org.directwebremoting.dwrp.Html4kScriptConduit Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * 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.directwebremoting.dwrp;

import java.io.IOException;

import javax.servlet.http.HttpServletResponse;

import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.extend.ConverterManager;
import org.directwebremoting.extend.EnginePrivate;
import org.directwebremoting.extend.MarshallException;
import org.directwebremoting.extend.ScriptBufferUtil;
import org.directwebremoting.util.MimeConstants;

/**
 * A ScriptConduit for use with HTML/PRE wrapped Javascript output.
 * Scripts begin with an html, body and pre tag followed by plain Javascript
 * without 'execute-in-parent-context' wrapping, but with script-start and
 * script-end markers.
 * 
If this conduit is used the client should direct the output to an iframe
 * and then poll, looking for new data into the iframe. The html tags should be
 * removed and script between script-start and script-end tags eval()ed.
 * 
This conduit also sends 4k of whitespace data on each flush. This causes
 * IE to recognise new content. This would be a significant network overhead
 * so it is important to use gzip on the connection. This complexity has caused
 * us to turn this conduit off at the moment.
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class Html4kScriptConduit extends BaseScriptConduit
{
    /**
     * Simple ctor
     * @param response Used to flush output
     * @param batchId The id of the batch that we are responding to
     * @param converterManager How we convert objects to script
     * @throws IOException If stream ops fail
     */
    public Html4kScriptConduit(HttpServletResponse response, String batchId, ConverterManager converterManager) throws IOException
    {
        super(response, batchId, converterManager);
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.dwrp.BaseCallMarshaller#getOutboundMimeType()
     */
    protected String getOutboundMimeType()
    {
        return MimeConstants.MIME_HTML;
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.dwrp.BaseScriptConduit#beginStream()
     */
    public void beginStream()
    {
        synchronized (out)
        {
            out.println("
");

            out.println(ProtocolConstants.SCRIPT_START_MARKER);
            out.println(EnginePrivate.remoteBeginIFrameResponse(batchId, false));
            out.println(ProtocolConstants.SCRIPT_END_MARKER);
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.dwrp.BaseScriptConduit#endStream()
     */
    public void endStream()
    {
        synchronized (out)
        {
            out.println(ProtocolConstants.SCRIPT_START_MARKER);
            out.println(EnginePrivate.remoteEndIFrameResponse(batchId, false));
            out.println(ProtocolConstants.SCRIPT_END_MARKER);

            out.println("");
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.ScriptConduit#addScript(org.directwebremoting.ScriptBuffer)
     */
    public boolean addScript(ScriptBuffer scriptBuffer) throws IOException, MarshallException
    {
        String script = ScriptBufferUtil.createOutput(scriptBuffer, converterManager);

        synchronized (out)
        {
            out.println(ProtocolConstants.SCRIPT_START_MARKER);
            out.println(script);
            out.println(ProtocolConstants.SCRIPT_END_MARKER);

            out.print(fourKFlushData);

            return flush();
        }
    }

    /**
     * The slab of data we send to IE to get it to stream
     */
    protected static final String fourKFlushData;
    static
    {
        StringBuffer buffer = new StringBuffer(409600);
        for (int i = 0; i < 4096; i++)
        {
            buffer.append(" ");
        }
        fourKFlushData = buffer.toString();
    }
}