HttpClient使用详解[转]
Http协议的重要性相信不用我多说了，HttpClient相比传统JDK自带的URLConnection，增加了易用性和灵活性（具体区别，日后我们再讨论），它不仅是客户端发送Http请求变得容易，而且也方便了开发人员测试接口（基于Http协议的），即提高了开发的效率，也方便提高代码的健壮性。因此熟练掌握HttpClient是很重要的必修内容，掌握HttpClient后，相信对于Http协议的了解会更加深入。
一、简介
HttpClient是Apache Jakarta Common下的子项目，用来提供高效的、最新的、功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和建议。HttpClient已经应用在很多的项目中，比如Apache Jakarta上很著名的另外两个开源项目Cactus和HTMLUnit都使用了HttpClient。
下载地址: http://hc.apache.org/downloads.cgi
二、特性
1. 基于标准、纯净的Java语言。实现了Http1.0和Http1.1
2. 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）。
3. 支持HTTPS协议。
4. 通过Http代理建立透明的连接。
5. 利用CONNECT方法通过Http代理建立隧道的https连接。
6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos认证方案。
7. 插件式的自定义认证方案。
8. 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。
9. 连接管理器支持多线程应用。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。
10. 自动处理Set-Cookie中的Cookie。
11. 插件式的自定义Cookie策略。
12. Request的输出流可以避免流中内容直接缓冲到socket服务器。
13. Response的输入流可以有效的从socket服务器直接读取相应内容。
14. 在http1.0和http1.1中利用KeepAlive保持持久连接。
15. 直接获取服务器发送的response code和 headers。
16. 设置连接超时的能力。
17. 实验性的支持http1.1 response caching。
18. 源代码基于Apache License 可免费获取。
三、使用方法
使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可。
1. 创建HttpClient对象。
2. 创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。
3. 如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数。
4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。
5. 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。
6. 释放连接。无论执行方法是否成功，都必须释放连接
四、实例
1 package com.test;
2
3 import java.io.File;
4 import java.io.FileInputStream;
5 import java.io.IOException;
6 import java.io.UnsupportedEncodingException;
7 import java.security.KeyManagementException;
8 import java.security.KeyStore;
9 import java.security.KeyStoreException;
10 import java.security.NoSuchAlgorithmException;
11 import java.security.cert.CertificateException;
12 import java.util.ArrayList;
13 import java.util.List;
14
15 import javax.net.ssl.SSLContext;
16
17 import org.apache.http.HttpEntity;
18 import org.apache.http.NameValuePair;
19 import org.apache.http.ParseException;
20 import org.apache.http.client.ClientProtocolException;
21 import org.apache.http.client.entity.UrlEncodedFormEntity;
22 import org.apache.http.client.methods.CloseableHttpResponse;
23 import org.apache.http.client.methods.HttpGet;
24 import org.apache.http.client.methods.HttpPost;
25 import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
26 import org.apache.http.conn.ssl.SSLContexts;
27 import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
28 import org.apache.http.entity.ContentType;
29 import org.apache.http.entity.mime.MultipartEntityBuilder;
30 import org.apache.http.entity.mime.content.FileBody;
31 import org.apache.http.entity.mime.content.StringBody;
32 import org.apache.http.impl.client.CloseableHttpClient;
33 import org.apache.http.impl.client.HttpClients;
34 import org.apache.http.message.BasicNameValuePair;
35 import org.apache.http.util.EntityUtils;
36 import org.junit.Test;
37
38 public class HttpClientTest {
39
40 @Test
41 public void jUnitTest() {
42 get();
43 }
44
45 /**
46 * HttpClient连接SSL
47 */
48 public void ssl() {
49 CloseableHttpClient httpclient = null;
50 try {
51 KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
52 FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore"));
53 try {
54 // 加载keyStore d:\\tomcat.keystore
55 trustStore.load(instream, "123456".toCharArray());
56 } catch (CertificateException e) {
57 e.printStackTrace();
58 } finally {
59 try {
60 instream.close();
61 } catch (Exception ignore) {
62 }
63 }
64 // 相信自己的CA和所有自签名的证书
65 SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
66 // 只允许使用TLSv1协议
67 SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
68 SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
69 httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
70 // 创建http请求(get方式)
71 HttpGet httpget = new HttpGet("https://localhost:8443/myDemo/Ajax/serivceJ.action");
72 System.out.println("executing request" + httpget.getRequestLine());
73 CloseableHttpResponse response = httpclient.execute(httpget);
74 try {
75 HttpEntity entity = response.getEntity();
76 System.out.println("----------------------------------------");
77 System.out.println(response.getStatusLine());
78 if (entity != null) {
79 System.out.println("Response content length: " + entity.getContentLength());
80 System.out.println(EntityUtils.toString(entity));
81 EntityUtils.consume(entity);
82 }
83 } finally {
84 response.close();
85 }
86 } catch (ParseException e) {
87 e.printStackTrace();
88 } catch (IOException e) {
89 e.printStackTrace();
90 } catch (KeyManagementException e) {
91 e.printStackTrace();
92 } catch (NoSuchAlgorithmException e) {
93 e.printStackTrace();
94 } catch (KeyStoreException e) {
95 e.printStackTrace();
96 } finally {
97 if (httpclient != null) {
98 try {
99 httpclient.close();
100 } catch (IOException e) {
101 e.printStackTrace();
102 }
103 }
104 }
105 }
106
107 /**
108 * post方式提交表单（模拟用户登录请求）
109 */
110 public void postForm() {
111 // 创建默认的httpClient实例.
