HTTP Components简介

基于版本4.5.x

简介

组件

HttpClient，核心组件

HC Fluent，提供了流式操作接口

HttpMime，提供文件上传时用到的一些工具类

HttpClient Cache，有待学习

HttpClient OSGi，有待学习

特性

基于标准、纯净的Java语言。实现了Http1.0和Http1.1

以可扩展的面向对象的结构实现了Http全部的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。

支持HTTPS（基于SSL的HTTP）协议。

通过HTTP代理建立透明的连接。

利用CONNECT方法通过HTTP代理建立隧道的HTTPS连接。

Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO, Kerberos认证方案。

插件式的自定义认证方案。

便携可靠的套接字工厂使它更容易的使用第三方解决方案(Pluggable secure socket factories, making it easier to use third party solutions)。

支持多线程应用的连接管理器。支持设置最大连接数，同时支持设置每个主机的最大连接数，发现并关闭过期的连接。

自动处理Set-Cookie中的Cookie。（Automatic Cookie handling for reading Set-Cookie: headers from the server and sending them back out in a Cookie: header when appropriate.）

插件式的自定义Cookie策略。

Request的输出流可以避免流中内容直接缓冲到socket服务器。（Request output streams to avoid buffering any content body by streaming directly to the socket to the server.）

Response的输入流可以有效的从socket服务器直接读取相应内容。

在http1.0和http1.1中利用KeepAlive保持持久连接。

直接获取服务器发送的response code和 headers。

可设置连接超时。

支持http1.1 response caching。

源代码基于Apache License 可免费获取。

Quick Start

HTTP Client

GET请求、POST请求 及 response处理

CloseableHttpClient httpclient = HttpClients.createDefault();

//GET请求及response处理
HttpGet httpGet = new HttpGet("http://targethost/homepage");
CloseableHttpResponse response1 = httpclient.execute(httpGet);
// The underlying HTTP connection is still held by the response object
// to allow the response content to be streamed directly from the network socket.
// In order to ensure correct deallocation of system resources
// the user MUST call CloseableHttpResponse#close() from a finally clause.
// Please note that if response content is not fully consumed the underlying
// connection cannot be safely re-used and will be shut down and discarded
// by the connection manager.
try {
System.out.println(response1.getStatusLine());
HttpEntity entity1 = response1.getEntity();
// do something useful with the response body
// and ensure it is fully consumed
EntityUtils.consume(entity1);
} finally {
response1.close();
}

//POST请求及response处理
HttpPost httpPost = new HttpPost("http://targethost/login");
List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("username", "vip"));
nvps.add(new BasicNameValuePair("password", "secret"));
httpPost.setEntity(new UrlEncodedFormEntity(nvps));
CloseableHttpResponse response2 = httpclient.execute(httpPost);

try {
System.out.println(response2.getStatusLine());
HttpEntity entity2 = response2.getEntity();
// do something useful with the response body
// and ensure it is fully consumed
EntityUtils.consume(entity2);
} finally {
response2.close();
}

官网的例子注释中有几点是需要注意的：

调用httpclient.execute(XXX)后，http连接会一直被response持有，需要调用CloseableHttpResponse#close()，当然也可是已使用jdk1.7的try-catch-resource。

如果response没有充分的被消耗掉（比如：chunk模式下，只取了部分），会被connection manager丢弃而不能复用，使用

EntityUtils.consume(entity)

可以确保response被充分消耗

HC Fluent 的流式接口

Request.Get("http://targethost/homepage")
.execute().returnContent();
Request.Post("http://targethost/login")
.bodyForm(Form.form().add("username",  "vip").add("password",  "secret").build())
.execute().returnContent();

HttpMime 提交文件

multipart/form 类型的POST，下面例子中的FileBody、StringBody、MultipartEntityBuilder等都是HttpMine模块中的类。

public class ClientMultipartFormPost {

public static void main(String[] args) throws Exception {
if (args.length != 1)  {
System.out.println("File path not given");
System.exit(1);
}
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
HttpPost httppost = new HttpPost("http://localhost:8080" +
"/fileUpload");

FileBody bin = new FileBody(new File(args[0]));
StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);

HttpEntity reqEntity = MultipartEntityBuilder.create()
.addPart("bin", bin)
.addPart("comment", comment)
.build();

httppost.setEntity(reqEntity);

System.out.println("executing request " + httppost.getRequestLine());
CloseableHttpResponse response = httpclient.execute(httppost);
try {
System.out.println("----------------------------------------");
System.out.println(response.getStatusLine());
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
System.out.println("Response content length: " + resEntity.getContentLength());
}
EntityUtils.consume(resEntity);
} finally {
response.close();
}
} finally {
httpclient.close();
}
}

}

参考

HTTP Client使用详解

HttpClient Quick start