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package com.sun.xml.internal.ws.api.pipe;

import com.sun.xml.internal.ws.api.message.Message;

import com.sun.xml.internal.ws.api.message.Packet;

import com.sun.xml.internal.ws.api.pipe.helper.AbstractFilterPipeImpl;

import com.sun.xml.internal.ws.api.pipe.helper.AbstractPipeImpl;

import javax.annotation.PreDestroy;

import javax.xml.ws.Dispatch;

import javax.xml.ws.Provider;

import javax.xml.ws.WebServiceException;

import javax.xml.ws.handler.Handler;

import javax.xml.ws.handler.LogicalHandler;

import javax.xml.ws.handler.MessageContext;

import javax.xml.ws.handler.soap.SOAPHandler;

/**

 * Abstraction of the intermediate layers in the processing chain

 * and transport.

 *

 * <h2>What is a {@link Pipe}?</h2>

 * <p>

 * Transport is a kind of pipe. It sends the {@link Packet}

 * through, say, HTTP connection, and receives the data back into another {@link Packet}.

 *

 * <p>

 * More often, a pipe is a filter. It acts on a packet,

 * and then it passes the packet into another pipe. It can

 * do the same on the way back.

 *

 * <p>

 * For example, XWSS will be a {@link Pipe}

 * that delegates to another {@link Pipe}, and it can wrap a {@link Packet} into

 * another {@link Packet} to encrypt the body and add a header, for example.

 *

 * <p>

 * Yet another kind of filter pipe is those that wraps {@link LogicalHandler}

 * and {@link SOAPHandler}. These pipes are heavy-weight; they often consume

 * a message in a packet and create a new one, and then pass it to the next pipe.

 * For performance reason it probably makes sense to have one {@link Pipe}

 * instance that invokes a series of {@link LogicalHandler}s, another one

 * for {@link SOAPHandler}.

 *

 * <p>

 * There would be a {@link Pipe} implementation that invokes {@link Provider}.

 * There would be a {@link Pipe} implementation that invokes a service method

 * on the user's code.

 * There would be a {@link Dispatch} implementation that invokes a {@link Pipe}.

 *

 * <p>

 * WS-MEX can be implemented as a {@link Pipe} that looks for

 * {@link Message#getPayloadNamespaceURI()} and serves the request.

 *

 *

 * <h2>Pipe Lifecycle</h2>

 * {@link Pipe}line is expensive to set up, so once it's created it will be reused.

 * A {@link Pipe}line is not reentrant; one pipeline is used to process one request/response

 * at at time. The same pipeline instance may serve request/response for different threads,

 * if one comes after another and they don't overlap.

 * <p>

 * Where a need arises to process multiple requests concurrently, a pipeline

 * gets cloned through {@link PipeCloner}. Note that this need may happen on

 * both server (because it quite often serves multiple requests concurrently)

 * and client (because it needs to support asynchronous method invocations.)

 * <p>

 * Created pipelines (including cloned ones and the original) may be discarded and GCed

 * at any time at the discretion of whoever owns pipelines. Pipes can, however, expect

 * at least one copy (or original) of pipeline to live at any given time while a pipeline

 * owner is interested in the given pipeline configuration (in more concerete terms,

 * for example, as long as a dispatch object lives, it's going to keep at least one

 * copy of a pipeline alive.)

 * <p>

 * Before a pipeline owner dies, it may invoke {@link #preDestroy()} on the last

 * remaining pipeline. It is "may" for pipeline owners that live in the client-side

 * of JAX-WS (such as dispatches and proxies), but it is a "must" for pipeline owners

 * that live in the server-side of JAX-WS.

 * <p>

 * This last invocation gives a chance for some pipes to clean up any state/resource

 * acquired (such as WS-RM's sequence, WS-Trust's SecurityToken), although as stated above,

 * this is not required for clients.

 *

 *

 *

 * <h2>Pipe and State</h2>

 * <p>

 * The lifecycle of pipelines is designed to allow a {@link Pipe} to store various

 * state in easily accessible fashion.

