NbObjectInputStream (NetBeans APIs) - NetBeans API Javadoc 4.1.0

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org.openide.util.io
Class NbObjectInputStream

java.lang.Object
  java.io.InputStream
      java.io.ObjectInputStream
          org.openide.util.io.NbObjectInputStream

All Implemented Interfaces:: DataInput, ObjectInput, ObjectStreamConstants

public class NbObjectInputStream
extends ObjectInputStream

Controlled deserialization stream using the system class loader. Employs the classloader available from lookup (currently that used for modules). Also contains static methods to safely read objects that might have problems during deserialization that should not corrupt the stream. The stream also provides support for changing name of stored classes.

See Also:: readClassDescriptor()

Nested Class Summary

Nested classes inherited from class java.io.ObjectInputStream

ObjectInputStream.GetField

Field Summary

Fields inherited from interface java.io.ObjectStreamConstants

baseWireHandle, PROTOCOL_VERSION_1, PROTOCOL_VERSION_2, SC_BLOCK_DATA, SC_EXTERNALIZABLE, SC_SERIALIZABLE, SC_WRITE_METHOD, STREAM_MAGIC, STREAM_VERSION, SUBCLASS_IMPLEMENTATION_PERMISSION, SUBSTITUTION_PERMISSION, TC_ARRAY, TC_BASE, TC_BLOCKDATA, TC_BLOCKDATALONG, TC_CLASS, TC_CLASSDESC, TC_ENDBLOCKDATA, TC_EXCEPTION, TC_LONGSTRING, TC_MAX, TC_NULL, TC_OBJECT, TC_PROXYCLASSDESC, TC_REFERENCE, TC_RESET, TC_STRING

Constructor Summary

NbObjectInputStream(InputStream is)
          Create a new object input.

Method Summary

protected ObjectStreamClass readClassDescriptor()
          Provides a special handling for renaming of serialized classes.

static Object readSafely(ObjectInput oi)
          Reads an object from the given object input.

protected Class resolveClass(ObjectStreamClass v)


static void skipSafely(ObjectInput oi)
          Skips an object from the given object input without loading it.

Methods inherited from class java.io.ObjectInputStream

available, close, defaultReadObject, enableResolveObject, read, read, readBoolean, readByte, readChar, readDouble, readFields, readFloat, readFully, readFully, readInt, readLine, readLong, readObject, readObjectOverride, readShort, readStreamHeader, readUnshared, readUnsignedByte, readUnsignedShort, readUTF, registerValidation, resolveObject, resolveProxyClass, skipBytes

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.io.ObjectInput

read, skip

Constructor Detail

NbObjectInputStream

public NbObjectInputStream(InputStream is)
                    throws IOException

Create a new object input.
Parameters:: is - underlying input stream
Throws:: IOException - for the usual reasons

Method Detail

resolveClass

protected Class resolveClass(ObjectStreamClass v)
                      throws IOException,
                             ClassNotFoundException

Throws:: IOException; ClassNotFoundException

readClassDescriptor

protected ObjectStreamClass readClassDescriptor()
                                         throws IOException,
                                                ClassNotFoundException

Provides a special handling for renaming of serialized classes.

Often, as the time goes the serialized classes evolve. They can be moved to new packages, renamed or changed (by a mistake) to not reflect the version of class stored in previous sessions.

This method deals with some of this incompatibilites and provides the module owners a way how to fix some of them.

When a class is read, the Utilities.translate is consulted to find out what whether the name of the class is listed there and what new value is assigned to it. This allows complete rename of the serialized class. For example: org.netbeans.core.NbMainExplorer can be renamed to org.netbeans.core.ui.NbExp - of course supposing that the new class is able to read the serialized fields of the old one.

Another useful feature of this method is the ability to supress wrong serialVersionUID. This was causing us a lot of problems, because people were forgetting to specify the serialVersionUID field in their sources and then it was hard to recover from it. Right now we have a solution: Just use Utilities.translate framework to assing your class org.yourpackage.YourClass the same name as it had e.g. org.yourpackage.YourClass. This will be interpreted by this method as a hit to suppress serialVersionUID and the NbObjectInputStream will ignore its value.

Please see Utilities.translate to learn how your module can provide list of classes that changed name or want to suppress serialVersionUID.

Throws:: IOException; ClassNotFoundException

readSafely

public static Object readSafely(ObjectInput oi)
                         throws IOException

Reads an object from the given object input. The object had to be saved by the NbObjectOutputStream.writeSafely(java.io.ObjectOutput, java.lang.Object) method.

Parameters:: oi - object input
Returns:: the read object
Throws:: IOException - if IO error occured; SafeException - if the operation failed but the stream is ok for further reading

skipSafely

public static void skipSafely(ObjectInput oi)
                       throws IOException

Skips an object from the given object input without loading it. The object had to be saved by the NbObjectOutputStream.writeSafely(java.io.ObjectOutput, java.lang.Object) method.

Parameters:: oi - object input
Throws:: IOException - if an I/O error occurred