org.eclipse.help/src/org/eclipse/help/internal/CachedEntityResolver.java

/*******************************************************************************
 * Copyright (c) 2007, 2015 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.help.internal;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.net.URL;
import java.net.URLConnection;

import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;


public class CachedEntityResolver implements EntityResolver {

	@Override
	public InputSource resolveEntity(String publicId, String systemId) {
        int index = systemId.lastIndexOf("/"); //$NON-NLS-1$
        File cachedCopy = null;
        if (index != -1) {
        	cachedCopy = new File(HelpPlugin.getConfigurationDirectory(), "/DTDs"); //$NON-NLS-1$
        	cachedCopy.mkdirs();
        	cachedCopy = new File(cachedCopy, systemId.substring(index));
        }
        if (cachedCopy != null) {
        	if (!cachedCopy.exists()) {
				try {
					URL system = new URL(systemId);
			        URLConnection sc = system.openConnection();
			        BufferedReader in = new BufferedReader(
			                                new InputStreamReader(
			                                sc.getInputStream()));
			        String inputLine;
			        BufferedWriter out = new BufferedWriter(new FileWriter(cachedCopy));
			        while ((inputLine = in.readLine()) != null) {
			            out.write(inputLine);
			        	out.newLine();
			        }
			        in.close();
			        out.flush();
			        out.close();
				} catch (IOException e) {}
        	}
	        try {
	        	InputSource is = new InputSource(new FileReader(cachedCopy));
	        	is.setSystemId(systemId);
	        	is.setPublicId(publicId);
	        	return is;
	        } catch (FileNotFoundException e) {}
        }
    	return new InputSource(new StringReader("")); //$NON-NLS-1$
	}

}