作者：diego lynn
日期：2001-3-25 10:55:47
JNLP API Examples
The JNLP API is designed to provide additional information to the application that would otherwise not be available using the standard Java 2 SE API. The following code examples show how the following services can be used: BasicService, ClipboardService, DownloadService, FileOpenService, FileSaveService, PrintService, and PersistenceService. 
The public classes and interfaces in the JNLP API are included in the jnlp.jar file. This JAR file must be included in the classpath when compiling source files that use the JNLP API. For example (on Windows): 

javac -classpath .;jnlp.jar *.java 

The jnlp.jar file is included in the JNLP Developers Pack 1.0. 
  

Using a BasicService Service
The javax.jnlp.BasicService service provides a set of methods for querying and interacting with the environment similar to what the AppletContext provides for a Java Applet. 
The showURL method uses the JNLP API to direct the default browser on the platform to show the given URL. The method returns true if the request successes, otherwise false. 

import javax.jnlp.*; 
   ... 

   // Method to show a URL 
   boolean showURL(URL url) { 
       try { 
           // Lookup the javax.jnlp.BasicService object 
           BasicService bs = (BasicService)ServiceManager.lookup("javax.jnlp.BasicService"); 
           // Invoke the showDocument method 
           return bs.showDocument(url); 
       } catch(UnavailableServiceException ue) { 
           // Service is not supported 
           return false; 
       } 
    } 

Using a ClipboardService Service
The javax.jnlp.ClipboardService service provides methods for accessing the shared system-wide clipboard, even for applications that are running in the restricted execution environment. 
Java Web Start will warn the user of the potential security risk of letting an untrusted application access potentially confidential information stored in the clipboard, or overwriting contents stored in the clipboard. 

import javax.jnlp; 
    ... 

    private ClipboardService cs; 

    try { 
        cs = (ClipboardService)ServiceManager.lookup 
                 ("javax.jnlp.ClipboardService"); 
    } catch (UnavailableServiceException e) { 
        cs = null; 
    } 

    if (cs != null) { 
        // set the system clipboard contents to a string selection 
        StringSelection ss = new StringSelection("Java Web Start!"); 
        cs.setContents(ss); 
        // get the contents of the system clipboard and print them 
        Transferable tr = cs.getContents(); 
        if (tr.isDataFlavorSupported(DataFlavor.stringFlavor)) { 
           try { 
                String s = (String)tr.getTransferData(DataFlavor.stringFlavor); 
                System.out.println("Clipboard contents: " + s); 
            } catch (Exception e) { 
                e.printStackTrace(); 
            } 
        } 
    } 

Using a DownloadService Service
The javax.jnlp.DownloadService service allows an application to control how its own resources are cached. 
The service allows an application to determine which of its resources are cached, to force resources to be cached, and to remove resources from the cache. 

import javax.jnlp.*; 
    ... 

    DownloadService ds; 

    try { 
        ds = (DownloadService)ServiceManager.lookup("javax.jnlp.DownloadService"); 
    } catch (UnavailableServiceException e) { 
        ds = null; 
    } 

    if (ds != null) { 

        try { 
           // determine if a particular resource is cached 
            URL url = 
                    new URL("http://java.sun.com/products/javawebstart/lib/draw.jar"); 
            boolean cached = ds.isResourceCached(url, "1.0"); 
           // remove the resource from the cache 
           if (cached) { 
                ds.removeResource(url, "1.0"); 
            } 
           // reload the resource into the cache 
            DownloadServiceListener dsl = ds.getDefaultProgressWindow(); 
            ds.loadResource(url, "1.0", dsl); 
        } catch (Exception e) { 
            e.printStackTrace(); 
        } 
    } 

Using a FileOpenService Service
The javax.jnlp.FileOpenService service provides methods for importing files from the local disk, even for applications that are running in the restricted execution environment. 
This interface is designed to provide the same kind of of disk access to potentially untrusted Web-deployed applications that a Web developer has when using HTML.  HTML forms support the inclusion of files by displaying a file open dialog. 

import javax.jnlp.*; 
    ... 

    FileOpenService fos; 

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

    if (fos != null) { 
        try { 
           // ask user to select a file through this service 
            FileContents fc = fos.openFileDialog(null, null); 
           // as user to select multiple files through this service 
            FileContents [] fcs = fos.openMultiFileDialog(null, null); 
        } catch (Exception e) { 
            e.printStackTrace(); 
        } 
    } 
Also see Using FileContents. 

Using a FileSaveService Service
The javax.jnlp.FileSaveService service provides methods for exporting files to the local disk, even for applications that are running in the restricted execution environment. 
This interface is designed to provide the same level of disk access to potentially untrusted Web-deployed applications that a Web browser provides for contents that it is displaying.  Most browsers provide a Save As... dialog as part of their user interface. 

    import javax.jnlp.*; 
    ... 

    FileSaveService fss; 
    FileOpenService fos; 

    try { 
        fos = (FileOpenService)ServiceManager.lookup("javax.jnlp.FileOpenService"); 
        fss = (FileSaveService)ServiceManager.lookup 
                                   ("javax.jnlp.FileSaveService"); 
    } catch (UnavailableServiceException 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(), "newFileName.txt"); 
           // another way to save a file 
            FileContents newfc2 = fss.saveAsFileDialog(null, null, fc); 

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

Also see Using FileContents.