 *

 *

 * <h3>Per-packet state</h3>

 * <p>

 * Any information that changes from a packet to packet should be

 * stored in {@link Packet}. This includes information like

 * transport-specific headers.

 *

 * <h3>Per-thread state</h3>

 * <p>

 * Any expensive objects that are non-reentrant can be stored in

 * instance variables of a {@link Pipe}, since {@link #process(Packet)} is

 * non reentrant. When a pipe is copied, new instances should be allocated

 * so that two {@link Pipe} instances don't share thread-unsafe resources.

 * This includes things like canonicalizers, JAXB unmarshallers, buffers,

 * and so on.

 *

 * <h3>Per-proxy/per-endpoint state</h3>

 * <p>

 * Information that is tied to a particular proxy/dispatch can be stored

 * in a separate object that is referenced from a pipe. When

 * a new pipe is copied, you can simply hand out a reference to the newly

 * created one, so that all copied pipes refer to the same instance.

 * See the following code as an example:

 *

 * <pre>

 * class PipeImpl {

 *   // this object stores per-proxy state

 *   class DataStore {

 *     int counter;

 *   }

 *

 *   private DataStore ds;

 *

 *   // create a fresh new pipe

 *   public PipeImpl(...) {

 *     ....

 *     ds = new DataStore();

 *   }

 *

 *   // copy constructor

 *   private PipeImpl(PipeImpl that, PipeCloner cloner) {

 *     cloner.add(that,this);

 *     ...

 *     this.ds = that.ds;

 *   }

 *

 *   public PipeImpl copy(PipeCloner pc) {

 *     return new PipeImpl(this,pc);

 *   }

 * }

 * </pre>

 *

 * <p>

 * Note that access to such resource often needs to be synchronized,

 * since multiple copies of pipelines may execute concurrently.

 *

 * <p>

 * If such information is read-only,

 * it can be stored as instance variables of a pipe,

 * and its reference copied as pipes get copied. (The only difference between

 * this and per-thread state is that you just won't allocate new things when

 * pipes get copied here.)

 *

 *

 * <h3>VM-wide state</h3>

 * <p>

 *

 *

 *

 * <h2>Pipes and Handlers</h2>

 * <p>

 * JAX-WS has a notion of {@link LogicalHandler} and {@link SOAPHandler}, and

 * we intend to have one {@link Pipe} implementation that invokes all the

 * {@link LogicalHandler}s and another {@link Pipe} implementation that invokes

 * all the {@link SOAPHandler}s. Those implementations need to convert a {@link Message}

 * into an appropriate format, but grouping all the handlers together eliminates

 * the intermediate {@link Message} instanciation between such handlers.

 * <p>

 * This grouping also allows such implementations to follow the event notifications

 * to handlers (i.e. {@link Handler#close(MessageContext)} method.

 *

 *

 * <pre>

 * TODO: Possible types of pipe:

 *      creator: create message from wire

 *          to SAAJ SOAP message

 *          to cached representation

 *          directly to JAXB beans

 *      transformer: transform message from one representation to another

 *          JAXB beans to encoded SOAP message

 *          StAX writing + JAXB bean to encoded SOAP message

 *      modifier: modify message

 *          add SOAP header blocks

 *          security processing

 *      header block processor:

 *          process certain SOAP header blocks

 *      outbound initiator: input from the client

 *          Manage input e.g. JAXB beans and associated with parts of the SOAP message

 *      inbound invoker: invoke the service

 *         Inkoke SEI, e.g. EJB or SEI in servlet.

 * </pre>

 *

 * @see AbstractPipeImpl

 * @see AbstractFilterPipeImpl

 * @deprecated

 *      Use {@link Tube}.

 */

public interface Pipe {

    /**

     * Sends a {@link Packet} and returns a response {@link Packet} to it.

     *

     * @throws WebServiceException

     *      On the server side, this signals an error condition where

     *      a fault reply is in order (or the exception gets eaten by

     *      the top-most transport {@link Pipe} if it's one-way.)

     *      This frees each {@link Pipe} from try/catching a

     *      {@link WebServiceException} in every layer.

