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25
26package com.sun.xml.internal.ws.api.server;
27
28import com.sun.istack.internal.NotNull;
29
30import javax.xml.ws.Provider;
31import javax.xml.ws.WebServiceContext;
32import java.util.concurrent.Executor;
33
34/**
35 * Asynchronous version of {@link Provider}.
36 *
37 * <p>
38 * Applications that use the JAX-WS RI can implement this interface instead of
39 * {@link Provider} to implement asynchronous web services (AWS.) AWS enables
40 * applications to perform operations with long latency without blocking a thread,
41 * and thus particularly suitable for highly scalable service implementation,
42 * at the expesnce of implementation complexity.
43 *
44 * <h2>Programming Model</h2>
45 * <p>
46 * Whenever a new reuqest arrives, the JAX-WS RI invokes the {@link #invoke} method
47 * to notify the application. Normally, the application then schedules an execution
48 * of this request, and exit from this method immediately (the point of AWS is not
49 * to use this calling thread for request processing.)
50 *
51 * <p>
52 * Unlike the synchronous version, which requires the response to be given as the return value,
53 * with AWS the JAX-WS RI will keep the connection with client open, until the application
54 * eventually notifies the JAX-WS RI via {@link AsyncProviderCallback}. When that
55 * happens that causes the JAX-WS RI to send back a response to the client.
56 *
57 * <p>
58 * The following code shows a very simple AWS example:
59 *
60 * <pre>
61 * &#64;WebService
62 * class MyAsyncEchoService implements AsyncProvider&lt;Source> {
63 *     private static final {@link Executor} exec = ...;
64 *
65 *     public void invoke( final Source request, final AsyncProviderCallback&lt;Source> callback, final WebServiceContext context) {
66 *         exec.execute(new {@link Runnable}() {
67 *             public void run() {
68 *                 Thread.sleep(1000);     // kill time.
69 *                 callback.send(request); // just echo back
70 *             }
71 *         });
72 *     }
73 * }
74 * </pre>
75 *
76 * <p>
77 * Please also check the {@link Provider} and its programming model for general
78 * provider programming model.
79 *
80 *
81 * <h2>WebServiceContext</h2>
82 * <p>
83 * In synchronous web services, the injected {@link WebServiceContext} instance uses
84 * the calling {@link Thread} to determine which request it should return information about.
85 * This no longer works with AWS, as you may need to call {@link WebServiceContext}
86 * much later, possibly from entirely different thread.
87 *
88 * <p>
89 * For this reason, {@link AsyncProvider} passes in {@link WebServiceContext} as
90 * a parameter. This object remains usable until you invoke {@link AsyncProviderCallback},
91 * and it can be invoked from any thread, even concurrently. AWS must not use the injected
92 * {@link WebServiceContext}, as its behavior is undefined.
93 *
94 * @see Provider
95 * @author Jitendra Kotamraju
96 * @author Kohsuke Kawaguchi
97 * @since 2.1
98 */
99public interface AsyncProvider<T> {
100    /**
101     * Schedules an execution of a request.
102     *
103     * @param request
104     *      Represents the request message or payload.
105     * @param callback
106     *      Application must notify this callback interface when the processing
107     *      of a request is complete.
108     * @param context
109     *      The web service context instance that can be used to retrieve
110     *      context information about the given request.
111     */
112    public void invoke(
113        @NotNull T request,
114        @NotNull AsyncProviderCallback<T> callback,
115        @NotNull WebServiceContext context);
116}
117