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Java example source code file (RequestHandler.java)

This example Java source code file (RequestHandler.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

broken, bytebuffer, channelio, connection, ioexception, malformedrequestexception, nio, reply, requesthandler, resource, should, stringcontent

The RequestHandler.java Java example source code

/*
 * Copyright (c) 2004, 2011, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


import java.io.*;
import java.nio.*;
import java.nio.channels.*;

/**
 * Primary driver class used by non-blocking Servers to receive,
 * prepare, send, and shutdown requests.
 *
 * @author Mark Reinhold
 * @author Brad R. Wetmore
 */
class RequestHandler implements Handler {

    private ChannelIO cio;
    private ByteBuffer rbb = null;

    private boolean requestReceived = false;
    private Request request = null;
    private Reply reply = null;

    private static int created = 0;

    RequestHandler(ChannelIO cio) {
        this.cio = cio;

        // Simple heartbeat to let user know we're alive.
        synchronized (RequestHandler.class) {
            created++;
            if ((created % 50) == 0) {
                System.out.println(".");
                created = 0;
            } else {
                System.out.print(".");
            }
        }
    }

    // Returns true when request is complete
    // May expand rbb if more room required
    //
    private boolean receive(SelectionKey sk) throws IOException {
        ByteBuffer tmp = null;

        if (requestReceived) {
            return true;
        }

        if (!cio.doHandshake(sk)) {
            return false;
        }

        if ((cio.read() < 0) || Request.isComplete(cio.getReadBuf())) {
            rbb = cio.getReadBuf();
            return (requestReceived = true);
        }
        return false;
    }

    // When parse is successfull, saves request and returns true
    //
    private boolean parse() throws IOException {
        try {
            request = Request.parse(rbb);
            return true;
        } catch (MalformedRequestException x) {
            reply = new Reply(Reply.Code.BAD_REQUEST,
                              new StringContent(x));
        }
        return false;
    }

    // Ensures that reply field is non-null
    //
    private void build() throws IOException {
        Request.Action action = request.action();
        if ((action != Request.Action.GET) &&
                (action != Request.Action.HEAD)) {
            reply = new Reply(Reply.Code.METHOD_NOT_ALLOWED,
                              new StringContent(request.toString()));
        }
        reply = new Reply(Reply.Code.OK,
                          new FileContent(request.uri()), action);
    }

    public void handle(SelectionKey sk) throws IOException {
        try {

            if (request == null) {
                if (!receive(sk))
                    return;
                rbb.flip();
                if (parse())
                    build();
                try {
                    reply.prepare();
                } catch (IOException x) {
                    reply.release();
                    reply = new Reply(Reply.Code.NOT_FOUND,
                                      new StringContent(x));
                    reply.prepare();
                }
                if (send()) {
                    // More bytes remain to be written
                    sk.interestOps(SelectionKey.OP_WRITE);
                } else {
                    // Reply completely written; we're done
                    if (cio.shutdown()) {
                        cio.close();
                        reply.release();
                    }
                }
            } else {
                if (!send()) {  // Should be rp.send()
                    if (cio.shutdown()) {
                        cio.close();
                        reply.release();
                    }
                }
            }
        } catch (IOException x) {
            String m = x.getMessage();
            if (!m.equals("Broken pipe") &&
                    !m.equals("Connection reset by peer")) {
                System.err.println("RequestHandler: " + x.toString());
            }

            try {
                /*
                 * We had a failure here, so we'll try to be nice
                 * before closing down and send off a close_notify,
                 * but if we can't get the message off with one try,
                 * we'll just shutdown.
                 */
                cio.shutdown();
            } catch (IOException e) {
                // ignore
            }

            cio.close();
            if (reply !=  null) {
                reply.release();
            }
        }

    }

    private boolean send() throws IOException {
        try {
            return reply.send(cio);
        } catch (IOException x) {
            if (x.getMessage().startsWith("Resource temporarily")) {
                System.err.println("## RTA");
                return true;
            }
            throw x;
        }
    }
}

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