     *

     *      Note that this method is also allowed to return a {@link Packet}

     *      that has a fault as the payload.

     *

     *      <p>

     *      On the client side, the {@link WebServiceException} thrown

     *      will be propagated all the way back to the calling client

     *      applications. (The consequence of that is that if you are

     *      a filtering {@link Pipe}, you must not catch the exception

     *      that your next {@link Pipe} threw.

     *

     * @throws RuntimeException

     *      Other runtime exception thrown by this method must

     *      be treated as a bug in the pipe implementation,

     *      and therefore should not be converted into a fault.

     *      (Otherwise it becomes very difficult to debug implementation

     *      problems.)

     *

     *      <p>

     *      On the server side, this exception should be most likely

     *      just logged. On the client-side it gets propagated to the

     *      client application.

     *

     *      <p>

     *      The consequence of this is that if a pipe calls

     *      into an user application (such as {@link SOAPHandler}

     *      or {@link LogicalHandler}), where a {@link RuntimeException}

     *      is *not* a bug in the JAX-WS implementation, it must be catched

     *      and wrapped into a {@link WebServiceException}.

     *

     * @param request

     *      The packet that represents a request message. Must not be null.

     *      If the packet has a non-null message, it must be a valid

     *      unconsumed {@link Message}. This message represents the

     *      SOAP message to be sent as a request.

     *      <p>

     *      The packet is also allowed to carry no message, which indicates

     *      that this is an output-only request.

     *      (that's called "solicit", right? - KK)

     *

     * @return

     *      The packet that represents a response message. Must not be null.

     *      If the packet has a non-null message, it must be

     *      a valid unconsumed {@link Message}. This message represents

     *      a response to the request message passed as a parameter.

     *      <p>

     *      The packet is also allowed to carry no message, which indicates

     *      that there was no response. This is used for things like

     *      one-way message and/or one-way transports.

     */

    Packet process( Packet request);

    /**

     * Invoked before the last copy of the pipeline is about to be discarded,

     * to give {@link Pipe}s a chance to clean up any resources.

     *

     * <p>

     * This can be used to invoke {@link PreDestroy} lifecycle methods

     * on user handler. The invocation of it is optional on the client side,

     * but mandatory on the server side.

     *

     * <p>

     * When multiple copies of pipelines are created, this method is called

     * only on one of them.

     *

     * @throws WebServiceException

     *      If the clean up fails, {@link WebServiceException} can be thrown.

     *      This exception will be propagated to users (if this is client),

     *      or recorded (if this is server.)

     */

    void preDestroy();

    /**

     * Creates an identical clone of this {@link Pipe}.

     *

     * <p>

     * This method creates an identical pipeline that can be used

     * concurrently with this pipeline. When the caller of a pipeline

     * is multi-threaded and need concurrent use of the same pipeline,

     * it can do so by creating copies through this method.

     *

     * <h3>Implementation Note</h3>

     * <p>

     * It is the implementation's responsibility to call

     * {@link PipeCloner#add(Pipe,Pipe)} to register the copied pipe

     * with the original. This is required before you start copying

     * the other {@link Pipe} references you have, or else there's a

     * risk of infinite recursion.

     * <p>

     * For most {@link Pipe} implementations that delegate to another

     * {@link Pipe}, this method requires that you also copy the {@link Pipe}

     * that you delegate to.

     * <p>

     * For limited number of {@link Pipe}s that do not maintain any

     * from this method (notice that even if you are stateless, if you

     * got a delegating {@link Pipe} and that one isn't stateless, you

     * still have to copy yourself.)

     *

     * <p>

     * Note that this method might be invoked by one thread while another

     * thread is executing the {@link #process(Packet)} method. See

     * the {@link Codec#copy()} for more discussion about this.

     *

     * @param cloner

     *      Use this object (in particular its {@link PipeCloner#copy(Pipe)} method

     *      to clone other pipe references you have

     *      in your pipe. See {@link PipeCloner} for more discussion

     *      about why.

     *

     * @return

     *      always non-null {@link Pipe}.

     */

    Pipe copy(PipeCloner cloner);

}