PATHJava Developer Documentation > Mac OS Runtime for Java > JManager > Programming With JManager

Instantiating Applets

After you have created a session, located the applet, and created an AWT context for the applet, you can instantiate it. An instantiated applet is defined by an JMAppletViewerRef object, and you use the JMNewAppletViewer function JMNewAppletViewer to create one. Listing 1-11 shows an example of instantiating an applet.

Listing 1-11 Instantiating an applet



 
JMAppletSecurity securitySettings = {

    kJMVersion,         /* should be kJMVersion */

    eAppletHostAccess,  /* applet network access option */

    eLocalAppletAccess, /* applet access to local file system */

    true,               /* restrict system.access packages */

    true,               /* restrict system.define packages */

    true,               /* restrict application.access packages */

    true                /* restrict application.define packages */

    };



JMAppletViewerCallbacks viewerCallbacks = {

    kJMVersion,         /* should be kJMVersion */

    MyShowDocument,     /* showDocument callback */

    MySetStatusMsg      /* setMessage callback */

    };



JMAppletViewerRef viewer;

err = JMNewAppletViewer(&viewer, context, locatorRef, 

        appletIndex, &securitySettings, &viewerCallbacks, 0);



/* reload the applet to get it going */

if (err == noErr) {

    err = JMReloadApplet(viewer);

    }

The JMNewAppletViewer function requires you to pass a security options data structure indicating the following security settings:

The applet network access field designates the applet's level of network access. Typically you should set this to eAppletHostAccess to indicate that an applet can access only its host server. See Applet Security Indicators for a list of available options.
The applet local file system access field designates whether an applet can access files stored on the host computer. Typically you should set this to eLocalAppletAccess to indicate that only an applet stored locally can access the local file system. See Applet Security Indicators for a list of available options.
The next four fields are flags that let you specify that whether to allow class access or class definitions outside the java.* classes. A flag that is set to true restricts access to the packages defined in the corresponding property:

mrj.security.system.access
mrj.security.system.define
mrj.security.application.access
mrj.security.application.define

See Applet Security Structure for more information about using these flags.

If you want to determine the current security levels for a particular applet, you can use the JMGetAppletViewerSecurity function JMGetAppletViewerSecurity. To change existing security levels, you can use The JMSetAppletViewerSecurity function.

In addition, you must define two callbacks, MyShowDocument and MySetStatusMsg, when calling the JMNewAppletViewer function. The MyShowDocument function displays the contents of a URL passed back from the applet, and MySetStatusMsg displays any status messages the applet may pass to the application. You must also specify the index of the applet you want to instantiate (as returned by the JMCountApplets function JMCountApplets).

After you have instantiated the applet viewer object, you must load and execute the applet code by calling the function JMReloadApplet.

You can set or retrieve client data associated with the applet by using the functions JMSetAppletViewerData and JMGetAppletViewerData.

At any time you can stop execution of the applet by calling the JMSuspendApplet function JMSuspendApplet and resume it by calling the JMResumeApplet function JMResumeApplet. If you want to restart the applet without reloading it from the server, use The JMRestartApplet function.

When you are finished with an applet, you can dispose of it by calling the JMDisposeAppletViewer function JMDisposeAppletViewer. This function automatically halts applet execution and removes any frames associated with the applet.