HttpClient实现HTTP文件通用下载类

 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.InputStream;  

 import org.apache.http.Header;
 import org.apache.http.HeaderElement;
 import org.apache.http.HttpEntity;
 import org.apache.http.HttpResponse;
 import org.apache.http.NameValuePair;
 import org.apache.http.client.HttpClient;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.impl.client.DefaultHttpClient;  

 /**
  * 说明
  * 利用httpclient下载文件
  * maven依赖
  * <dependency>
 *           <groupId>org.apache.httpcomponents</groupId>
 *           <artifactId>httpclient</artifactId>
 *           <version>4.0.1</version>
 *       </dependency>
 *  可下载http文件、图片、压缩文件
 *  bug：获取response header中Content-Disposition中filename中文乱码问题
  * @author tanjundong
  *
  */
 public class HttpDownload {  

     public static final int cache = 10 * 1024;
     public static final boolean isWindows;
     public static final String splash;
     public static final String root;
     static {
         if (System.getProperty("os.name") != null && System.getProperty("os.name").toLowerCase().contains("windows")) {
             isWindows = true;
             splash = "\\";
             root="D:";
         } else {
             isWindows = false;
             splash = "/";
             root="/search";
         }
     }  

     /**
      * 根据url下载文件，文件名从response header头中获取
      * @param url
      * @return
      */
     public static String download(String url) {
         return download(url, null);
     }  

     /**
      * 根据url下载文件，保存到filepath中
      * @param url
      * @param filepath
      * @return
      */
     public static String download(String url, String filepath) {
         try {
             HttpClient client = new DefaultHttpClient();
             HttpGet httpget = new HttpGet(url);
             HttpResponse response = client.execute(httpget);  

             HttpEntity entity = response.getEntity();
             InputStream is = entity.getContent();
             if (filepath == null)
                 filepath = getFilePath(response);
             File file = new File(filepath);
             file.getParentFile().mkdirs();
             FileOutputStream fileout = new FileOutputStream(file);
             /**
              * 根据实际运行效果 设置缓冲区大小
              */
             byte[] buffer=new byte[cache];
             int ch = 0;
             while ((ch = is.read(buffer)) != -1) {
                 fileout.write(buffer,0,ch);
             }
             is.close();
             fileout.flush();
             fileout.close();  

         } catch (Exception e) {
             e.printStackTrace();
         }
         return null;
     }
     /**
      * 获取response要下载的文件的默认路径
      * @param response
      * @return
      */
     public static String getFilePath(HttpResponse response) {
         String filepath = root + splash;
         String filename = getFileName(response);  

         if (filename != null) {
             filepath += filename;
         } else {
             filepath += getRandomFileName();
         }
         return filepath;
     }
     /**
      * 获取response header中Content-Disposition中的filename值
      * @param response
      * @return
      */
     public static String getFileName(HttpResponse response) {
         Header contentHeader = response.getFirstHeader("Content-Disposition");
         String filename = null;
         if (contentHeader != null) {
             HeaderElement[] values = contentHeader.getElements();
             if (values.length == 1) {
                 NameValuePair param = values[0].getParameterByName("filename");
                 if (param != null) {
                     try {
                         //filename = new String(param.getValue().toString().getBytes(), "utf-8");
                         //filename=URLDecoder.decode(param.getValue(),"utf-8");
                         filename = param.getValue();
                     } catch (Exception e) {
                         e.printStackTrace();
                     }
                 }
             }
         }
         return filename;
     }
     /**
      * 获取随机文件名
      * @return
      */
     public static String getRandomFileName() {
         return String.valueOf(System.currentTimeMillis());
     }
     public static void outHeaders(HttpResponse response) {
         Header[] headers = response.getAllHeaders();
         for (int i = 0; i < headers.length; i++) {
             System.out.println(headers[i]);
         }
     }
     public static void main(String[] args) {
 //      String url = "http://bbs.btwuji.com/job.php?action=download&pid=tpc&tid=320678&aid=216617";
         String url="http://www.dy1000.com/img/20120701/1999311085_150_200.JPG";
 //      String filepath = "D:\\test\\a.torrent";
         String filepath = "D:\\test\\a.jpg";
         HttpDownload.download(url, filepath);
     }
 }  

参考资料： 
http://eyecm.com/httpclient4-1-tutorial-official-examples-to-explain-httpclient4-1-usage/ 
http://eyecm.com/httpclient-download/