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Tomcat example source code file (

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

Java - Tomcat tags/keywords

channeljni, channeljni, io, ioexception, ioexception, jk_handle_jni_dispatch, jkchannel, jnihandler, msg, msg, msgcontext, msgcontext, no, setting, string

The Tomcat source code

 *  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
 *  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.apache.jk.common;


import org.apache.jk.core.JkHandler;
import org.apache.jk.core.Msg;
import org.apache.jk.core.MsgContext;
import org.apache.jk.core.JkChannel;

import org.apache.coyote.Request;
/** Pass messages using jni 
 * @author Costin Manolache
public class ChannelJni extends JniHandler implements JkChannel {
    int receivedNote=1;

    public ChannelJni() {
        // we use static for now, it's easier on the C side.
        // Easy to change after we get everything working

    public void init() throws IOException {

        if( apr==null ) return;
        // We'll be called from C. This deals with that.
        apr.addJkHandler( "channelJni", this );       "JK: listening on channel.jni:jni" );
        if( next==null ) {
            if( nextName!=null ) 
                setNext( wEnv.getHandler( nextName ) );
            if( next==null )
                next=wEnv.getHandler( "dispatch" );
            if( next==null )
                next=wEnv.getHandler( "request" );
            if( log.isDebugEnabled() )
                log.debug("Setting default next " + next.getClass().getName());

    /** Receives does nothing - send will put the response
     *  in the same buffer
    public int receive( Msg msg, MsgContext ep )
        throws IOException
        Msg sentResponse=(Msg)ep.getNote( receivedNote );
        ep.setNote( receivedNote, null );

        if( sentResponse == null ) {
            if( log.isDebugEnabled() )
                log.debug("No send() prior to receive(), no data buffer");
            // No sent() was done prior to receive.
            sentResponse = msg;

        if( log.isTraceEnabled() )
            sentResponse.dump("received response ");

        if( msg != sentResponse ) {
            log.error( "Error, in JNI mode the msg used for receive() must be identical with the one used for send()");
        return 0;

    /** Send the packet. XXX This will modify msg !!!
     *  We could use 2 packets, or sendAndReceive().
    public int send( Msg msg, MsgContext ep )
        throws IOException
        ep.setNote( receivedNote, null );
        if( log.isDebugEnabled() ) log.debug("ChannelJni.send: "  +  msg );

        int rc=super.nativeDispatch( msg, ep, JK_HANDLE_JNI_DISPATCH, 0);

        // nativeDispatch will put the response in the same buffer.
        // Next receive() will just get it from there. Very tricky to do
        // things in one thread instead of 2.
        ep.setNote( receivedNote, msg );
        return rc;

    public int flush(Msg msg, MsgContext ep) throws IOException {
        ep.setNote( receivedNote, null );
        return OK;

    public boolean isSameAddress(MsgContext ep) {
        return true;

    public void registerRequest(Request req, MsgContext ep, int count) {
        // Not supported.

    public String getChannelName() {
        return getName();
    /** Receive a packet from the C side. This is called from the C
     *  code using invocation, but only for the first packet - to avoid
     *  recursivity and thread problems.
     *  This may look strange, but seems the best solution for the
     *  problem ( the problem is that we don't have 'continuation' ).
     *  sendPacket will move the thread execution on the C side, and
     *  return when another packet is available. For packets that
     *  are one way it'll return after it is processed too ( having
     *  2 threads is far more expensive ).
     *  Again, the goal is to be efficient and behave like all other
     *  Channels ( so the rest of the code can be shared ). Playing with
     *  java objects on C is extremely difficult to optimize and do
     *  right ( IMHO ), so we'll try to keep it simple - byte[] passing,
     *  the conversion done in java ( after we know the encoding and
     *  if anyone asks for it - same lazy behavior as in 3.3 ).
    public  int invoke(Msg msg, MsgContext ep )  throws IOException {
        if( apr==null ) return -1;
        long xEnv=ep.getJniEnv();
        long cEndpointP=ep.getJniContext();

        int type=ep.getType();
        if( log.isDebugEnabled() ) log.debug("ChannelJni.invoke: "  + ep + " " + type);

        switch( type ) {
        case JkHandler.HANDLE_RECEIVE_PACKET:
            return receive( msg, ep );
        case JkHandler.HANDLE_SEND_PACKET:
            return send( msg, ep );
        case JkHandler.HANDLE_FLUSH:
            return flush(msg, ep);

        // Reset receivedNote. It'll be visible only after a SEND and before a receive.
        ep.setNote( receivedNote, null );

        // Default is FORWARD - called from C 
        try {
            // first, we need to get an endpoint. It should be
            // per/thread - and probably stored by the C side.
            if( log.isDebugEnabled() ) log.debug("Received request " + xEnv);
            // The endpoint will store the message pt.

            if( log.isTraceEnabled() ) msg.dump("Incoming msg ");

            int status= next.invoke(  msg, ep );
            if( log.isDebugEnabled() ) log.debug("after processCallbacks " + status);
            return status;
        } catch( Exception ex ) {
        return 0;

    private static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog( ChannelJni.class );


Other Tomcat examples (source code examples)

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