edu.mayo.cts2.framework.webapp.rest.osgi.ProxyServlet.java Source code

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Here is the source code for edu.mayo.cts2.framework.webapp.rest.osgi.ProxyServlet.java

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package edu.mayo.cts2.framework.webapp.rest.osgi;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

import java.io.IOException;

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

import org.apache.felix.http.proxy.DispatcherTracker;
import org.osgi.framework.BundleContext;
import org.osgi.util.tracker.ServiceTracker;
import org.springframework.util.Assert;

public final class ProxyServlet extends HttpServlet {

    private static final long serialVersionUID = -8648910455822026016L;

    private transient ServiceTracker tracker;

    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);

        Assert.notNull(config.getServletContext());

        try {
            doInit(config);
        } catch (ServletException e) {
            throw e;
        } catch (Exception e) {
            throw new ServletException(e);
        }
    }

    private void doInit(ServletConfig config) throws Exception {
        this.tracker = new DispatcherTracker(getBundleContext(), null, getServletConfig());
        this.tracker.open();

        config.getServletContext().setAttribute("osgi-servlet-tracker", this.tracker);
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {

        HttpServlet dispatcher = (HttpServlet) this.tracker.getService();
        if (dispatcher != null) {
            dispatcher.service(req, res);
        } else {
            res.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
        }
    }

    @Override
    public void destroy() {
        this.tracker.close();
        super.destroy();
    }

    private BundleContext getBundleContext() throws ServletException {
        Object context = getServletContext().getAttribute(BundleContext.class.getName());
        if (context instanceof BundleContext) {
            return (BundleContext) context;
        }

        throw new ServletException(
                "Bundle context attribute [" + BundleContext.class.getName() + "] not set in servlet context");
    }
}