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  1. JDK
  2. JDK-6180799

Java Bean with zero properties will cause a NullPointerException when getBeanInf

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P2
    • Resolution: Duplicate
    • Affects Version/s: 1.4.2_06
    • Fix Version/s: 1.4.2_06
    • Component/s: client-libs
    • Labels:

      Description

      In JDK 1.4.2_06, a Java Bean with zero properties will cause a NullPointerException when getBeanInfo() is called.

        From my inspection of the source code of java/bean/Introspection.java, I believe this is caused because the pdStore Map is not instantiated until addPropertyDescriptor(PropertyDescriptor) is called. If a bean has no properties, this is never called. Then when processPropertyDescriptors() is called, the null pdStore results in immediate return before properties can be assigned to a new HashMap. In getTargetPropertyInfo(), the call to properties.size() on line 591 then results in a NPE.

      Below is a simple test case and instructions on its execution.

      Instructions to Compile and Execute:

      javac -g Bisc.java beans/nb.java
      java Bisc beans.nb


      Results of Execution with JDK 1.4.2_05 (Correct Behavior)

      bash-2.05$ java -version
      java version "1.4.2_05"
      Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_05-b04)
      Java HotSpot(TM) Client VM (build 1.4.2_05-b04, mixed mode)
      bash-2.05$ java Bisc beans.nb
      Class beans.nb
       
      Methods via Bean
      bash-2.05$



      Results of Execution with JDK 1.4.2_06 (Incorrect Behavior)

      bash-2.05$ java -version
      java version "1.4.2_06"
      Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_06-b02)
      Java HotSpot(TM) Client VM (build 1.4.2_06-b02, mixed mode)
      bash-2.05$ java Bisc beans.nb
      java.lang.NullPointerException
              at java.beans.Introspector.getTargetPropertyInfo(Introspector.java:591)
              at java.beans.Introspector.getBeanInfo(Introspector.java:380)
              at java.beans.Introspector.getBeanInfo(Introspector.java:215)
              at java.beans.Introspector.getBeanInfo(Introspector.java:201)
              at Bisc.main(Bisc.java:15)
      bash-2.05$


      /////////////////////////
      /// File: beans/nb.java
      /////////////////////////

      package beans;

      public class nb
      {
      }
      /// End File: beans/nb.java

      /////////////////////////
      /// File: Bisc.java
      /////////////////////////

      import java.beans.*;
      import java.lang.reflect.Method;
      import java.lang.reflect.Modifier;

      public class Bisc
      {
          public static void main(String[] args)
          {
              if (args.length != 1)
                  System.err.println("Usage: java Bisc <JavaBeanClassName>");

              try
              {
                  Class cl = Class.forName(args[0]);
                  BeanInfo bi = Introspector.getBeanInfo(cl, cl.getSuperclass());

                  PropertyDescriptor[] pds = bi.getPropertyDescriptors();

                  System.out.println("Class " + args[0]);

                  System.out.println("\nMethods via Bean");
                  for (int i = 0; i < pds.length; i++)
                  {
                      PropertyDescriptor pd = pds[i];
                      System.out.println("Prop " + pd.getName());
                      Method rm = pd.getReadMethod();
                      Method wm = pd.getWriteMethod();

                      if (rm != null)
                      {
                          System.out.print("Read method: ");
                          methodInfo(rm);
                      }
                      else
                          System.out.println("Read method is null");

                      if (wm != null)
                      {
                          System.out.print("Write method: ");
                          methodInfo(wm);
                      }
                      else
                          System.out.println("Write method is null");
                  }
              }
              catch (Exception e)
              {
                  e.printStackTrace();
              }
          }

          static void methodInfo(Method m)
          {
              System.out.println(m.getName());
              System.out.println(" modifiers: " +
                  Modifier.toString(m.getModifiers()));
              System.out.println(" declaring class: " + m.getDeclaringClass());
          }
      }

      /// End File: Bisc.java
      ###@###.### 10/18/04 21:17 GMT

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              Assignee:
              kereminsunw Konstantin Eremin (Inactive)
              Reporter:
              mmma Marvin Ma (Inactive)
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