无法使用JNLP保存

Question

我正在尝试使用JNLP在本地系统中保存applet但是获取异常

Exception in thread "AWT-EventQueue-2" java.lang.NullPointerException

以下是摘录

public void genericDocSave() {
                System.out.println("in genericDocSavedfdd");
                 FileSaveService fss; 
                    FileOpenService fos; 

                    try { 
                        fos = (FileOpenService)ServiceManager.lookup("javax.jnlp.FileOpenService"); 
                        fss = (FileSaveService)ServiceManager.lookup 
                                                   ("javax.jnlp.FileSaveService"); 
                    } catch (Exception e) { 
                        fss = null; 
                        fos = null; 
                    } 

                    if (fss != null && fos != null) { 
                        try { 
                            // get a file with FileOpenService 
                            FileContents fc = fos.openFileDialog(null, null); 
                            // one way to save a file 
                            FileContents newfc = fss.saveFileDialog(null, null, 
                            fc.getInputStream(), "C:\\abc.tiff"); 

                        } catch (Exception e) { 
                            e.printStackTrace(); 
                        } 
                    }