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JSR 356: Java API for WebSocket
/*
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*
* Copyright (c) 2012-2013 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* http://glassfish.java.net/public/CDDL+GPL_1_1.html
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* language governing permissions and limitations under the License.
*
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* file and include the License file at packager/legal/LICENSE.txt.
*
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* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
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*/
package javax.websocket;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* This method level annotation can be used to make a Java method receive incoming web socket messages. Each websocket
* endpoint may only have one message handling method for each of the native websocket message formats: text, binary and pong. Methods
* using this annotation are allowed to have
* parameters of types described below, otherwise the container will generate an error at deployment time.
* The allowed parameters are:
*
* - Exactly one of any of the following choices
*
* if the method is handling text messages:
* - {@link java.lang.String} to receive the whole message
* - Java primitive or class equivalent to receive the whole message converted to that type
* - String and boolean pair to receive the message in parts
* - {@link java.io.Reader} to receive the whole message as a blocking stream
* - any object parameter for which the endpoint has a text decoder ({@link Decoder.Text} or
* {@link Decoder.TextStream}).
* if the method is handling binary messages:
* - byte[] or {@link java.nio.ByteBuffer} to receive the whole message
* - byte[] and boolean pair, or {@link java.nio.ByteBuffer} and boolean pair to receive the message in parts
* - {@link java.io.InputStream} to receive the whole message as a blocking stream
* - any object parameter for which the endpoint has a binary decoder ({@link Decoder.Binary} or
* {@link Decoder.BinaryStream}).
* if the method is handling pong messages:
* - {@link PongMessage} for handling pong messages
*
* - and Zero to n String or Java primitive parameters
* annotated with the {@link javax.websocket.server.PathParam} annotation for server endpoints.
* - and an optional {@link Session} parameter
*
*
* The parameters may be listed in any order.
* The method may have a non-void return type, in which case the web socket runtime must interpret this as a
* web socket message to return to the peer. The allowed data types for this return type, other than void, are
* String, ByteBuffer, byte[], any Java primitive or class equivalent, and anything for which there is an encoder.
* If the method uses a Java primitive as a return value, the implementation must construct the text
* message to send using the standard Java string representation of the Java primitive. If the method uses a class
* equivalent of a Java primitive as a return value, the implementation must construct the text message
* from the Java primitive equivalent as described above.
*
* Developers should
* note that if developer closes the session during the invocation of a method with a return type, the method will complete but the
* return value will not be delivered to the remote endpoint. The send failure will be passed back into the endpoint's error handling method.
*
* For example:
*
*
* @OnMessage
* public void processGreeting(String message, Session session) {
* System.out.println("Greeting received:" + message);
* }
*
*
* For example:
*
*
* @OnMessage
* public void processUpload(byte[] b, boolean last, Session session) {
* // process partial data here, which check on last to see if these is more on the way
* }
*
*
* Developers should not continue to reference message objects of type {@link java.io.Reader}, {@link java.nio.ByteBuffer}
* or {@link java.io.InputStream} after the annotated method has completed, since they
* may be recycled by the implementation.
*
* @author dannycoward
* @since Draft 002
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface OnMessage {
/**
* Specifies the maximum size of message in bytes that the method
* this annotates will be able to process, or -1 to indicate
* that there is no maximum. The default is -1.
*
* @return the maximum size in bytes.
*/
public long maxMessageSize() default -1;
}