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  1. JDK
  2. JDK-4168475

beta4: Introspector doesn't let you override BeanInfo for core classes

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P3
    • Resolution: Fixed
    • Affects Version/s: 1.2.0
    • Fix Version/s: 1.2.0
    • Component/s: client-libs
    • Labels:
      None
    • Subcomponent:
    • Resolved In Build:
      1.2fcs
    • CPU:
      x86
    • OS:
      windows_nt
    • Verification:
      Not verified

      Description

      In JDK 1.2 beta4, it is not possible for a user to provide BeanInfo for
      any of the core classes. I have reported this as a bug using the bug
      submission form, but I thought I would mail you about it as well, as I
      very much hope that it will be fixed as soon as possible. The details of the
      problem are as follows:

      I would like to provide a BeanInfo for a core class, lets say
      java.awt.Component, for example. So I write a
      my.beans.infos.ComponentBeanInfo class, and use the
      Introspector.setBeanInfoSearchPath() method to put my.beans.infos on
      the search path. Example source code for this is provided below. This
      all works OK under 1.2beta3 and earlier, but under 1.2beta4 the
      Introspector fails to find my BeanInfo. It does work if you use the
      1.2Beta4 oldjava program. I believe the problem is due to the changes
      in class loading in 1.2Beta4. What happens is that the Introspector
      tries to get a classloader by using the getClassLoader() method, but
      for the java.awt.Component class this returns null, because
      java.awt.Component is a bootstrap class. Therefore the Introspector
      uses Class.forName("my.beans.infos.ComponentBeanInfo") instead. This
      fails because Class.forName() uses the classloader of the class it is
      called from, and java.beans.Introspector is a bootstrap class, and the
      bootstrap classloader fails because my.beans.infos.ComponentBeanInfo is
      not a bootstrap class.

      Note that a similar problem occurs with property editors and the
      PropertyEditorManager.

      Here is some source code that shows the problem:

      BeanInfoCheck.java:
      import java.beans.*;

      public class BeanInfoCheck {

          public static void main(String[] args) throws Exception {
              String[] beanInfoPath = {"my.beans.infos"};
              Introspector.setBeanInfoSearchPath(beanInfoPath);
              BeanInfo bi = Introspector.getBeanInfo(java.awt.Component.class);
              PropertyDescriptor[] pds = bi.getPropertyDescriptors();
              for (int j = 0; j < pds.length; j++) {
                  System.out.println(pds[j].getName());
              }
          }

      }

      my.beans.infos.ComponentBeanInfo.java:
      package my.beans.infos;

      import java.beans.*;

      public class ComponentBeanInfo extends SimpleBeanInfo {

          public PropertyDescriptor[] getPropertyDescriptors() {
              try {
                  PropertyDescriptor name =
                      new PropertyDescriptor("name", java.awt.Component.class);
                  PropertyDescriptor[] rv = {name};
                  return rv;
              } catch (IntrospectionException e) {
                  throw new Error(e.toString());
              }
          }
      }

      Instructions:
      Run "java BeanInfoCheck". It should just print out "name", but in fact
      it prints out all the properties. It works correctly with oldjave or
      previous JDKs.

      [This came in on the java.beans alias]

      graham.hamilton@Eng 1998-08-22

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              Assignee:
              ghamiltosunw Graham Hamilton (Inactive)
              Reporter:
              ghamiltosunw Graham Hamilton (Inactive)
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