.response.getWriter();
    }

    /**
     * Sends a response for a get e.g. query request. This method must not
     * invoked in a case of an error performing the requested action.
     * 
     * @param feed -
     *            the feed to respond to the client
     * @param service - the service to render the feed
     * 
     * @throws IOException -
     *             if an I/O exception occurs, often caused by an already
     *             closed Writer or OutputStream
     * 
     */
    public void sendResponse(final BaseFeed feed, final ProvidedService service)
            throws IOException {
        if (feed == null)
            throw new IllegalArgumentException("feed must not be null");
        if (service == null)
            throw new IllegalArgumentException(
                    "provided service must not be null");
        DateTime time = feed.getUpdated();
        if (time != null)
            setLastModifiedHeader(time.getValue());
        FormatWriter writer = FormatWriter.getFormatWriter(this,service);
        writer.generateOutputFormat(feed,this.response);

    }

    /**
     * 
     * Sends a response for an update, insert or delete request. This method
     * must not invoked in a case of an error performing the requested action. If
     * the specified response format is ATOM the default namespace will be set
     * to ATOM.
     * 
     * @param entry -
     *            the modified / created entry to send