org.overlord.apiman.gateway.http.HTTPGateway.java Source code

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Here is the source code for org.overlord.apiman.gateway.http.HTTPGateway.java

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/*
 * 2012-3 Red Hat Inc. and/or its affiliates and other contributors.
 *
 * 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.overlord.apiman.gateway.http;

import org.apache.http.message.BasicHeader;
import org.apache.http.message.HeaderGroup;
import org.overlord.apiman.Request;
import org.overlord.apiman.Response;
import org.overlord.apiman.gateway.Gateway;

import javax.inject.Inject;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;

/**
 * This class implements the HTTP based wrapper for the gateway.
 * 
 * Based on the http servlet proxy implemented by David Smiley:
 * https://github.com/dsmiley/HTTP-Proxy-Servlet
 */
public class HTTPGateway extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Inject
    private Gateway _gateway = null;

    /**
     * This method returns the gateway.
     * 
     * @return The gateway
     */
    public Gateway getGateway() {
        return (_gateway);
    }

    /**
     * This method sets the gateway.
     * 
     * @param gw The gateway
     */
    public void setGateway(Gateway gw) {
        _gateway = gw;
    }

    @Override
    protected void service(HttpServletRequest servletRequest, HttpServletResponse servletResponse)
            throws IOException {

        if (_gateway == null) {
            throw new IOException("No gateway available");
        }

        try {
            // Forward the request to the gateway
            Request request = new HTTPGatewayRequest(servletRequest);

            Response resp = _gateway.process(request);

            servletResponse.setStatus(resp.getStatusCode());

            copyResponseHeaders(resp, servletResponse);

            // Send the content to the client
            copyResponseContent(resp, servletResponse);

        } catch (IOException ioe) {
            throw ioe;
        } catch (Exception e) {
            throw new IOException("Failed to process gateway request", e);
        }
    }

    /** Copy proxied response headers back to the servlet client. */
    protected void copyResponseHeaders(Response proxyResponse, HttpServletResponse servletResponse) {
        for (int i = 0; i < proxyResponse.getHeaders().size(); i++) {
            org.overlord.apiman.NameValuePair nvp = proxyResponse.getHeaders().get(i);

            if (hopByHopHeaders.containsHeader(nvp.getName())) {
                continue;
            }

            servletResponse.addHeader(nvp.getName(), (String) nvp.getValue());
        }
    }

    /** Copy response body data (the entity) from the proxy to the servlet client. */
    protected void copyResponseContent(Response proxyResponse, HttpServletResponse servletResponse)
            throws IOException {
        OutputStream servletOutputStream = servletResponse.getOutputStream();

        try {
            servletOutputStream.write(proxyResponse.getContent());

        } finally {
            try {
                //is.close();
                servletOutputStream.close();
            } catch (Exception e) {
                log(e.getMessage(), e);
            }
        }
    }

    /** These are the "hop-by-hop" headers that should not be copied.
      * http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
      * I use an HttpClient HeaderGroup class instead of Set<String> because this
      * approach does case insensitive lookup faster.
      */
    protected static final HeaderGroup hopByHopHeaders;
    static {
        hopByHopHeaders = new HeaderGroup();
        String[] headers = new String[] { "Connection", "Keep-Alive", "Proxy-Authenticate", "Proxy-Authorization",
                "TE", "Trailers", "Transfer-Encoding", "Upgrade" };
        for (String header : headers) {
            hopByHopHeaders.addHeader(new BasicHeader(header, null));
        }
    }

}