HttpClient使用詳解
Http協議的重要性相信不用我多說了，HttpClient相比傳統JDK自帶的URLConnection，增長了易用性和靈活性（具體區別，往後咱們再討論），它不只是客戶端發送Http請求變得容易，並且也方便了開發人員測試接口（基於Http協議的），即提升了開發的效率，也方便提升代碼的健壯性。所以熟練掌握HttpClient是很重要的必修內容，掌握HttpClient後，相信對於Http協議的瞭解會更加深刻。java
1、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協議的客戶端編程工具包，而且它支持HTTP協議最新的版本和建議。HttpClient已經應用在不少的項目中，好比Apache Jakarta上很著名的另外兩個開源項目Cactus和HTMLUnit都使用了HttpClient。apache
下載地址: http://hc.apache.org/downloads.cgi編程
2、特性
1. 基於標準、純淨的Java語言。實現了Http1.0和Http1.1tomcat
2. 以可擴展的面向對象的結構實現了Http所有的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。服務器
3. 支持HTTPS協議。多線程
4. 經過Http代理創建透明的鏈接。socket
5. 利用CONNECT方法經過Http代理創建隧道的https鏈接。工具
6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos認證方案。post
7. 插件式的自定義認證方案。測試
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. 鏈接管理器支持多線程應用。支持設置最大鏈接數，同時支持設置每一個主機的最大鏈接數，發現並關閉過時的鏈接。
10. 自動處理Set-Cookie中的Cookie。
11. 插件式的自定義Cookie策略。
12. Request的輸出流能夠避免流中內容直接緩衝到socket服務器。
13. Response的輸入流能夠有效的從socket服務器直接讀取相應內容。
14. 在http1.0和http1.1中利用KeepAlive保持持久鏈接。
15. 直接獲取服務器發送的response code和 headers。
16. 設置鏈接超時的能力。
17. 實驗性的支持http1.1 response caching。
18. 源代碼基於Apache License 可免費獲取。
3、使用方法
使用HttpClient發送請求、接收響應很簡單，通常須要以下幾步便可。
1. 建立HttpClient對象。
2. 建立請求方法的實例，並指定請求URL。若是須要發送GET請求，建立HttpGet對象；若是須要發送POST請求，建立HttpPost對象。
3. 若是須要發送請求參數，可調用HttpGet、HttpPost共同的setParams(HetpParams params)方法來添加請求參數；對於HttpPost對象而言，也可調用setEntity(HttpEntity entity)方法來設置請求參數。
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)等方法可獲取服務器的響應頭；調用HttpResponse的getEntity()方法可獲取HttpEntity對象，該對象包裝了服務器的響應內容。程序可經過該對象獲取服務器的響應內容。
6. 釋放鏈接。不管執行方法是否成功，都必須釋放鏈接
4、實例
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鏈接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) {
}
}
// 相信本身的CA和全部自簽名的證書
SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
// 只容許使用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（模擬用戶登陸請求）
*/
public void postForm() {
// 建立默認的httpClient實例.
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<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 {
// 關閉鏈接,釋放資源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 發送 post請求訪問本地應用並根據傳遞參數不一樣返回不一樣結果
*/
public void post() {
// 建立默認的httpClient實例.
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<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 {
// 關閉鏈接,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());
// 執行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
System.out.println(response.getStatusLine());
if (entity != null) {
// 打印響應內容長度
System.out.println("Response content length: " + entity.getContentLength());
// 打印響應內容
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 {
// 關閉鏈接,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();
}
}
}
}
本實例是採用HttpClient4.3最新版本。該版本與以前的代碼寫法風格相差較大，你們多留意下。
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