Create a Java Class that extends RuntimeException.

package com.flex3.exception;
public class FlexException extends RuntimeException
{
public FlexException(String message)
{
super(message);
}
}


2. Create a matching flex class called FlexException, and put the usual RemoteObject tag in their so BlazeDS will know what to look for. Also remember in actionscript, each object must be instantiated at least once, so be sure to do that somewhere with FlexException.

3. In Java, whenever there is a known exception, or some error where the end user needs to be shown a message, throw a FlexException and pass in the message the user should see in the constructor. Let’s say the user just entered an invalid password. throw new FlexException(”Wrong Password Entered, Please Try Again.”); Read more…

• Handling Java Exceptions in Flex application
• What is Flex?
• Flex Component Kit
• Flex 3 Cookbook
• Flex Ajax Bridge
• Rich Internet applications (RIAs)
• Flex Tricks
• Embedded Fonts in Flex
• Exception Handling
• styling the last button in a buttonbar control in flex

Throughout this book, we’ve encountered plenty of compile-time errors—errors reported in the Output panel when a movie is exported. If a compile-time error occurs in an ActionScript 2.0 program, compilation fails and Flash won’t generate a .swf file to execute. But not all ActionScript errors occur at compile time. Some errors don’t occur until runtime, and they may not cause the program to fail completely. For example, suppose we attempt to load an XML file from disk, but the file is not found. If the movie is running in Test Movie mode, the failed load causes the Output panel to display an error message—but the movie continues to run. The following code demonstrates:

// If the specified file doesn’t exist…
var xmlDoc:XML = new XML( );
xmlDoc.load(“http://www.somenonexistentsite.com/someNonExistentFile.xml”);

// …the Output panel displays:
Error opening URL
“http://www.somenonexistentsite.com/someNonExistentFile.xml”

In an ideal world, we’d like to be able to recover from nonfatal error conditions such as a file-not-found. We’d like to tell the user there was a problem loading the file and perhaps display the problematic filename.

Unfortunately, in ActionScript there are precious few built-in runtime errors and, what’s worse, there’s no standard error-handling mechanism for dealing with the errors that do occur at runtime—at least, not for the errors that are generated by ActionScript itself. Most errors in ActionScript occur in the form of custom error codes and return values. For example, a method might return the value -1, false, or nullto indicate that some operation failed. This requires us to write different, individualized code for each kind of error generated by ActionScript. Read more…

• Exception Handling with BlazeDS and Flex
• Handling Java Exceptions in Flex application

Accessing the Throwable object in Flex

RemoteObject component invokes the fault event when an error occurs while remote method invocation. The fault event handler is provided with the FaultEvent object. This FaultEvent object has property named message of type mx.messaging.messages.ErrorMessage. The message property holds the Throwable object from the Java method in the rootCause property. We need to use this rootCause property to retrieve the properties which are set to the Throwable object in Java. All the public properties from the Throwable object are available.

We will see a sample application. In this application I am creating a custom Exception and adding a getter method to that, which will return my custom data. From the Flex application I will access both the error message and the custom data.

MyException.java

public class MyException extends Exception {

public MyException(String message) {

super(message);

}

public String getMyName(){

return “Sujit Reddy G”;

}

}

 

Method throwing exception

This method will throw the custom exception created above, add this method to a Java class. Invoke the below method using RemoteObject component in Flex.

public void throwCheckedException() throws Exception{

throw new MyException(”This is a checked exception”);

}

Reading values in Flex application

We add the method below as the fault event handler to the RemoteObject component in the Flex application. You can see that we accessed the rootCauseobject to retrieve the properties of the custom Exception object returned from the Java method. Read more…

• Exception Handling with BlazeDS and Flex
• styling the last button in a buttonbar control in flex
• learn Flex Application Frameworks
• Add FlexComponents to your mailing lists!
• Great Ways to Learn ActionScript 3 in Flash
• How to Learn Flex
• What is Flex?
• Flex Component Kit
• Flex 3 Cookbook
• Flex Ajax Bridge