JAVABEANS FAQ: HELP WITH COMMON PROBLEMS

Why do my event hookups fail to find sun/tools/javac/Main?

You need to make sure that the JDK 1.1 version of the "java" command comes before any other version of java on your PATH. The Java Development Kit (JDK) 1.1 includes the javac compiler classes that are needed by the BeanBox. If you have installed another JDK 1.1 tool (such as HotJava) that doesn't include the compiler classes, then you must put it after the JDK 1.1 bin directory on your PATH.

How do I find out what version of JDK and the BDK I am using?

Use "java -version" to check the version of the JDK on your path. The output should be something like

        java version "JDK 1.1_Final"

 

Starting with the February 1997 release of BDK 1.0, you can check the version of your BeanBox by typing (on Windows 95 and Windows NT - for Solaris replace the "set" with the appropriate "setenv"):

        cd beanbox

        set CLASSPATH=classes

        java sun.beanbox.BeanBoxFrame -version

 

The output should be something like:

        BeanBox version: BDK 1.0 - February 1997

When I try to build the example Beans I get compiler errors. What's wrong?

You need to use the JDK1.1 version of javac to compile the BDK. If you use the JDK 1.0.2 compiler then you will get errors when compiling various parts of the BDK sources. See above for details on how to find out what version you are using.

I'm having trouble with the "Simplest Bean" from the February '97 tutorial; what's the problem?

The original tutorial included in the February '97 release of BDK had a few typographical errors, particularly in the use of "/" and "\", and in some instructions on how to run nmake. There is a corrected version of the tutorial, February '97 rev 3 that can be downloaded from our web site in Adobe's PDF or Postscript formats.

Why do I get a null pointer when loading a JAR file into the BeanBox?

Usually this is because of a mistake in the JAR file being loaded. The class loader used by the BeanBox should give a better error message. This will be addressed in a future release of the BDK. In the meantime, typical errors include:

• The MANIFEST file uses classes using the wrong file separator ("/" should be used in all platforms).
• The MANIFEST file refers to classes in a package but the actual .class files are not really in that package.

Why do I get a duplicate name error when loading a JAR file

The most common reason for a "java.lang.ClassFormatError: Duplicate name" error is that a .class file in the JAR contains a class whose class name is different from the expected name. So for example if you have a file called "a/B.class" and it contains a class called "B" or "a.X" instead of the class "a.B" then you will get this error.

The most common causes for this problem are either forgetting to include a "package a;" statement or having a "package" statement with the wrong name.

Why does my Beans.instantiate() fail?

Beans.instantiate() does two things: it loads a class and creates a Class object, and it then instantiates an object of that class. If the Bean name corresponds to a serialized Bean prototype, it uses that prototype. Otherwise the instantiation uses a zero-argument constructor. Several things may fail in these actions, including:

• There may not be a class of the given name
• The class may not be public
• The class may be in a package that cannot be created given the existing Security Manager (for example, the Applet Security Manager typically will not let the applet instantiate "java.*" and "sun.*" classes)
• There may not be any public zero-argument constructor for the class.
• The serialized stream may contain a version of the class that is not compatible with the one loaded (or available through the classloader argument) in the JVM.

A typical idiom to use Beans.instantiate is Beans.instantiate(this.getClass().getClassLoader(), theBeanName)

Why does my BeanBox fail with a NullPointerException at start-up time?

This is a bug in JDK 1.1 that affects a Java application running JDK 1.1 under Solaris. It generally appears when displaying against a remote X server. The bug has been fixed in the upcoming JDK 1.1.1 maintenance release.

From the bug description:

• You may get a NullPointerException if the default font listed in the $JAVA_HOME/lib/font.properties file is not available on Unix environments. In order to workaround this, change the default font in this file to a font which does exist on your system. If you don't need to run in a multifont (internationalized) environment, you can simply remove this file.

Where can I get a copy of nmake for Windows?

Nmake is available as a self-extracting .exe for download from: ftp.microsoft.com/Softlib/MSLFILES/nmake15.exe

When I try to implement an event on another bean, I get the statement "generating adapter class" and it hangs.

There is a bug in the BDK with the default installation in the "Program Files" directory. The command that compiles the adapter class can't execute correctly because of the space in the path.

To fix it, you should re-install the BDK in a different location. Perhaps c:\bdk1.1.

This bug is discussed in the following bug report. http://developer.java.sun.com/developer/bugParade/bugs/4257660.html

When I run the BeanBox under J2SE v 1.4 I get an exception. What's going on here?

There were some changes made to the Introspector in order for EventSets created by the Intospector to conform to the JavaBeans specification. See bugs 4402159 and 4407239 for details. Unfortunately, the ExplicitButtonBeanInfo class that shipped with the BDK do not conform to the JavaBeans specification and are rejected. This is not as bad as it seems. Other than the exeption being thrown at startup and the failure to load the buttons.jar file, the rest of the BeanBox will work fine.

As a work around, you may want to go into the sunw.demo.buttons.ExplicitBeanInfo.getEventSetDescriptors() source file, change the first actionPerformed string in the first EventSetDescriptor to be action and recompile the class. The source file for the demo beans used in the BeanBox is in <BDK_INSTALL_DIR>demo\sunw\demo\buttons\ExplicitButtonBeanInfo.java. At around line 47, change:

            EventSetDescriptor push = new EventSetDescriptor(beanClass,
                    "actionPerformed",
            java.awt.event.ActionListener.class,
            "actionPerformed");

            EventSetDescriptor push = new EventSetDescriptor(beanClass,
                    "action",
            java.awt.event.ActionListener.class,
            "actionPerformed");