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Apache HttpComponents Core (blocking I/O)
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/*
 * ====================================================================
 * 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
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 *
 */

package org.apache.http;

import java.io.Closeable;
import java.io.IOException;

/**
 * A generic HTTP connection, useful on client and server side.
 *
 * @since 4.0
 */
public interface HttpConnection extends Closeable {

    /**
     * Closes this connection gracefully.
     * This method will attempt to flush the internal output
     * buffer prior to closing the underlying socket.
     * This method MUST NOT be called from a different thread to force
     * shutdown of the connection. Use {@link #shutdown shutdown} instead.
     */
    @Override
    void close() throws IOException;

    /**
     * Checks if this connection is open.
     * @return true if it is open, false if it is closed.
     */
    boolean isOpen();

    /**
     * Checks whether this connection has gone down.
     * Network connections may get closed during some time of inactivity
     * for several reasons. The next time a read is attempted on such a
     * connection it will throw an IOException.
     * This method tries to alleviate this inconvenience by trying to
     * find out if a connection is still usable. Implementations may do
     * that by attempting a read with a very small timeout. Thus this
     * method may block for a small amount of time before returning a result.
     * It is therefore an expensive operation.
     *
     * @return  {@code true} if attempts to use this connection are
     *          likely to succeed, or {@code false} if they are likely
     *          to fail and this connection should be closed
     */
    boolean isStale();

    /**
     * Sets the socket timeout value.
     *
     * @param timeout timeout value in milliseconds
     */
    void setSocketTimeout(int timeout);

    /**
     * Returns the socket timeout value.
     *
     * @return positive value in milliseconds if a timeout is set,
     * {@code 0} if timeout is disabled or {@code -1} if
     * timeout is undefined.
     */
    int getSocketTimeout();

    /**
     * Force-closes this connection.
     * This is the only method of a connection which may be called
     * from a different thread to terminate the connection.
     * This method will not attempt to flush the transmitter's
     * internal buffer prior to closing the underlying socket.
     */
    void shutdown() throws IOException;

    /**
     * Returns a collection of connection metrics.
     *
     * @return HttpConnectionMetrics
     */
    HttpConnectionMetrics getMetrics();

}