HttpClient使用具體解釋

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Http協議的重要性相信不用我多說了，HttpClient相比傳統JDK內建的URLConnection，添加了易用性和靈活性（詳細差別，日後我們再討論），它不僅是client發送Http請求變得easy，並且也方便了開發人員測試介面（基於Http協議的），即提高了開發的效率，也方便提高代碼的健壯性。因此熟練掌握HttpClient是非常重要的必修內容，掌握HttpClient後，相信對於Http協議的瞭解會更加深入。

一、簡單介紹

HttpClient是Apache Jakarta Common下的子項目，用來提供高效的、最新的、功能豐富的支援HTTP協議的client編程工具包，而且它支援HTTP協議最新的版本號碼和建議。HttpClient已經應用在非常多的項目中，比方Apache Jakarta上非常著名的另外兩個開源項目Cactus和HTMLUnit都使用了HttpClient。

: http://hc.apache.org/downloads.cgi

二、特性

1. 基於標準、純淨的java語言。實現了Http1.0和Http1.1

2. 以可擴充的物件導向的結構實現了Http所有的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。

3. 支援HTTPS協議。

4. 通過Http代理建立透明的串連。

5. 利用CONNECT方法通過Http代理建立隧道的https串連。

6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos認證方案。

7. 外掛程式式的自己定義認證方案。

8. 便攜可靠的通訊端工廠使它更easy的使用第三方解決方式。

9. 連線管理員支援多線程應用。支援設定最大串連數，同一時候支援設定每一個主機的最大串連數，發現並關閉到期的串連。

10. 自己主動處理Set-Cookie中的Cookie。

11. 外掛程式式的自己定義Cookie策略。

12. Request的輸出資料流能夠避免流中內容直接緩衝到socketserver。

13. Response的輸入資料流能夠有效從socketserver直接讀取對應內容。

14. 在http1.0和http1.1中利用KeepAlive保持持久串連。

15. 直接擷取server發送的response code和 headers。

16. 設定連線逾時的能力。

17. 實驗性的支援http1.1 response caching。

18. 源碼基於Apache License 可免費擷取。

三、用法

使用HttpClient發送請求、接收響應非常easy，一般須要例如以下幾步就可以。

1. 建立HttpClient對象。

2. 建立要求方法的執行個體，並指定請求URL。假設須要發送GET請求，建立HttpGet對象；假設須要發送POST請求，建立HttpPost對象。

3. 假設須要發送請求參數，可調用HttpGet、HttpPost共同的setParams(HetpParams params)方法來加入請求參數；對於HttpPost對象而言，也可調用setEntity(HttpEntity entity)方法來佈建要求參數。

4. 調用HttpClient對象的execute(HttpUriRequest request)發送請求，該方法返回一個HttpResponse。

5. 調用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可擷取server的回應標頭；調用HttpResponse的getEntity()方法可擷取HttpEntity對象，該對象封裝了server的響應內容。程式可通過該對象擷取server的響應內容。

6. 釋放串連。不管運行方法是否成功，都必須釋放串連

四、執行個體

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 {@Testpublic void jUnitTest() {get();}/** * HttpClient串連SSL */public void ssl() {CloseableHttpClient httpclient = null;try {KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore"));try {// 載入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和全部自簽名的認證SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();// 僅僅同意使用TLSv1協議SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();// 建立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（類比使用者登入請求） */public void postForm() {// 建立預設的httpClient執行個體.  CloseableHttpClient httpclient = HttpClients.createDefault();// 建立httppost  HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");// 建立參數隊列  List formparams = new ArrayList();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 {// 關閉串連,釋放資源  try {httpclient.close();} catch (IOException e) {e.printStackTrace();}}}/** * 發送 post請求訪問本地應用並依據傳遞參數不同返回不同結果 */public void post() {// 建立預設的httpClient執行個體.  CloseableHttpClient httpclient = HttpClients.createDefault();// 建立httppost  HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");// 建立參數隊列  List formparams = new ArrayList();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 {// 關閉串連,釋放資源  try {httpclient.close();} catch (IOException e) {e.printStackTrace();}}}/** * 發送 get請求 */public void get() {CloseableHttpClient httpclient = HttpClients.createDefault();try {// 建立httpget.  HttpGet httpget = new HttpGet("http://www.baidu.com/");System.out.println("executing request " + httpget.getURI());// 運行get請求.  CloseableHttpResponse response = httpclient.execute(httpget);try {// 擷取響應實體  HttpEntity entity = response.getEntity();System.out.println("--------------------------------------");// 列印響應狀態  System.out.println(response.getStatusLine());if (entity != null) {// 列印響應內容長度  System.out.println("Response content length: " + entity.getContentLength());// 列印響應內容  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 {// 關閉串連,釋放資源  try {httpclient.close();} catch (IOException e) {e.printStackTrace();}}}/** * 上傳檔案 */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();}}}}

本執行個體是採用HttpClient4.3最新版本號碼。該版本號碼與之前的代碼寫法風格相差較大，大家多留意下。

HttpClient使用具體解釋