HttpEntity类型有哪些

BasicHttpEntity

 

 代表底层流的基本实体。通常是在http报文中获取的实体。他只有一个空参的构造方法。

刚创建时没有内容，长度为负值。需要通过两个方法，把值赋进去。

 

/**
     * BasicHttpEntity
     * @throws IOException
     */
    public static void testBasicHttpEntity() throws IOException{
        InputStream is = null;
        //BasicHttpEntity这类就是一个输入流的内容包装类，包装内容的相关的编码格式，长度等
        BasicHttpEntity entity = new BasicHttpEntity();
        //设置内容
        entity.setContent(is);
        //设置长度
        entity.setContentLength(is.available());
        //没搞懂chunked这个属性啥意思
        entity.setChunked(false);
    }

 

ByteArrayEntity

 是自我包含的，可重复获得使用的，从指定的字节数组中取出内容的实体。

字节数组是这个实体的构造方法的参数

 

/**
     * ByteArrayEntity
     * @throws IOException
     */
    public static void testByteArrayEntity() throws IOException{
        ByteArrayEntity entity = new ByteArrayEntity("内容".getBytes());
        ByteArrayInputStream is = (ByteArrayInputStream) entity.getContent();
        //上面这行代码返回的其实是一个ByteArrayInputStream对象
        /*public InputStream getContent() {
            return new ByteArrayInputStream(this.b, this.off, this.len);
        }*/
    }

 

StringEntity

是自我包含的可重复的实体。通过String创建的实体

有两个构造方法，一个是自Sring为参数的构造方法，一个是以String和字符编码为参数的构造方法。

 

/**
     * StringEntity
     * @throws IOException
     */
    public static void testStringEntity() throws IOException{
         StringBuilder sb = new StringBuilder();
         //获取系统的信息集合，这个集合是不可以修改的
         Map<String, String> nev = System.getenv();
         for(Entry<String, String> entry : nev.entrySet()){
             sb.append(entry.getKey()).append("=")
             .append(entry.getValue()).append("\n");
         }
         String content = sb.toString();
         System.out.println(content);
         //创建只带字符串参数的
         StringEntity entity = new StringEntity(content);
         //创建带字符创参数和字符编码的
         StringEntity entity2 = new StringEntity(content, "UTF-8");

    }

 

InputreamEntity

是流式不可以重复的实体。构造方法是InputStream 和内容长度，内容长度是输入流的长度

 

/**
     * InputStreamEntity
     * @throws IOException
     */
    public static void testInputStreamEntity() throws IOException{
        InputStream is = null;
        //InputStreamEntity严格是对内容和长度相匹配的。用法和BasicHttpEntity类似
        InputStreamEntity entity = new InputStreamEntity(is, is.available());
    }

 

FileEntity

自我包含式，可以重复的实体。参数传入文件和文件类型。

 

 

/**
     * FileEntity
     * @throws IOException
     */
    public static void testFileEntity() throws IOException{
         FileEntity entity = new FileEntity(new File(""), ContentType.APPLICATION_FORM_URLENCODED);
         FileEntity entity2 = new FileEntity(new File(""), "application/java-achive");

    }

 

EntityTemplete

从ContentProducer接口接受内容的实体。

在ContentProducer的实现类中写入想要写入的内容。

 

/**
     * EntityTemplate
     * @throws IOException
     */
    public static void testEntityTemplate() throws IOException{
        ContentProducer producer = new ContentProducer() {

            @Override
            public void writeTo(OutputStream outstream) throws IOException {
                outstream.write("这是什么东东》。".getBytes());
            }
        };

        EntityTemplate entity = new EntityTemplate(producer);
        entity.writeTo(System.out);
    }

 

 

HttpEntityWrapper

这个是创建被包装实体的基类，有被包装实体的引用。

相当于实体的代理类，被包装实体是他的一个属性。

下面是这个类的源码：

 

/*
 * ====================================================================
 * 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.entity;

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

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.annotation.NotThreadSafe;

/**
 * Base class for wrapping entities.
 * Keeps a {@link #wrappedEntity wrappedEntity} and delegates all
 * calls to it. Implementations of wrapping entities can derive
 * from this class and need to override only those methods that
 * should not be delegated to the wrapped entity.
 *
 * @since 4.0
 */
@NotThreadSafe
public class HttpEntityWrapper implements HttpEntity {

