http://hc.apache.org/httpcomponents-core-ga: Apache HttpComponents Core (blocking I/O) (The Apache Software Foundation)
  • Julius Davies
  • Andrea Selva
  • Steffen Pingel
  • Quintin Beukes
  • Marc Beyerle
  • James Abley
  • Michajlo Matijkiw 
/*
 * ====================================================================
 * 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
 * <http://www.apache.org/>.
 *
 */

package org.apache.http;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;


An entity that can be sent or received with an HTTP message. Entities can be found in some requests and in responses, where they are optional. 
 There are three distinct types of entities in HttpCore, depending on where their content originates: 
    

  • streamed: The content is received from a stream, or generated on the fly. In particular, this category includes entities being received from a connection. Streamed entities are generally not repeatable. 
    • 

  • self-contained: The content is in memory or obtained by means that are independent from a connection or other entity. Self-contained entities are generally repeatable. 
    • 

  • wrapping: The content is obtained from another entity.
    
    • 


This distinction is important for connection management with incoming
entities. For entities that are created by an application and only sent
using the HTTP components framework, the difference between streamed
and self-contained is of little importance. In that case, it is suggested
to consider non-repeatable entities as streamed, and those that are
repeatable (without a huge effort) as self-contained.

Since:4.0
/**
 * An entity that can be sent or received with an HTTP message.
 * Entities can be found in some
 * {@link HttpEntityEnclosingRequest requests} and in
 * {@link HttpResponse responses}, where they are optional.
 * <p>
 * There are three distinct types of entities in HttpCore,
 * depending on where their {@link #getContent content} originates:
 * <ul>
 * <li><b>streamed</b>: The content is received from a stream, or
 *     generated on the fly. In particular, this category includes
 *     entities being received from a {@link HttpConnection connection}.
 *     {@link #isStreaming Streamed} entities are generally not
 *      {@link #isRepeatable repeatable}.
 *     </li>
 * <li><b>self-contained</b>: The content is in memory or obtained by
 *     means that are independent from a connection or other entity.
 *     Self-contained entities are generally {@link #isRepeatable repeatable}.
 *     </li>
 * <li><b>wrapping</b>: The content is obtained from another entity.
 *     </li>
 * </ul>
 * This distinction is important for connection management with incoming
 * entities. For entities that are created by an application and only sent
 * using the HTTP components framework, the difference between streamed
 * and self-contained is of little importance. In that case, it is suggested
 * to consider non-repeatable entities as streamed, and those that are
 * repeatable (without a huge effort) as self-contained.
 *
 * @since 4.0
 */
public interface HttpEntity {

    
Tells if the entity is capable of producing its data more than once.
A repeatable entity's getContent() and writeTo(OutputStream) methods
can be called more than once whereas a non-repeatable entity's can not.

Returns:true if the entity is repeatable, false otherwise.
/**
     * Tells if the entity is capable of producing its data more than once.
     * A repeatable entity's getContent() and writeTo(OutputStream) methods
     * can be called more than once whereas a non-repeatable entity's can not.
     * @return true if the entity is repeatable, false otherwise.
     */
    boolean isRepeatable();

    
Tells about chunked encoding for this entity.
The primary purpose of this method is to indicate whether
chunked encoding should be used when the entity is sent.
For entities that are received, it can also indicate whether
the entity was received with chunked encoding.


The behavior of wrapping entities is implementation dependent,
but should respect the primary purpose.



Returns: true if chunked encoding is preferred for this entity, or false if it is not
/**
     * Tells about chunked encoding for this entity.
     * The primary purpose of this method is to indicate whether
     * chunked encoding should be used when the entity is sent.
     * For entities that are received, it can also indicate whether
     * the entity was received with chunked encoding.
     * <p>
     * The behavior of wrapping entities is implementation dependent,
     * but should respect the primary purpose.
     * </p>
     *
     * @return  {@code true} if chunked encoding is preferred for this
     *          entity, or {@code false} if it is not
     */
    boolean isChunked();

    
Tells the length of the content, if known.

Returns: the number of bytes of the content, or a negative number if unknown. If the content length is known but exceeds Long.MAX_VALUE, a negative number is returned.
/**
     * Tells the length of the content, if known.
     *
     * @return  the number of bytes of the content, or
     *          a negative number if unknown. If the content length is known
     *          but exceeds {@link java.lang.Long#MAX_VALUE Long.MAX_VALUE},
     *          a negative number is returned.
     */
    long getContentLength();

    
Obtains the Content-Type header, if known.
This is the header that should be used when sending the entity,
or the one that was received with the entity. It can include a
charset attribute.

