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一 HttpEntity的类型

1  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。

1. /**

2. * BasicHttpEntity

3. * @throws IOException

4. */

5. public static void testBasicHttpEntity() throws IOException{


6. InputStream is = null;

7. //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

8. BasicHttpEntity entity = new BasicHttpEntity();

9. //设置内容

10. entity.setContent(is);

11. //设置长度

12. entity.setContentLength(is.available());

13. //没搞懂chunked这个属性啥意思

14. entity.setChunked(false);

15. }

2  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。

1. /**

2. * ByteArrayEntity

3. * @throws IOException

4. */

5. public static void testByteArrayEntity() throws IOException{


6. ByteArrayEntity entity = new ByteArrayEntity("内容".getBytes());

7. ByteArrayInputStream is = (ByteArrayInputStream) entity.getContent();

8. //上面这行代码返回的其实是一个ByteArrayInputStream对象

9. /*public InputStream getContent() {


10. return new ByteArrayInputStream(this.b, this.off, this.len);

11. }*/

12. }

3  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。

1. /**

2. * StringEntity

3. * @throws IOException

4. */

5. public static void testStringEntity() throws IOException{


6. StringBuilder sb = new StringBuilder();

7. //获取系统的信息集合，这个集合是不可以修改的

8. Map<String, String> nev = System.getenv();

9. for(Entry<String, String> entry : nev.entrySet()){


10. sb.append(entry.getKey()).append("=")

11. .append(entry.getValue()).append("\n");

12. }

13. String content = sb.toString();

14. System.out.println(content);

15. //创建只带字符串参数的

16. StringEntity entity = new StringEntity(content);

17. //创建带字符创参数和字符编码的

18. StringEntity entity2 = new StringEntity(content, "UTF-8");

19.  

20. }

4  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。

1. /**

2. * InputStreamEntity

3. * @throws IOException

4. */

5. public static void testInputStreamEntity() throws IOException{


6. InputStream is = null;

7. //InputStreamEntity严格是对内容和长度相匹配的。用法和BasicHttpEntity类似

8. InputStreamEntity entity = new InputStreamEntity(is, is.available());

9. }

5  FileEntity

    自我包含式，可以重复的实体。参数传入文件和文件类型。

1. /**

2. * FileEntity

3. * @throws IOException

4. */

5. public static void testFileEntity() throws IOException{


6. FileEntity entity = new FileEntity(new File(""), ContentType.APPLICATION_FORM_URLENCODED);

7. FileEntity entity2 = new FileEntity(new File(""), "application/java-achive");

8.  

9. }

6  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。

1. /**

2. * EntityTemplate

3. * @throws IOException

4. */

5. public static void testEntityTemplate() throws IOException{


6. ContentProducer producer = new ContentProducer() {


7.  

8. @Override

9. public void writeTo(OutputStream outstream) throws IOException {


10. outstream.write("这是什么东东》。".getBytes());

11. }

12. };

13.  

14. EntityTemplate entity = new EntityTemplate(producer);

15. entity.writeTo(System.out);

16. }

7  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：

1. /*

2. * ====================================================================

3. * Licensed to the Apache Software Foundation (ASF) under one

4. * or more contributor license agreements. See the NOTICE file

5. * distributed with this work for additional information

6. * regarding copyright ownership. The ASF licenses this file

7. * to you under the Apache License, Version 2.0 (the

8. * "License"); you may not use this file except in compliance

9. * with the License. You may obtain a copy of the License at

10. *

11. * http://www.apache.org/licenses/LICENSE-2.0

12. *

13. * Unless required by applicable law or agreed to in writing,

14. * software distributed under the License is distributed on an

15. * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

16. * KIND, either express or implied. See the License for the

17. * specific language governing permissions and limitations

18. * under the License.

19. * ====================================================================

20. *

21. * This software consists of voluntary contributions made by many

22. * individuals on behalf of the Apache Software Foundation. For more

23. * information on the Apache Software Foundation, please see

24. * <http://www.apache.org/>.

25. *

26. */

27.  

28. package org.apache.http.entity;

29.  

30. import java.io.IOException;

31. import java.io.InputStream;

32. import java.io.OutputStream;

33.  

34. import org.apache.http.Header;

35. import org.apache.http.HttpEntity;

36. import org.apache.http.annotation.NotThreadSafe;

37.  

