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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 boilerplate code between the web browser and your Java code. This version 4.0.2 works with Jakarta Servlet 4.0.2.

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package org.directwebremoting.impl;

import java.lang.reflect.Method;

import org.directwebremoting.extend.Compressor;
import org.directwebremoting.util.Loggers;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.ContextAction;
import org.mozilla.javascript.tools.ToolErrorReporter;
import org.mozilla.javascript.tools.shell.Global;
import org.mozilla.javascript.tools.shell.Main;

/**
 * JavaScript Compression Implementation using Dojo ShrinkSafe.
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 * @author Randy Jones (Updater)
 */
public class ShrinkSafeCompressor implements Compressor
{
    /**
     * @throws Exception Likely if YUI is present, and not ShrinkSafe
     */
    public ShrinkSafeCompressor() throws Exception
    {
        // This should fail if ShrinkSafe is not in classpath
        try
        {
            global = Main.getGlobal();
            ToolErrorReporter errorReporter = new ToolErrorReporter(false, global.getErr());
            Main.shellContextFactory.setErrorReporter(errorReporter);

            // Do a trial compression to check
            compressJavaScript("");
        }
        catch (NoClassDefFoundError ex)
        {
            throw new InstantiationException("Could not setup ShrinkSafeCompressor because a class is missing, assuming shrinksafe.jar and js.jar are not in the classpath.");
        }
        catch (Exception ex)
        {
            Loggers.STARTUP.error("ShrinkSafeCompressor startup", ex);
            throw new InstantiationException("Could not setup ShrinkSafeCompressor, assuming shrinksafe.jar and js.jar are not in the classpath. Exception caught was " + ex);
        }

    }

    /* (non-Javadoc)
     * @see org.directwebremoting.extend.Compressor#compressJavaScript(java.lang.String)
     */
    public String compressJavaScript(final String source) throws Exception
    {
        final Exception[] thrown = new Exception[1];
        String reply = (String) Main.shellContextFactory.call(new ContextAction()
        {
            public Object run(Context cx)
            {
                try
                {
                    // The shrinksafe Compressor only obfuscates the javascript. Line breaks are removed
                    // by the dojo build. Adding the removal of line breaks to make the optimization that
                    // would come from using the dojo build. See
                    // http://svn.dojotoolkit.org/src/tags/release-1.5.0/util/buildscripts/jslib/buildUtil.js
                    // in the buildUtil.optimizeJs function which has the following:
                    // if(optimizeType.indexOf("shrinksafe") == 0 || optimizeType == "packer"){
                    //     //Apply compression using custom compression call in Dojo-modified rhino.
                    //     fileContents = new String(Packages.org.dojotoolkit.shrinksafe.Compressor.compressScript(fileContents, 0, 1, stripConsole));
                    //     if(optimizeType.indexOf(".keepLines") == -1){
                    //         fileContents = fileContents.replace(/[\r\n]/g, "");
                    //     }
                    // }
                    String obfuscated = org.dojotoolkit.shrinksafe.Compressor.compressScript(source, 0, 1, false, null);
                    return obfuscated.replaceAll("[\\r\\n]", "");
                }
                catch (Exception ex)
                {
                    ex.printStackTrace();
                    thrown[0] = ex;
                }
                return null;
            }
        });

        if (thrown[0] != null)
        {
            throw thrown[0];
        }
        else
        {
            return reply;
        }
    }

    protected Global global;
    protected Method compressReaderMethod;
}