Returns: the Content-Type header for this entity, or null if the content type is unknown
/**
     * Obtains the Content-Type header, if known.
     * This is the header that should be used when sending the entity,
     * or the one that was received with the entity. It can include a
     * charset attribute.
     *
     * @return  the Content-Type header for this entity, or
     *          {@code null} if the content type is unknown
     */
    Header getContentType();

    
Obtains the Content-Encoding header, if known.
This is the header that should be used when sending the entity,
or the one that was received with the entity.
Wrapping entities that modify the content encoding should
adjust this header accordingly.

Returns: the Content-Encoding header for this entity, or null if the content encoding is unknown
/**
     * Obtains the Content-Encoding header, if known.
     * This is the header that should be used when sending the entity,
     * or the one that was received with the entity.
     * Wrapping entities that modify the content encoding should
     * adjust this header accordingly.
     *
     * @return  the Content-Encoding header for this entity, or
     *          {@code null} if the content encoding is unknown
     */
    Header getContentEncoding();

    
Returns a content stream of the entity. Repeatable entities are expected to create a new instance of InputStream for each invocation of this method and therefore can be consumed multiple times. Entities that are not repeatable are expected to return the same InputStream instance and therefore may not be consumed more than once. 
 IMPORTANT: Please note all entity implementations must ensure that all allocated resources are properly deallocated after the InputStream.close() method is invoked. 
Throws:
See Also:
Returns:content stream of the entity.
/**
     * Returns a content stream of the entity.
     * {@link #isRepeatable Repeatable} entities are expected
     * to create a new instance of {@link InputStream} for each invocation
     * of this method and therefore can be consumed multiple times.
     * Entities that are not {@link #isRepeatable repeatable} are expected
     * to return the same {@link InputStream} instance and therefore
     * may not be consumed more than once.
     * <p>
     * IMPORTANT: Please note all entity implementations must ensure that
     * all allocated resources are properly deallocated after
     * the {@link InputStream#close()} method is invoked.
     *
     * @return content stream of the entity.
     *
     * @throws IOException if the stream could not be created
     * @throws UnsupportedOperationException
     *  if entity content cannot be represented as {@link java.io.InputStream}.
     *
     * @see #isRepeatable()
     */
    InputStream getContent() throws IOException, UnsupportedOperationException;

    
Writes the entity content out to the output stream.


IMPORTANT: Please note all entity implementations must ensure that
all allocated resources are properly deallocated when this method
returns.

Params:
  • outStream – the output stream to write entity content to
Throws:
/**
     * Writes the entity content out to the output stream.
     * <p>
     * IMPORTANT: Please note all entity implementations must ensure that
     * all allocated resources are properly deallocated when this method
     * returns.
     *
     * @param outStream the output stream to write entity content to
     *
     * @throws IOException if an I/O error occurs
     */
    void writeTo(OutputStream outStream) throws IOException;

    
Tells whether this entity depends on an underlying stream. Streamed entities that read data directly from the socket should return true. Self-contained entities should return false. Wrapping entities should delegate this call to the wrapped entity. 
Returns: true if the entity content is streamed, false otherwise
/**
     * Tells whether this entity depends on an underlying stream.
     * Streamed entities that read data directly from the socket should
     * return {@code true}. Self-contained entities should return
     * {@code false}. Wrapping entities should delegate this call
     * to the wrapped entity.
     *
     * @return  {@code true} if the entity content is streamed,
     *          {@code false} otherwise
     */
    boolean isStreaming(); // don't expect an exception here

    
This method is deprecated since version 4.1. Please use standard java convention to ensure resource deallocation by calling InputStream.close() on the input stream returned by getContent() 

This method is called to indicate that the content of this entity
is no longer required. All entity implementations are expected to
release all allocated resources as a result of this method
invocation. Content streaming entities are also expected to
dispose of the remaining content, if any. Wrapping entities should
delegate this call to the wrapped entity.

 This method is of particular importance for entities being received from a connection. The entity needs to be consumed completely in order to re-use the connection with keep-alive. 
Throws:
See Also:
Deprecated:(4.1) Use EntityUtils.consume(HttpEntity)
/**
     * This method is deprecated since version 4.1. Please use standard
     * java convention to ensure resource deallocation by calling
     * {@link InputStream#close()} on the input stream returned by
     * {@link #getContent()}
     * <p>
     * This method is called to indicate that the content of this entity
     * is no longer required. All entity implementations are expected to
     * release all allocated resources as a result of this method
     * invocation. Content streaming entities are also expected to
     * dispose of the remaining content, if any. Wrapping entities should
     * delegate this call to the wrapped entity.
     * <p>
     * This method is of particular importance for entities being
     * received from a {@link HttpConnection connection}. The entity
     * needs to be consumed completely in order to re-use the connection
     * with keep-alive.
     *
     * @throws IOException if an I/O error occurs.
     *
     * @deprecated (4.1) Use {@link org.apache.http.util.EntityUtils#consume(HttpEntity)}
     *
     * @see #getContent() and #writeTo(OutputStream)
     */
    @Deprecated
    void consumeContent() throws IOException;

}