38. /**

39. * Base class for wrapping entities.

40. * Keeps a {@link #wrappedEntity wrappedEntity} and delegates all

41. * calls to it. Implementations of wrapping entities can derive

42. * from this class and need to override only those methods that

43. * should not be delegated to the wrapped entity.

44. *

45. * @since 4.0

46. */

47. @NotThreadSafe

48. public class HttpEntityWrapper implements HttpEntity {


49.  

50. /** The wrapped entity. */

51. protected HttpEntity wrappedEntity;

52.  

53. /**

54. * Creates a new entity wrapper.

55. *

56. * @param wrapped the entity to wrap, not null

57. * @throws IllegalArgumentException if wrapped is null

58. */

59. public HttpEntityWrapper(HttpEntity wrapped) {


60. super();

61.  

62. if (wrapped == null) {


63. throw new IllegalArgumentException

64. ("wrapped entity must not be null");

65. }

66. wrappedEntity = wrapped;

67.  

68. } // constructor

69.  
70.  

71. public boolean isRepeatable() {


72. return wrappedEntity.isRepeatable();

73. }

74.  

75. public boolean isChunked() {


76. return wrappedEntity.isChunked();

77. }

78.  

79. public long getContentLength() {


80. return wrappedEntity.getContentLength();

81. }

82.  

83. public Header getContentType() {


84. return wrappedEntity.getContentType();

85. }

86.  

87. public Header getContentEncoding() {


88. return wrappedEntity.getContentEncoding();

89. }

90.  

91. public InputStream getContent()

92. throws IOException {


93. return wrappedEntity.getContent();

94. }

95.  

96. public void writeTo(OutputStream outstream)

97. throws IOException {


98. wrappedEntity.writeTo(outstream);

99. }

100.  

101. public boolean isStreaming() {


102. return wrappedEntity.isStreaming();

103. }

104.  

105. /**

106. * @deprecated (4.1) Either use {@link #getContent()} and call {@link java.io.InputStream#close()} on that;

107. * otherwise call {@link #writeTo(OutputStream)} which is required to free the resources.

108. */

109. @Deprecated

110. public void consumeContent() throws IOException {


111. wrappedEntity.consumeContent();

112. }

113.  

114. }

115.  

8  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：

1. /*

2. * ====================================================================

3. * Licensed to the Apache Software Foundation (ASF) under one

4. * or more contributor license agreements. See the NOTICE file

5. * distributed with this work for additional information

6. * regarding copyright ownership. The ASF licenses this file

7. * to you under the Apache License, Version 2.0 (the

8. * "License"); you may not use this file except in compliance

9. * with the License. You may obtain a copy of the License at

10. *

11. * http://www.apache.org/licenses/LICENSE-2.0

12. *

13. * Unless required by applicable law or agreed to in writing,

14. * software distributed under the License is distributed on an

15. * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

16. * KIND, either express or implied. See the License for the

17. * specific language governing permissions and limitations

18. * under the License.

19. * ====================================================================

20. *

21. * This software consists of voluntary contributions made by many

22. * individuals on behalf of the Apache Software Foundation. For more

23. * information on the Apache Software Foundation, please see

24. * <http://www.apache.org/>.

25. *

26. */

27.  

28. package org.apache.http.entity;

29.  

30. import java.io.ByteArrayInputStream;

31. import java.io.IOException;

32. import java.io.InputStream;

33. import java.io.OutputStream;

34.  

35. import org.apache.http.HttpEntity;

36. import org.apache.http.annotation.NotThreadSafe;

37. import org.apache.http.util.EntityUtils;

38.  

39. /**

40. * A wrapping entity that buffers it content if necessary.

41. * The buffered entity is always repeatable.

42. * If the wrapped entity is repeatable itself, calls are passed through.

43. * If the wrapped entity is not repeatable, the content is read into a

44. * buffer once and provided from there as often as required.

45. *

46. * @since 4.0

47. */

48. @NotThreadSafe

49. public class BufferedHttpEntity extends HttpEntityWrapper {


50.  

51. private final byte[] buffer;

52.  

53. /**

54. * Creates a new buffered entity wrapper.

