HttpClient实现HTTP文件通用下载类

Java代码  

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/