org.directwebremoting.extend.EnginePrivate 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.extend;

import java.io.IOException;

import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.Log;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.dwrp.ProtocolConstants;
import org.directwebremoting.impl.DefaultRemoter;
import org.directwebremoting.proxy.ScriptProxy;
import org.directwebremoting.util.JavascriptUtil;

/**
 * An abstraction of the DWREngine Javascript class for use by
 * {@link org.directwebremoting.dwrp.BaseCallMarshaller},
 * {@link org.directwebremoting.dwrp.PollHandler} and a few others that need
 * to call internal functions in engine.js
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class EnginePrivate extends ScriptProxy
{
    /**
     * Call the dwr.engine.remote.handleResponse() in the browser
     * @param conduit The browser pipe to write to
     * @param batchId The identifier of the batch that we are handling a response for
     * @param callId The identifier of the call that we are handling a response for
     * @param data The data to pass to the callback function
     * @throws IOException If writing fails.
     * @throws MarshallException If objects in the script can not be marshalled
     */
    public static void remoteHandleCallback(ScriptConduit conduit, String batchId, String callId, Object data) throws IOException, MarshallException
    {
        ScriptBuffer script = new ScriptBuffer();
        script.appendCall("dwr.engine.remote.handleCallback", batchId, callId, data);
        conduit.addScript(script);
    }

    /**
     * Call dwr.engine.remote.handleException() in the browser
     * @param conduit The browser pipe to write to
     * @param batchId The identifier of the batch that we are handling a response for
     * @param callId The id of the call we are replying to
     * @param ex The exception to throw on the remote end
     * @throws IOException If writing fails.
     */
    public static void remoteHandleException(ScriptConduit conduit, String batchId, String callId, Throwable ex) throws IOException
    {
        try
        {
            ScriptBuffer script = new ScriptBuffer();
            script.appendCall("dwr.engine.remote.handleException", batchId, callId, ex);
            conduit.addScript(script);
        }
        catch (MarshallException mex)
        {
            log.warn("This exception can't happen. Really.", ex);
        }
    }

    /**
     * Call dwr.engine.remote.handleNewScriptSession() in the browser
     * @param session The browser page to write to
     * @param newSessionId The new script session id for the browser to reuse
     */
    public static void remoteHandleNewScriptSession(ScriptSession session, String newSessionId)
    {
        ScriptBuffer script = new ScriptBuffer();
        script.appendCall("dwr.engine.remote.handleNewScriptSession", newSessionId);
        session.addScript(script);
    }

    /**
     * Call dwr.engine.remote.handleNewWindowName() in the browser
     * @param session The browser page to write to
     * @param windowName The new window name for the page
     */
    public static void remoteHandleNewWindowName(ScriptSession session, String windowName)
    {
        ScriptBuffer script = new ScriptBuffer();
        script.appendCall("dwr.engine.remote.handleNewWindowName", windowName);
        session.addScript(script);
    }

    /**
     * Call the dwr.engine.remote.handleServerException() in the browser
     * @param batchId The identifier of the batch that we are handling a response for
     * @param ex The exception from which we make a reply
     * @return The script to send to the browser
     */
    public static String getRemoteHandleBatchExceptionScript(String batchId, Exception ex)
    {
        StringBuffer reply = new StringBuffer();

        String output = JavascriptUtil.escapeJavaScript(ex.getMessage());
        String params = "{ name:'" + ex.getClass().getName() + "', message:'" + output + "' }";
        if (batchId != null)
        {
            params += ", '" + batchId + "'";
        }

        reply.append(ProtocolConstants.SCRIPT_CALL_REPLY).append("\r\n");
        reply.append("if (window.dwr) dwr.engine.remote.handleBatchException(").append(params).append(");\r\n");
        reply.append("else if (window.parent.dwr) window.parent.dwr.engine.remote.handleBatchException(").append(params).append(");\r\n");

        return reply.toString();
    }

    /**
     * Call the dwr.engine.remote.pollCometDisabled() in the browser
     * @param batchId The identifier of the batch that we are handling a response for
     * @return The script to send to the browser
     */
    public static String getRemotePollCometDisabledScript(String batchId)
    {
        StringBuffer reply = new StringBuffer();

