org.graalvm.polyglot.io.MessageTransport Maven / Gradle / Ivy
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package org.graalvm.polyglot.io;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.WritableByteChannel;
import org.graalvm.polyglot.Engine;
/**
* Allows to take over transport of message communication initiated by an instrument. Implement this
* interface to provide a transport of message communication. When an instrument is about to create
* a server endpoint, it calls the {@link MessageTransport#open(URI, MessageEndpoint)} method with
* the server URI.
*
* Usage example: {@link MessageTransportSnippets#example}
*
* @see org.graalvm.polyglot.Engine.Builder#serverTransport(MessageTransport)
* @see org.graalvm.polyglot.Context.Builder#serverTransport(MessageTransport)
* @since 19.0
*/
public interface MessageTransport {
/**
* Called when a connection to an URI is to be established. The virtualized connection is either
* opened and an endpoint call back is returned, or the connection is not virtualized in which
* case null is returned.
*
* This method can be called concurrently from multiple threads. However, the
* {@link MessageEndpoint} ought to be called on one thread at a time, unless you're sure that
* the particular implementation can handle concurrent calls. The same holds true for the
* returned endpoint, it's called synchronously.
*
* @param uri the connection URI
* @param peerEndpoint the peer endpoint representation
* @return an implementation of {@link MessageEndpoint} call back, or null.
* @throws VetoException to veto connection to the URL.
* @since 19.0
*/
MessageEndpoint open(URI uri, MessageEndpoint peerEndpoint) throws IOException, VetoException;
/**
* Thrown when a transport connection is vetoed. The initiator of the connection is obliged to
* abandon it when this exception is thrown.
*
* @since 19.0
*/
final class VetoException extends Exception {
/**
* Create a new VetoException.
*
* @since 19.0
*/
public VetoException(String message) {
super(message);
}
private static final long serialVersionUID = 3493487569356378902L;
}
}
@SuppressWarnings("all")
class MessageTransportSnippets {
final URI routedURI = URI.create("");
final String denyHost = "";
private InputStream getRouterInputStream() {
return null;
}
private OutputStream getRouterOutputStream() {
return null;
}
public void example() {
// @formatter:off
// BEGIN: MessageTransportSnippets#example
class RoutedServer implements MessageEndpoint {
private final MessageEndpoint remoteEndpoint;
private final OutputStream routerOut = getRouterOutputStream();
private final WritableByteChannel routerOutChannel;
RoutedServer(MessageEndpoint remoteEndpoint) {
this.remoteEndpoint = remoteEndpoint;
this.routerOutChannel = Channels.newChannel(routerOut);
new Thread(() -> {
try {
runInputLoop();
} catch (IOException ex) {
}
}).start();
}
@Override
public void sendText(String text) throws IOException {
routerOut.write(text.getBytes());
routerOut.flush();
}
@Override
public void sendBinary(ByteBuffer data) throws IOException {
routerOutChannel.write(data);
routerOut.flush();
}
@Override
public void sendPing(ByteBuffer data) throws IOException {
remoteEndpoint.sendPong(data);
}
@Override
public void sendPong(ByteBuffer data) throws IOException {
// Did we send ping?
}
@Override
public void sendClose() throws IOException {
routerOut.close();
}
private void runInputLoop() throws IOException {
try (InputStream routerIn = getRouterInputStream()) {
byte[] buf = new byte[1024];
ByteBuffer bb = ByteBuffer.wrap(buf);
int l;
while ((l = routerIn.read(buf)) > 0) {
bb.limit(l);
remoteEndpoint.sendBinary(bb);
bb.rewind();
}
} finally {
remoteEndpoint.sendClose();
}
}
}
Engine.newBuilder().serverTransport(
(uri, peerEndpoint) -> {
if (denyHost.equals(uri.getHost())) {
throw new MessageTransport.VetoException("Denied access.");
} else if (routedURI.equals(uri)) {
return new RoutedServer(peerEndpoint);
} else {
// Permit instruments to setup the servers themselves
return null;
}
}
).build();
// END: MessageTransportSnippets#example
// @formatter:on
}
}