112 CloseableHttpClient httpclient = HttpClients.createDefault();
113 // 创建httppost
114 HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
115 // 创建参数队列
116 List<namevaluepair> formparams = new ArrayList<namevaluepair>();
117 formparams.add(new BasicNameValuePair("username", "admin"));
118 formparams.add(new BasicNameValuePair("password", "123456"));
119 UrlEncodedFormEntity uefEntity;
120 try {
121 uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
122 httppost.setEntity(uefEntity);
123 System.out.println("executing request " + httppost.getURI());
124 CloseableHttpResponse response = httpclient.execute(httppost);
125 try {
126 HttpEntity entity = response.getEntity();
127 if (entity != null) {
128 System.out.println("--------------------------------------");
129 System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));
130 System.out.println("--------------------------------------");
131 }
132 } finally {
133 response.close();
134 }
135 } catch (ClientProtocolException e) {
136 e.printStackTrace();
137 } catch (UnsupportedEncodingException e1) {
138 e1.printStackTrace();
139 } catch (IOException e) {
140 e.printStackTrace();
141 } finally {
142 // 关闭连接,释放资源
143 try {
144 httpclient.close();
145 } catch (IOException e) {
146 e.printStackTrace();
147 }
148 }
149 }
150
151 /**
152 * 发送 post请求访问本地应用并根据传递参数不同返回不同结果
153 */
154 public void post() {
155 // 创建默认的httpClient实例.
156 CloseableHttpClient httpclient = HttpClients.createDefault();
157 // 创建httppost
158 HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
159 // 创建参数队列
160 List<namevaluepair> formparams = new ArrayList<namevaluepair>();
161 formparams.add(new BasicNameValuePair("type", "house"));
162 UrlEncodedFormEntity uefEntity;
163 try {
164 uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
165 httppost.setEntity(uefEntity);
166 System.out.println("executing request " + httppost.getURI());
167 CloseableHttpResponse response = httpclient.execute(httppost);
168 try {
169 HttpEntity entity = response.getEntity();
170 if (entity != null) {
171 System.out.println("--------------------------------------");
172 System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));
173 System.out.println("--------------------------------------");
174 }
175 } finally {
176 response.close();
177 }
178 } catch (ClientProtocolException e) {
179 e.printStackTrace();
180 } catch (UnsupportedEncodingException e1) {
181 e1.printStackTrace();
182 } catch (IOException e) {
183 e.printStackTrace();
184 } finally {
185 // 关闭连接,释放资源
186 try {
187 httpclient.close();
188 } catch (IOException e) {
189 e.printStackTrace();
190 }
191 }
192 }
193
194 /**
195 * 发送 get请求
196 */
197 public void get() {
198 CloseableHttpClient httpclient = HttpClients.createDefault();
199 try {
200 // 创建httpget.
201 HttpGet httpget = new HttpGet("http://www.baidu.com/");
202 System.out.println("executing request " + httpget.getURI());
203 // 执行get请求.
204 CloseableHttpResponse response = httpclient.execute(httpget);
205 try {
206 // 获取响应实体
207 HttpEntity entity = response.getEntity();
208 System.out.println("--------------------------------------");
209 // 打印响应状态
210 System.out.println(response.getStatusLine());
211 if (entity != null) {
212 // 打印响应内容长度
213 System.out.println("Response content length: " + entity.getContentLength());
214 // 打印响应内容
215 System.out.println("Response content: " + EntityUtils.toString(entity));
216 }
217 System.out.println("------------------------------------");
218 } finally {
219 response.close();
220 }
221 } catch (ClientProtocolException e) {
222 e.printStackTrace();
223 } catch (ParseException e) {
224 e.printStackTrace();
225 } catch (IOException e) {
226 e.printStackTrace();
227 } finally {
228 // 关闭连接,释放资源
229 try {
230 httpclient.close();
231 } catch (IOException e) {
232 e.printStackTrace();
233 }
234 }
235 }
236
237 /**
238 * 上传文件
239 */
240 public void upload() {
241 CloseableHttpClient httpclient = HttpClients.createDefault();
242 try {
243 HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceFile.action");
244
245 FileBody bin = new FileBody(new File("F:\\image\\sendpix0.jpg"));
246 StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);
247
248 HttpEntity reqEntity = MultipartEntityBuilder.create().addPart("bin", bin).addPart("comment", comment).build();
249
250 httppost.setEntity(reqEntity);
251
252 System.out.println("executing request " + httppost.getRequestLine());
253 CloseableHttpResponse response = httpclient.execute(httppost);
254 try {
255 System.out.println("----------------------------------------");
256 System.out.println(response.getStatusLine());
257 HttpEntity resEntity = response.getEntity();
258 if (resEntity != null) {
259 System.out.println("Response content length: " + resEntity.getContentLength());
260 }
261 EntityUtils.consume(resEntity);
262 } finally {
263 response.close();
264 }
265 } catch (ClientProtocolException e) {
266 e.printStackTrace();
267 } catch (IOException e) {
268 e.printStackTrace();
269 } finally {
270 try {
271 httpclient.close();
272 } catch (IOException e) {
273 e.printStackTrace();
274 }
275 }
276 }
277 }
本实例是采用HttpClient4.3最新版本。该版本与之前的代码写法风格相差较大，大家多留意下。
转自:wangpeng047