55. *

56. * @param entity the entity to wrap, not null

57. * @throws IllegalArgumentException if wrapped is null

58. */

59. public BufferedHttpEntity(final HttpEntity entity) throws IOException {


60. super(entity);

61. if (!entity.isRepeatable() || entity.getContentLength() < 0) {


62. this.buffer = EntityUtils.toByteArray(entity);

63. } else {


64. this.buffer = null;

65. }

66. }

67.  

68. @Override

69. public long getContentLength() {


70. if (this.buffer != null) {


71. return this.buffer.length;

72. } else {


73. return wrappedEntity.getContentLength();

74. }

75. }

76.  

77. @Override

78. public InputStream getContent() throws IOException {


79. if (this.buffer != null) {


80. return new ByteArrayInputStream(this.buffer);

81. } else {


82. return wrappedEntity.getContent();

83. }

84. }

85.  

86. /**

87. * Tells that this entity does not have to be chunked.

88. *

89. * @return <code>false</code>

90. */

91. @Override

92. public boolean isChunked() {


93. return (buffer == null) && wrappedEntity.isChunked();

94. }

95.  

96. /**

97. * Tells that this entity is repeatable.

98. *

99. * @return <code>true</code>

100. */

101. @Override

102. public boolean isRepeatable() {


103. return true;

104. }

105.  
106.  

107. @Override

108. public void writeTo(final OutputStream outstream) throws IOException {


109. if (outstream == null) {


110. throw new IllegalArgumentException("Output stream may not be null");

111. }

112. if (this.buffer != null) {


113. outstream.write(this.buffer);

114. } else {


115. wrappedEntity.writeTo(outstream);

116. }

117. }

118.  
119.  

120. // non-javadoc, see interface HttpEntity

121. @Override

122. public boolean isStreaming() {


123. return (buffer == null) && wrappedEntity.isStreaming();

124. }

125.  

126. } // class BufferedHttpEntity

127.  

二 HttpEntity 的使用

1  HttpEntity实体即可以使流也可以使字符串形式。具体有什么用法看他的方法解释：

1. package com.scl.base;

2.  

3. import java.io.IOException;

4. import java.io.UnsupportedEncodingException;

5.  

6. import org.apache.http.HttpEntity;

7. import org.apache.http.ParseException;

8. import org.apache.http.entity.StringEntity;

9. import org.apache.http.util.EntityUtils;

10.  

11. public class HttpClientDemo06 {


12.  

13. /**

14. * @param args

15. */

16. public static void main(String[] args) {


17. try {


18. HttpEntity entity = new StringEntity("这一个字符串实体", "UTF-8");

19. //内容类型

20. System.out.println(entity.getContentType());

21. //内容的编码格式

22. System.out.println(entity.getContentEncoding());

23. //内容的长度

24. System.out.println(entity.getContentLength());

25. //把内容转成字符串

26. System.out.println(EntityUtils.toString(entity));

27. //内容转成字节数组

28. System.out.println(EntityUtils.toByteArray(entity).length);

29. //还有个直接获得流

30. //entity.getContent();

31. } catch (UnsupportedEncodingException e) {


32. throw new RuntimeException(e);

33. } catch (ParseException e) {


34. } catch (IOException e) {


35. }

36.  

37. }

38.  

39. }

2  对于实体的资源使用完之后要适当的回收资源，特别是对于流实体。例子代码如下:

1. public static void test() throws IllegalStateException, IOException{


2. HttpResponse response = null;

3. HttpEntity entity = response.getEntity();

4.  

5. if(entity!=null){


6.  

7. InputStream is = entity.getContent();

8. try{


9. //做一些操作

10. }finally{


11. //最后别忘了关闭应该关闭的资源，适当的释放资源

12. if(is != null){


13. is.close();

14. }

15. //这个方法也可以把底层的流给关闭了

16. EntityUtils.consume(entity);

17. //下面是这方法的源码

18. /*public static void consume(final HttpEntity entity) throws IOException {


19. if (entity == null) {


20. return;

21. }

22. if (entity.isStreaming()) {


23. InputStream instream = entity.getContent();

24. if (instream != null) {


25. instream.close();

26. }

27. }

28. }*/

29. }

30. }

FROM: http://blog.csdn.net/athenamax/article/details/8185043http://blog.csdn.net/athenamax/article/details/8185041

原文字体太小，看着眼睛疼，特此加大字体转载