ResourceServlet.java

/**
 * Copyright 2010 Marko Lavikainen
 *
 * 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 net.contextfw.web.application.internal.servlet;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.regex.Pattern;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.contextfw.web.application.WebApplicationException;
import net.contextfw.web.application.internal.util.ResourceEntry;
import net.contextfw.web.application.internal.util.ResourceScanner;

import org.apache.commons.io.IOUtils;

public abstract class ResourceServlet extends HttpServlet {

    private static final long serialVersionUID = -1979474932427776224L;

    private volatile String content = null;

    public void clean() {
        content = null;
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,
            IOException {

        if (clear()) {
            clean();
        }

        resp.setContentType(getContentType());

        if (content == null) {
            reloadResources();
        }

        resp.getWriter().print(content);
        resp.getWriter().close();
    }

    private synchronized void reloadResources() {
        if (content == null) {
            StringBuilder contentBuilder = new StringBuilder();
            List<ResourceEntry> files = ResourceScanner
                    .findResources(getRootPaths(), getAcceptor());
            for (ResourceEntry file : files) {
                addContent(contentBuilder, file);
            }
            content = contentBuilder.toString();
        }
    }

    private void addContent(StringBuilder contentBuilder, ResourceEntry file) {
        try {
            InputStream stream = file.getInputStream();
            contentBuilder.append(IOUtils.toString(stream));
            if (contentBuilder.length() == 0 || contentBuilder.charAt(contentBuilder.length() - 1) != '\n') {
                contentBuilder.append("\n");
            }
            stream.close();
        } catch (FileNotFoundException e) {
            throw new WebApplicationException(e);
        } catch (IOException e) {
            throw new WebApplicationException(e);
        }
    }

    public abstract boolean clear();

    protected abstract Pattern getAcceptor();

    protected abstract List<String> getRootPaths();

    protected abstract String getContentType();
}