        String params = "{ name:'dwr.engine.pollAndCometDisabled', message:'Polling and Comet are disabled. See the server logs.' }";
        if (batchId != null)
        {
            params += ", '" + batchId + "'";
        }

        reply.append(ProtocolConstants.SCRIPT_CALL_REPLY).append("\r\n");
        reply.append("if (window.dwr) dwr.engine.remote.pollCometDisabled(").append(params).append(");\r\n");
        reply.append("else if (window.parent.dwr) window.parent.dwr.engine.remote.pollCometDisabled(").append(params).append(");\r\n");

        return reply.toString();
    }

    /**
     * Take an XML string, and convert it into some Javascript that when
     * executed will return a DOM object that represents the same XML object
     * @param xml The XML string to convert
     * @return The Javascript
     */
    public static String xmlStringToJavascriptDom(String xml)
    {
        String xmlout = JavascriptUtil.escapeJavaScript(xml);
        return "dwr.engine.serialize.toDom(\"" + xmlout + "\")";
    }

    /**
     * Get a string which will initialize a dwr.engine object
     * @return A dwr.engine init script
     */
    public static String getEngineInitScript()
    {
        return "// Provide a default path to dwr.engine\n" +
               "if (typeof this['dwr'] == 'undefined') this.dwr = {};\n" +
               "if (typeof dwr['engine'] == 'undefined') dwr.engine = {};\n" +
               '\n';
    }

    /**
     * {@link DefaultRemoter} needs to know the name of the execute function
     * @return The execute function name
     */
    public static String getExecuteFunctionName()
    {
        return "dwr.engine._execute";
    }

    /**
     * A script to send at the beginning of an iframe response
     * @param batchId The id of the current batch
     * @param useWindowParent Will the exec happen from a child iframe which is
     * the case for normal iframe based calls, or from the main window, which is
     * the case for iframe streamed polling.
     * @return A script to init the environment
     */
    public static String remoteBeginIFrameResponse(String batchId, boolean useWindowParent)
    {
        String script = "dwr.engine.transport.iframe.remote.beginIFrameResponse(this.frameElement"+(batchId == null?"":", '" + batchId+"'") + ");";
        if (useWindowParent)
        {
            script = addWindowParent(script);
        }

        return script;
    }

    /**
     * A script to send at the end of an iframe response
     * @param batchId The id of the current batch
     * @param useWindowParent Will the exec happen from a child iframe which is
     * the case for normal iframe based calls, or from the main window, which is
     * the case for iframe streamed polling.
     * @return A script to tidy up the environment
     */
    public static String remoteEndIFrameResponse(String batchId, boolean useWindowParent)
    {
        String script = "dwr.engine.transport.iframe.remote.endIFrameResponse("+(batchId == null?"":"'" + batchId+"'")+");";
        if (useWindowParent)
        {
            script = addWindowParent(script);
        }

        return script;
    }

    /**
     * Prepare a script for execution in an iframe environment
     * @param script The script to modify
     * @return The modified script
     */
    public static String remoteEval(String script)
    {
        String script2 = "dwr.engine._eval(\"" + JavascriptUtil.escapeJavaScript(script) + "\");";
        return addWindowParent(script2);
    }

    /**
     * Evade the 2 connection limit by sending scripts to the wrong window and
     * having that use window.name to push it to the right window
     * @param original The script that we wish to be proxied
     * @param windowName The window to which we wish the window to be proxied
     * @return A script to send to a different window to cause proxying
     */
    public static ScriptBuffer createForeignWindowProxy(String windowName, ScriptBuffer original)
    {
        String proxy = JavascriptUtil.escapeJavaScript(original.toString());

        ScriptBuffer reply = new ScriptBuffer();
        reply.appendCall("dwr.engine.remote.handleForeign", windowName, proxy);
        reply.appendData(proxy);
        return reply;
    }

    /**
     * A Utility to add a try/catch block to get rid of the infamous IE
     * "Can't execute code from a freed script" errors
     * @param script The script to wrap in a try/catch
     * @return The wrapped script
     */
    private static String addWindowParent(String script)
    {
        return "try { window.parent." + script + " } catch(ex) { if (!(ex.number && ex.number == -2146823277)) { throw ex; }}";
    }

    /**
     * The log stream
     */
    private static final Log log = LogFactory.getLog(EnginePrivate.class);
}