HTTP協議是目前互聯網上最重要的協議，許多軟件與服務都需要依賴HTTP協議。
雖然java.net這個package中包含了對HTTP的基本支持，但還有很多高級和復雜的功能無法實現，這不能不說是一個遺憾。
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HttpClient作為Apache的開源項目項目之一，為基于HTTP協議的操作提供了強大的客戶端執行支持，最新的版本為3.0RC3。
下面通過一個例子簡要展示HttpClient的使用方法：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
iimport java.io.UnsupportedEncodingException;
import java.util.*;
import org.apache.commons.httpclient.Header;
import org.apache.commons.httpclient.HostConfiguration;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpConnection;
import org.apache.commons.httpclient.MultiThreadedHttpConnectionManager;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
/**
* @author steven
*/
public class HttpClientExample {
//獲得ConnectionManager，設置相關參數
private static MultiThreadedHttpConnectionManager manager =
new MultiThreadedHttpConnectionManager();
private static int connectionTimeOut = 20000;
private static int socketTimeOut = 10000;
private static int maxConnectionPerHost = 5;
private static int maxTotalConnections = 40;
//標志初始化是否完成的flag
private static boolean initialed = false;
//初始化ConnectionManger的方法
public static void SetPara() {
manager.getParams().setConnectionTimeout(connectionTimeOut);
manager.getParams().setSoTimeout(socketTimeOut);
manager.getParams()
.setDefaultMaxConnectionsPerHost(maxConnectionPerHost);
manager.getParams().setMaxTotalConnections(maxTotalConnections);
initialed = true;
}
//通過get方法獲取網頁內容
public static String getGetResponseWithHttpClient(String url, String encode) {
HttpClient client = new HttpClient(manager);
if (initialed) {
HttpClientExample.SetPara();
}
GetMethod get = new GetMethod(url);
get.setFollowRedirects(true);
String result = null;
StringBuffer resultBuffer = new StringBuffer();
try {
client.executeMethod(get);
//在目標頁面情況未知的條件下，不推薦使用getResponseBodyAsString()方法
//String strGetResponseBody = post.getResponseBodyAsString();
BufferedReader in = new BufferedReader(
new InputStreamReader(
get.getResponseBodyAsStream(),
get.getResponseCharSet()));
String inputLine = null;
while ((inputLine = in.readLine()) != null) {
resultBuffer.append(inputLine);
resultBuffer.append("\n");
}
in.close();
result = resultBuffer.toString();
//iso-8859-1 is the default reading encode
result = HttpClientExample.ConverterStringCode(resultBuffer.toString(),
get.getResponseCharSet(),
encode);
} catch (Exception e) {
e.printStackTrace();
result = "";
} finally {
get.releaseConnection();
return result;
}
}
public static String getPostResponseWithHttpClient(String url,
String encode) {
HttpClient client = new HttpClient(manager);
if (initialed) {
HttpClientExample.SetPara();
}
PostMethod post = new PostMethod(url);
post.setFollowRedirects(false);
StringBuffer resultBuffer = new StringBuffer();
String result = null;
try {
client.executeMethod(post);
BufferedReader in = new BufferedReader(
new InputStreamReader(
post.getResponseBodyAsStream(),
post.getResponseCharSet()));
String inputLine = null;
while ((inputLine = in.readLine()) != null) {
resultBuffer.append(inputLine);
resultBuffer.append("\n");
}
in.close();
//iso-8859-1 is the default reading encode
result = HttpClientExample.ConverterStringCode(resultBuffer.toString(),
post.getResponseCharSet(),
encode);
} catch (Exception e) {
e.printStackTrace();
result = "";
} finally {
post.releaseConnection();
return result;
}
}
public static String getPostResponseWithHttpClient(String url,
String encode,
NameValuePair[] nameValuePair) {
HttpClient client = new HttpClient(manager);
if (initialed) {
HttpClientExample.SetPara();
}
PostMethod post = new PostMethod(url);
post.setRequestBody(nameValuePair);
post.setFollowRedirects(false);
String result = null;
StringBuffer resultBuffer = new StringBuffer();
try {
client.executeMethod(post);
BufferedReader in = new BufferedReader(
new InputStreamReader(
post.getResponseBodyAsStream(),
post.getResponseCharSet()));
String inputLine = null;
while ((inputLine = in.readLine()) != null) {
resultBuffer.append(inputLine);
resultBuffer.append("\n");
}
in.close();
//iso-8859-1 is the default reading encode
result = HttpClientExample.ConverterStringCode(resultBuffer.toString(),
post.getResponseCharSet(),
encode);
} catch (Exception e) {
e.printStackTrace();
result = "";
} finally {
post.releaseConnection();
return result;
}
}
private static String ConverterStringCode(String source, String srcEncode, String destEncode) {
if (src != null) {
try {
return new String(src.getBytes(srcEncode), destEncode);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return "";
}
} else {
return "";
}
}
}
之后，就可以通過下面的代碼獲得目標網頁：
String source = HttpClientExample.getGetResponseWithHttpClient("www.sina.com.cn", "GBK");
注意，在默認情況下，HttpClient的Request的Head中
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User-Agent的值是Jakarta Commons-HttpClient 3.0RC1，如果需要改變它（例如，變為Mozilla/4.0），必須在調用之前運行如下語句：
System.getProperties().setProperty("httpclient.useragent", "Mozilla/4.0");
來自:http://www.cnjm.net/tech/article1153.html
posted on 2009-06-23 17:56
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