Java PrintService属性的序列化

Question

From my search, I think this is a pretty good summary of my problem. Perhaps, I'm serializing or de-serializing the objects wrong? Or if the serialization is correct, is there a fix/workaround to my issue?

I've been using this as reference to the Win32MediaSize class. I've got another slightly related question regarding the referenced Win32MediaSize class. See the code that begins at 1640 which is the static initializer. I tried to reproduce that so I could see execution order:

public clsss Why {

  static {
    String a = "Hello";
  }

  public class Not {
    static { // gives me a Cannot define static initializer in inner type error
      String b = "World";
    }
  }
}

This isn't the main issue but it would be great if someone could shed some light here. I personally believe its the problem in Win32MediaSize but I don't know why. I also tried what they did on line 85 and double brackets and neither works. Removing the keyword static does resolve the error but I think that produces different behavior per my understanding.

The basic problem is that I need to execute getSupportedAttributeValues for each PrintService in order to read in serialized data which defeats the purpose of serializing the data. The reason for serializing the data is because getSupportedAttributeValues takes too long to finish (40+ seconds).

Here's the exception (the value and range varies depending on far along the PrintService has loaded - in the actual program it's loading in another thread; see this for reference):

java.io.InvalidObjectException: Integer value = 124 not in valid range 0..3for class class sun.print.Win32MediaSize
    at javax.print.attribute.EnumSyntax.readResolve(EnumSyntax.java:184)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at java.io.ObjectStreamClass.invokeReadResolve(ObjectStreamClass.java:1056)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1761)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1328)
    at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1666)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1322)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:350)
    at java.util.HashMap.readObject(HashMap.java:1030)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:969)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1848)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1752)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1328)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:350)
    at com.iii.print.PrintServiceLoader.readCachedData(PrintServiceLoader.java:355)
    at com.iii.print.PrintServiceLoader.main(PrintServiceLoader.java:420)

Here's the relevant code bits:

Methods works() and fails() is what I'm having issues with.

void works() {
  HashMap<String, Object> m = null;
  HashMap<String, Object> mpa = null;
  doLookup(); // this is what causes the following call to not fail
  m = readCachedData( "a" );
  mpa = readCachedData( "b" );
}

void fails() {
  /* Assuming the files have already been created */
  HashMap<String, Object> m = null;
  HashMap<String, Object> mpa = null;
  m = readCachedData( "a" ); // this fails (see exception)
  mpa = readCachedData( "b" ); // this will work just fine
}


void doLookup() {
  PrintService[] psList = PrintServiceLookup.lookupPrintServices( DocFlavor.SERVICE_FORMATTED.PRINTABLE, null );

  HashMap<String, Object> cachedMedia = new HashMap<String, Object>();
  HashMap<String, Object> cachedMediaPrintableArea = new HashMap<String, Object>();
  for ( PrintService ps : psList ) {
    Object media = ps.getSupportedAttributeValues( Media.class, null, null );
    Object mediaPrintableArea = ps.getSupportedAttributeValues( MediaPrintableArea.class, null, null );
    cachedMedia.put( ps.getName(), media );
    cachedMediaPrintableArea.put( ps.getName(), mediaPrintableArea );
  }

  writeCachedData( "a", cachedMedia );
  writeCachedData( "b", cachedMediaPrintableArea );
}

boolean writeCachedData( String filename, Map<String, Object> data ) {
  boolean successful = true;

  if ( filename != null && !filename.isEmpty() && data != null && !data.isEmpty() ) {
    FileOutputStream fileOutStream = null;
    ObjectOutputStream objOutStream = null;

    try {
      fileOutStream = new FileOutputStream( filename );
      objOutStream = new ObjectOutputStream( fileOutStream );
      objOutStream.writeObject( data );
    } catch ( FileNotFoundException e ) {
      e.printStackTrace();
      successful = false;
    } catch ( IOException e ) {
      e.printStackTrace();
      successful = false;
    } finally {
      try {
        if ( objOutStream != null ) {
          objOutStream.close();
        }
      } catch ( IOException e ) {
        e.printStackTrace();
        successful = false;
      }
      try {
        if ( fileOutStream != null ) {
          fileOutStream.close();
        }
      } catch ( IOException e ) {
        e.printStackTrace();
        successful = false;
      }
    }

  } else {
    successful = false;
  }

  return successful;
}

Map<String, Object> readCachedData( String filename ) {
  Map<String, Object> cachedData = null;

  if ( filename != null && !filename.isEmpty() ) {
    File f = new File( ".", filename );
    if ( f.exists() ) {
      FileInputStream fileInStream = null;
      ObjectInputStream objInStream = null;

      try {
        fileInStream = new FileInputStream( f );
        objInStream = new ObjectInputStream( fileInStream );
        cachedData = (Map<String, Object>) objInStream.readObject();
      } catch ( FileNotFoundException e ) {
        e.printStackTrace();
      } catch ( IOException e ) {
        e.printStackTrace();
      } catch ( ClassNotFoundException e ) {
        e.printStackTrace();
      } finally {
        try {
          if ( fileInStream != null ) {
            fileInStream.close();
          }
        } catch ( IOException e ) {
          e.printStackTrace();
        }
        try {
          if ( objInStream != null ) {
            objInStream.close();
          }
        } catch ( IOException e ) {
          e.printStackTrace();
        }
      }
    }
  }

  return cachedData;
}

As you can tell, I'm on Windows 7 x64 and using jdk 1.6.0_31. Let me know if I left out relevant information.

Answer 1

Concerning your first problem:

class Not should be public static, not public.

public class Test {

    static {

    }

    public static class Not {
        static { 
            String b = "World";
        }
    }
}