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:
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
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package com.test;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.IOException;
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import java.io.UnsupportedEncodingException;
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import java.security.KeyManagementException;
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import java.security.KeyStore;
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import java.security.KeyStoreException;
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import java.security.NoSuchAlgorithmException;
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import java.security.cert.CertificateException;
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import java.util.ArrayList;
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import java.util.List;
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import javax.net.ssl.SSLContext;
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import org.apache.http.HttpEntity;
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import org.apache.http.NameValuePair;
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import org.apache.http.ParseException;
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import org.apache.http.client.ClientProtocolException;
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import org.apache.http.client.entity.UrlEncodedFormEntity;
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import org.apache.http.client.methods.CloseableHttpResponse;
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import org.apache.http.client.methods.HttpGet;
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import org.apache.http.client.methods.HttpPost;
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import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
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import org.apache.http.conn.ssl.SSLContexts;
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import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
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import org.apache.http.entity.ContentType;
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import org.apache.http.entity.mime.MultipartEntityBuilder;
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import org.apache.http.entity.mime.content.FileBody;
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import org.apache.http.entity.mime.content.StringBody;
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import org.apache.http.impl.client.CloseableHttpClient;
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import org.apache.http.impl.client.HttpClients;
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import org.apache.http.message.BasicNameValuePair;
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import org.apache.http.util.EntityUtils;
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import org.junit.Test;
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public class HttpClientTest {
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@Test
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public void jUnitTest() {
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get();
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}
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/**
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* HttpClient连接SSL
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*/
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public void ssl() {
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CloseableHttpClient httpclient = null;
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try {
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KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
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FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore"));
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try {
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// 加载keyStore d:\\tomcat.keystore
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trustStore.load(instream, "123456".toCharArray());
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} catch (CertificateException e) {
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e.printStackTrace();
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} finally {
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try {
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instream.close();
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} catch (Exception ignore) {
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}
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}
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// 相信自己的CA和所有自签名的证书
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SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
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// 只允许使用TLSv1协议
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SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
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SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
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httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
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// 创建http请求(get方式)
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HttpGet httpget = new HttpGet("");
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System.out.println("executing request" + httpget.getRequestLine());
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CloseableHttpResponse response = httpclient.execute(httpget);
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try {
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HttpEntity entity = response.getEntity();
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System.out.println("----------------------------------------");
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System.out.println(response.getStatusLine());
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if (entity != null) {
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System.out.println("Response content length: " + entity.getContentLength());
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System.out.println(EntityUtils.toString(entity));
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EntityUtils.consume(entity);
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}
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} finally {
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response.close();
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}
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} catch (ParseException e) {
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e.printStackTrace();
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} catch (IOException e) {
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e.printStackTrace();
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} catch (KeyManagementException e) {
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e.printStackTrace();
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} catch (NoSuchAlgorithmException e) {
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e.printStackTrace();
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} catch (KeyStoreException e) {
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e.printStackTrace();
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} finally {
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if (httpclient != null) {
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try {
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httpclient.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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}
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/**
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* post方式提交表单(模拟用户登录请求)
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*/
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public void postForm() {
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// 创建默认的httpClient实例.
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CloseableHttpClient httpclient = HttpClients.createDefault();
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// 创建httppost
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HttpPost httppost = new HttpPost("");
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// 创建参数队列
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List formparams = new ArrayList();
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formparams.add(new BasicNameValuePair("username", "admin"));
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formparams.add(new BasicNameValuePair("password", "123456"));
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UrlEncodedFormEntity uefEntity;
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try {
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uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
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httppost.setEntity(uefEntity);
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System.out.println("executing request " + httppost.getURI());
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CloseableHttpResponse response = httpclient.execute(httppost);
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try {
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HttpEntity entity = response.getEntity();
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if (entity != null) {
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System.out.println("--------------------------------------");
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System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));
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System.out.println("--------------------------------------");
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}
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} finally {
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response.close();
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}
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} catch (ClientProtocolException e) {
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e.printStackTrace();
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} catch (UnsupportedEncodingException e1) {
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e1.printStackTrace();
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} catch (IOException e) {
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e.printStackTrace();
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} finally {
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// 关闭连接,释放资源
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try {
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httpclient.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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/**
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* 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
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*/
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public void post() {
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// 创建默认的httpClient实例.
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CloseableHttpClient httpclient = HttpClients.createDefault();
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// 创建httppost
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HttpPost httppost = new HttpPost("");
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// 创建参数队列
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List formparams = new ArrayList();
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formparams.add(new BasicNameValuePair("type", "house"));
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UrlEncodedFormEntity uefEntity;
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try {
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uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
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httppost.setEntity(uefEntity);
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System.out.println("executing request " + httppost.getURI());
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CloseableHttpResponse response = httpclient.execute(httppost);
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try {
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HttpEntity entity = response.getEntity();
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if (entity != null) {
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System.out.println("--------------------------------------");
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System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));
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System.out.println("--------------------------------------");
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}
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} finally {
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response.close();
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}
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} catch (ClientProtocolException e) {
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e.printStackTrace();
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} catch (UnsupportedEncodingException e1) {
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e1.printStackTrace();
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} catch (IOException e) {
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e.printStackTrace();
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} finally {
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// 关闭连接,释放资源
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try {
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httpclient.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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/**
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* 发送 get请求
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*/
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public void get() {
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CloseableHttpClient httpclient = HttpClients.createDefault();
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try {
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// 创建httpget.
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HttpGet httpget = new HttpGet("");
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System.out.println("executing request " + httpget.getURI());
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// 执行get请求.
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CloseableHttpResponse response = httpclient.execute(httpget);
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try {
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// 获取响应实体
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HttpEntity entity = response.getEntity();
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System.out.println("--------------------------------------");
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// 打印响应状态
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System.out.println(response.getStatusLine());
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if (entity != null) {
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// 打印响应内容长度
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System.out.println("Response content length: " + entity.getContentLength());
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// 打印响应内容
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System.out.println("Response content: " + EntityUtils.toString(entity));
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}
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System.out.println("------------------------------------");
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} finally {
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response.close();
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}
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} catch (ClientProtocolException e) {
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e.printStackTrace();
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} catch (ParseException e) {
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e.printStackTrace();
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} catch (IOException e) {
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e.printStackTrace();
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} finally {
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// 关闭连接,释放资源
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try {
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httpclient.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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/**
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* 上传文件
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*/
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public void upload() {
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CloseableHttpClient httpclient = HttpClients.createDefault();
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try {
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HttpPost httppost = new HttpPost("");
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FileBody bin = new FileBody(new File("F:\\image\\sendpix0.jpg"));
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StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);
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HttpEntity reqEntity = MultipartEntityBuilder.create().addPart("bin", bin).addPart("comment", comment).build();
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httppost.setEntity(reqEntity);
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System.out.println("executing request " + httppost.getRequestLine());
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CloseableHttpResponse response = httpclient.execute(httppost);
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try {
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System.out.println("----------------------------------------");
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System.out.println(response.getStatusLine());
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HttpEntity resEntity = response.getEntity();
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if (resEntity != null) {
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System.out.println("Response content length: " + resEntity.getContentLength());
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}
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EntityUtils.consume(resEntity);
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} finally {
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response.close();
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}
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} catch (ClientProtocolException e) {
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e.printStackTrace();
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} catch (IOException e) {
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e.printStackTrace();
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} finally {
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try {
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httpclient.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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}
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。
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