如何使用 HttpClient

[honeymoose]

HttpClient 是用来写 http 客户端程序的非常好的包。

下面的代码初步展示了如何使用这个了写客户端。

我们没有对这个程序进行测试，这里仅供参考。[code]package base.helper;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.commons.httpclient.Header;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpException;
import org.apache.commons.httpclient.HttpStatus;
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;

public class HttpClientHelper {
private HttpClient client = null;

private String baseUrl;

private String encoder;

public HttpClientHelper(String baseUrl, String encoder) {

	createClient();
	this.baseUrl = baseUrl;
	this.encoder = encoder;
}

private void createClient() {
	System.getProperties().setProperty("httpclient.useragent",
			"Mozilla/4.0");
	client = new HttpClient(new MultiThreadedHttpConnectionManager());

}

/**
 * Download the url as html String
 * 
 * @param url
 *            the url to be download.
 * @return
 */
public String html(String url) {
	url = MiscHelper.toAbsoluteUrl(this.baseUrl, url);
	GetMethod get = new GetMethod(url);
	get.setRequestHeader("User-Agent",
			"Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");
	get.setFollowRedirects(true);

	try {
		client.executeMethod(get);
		return MiscHelper.method(get, this.encoder);

	} catch (Exception e) {
		createClient();
		e.printStackTrace();
	} finally {
		get.releaseConnection();
	}
	return null;
}

/**
 * Download the url conent and save into the file. It can use to download
 * images,pdf,flash etc.
 * 
 * @param url
 * @param file
 * @return
 */
public boolean file(String url, File file) {
	url = MiscHelper.toAbsoluteUrl(this.baseUrl, url);
	GetMethod get = new GetMethod(url);
	get.setRequestHeader("User-Agent",
			"Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");

	get.setFollowRedirects(true);
	boolean result = true;
	try {
		client.executeMethod(get);
		InputStream in = get.getResponseBodyAsStream();
		FileOutputStream out = new FileOutputStream(file);
		byte[] buffer = new byte[1024];
		int count = -1;
		while ((count = in.read(buffer)) != -1) {
			out.write(buffer, 0, count);
		}
		out.flush();
		out.close();
	} catch (Exception e) {
		e.printStackTrace();
		createClient();
		result = false;
	} finally {
		get.releaseConnection();
	}
	return result;
}

public boolean file(String url) {
	int i = url.lastIndexOf('/');
	String fileName = url.substring(i + 1);
	return file(url, new File(fileName));
}

/**

• Submit the form to the url.

• @param url

• @param params

• @return

• @throws HttpException

• @throws IOException
  */
  public String postForm(String url, List params)
  throws HttpException, IOException {
  url = MiscHelper.toAbsoluteUrl(this.baseUrl, url);
  PostMethod authpost = new UTF8PostMethod(url);
  authpost.setRequestHeader(“ContentType”,
  “application/x-www-form-urlencoded;charset=UTF-8”);
  // authpost.addRequestHeader(“Content-Type”,“Content-Type: text/html;
  // charset=utf-8”);
  // Prepare login parameters
  NameValuePair postParams = new NameValuePair[params.size()];
  params.toArray(postParams);
  authpost.setRequestBody(postParams);
  client.executeMethod(authpost);
  authpost.releaseConnection();
  int statuscode = authpost.getStatusCode();
  if ((statuscode == HttpStatus.SC_MOVED_TEMPORARILY)
  || (statuscode == HttpStatus.SC_MOVED_PERMANENTLY)
  || (statuscode == HttpStatus.SC_SEE_OTHER)
  || (statuscode == HttpStatus.SC_TEMPORARY_REDIRECT)) {
  Header header = authpost.getResponseHeader(“location”);
  if (header != null) {
  String newuri = header.getValue();
  if ((newuri == null) || (newuri.equals(“”))) {
  newuri = “/”;
  }
  return newuri;
  }
  }
  return null;

  }

  public static class UTF8PostMethod extends PostMethod {
  public UTF8PostMethod(String url) {
  super(url);
  }

   @Override
   public String getRequestCharSet() {
   	// return super.getRequestCharSet();
   	return "UTF-8";
   }
  

  }

}[/code]