JAVA下載的幾種方式：

jsp下載的幾種方式：
1、運用struts的下載類DownloadAction
2、直接流

1、運用struts的下載類DownloadAction

1. package cn.finefuture.common.faxserver.struts;
2. import java.io.IOException;
3. import java.io.InputStream;
4. import javax.servlet.http.HttpServletRequest;
5. import javax.servlet.http.HttpServletResponse;
6. import org.apache.struts.action.ActionForm;
7. import org.apache.struts.action.ActionForward;
8. import org.apache.struts.action.ActionMapping;
9. import org.apache.struts.actions.DownloadAction;
10. import cn.finefuture.common.faxserver.service.FaxServerService;
11. import cn.finefuture.common.faxserver.service.impl.FaxServerServiceImp;
12. public class FaxDownAction extends DownloadAction {
13. private FaxServerService faxServerService = new FaxServerServiceImp();
14. public void setFaxServerService(FaxServerService faxServerService) {
15. this .faxServerService = faxServerService;
16. }
17. @Override
18. protected StreamInfo getStreamInfo(ActionMapping mapping, ActionForm form,
19. HttpServletRequest request, HttpServletResponse response)
20. throws Exception {
21. // 傳真編號
22. String faxId = request.getParameter( "faxId" );
23. InputStream inStream = null ;
24. if (faxId != null && !(faxId.equals( "" ))) {
25. //獲取InputStream
26. inStream = this .faxServerService.getFaxInAtt(faxId);
27. }
28. final InputStream in = inStream;
29. final String contentType = "application/file" ;
30. // 建
31. // 無法在保存文件對話框中顯示正確的文件名
32. response.setHeader( "content-disposition" , "attachment; filename="
33. + faxId);
34. return new DownloadAction.StreamInfo() //使用隱式的方法實現了StreamInfo接口
35. {
36. public String getContentType() {
37. return contentType;
38. }
39. public InputStream getInputStream() throws IOException {
40. return in;
41. }
42. };
43. }
44. // 如果Struts動作不加file請求參數，則通過execute方法將指定目錄中文件列表輸出到客戶端
45. public ActionForward execute(ActionMapping mapping, ActionForm form,
46. HttpServletRequest request, HttpServletResponse response)
47. throws Exception {
48. // 當file參數存在時，則調用DownloadAction中的execute方法
49. // 實際上，在DownloadAction類中的execute方法調用了getStreamInfo方法
50. // 這條語句就相當於調用了getStreamInfo方法
51. return super .execute(mapping, form, request, response);
52. }
53. }

2、第二種自己寫輸出流

1. /**
2. * 下載附件
3. *
4. * @param mapping
5. * @param form
6. * @param request
7. * @param response
8. * @return
9. */
10. public ActionForward doDownLoadAttachment(ActionMapping mapping,
11. ActionForm form, HttpServletRequest request,
12. HttpServletResponse response) {
13. // 傳真編號
14. String faxId = request.getParameter( "faxId" );
15. InputStream inStream = null ;
16. if (faxId != null && !(faxId.equals( "" ))) {
17. inStream = this .faxServerService.getFaxInAtt(faxId);
18. }
19. // 流不等於null
20. if (inStream != null ) {
21. try {
22. // 設置輸出的格式
23. response.reset();
24. response.setContentType( "bin" );
25. // 給中文字符轉碼
26. faxId = new String(faxId.getBytes( "GBK" ), "iso8859-1" );
27. // 設置文件名
28. response.setHeader( "Content-Disposition" ,
29. "attachment;filename=" + faxId);
30. // 循環取出流中的數據
31. byte [] b = new byte [ 1024 ];
32. int len;
33. while ((len = inStream.read(b)) > 0 ) {
34. response.getOutputStream().write(b, 0 , len);
35. }
36. } catch (IOException e) {
37. e.printStackTrace();
38. } finally {
39. try {
40. inStream.close();
41. } catch (IOException e) {
42. e.printStackTrace();
43. }
44. }
45. }
46. return null ;
47. }

參考:

http://blog.csdn.net/chenyanbo/archive/2011/01/20/6154260.aspx