如何使pdf成爲下載選項而不是在瀏覽器上呈現？

Question

我在我的項目中使用Jasper Reports來生成多種格式的報告。雖然所有的代碼示例運行良好，但我遇到了一個概念問題。

我寫這在瀏覽器產生一個PDF的下載選項，這個簡單的代碼：

@GET 
    @Path("/basicdbreport") 
    @Produces("application/pdf") 
    public Response basicDbReport(@Context ServletContext context, 
      @Context HttpServletResponse response) throws JRException, 
      IOException { 
     Connection connection = null; 
     byte[] reportBytes = null; 
     String reportName = "firstsqlexample"; 

     File file = new File(path + reportName + JASPER_EXTENSION); 

     // check if compiled report exists 
     if (!file.exists()) { 
      compileReport(context.getRealPath(path + reportName + JRXML_EXTENSTION)); 
     } 

     // input stream for filling the compiled report 
     InputStream compiledReportStream = context.getResourceAsStream(path 
       + reportName + JASPER_EXTENSION); 

     try { 
      connection = dataSource.getConnection(); 
      reportBytes = JasperRunManager.runReportToPdf(compiledReportStream, 
        new HashMap<String, Object>(), connection); 

     } catch (SQLException e) { 
      e.printStackTrace(); 
     } finally { 
      try { 
       connection.close(); 
      } catch (SQLException e) { 
       e.printStackTrace(); 
      } 
     } 

     if (reportBytes != null) { 
      ServletOutputStream outputStream = response.getOutputStream(); 
      outputStream.write(reportBytes); 
     } 

     ResponseBuilder restResponse = Response.ok(); 
     restResponse.header("Content-Disposition", 
       "attachment; filename=firstSQLReport.pdf"); 
     return restResponse.build(); 
    } 

的代碼運行正常，我在瀏覽器中得到下載提示。但是，當我深入研究Jasper API時，我發現了一種方法runReportToPdfStream()，它將爲我處理輸出流。

新的代碼看起來是這樣的：

@GET 
    @Path("/basicdbreport") 
    @Produces("application/pdf") 
    public Response basicDbReport(@Context ServletContext context, 
      @Context HttpServletResponse response) throws JRException, 
      IOException { 
     ServletOutputStream outputStream = response.getOutputStream(); 
     Connection connection = null; 
     String reportName = "firstsqlexample"; 

     File file = new File(path + reportName + JASPER_EXTENSION); 

     // check if compiled report exists 
     if (!file.exists()) { 
      compileReport(context.getRealPath(path + reportName + JRXML_EXTENSTION)); 
     } 

     // input steam to fill complied report 
     InputStream compiledReportStream = context.getResourceAsStream(path 
       + reportName + JASPER_EXTENSION); 

     try { 
      connection = dataSource.getConnection(); 
      JasperRunManager.runReportToPdfStream(compiledReportStream, outputStream, new HashMap<String, Object>(), connection); 

     } catch (SQLException e) { 
      e.printStackTrace(); 
     } finally { 
      try { 
       connection.close(); 
      } catch (SQLException e) { 
       e.printStackTrace(); 
      } 
     } 

     ResponseBuilder restResponse = Response.ok(); 
     restResponse.header("Content-Disposition", 
       "attachment; filename=firstSQLReport.pdf"); 
     return restResponse.build(); 
    } 

的代碼運行正常，但我沒有得到任何下載提示，則PDF獲取呈現在瀏覽器。響應頭如下（瀏覽器）：

HTTP/1.1 200 OK 
Server: Apache-Coyote/1.1 
Transfer-Encoding: chunked 
Date: Wed, 21 Aug 2013 05:51:42 GMT 

那是什麼代碼現在不能提供下載提示的原因是什麼？我不是以HTTP的王牌，但我想這一點：

restResponse.header("Content-Disposition", 
        "attachment; filename=firstSQLReport.pdf"); 

負責下載選項。儘管我將它包含在代碼中，但它並未在迴應中出現。請指教。

Answer 1

是的，你是對的，Content-Disposition是，你需要設置觸發客戶端瀏覽器的下載動作響應頭。

我認爲你需要先寫入響應輸出流之前設置的響應頭。