Name: mgC56079 Date: 09/26/97



  The java.awt.FontMetrics class is incorrectly deserialized when its
serialization processes has been performed on a platform that differs from
the one that class has been serialized on.

  This is caused by a fact that FontMetrics is an abstract class and any its
instance being serialized is an instance of a platform-specific class that
extends FontMetrics. Therefore, while that instance being deserialized on an
another platform, this platform may not support the class the instance of which
has actually been serialized and that causes the deserialization process to
fail.

Here is the test demonstrating the bug:

----------------FontMetricsTest.java--------------

import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Panel;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class FontMetricsTest {

  public static void main(String args[]) {

    FontMetrics fontMetrics;

    if (args.length != 2) {

      System.out.println("There should be exactly two arguments");

    } else {

      String filepath = args[1] + "FontMetrics.ser";

      if (args[0].equals("write")) {

        fontMetrics = new Panel().getFontMetrics(
          new Font("Helvetica", Font.PLAIN, 12)
        );

        ObjectOutputStream stream = null;

        try {

          stream = new ObjectOutputStream(
            new FileOutputStream(filepath)
          );

        } catch(IOException e) {
          System.out.println("Couldn't create " + filepath + " : " + e);
          System.exit(1);
        }

        try {

          stream.writeObject(fontMetrics);
          stream.close();

        } catch(IOException e) {
          System.out.println("Couldn't write to " + filepath + " : " + e);
          System.exit(1);
        }

        System.out.println("FontMetrics written successfully");

      } else if (args[0].equals("read")) {

        ObjectInputStream stream = null;

        try {

          stream = new ObjectInputStream(
            new FileInputStream(filepath)
          );

        } catch(IOException e) {
          System.out.println("Test failed: " + filepath + " not found");
          System.exit(1);
        }

        try {

          fontMetrics = (FontMetrics)stream.readObject();

        } catch(ClassNotFoundException e) {
          System.out.println("Test failed:" + e);
          System.exit(1);
        } catch(IOException e) {
          System.out.println(
            "Test failed: couldn't read from" + filepath + " : " + e
          );
          System.exit(1);
        }

        System.out.println("Test passed");

      } else {
        System.out.println(
          "The first argument should be either 'read' or 'write'"
        );
        System.exit(1);
      }

    }

    System.exit(0);

  }

}

---Writing the test data under Solaris platform----
>java FontMetricsTest write tmp
FontMetrics written succesfully

--Reading the test data under Solaris platform----
>java FontMetricsTest read tmp
Test passed

---Reading the test data under Windows platform
>java FontMetricsTest read tmp
Test failed:java.lang.ClassNotFoundException: /sun/awt/motif/X11FontMetrics

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