談談HttpClient使用詳解

更新時間：2015年10月19日 11:34:24 作者：wangpeng047

這篇文章給大家介紹HttpClient使用，httpClient是一個客戶端的http通信實現(xiàn)庫，HttpClient的目標是發(fā)送和接收HTTP報文。本文講解的非常詳細，對HttpClient使用感興趣的朋友可以參考下

HttpClient是一個客戶端的HTTP通信實現(xiàn)庫。HttpClient的目標是發(fā)送和接收HTTP報文。

Http協(xié)議的重要性相信不用我多說了，HttpClient相比傳統(tǒng)JDK自帶的URLConnection，增加了易用性和靈活性（具體區(qū)別，日后我們再討論），它不僅是客戶端發(fā)送Http請求變得容易，而且也方便了開發(fā)人員測試接口（基于Http協(xié)議的），即提高了開發(fā)的效率，也方便提高代碼的健壯性。因此熟練掌握HttpClient是很重要的必修內(nèi)容，掌握HttpClient后，相信對于Http協(xié)議的了解會更加深入。

一、簡介

HttpClient是Apache Jakarta Common下的子項目，用來提供高效的、最新的、功能豐富的支持HTTP協(xié)議的客戶端編程工具包，并且它支持HTTP協(xié)議最新的版本和建議。HttpClient已經(jīng)應用在很多的項目中，比如Apache Jakarta上很著名的另外兩個開源項目Cactus和HTMLUnit都使用了HttpClient。

下載地址: http://hc.apache.org/downloads.cgi

二、特性

1. 基于標準、純凈的java語言。實現(xiàn)了Http1.0和Http1.1
2. 以可擴展的面向?qū)ο蟮慕Y(jié)構(gòu)實現(xiàn)了Http全部的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。
3. 支持HTTPS協(xié)議。
4. 通過Http代理建立透明的連接。
5. 利用CONNECT方法通過Http代理建立隧道的https連接。
6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos認證方案。
7. 插件式的自定義認證方案。
8. 便攜可靠的套接字工廠使它更容易的使用第三方解決方案。
9. 連接管理器支持多線程應用。支持設置最大連接數(shù)，同時支持設置每個主機的最大連接數(shù)，發(fā)現(xiàn)并關閉過期的連接。
10. 自動處理Set-Cookie中的Cookie。
11. 插件式的自定義Cookie策略。
12. Request的輸出流可以避免流中內(nèi)容直接緩沖到socket服務器。
13. Response的輸入流可以有效的從socket服務器直接讀取相應內(nèi)容。
14. 在http1.0和http1.1中利用KeepAlive保持持久連接。
15. 直接獲取服務器發(fā)送的response code和 headers。
16. 設置連接超時的能力。
17. 實驗性的支持http1.1 response caching。
18. 源代碼基于Apache License 可免費獲取。

三、使用方法

使用HttpClient發(fā)送請求、接收響應很簡單，一般需要如下幾步即可。

1. 創(chuàng)建HttpClient對象。
2. 創(chuàng)建請求方法的實例，并指定請求URL。如果需要發(fā)送GET請求，創(chuàng)建HttpGet對象；如果需要發(fā)送POST請求，創(chuàng)建HttpPost對象。
3. 如果需要發(fā)送請求參數(shù)，可調(diào)用HttpGet、HttpPost共同的setParams(HetpParams params)方法來添加請求參數(shù)；對于HttpPost對象而言，也可調(diào)用setEntity(HttpEntity entity)方法來設置請求參數(shù)。
4. 調(diào)用HttpClient對象的execute(HttpUriRequest request)發(fā)送請求，該方法返回一個HttpResponse。
5. 調(diào)用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取服務器的響應頭；調(diào)用HttpResponse的getEntity()方法可獲取HttpEntity對象，該對象包裝了服務器的響應內(nèi)容。程序可通過該對象獲取服務器的響應內(nèi)容。
6. 釋放連接。無論執(zhí)行方法是否成功，都必須釋放連接

四、實例

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連接SSL 
   */ 
  public void ssl() { 
    CloseableHttpClient httpclient = null; 
    try { 
      KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); 
      FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore")); 
      try { 
        // 加載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和所有自簽名的證書 
      SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build(); 
      // 只允許使用TLSv1協(xié)議 
      SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null, 
          SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER); 
      httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build(); 
      // 創(chuàng)建http請求(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方式提交表單（模擬用戶登錄請求） 
   */ 
  public void postForm() { 
    // 創(chuàng)建默認的httpClient實例.  
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    // 創(chuàng)建httppost  
    HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action"); 
    // 創(chuàng)建參數(shù)隊列  
    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 { 
      // 關閉連接,釋放資源  
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
  /** 
   * 發(fā)送 post請求訪問本地應用并根據(jù)傳遞參數(shù)不同返回不同結(jié)果 
   */ 
  public void post() { 
    // 創(chuàng)建默認的httpClient實例.  
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    // 創(chuàng)建httppost  
    HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action"); 
    // 創(chuàng)建參數(shù)隊列  
    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 { 
      // 關閉連接,釋放資源  
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
  /** 
   * 發(fā)送 get請求 
   */ 
  public void get() { 
    CloseableHttpClient httpclient = HttpClients.createDefault(); 
    try { 
      // 創(chuàng)建httpget.  
      HttpGet httpget = new HttpGet("http://www.baidu.com/"); 
      System.out.println("executing request " + httpget.getURI()); 
      // 執(zhí)行get請求.  
      CloseableHttpResponse response = httpclient.execute(httpget); 
      try { 
        // 獲取響應實體  
        HttpEntity entity = response.getEntity(); 
        System.out.println("--------------------------------------"); 
        // 打印響應狀態(tài)  
        System.out.println(response.getStatusLine()); 
        if (entity != null) { 
          // 打印響應內(nèi)容長度  
          System.out.println("Response content length: " + entity.getContentLength()); 
          // 打印響應內(nèi)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 { 
      // 關閉連接,釋放資源  
      try { 
        httpclient.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
  /** 
   * 上傳文件 
   */ 
  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>

本實例是采用HttpClient4.3最新版本。該版本與之前的代碼寫法風格相差較大，大家多留意下。

好了，以上所述就是本文的全部內(nèi)容，希望大家喜歡。

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