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HttpClient 在Java项目中的使用详解

作者:wangpeng047

HttpClient作为访问Http服务的客户端访问程序已经被广泛使用,提高了开发效率,也提高了代码的健壮性。因此熟练掌握HttpClient是必需的,关于httpclient感兴趣的朋友可以参考本篇文章

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

package com.test; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.IOException; 
import java.io.UnsupportedEncodingException; 
import java.security.KeyManagementException; 
import java.security.KeyStore; 
import java.security.KeyStoreException; 
import java.security.NoSuchAlgorithmException; 
import java.security.cert.CertificateException; 
import java.util.ArrayList; 
import java.util.List; 
import javax.net.ssl.SSLContext; 
import org.apache.http.HttpEntity; 
import org.apache.http.NameValuePair; 
import org.apache.http.ParseException; 
import org.apache.http.client.ClientProtocolException; 
import org.apache.http.client.entity.UrlEncodedFormEntity; 
import org.apache.http.client.methods.CloseableHttpResponse; 
import org.apache.http.client.methods.HttpGet; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.conn.ssl.SSLConnectionSocketFactory; 
import org.apache.http.conn.ssl.SSLContexts; 
import org.apache.http.conn.ssl.TrustSelfSignedStrategy; 
import org.apache.http.entity.ContentType; 
import org.apache.http.entity.mime.MultipartEntityBuilder; 
import org.apache.http.entity.mime.content.FileBody; 
import org.apache.http.entity.mime.content.StringBody; 
import org.apache.http.impl.client.CloseableHttpClient; 
import org.apache.http.impl.client.HttpClients; 
import org.apache.http.message.BasicNameValuePair; 
import org.apache.http.util.EntityUtils; 
import org.junit.Test; 
public class HttpClientTest { 
  @Test 
  public void jUnitTest() { 
    get(); 
  } 
  /** 
   * HttpClient连接SSL 
   */ 
  public void ssl() { 
    CloseableHttpClient httpclient = null; 
    try { 
      KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); 
      FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore")); 
      try { 
        // 加载keyStore d:\\tomcat.keystore  
        trustStore.load(instream, "123456".toCharArray()); 
      } catch (CertificateException e) { 
        e.printStackTrace(); 
      } finally { 
        try { 
          instream.close(); 
        } catch (Exception ignore) { 
        } 
      } 
      // 相信自己的CA和所有自签名的证书 
      SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build(); 
      // 只允许使用TLSv1协议 
      SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null, 
          SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER); 
      httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build(); 
      // 创建http请求(get方式) 
      HttpGet httpget = new HttpGet("https://localhost:8443/myDemo/Ajax/serivceJ.action"); 
      System.out.println("executing request" + httpget.getRequestLine()); 
      CloseableHttpResponse response = httpclient.execute(httpget); 
      try { 
        HttpEntity entity = response.getEntity(); 
        System.out.println("----------------------------------------"); 
        System.out.println(response.getStatusLine()); 
        if (entity != null) { 
          System.out.println("Response content length: " + entity.getContentLength()); 
          System.out.println(EntityUtils.toString(entity)); 
          EntityUtils.consume(entity); 
        } 
      } finally { 
        response.close(); 
      } 
    } catch (ParseException e) { 
      e.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } catch (KeyManagementException e) { 
      e.printStackTrace(); 
    } catch (NoSuchAlgorithmException e) { 
      e.printStackTrace(); 
    } catch (KeyStoreException e) { 
      e.printStackTrace(); 
    } finally { 
      if (httpclient != null) { 
        try { 
          httpclient.close(); 
        } catch (IOException e) { 
          e.printStackTrace(); 
        } 
      } 
    } 
  } 
  /** 
   * post方式提交表单(模拟用户登录请求) 
   */ 
  public void postForm() { 
    // 创建默认的httpClient实例.  
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    // 创建httppost  
    HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action"); 
    // 创建参数队列  
    List<namevaluepair> formparams = new ArrayList<namevaluepair>(); 
    formparams.add(new BasicNameValuePair("username", "admin")); 
    formparams.add(new BasicNameValuePair("password", "123456")); 
    UrlEncodedFormEntity uefEntity; 
    try { 
      uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); 
      httppost.setEntity(uefEntity); 
      System.out.println("executing request " + httppost.getURI()); 
      CloseableHttpResponse response = httpclient.execute(httppost); 
      try { 
        HttpEntity entity = response.getEntity(); 
        if (entity != null) { 
          System.out.println("--------------------------------------"); 
          System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8")); 
          System.out.println("--------------------------------------"); 
        } 
      } finally { 
        response.close(); 
      } 
    } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
    } catch (UnsupportedEncodingException e1) { 
      e1.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } finally { 
      // 关闭连接,释放资源  
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
  /** 
   * 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 
   */ 
  public void post() { 
    // 创建默认的httpClient实例.  
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    // 创建httppost  
    HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action"); 
    // 创建参数队列  
    List<namevaluepair> formparams = new ArrayList<namevaluepair>(); 
    formparams.add(new BasicNameValuePair("type", "house")); 
    UrlEncodedFormEntity uefEntity; 
    try { 
      uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); 
      httppost.setEntity(uefEntity); 
      System.out.println("executing request " + httppost.getURI()); 
      CloseableHttpResponse response = httpclient.execute(httppost); 
      try { 
        HttpEntity entity = response.getEntity(); 
        if (entity != null) { 
          System.out.println("--------------------------------------"); 
          System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8")); 
          System.out.println("--------------------------------------"); 
        } 
      } finally { 
        response.close(); 
      } 
    } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
    } catch (UnsupportedEncodingException e1) { 
      e1.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } finally { 
      // 关闭连接,释放资源  
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
  /** 
   * 发送 get请求 
   */ 
  public void get() { 
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    try { 
      // 创建httpget.  
      HttpGet httpget = new HttpGet("http://www.baidu.com/"); 
      System.out.println("executing request " + httpget.getURI()); 
      // 执行get请求.  
      CloseableHttpResponse response = httpclient.execute(httpget); 
      try { 
        // 获取响应实体  
        HttpEntity entity = response.getEntity(); 
        System.out.println("--------------------------------------"); 
        // 打印响应状态  
        System.out.println(response.getStatusLine()); 
        if (entity != null) { 
          // 打印响应内容长度  
          System.out.println("Response content length: " + entity.getContentLength()); 
          // 打印响应内容  
          System.out.println("Response content: " + EntityUtils.toString(entity)); 
        } 
        System.out.println("------------------------------------"); 
      } finally { 
        response.close(); 
      } 
    } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
    } catch (ParseException e) { 
      e.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } finally { 
      // 关闭连接,释放资源  
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
  /** 
   * 上传文件 
   */ 
  public void upload() { 
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    try { 
      HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceFile.action"); 
      FileBody bin = new FileBody(new File("F:\\image\\sendpix0.jpg")); 
      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(); 
      } 
    } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } finally { 
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
}
</namevaluepair></namevaluepair>
</namevaluepair></namevaluepair> 

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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