从applet调用javascript方法时出错

Question

我试图使用netscapte.java.JSObject从Applet调用javascript方法。

在小程序中：

JSObject window = JSObject.getWindow(this.Class); 
Object[] args = ....  //arguments 
window.call("javascriptMethodName", args); 

但我在window.call得到了异常：

JavaScript error while calling "callFromJava"
netscape.javascript.JSException: JavaScript error while calling "callFromJava"
    at sun.plugin2.main.client.MessagePassingJSObject.newJSException(Unknown Source)
    at sun.plugin2.main.client.MessagePassingJSObject.waitForReply(Unknown Source)
    at sun.plugin2.main.client.MessagePassingJSObject.call(Unknown Source)
    at TextBoxApplet.jButton1_actionPerformed(TextBoxApplet.java:57)
    at TextBoxApplet.access$000(TextBoxApplet.java:16)
    at TextBoxApplet$1.actionPerformed(TextBoxApplet.java:36)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

JSObject不为null 。 有没有遇到过这个？ 非常感谢。

Answer 1

我做了一个快速测试，我的发现与musicfreak的评论很好地相关。

使用以下Applet：

public class MyClass extends JApplet {
    public void init() {
        JSObject window = JSObject.getWindow(this); 
        Object[] args = new String[] { "bar" }; 
        window.call("foo", args); 
    }
}

和以下标记（注意错误的JavaScript - 我传递的bar参数中没有baz方法）：

<html>
  <head>
    <title>MyAppletTest</title>
  </head>
  <body>
    <script type="text/javascript">
      function foo(bar) { bar.baz(); }
    </script>
    <applet code="MyApplet.class"></applet>
  </body>
</html>

我收到错误：

netscape.javascript.JSException: JavaScript error while calling "foo"
    at sun.plugin2.main.client.MessagePassingJSObject.newJSException(Unknown Source)
    at sun.plugin2.main.client.MessagePassingJSObject.waitForReply(Unknown Source)
    at sun.plugin2.main.client.MessagePassingJSObject.call(Unknown Source)
    at MyApplet.init(MyApplet.java:13)

如果我通过将bar.baz()替换为alert(bar)来修复我的JavaScript函数，那么一切正常。

简而言之 - 再看看你想要调用的JavaScript函数，以及你的Applet随调用传递的参数。

Answer 2

在运行与JavaScript交互的applet之前还有一个要求。 作为安全预防措施，除非网页作者（可能与applet作者不同）明确授予applet这样做的权限，否则不允许applet使用JavaScript。 要授予此权限，您必须在HTML文件的applet标记中包含新的MAYSCRIPT属性。

例19.5显示了一个使用JavaScript显示警告对话框的applet片段。 成功编译此applet后，您可以将其包含在HTML文件中，其中包含以下HTML代码：

如果您不记得包含MAYSCRIPT标记，则不允许该applet与JavaScript交互。

http://docstore.mik.ua/orelly/web/jscript/ch19_06.html