    /** The wrapped entity. */
    protected HttpEntity wrappedEntity;

    /**
     * Creates a new entity wrapper.
     *
     * @param wrapped   the entity to wrap, not null
     * @throws IllegalArgumentException if wrapped is null
     */
    public HttpEntityWrapper(HttpEntity wrapped) {
        super();

        if (wrapped == null) {
            throw new IllegalArgumentException
                ("wrapped entity must not be null");
        }
        wrappedEntity = wrapped;

    } // constructor


    public boolean isRepeatable() {
        return wrappedEntity.isRepeatable();
    }

    public boolean isChunked() {
        return wrappedEntity.isChunked();
    }

    public long getContentLength() {
        return wrappedEntity.getContentLength();
    }

    public Header getContentType() {
        return wrappedEntity.getContentType();
    }

    public Header getContentEncoding() {
        return wrappedEntity.getContentEncoding();
    }

    public InputStream getContent()
        throws IOException {
        return wrappedEntity.getContent();
    }

    public void writeTo(OutputStream outstream)
        throws IOException {
        wrappedEntity.writeTo(outstream);
    }

    public boolean isStreaming() {
        return wrappedEntity.isStreaming();
    }

    /**
     * @deprecated (4.1) Either use {@link #getContent()} and call {@link java.io.InputStream#close()} on that;
     * otherwise call {@link #writeTo(OutputStream)} which is required to free the resources.
     */
    @Deprecated
    public void consumeContent() throws IOException {
        wrappedEntity.consumeContent();
    }

}

 

BufferedHttpEntity

是HttpEntityWarpper的子类，可以把不可以重复的实体，实现成可以重复的实体。

它从提供的实体中读取内容，缓存到内容中。

源码如下：

 

/*
 * ====================================================================
 * 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.entity;

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

import org.apache.http.HttpEntity;
import org.apache.http.annotation.NotThreadSafe;
import org.apache.http.util.EntityUtils;

/**
 * A wrapping entity that buffers it content if necessary.
 * The buffered entity is always repeatable.
 * If the wrapped entity is repeatable itself, calls are passed through.
 * If the wrapped entity is not repeatable, the content is read into a
 * buffer once and provided from there as often as required.
 *
 * @since 4.0
 */
@NotThreadSafe
public class BufferedHttpEntity extends HttpEntityWrapper {

    private final byte[] buffer;

    /**
     * Creates a new buffered entity wrapper.
     *
     * @param entity   the entity to wrap, not null
     * @throws IllegalArgumentException if wrapped is null
     */
    public BufferedHttpEntity(final HttpEntity entity) throws IOException {
        super(entity);
        if (!entity.isRepeatable() || entity.getContentLength() < 0) {
            this.buffer = EntityUtils.toByteArray(entity);
        } else {
            this.buffer = null;
        }
    }

    @Override
    public long getContentLength() {
        if (this.buffer != null) {
            return this.buffer.length;
        } else {
            return wrappedEntity.getContentLength();
        }
    }

    @Override
    public InputStream getContent() throws IOException {
        if (this.buffer != null) {
            return new ByteArrayInputStream(this.buffer);
        } else {
            return wrappedEntity.getContent();
        }
    }

    /**
     * Tells that this entity does not have to be chunked.
     *
     * @return  <code>false</code>
     */
    @Override
    public boolean isChunked() {
        return (buffer == null) && wrappedEntity.isChunked();
    }

    /**
     * Tells that this entity is repeatable.
     *
     * @return  <code>true</code>
     */
    @Override
    public boolean isRepeatable() {
        return true;
    }


    @Override
    public void writeTo(final OutputStream outstream) throws IOException {
        if (outstream == null) {
            throw new IllegalArgumentException("Output stream may not be null");
        }
        if (this.buffer != null) {
            outstream.write(this.buffer);
        } else {
            wrappedEntity.writeTo(outstream);
        }
    }


    // non-javadoc, see interface HttpEntity
    @Override
    public boolean isStreaming() {
        return (buffer == null) && wrappedEntity.isStreaming();
    }

} // class BufferedHttpEntity