Thursday, March 12, 2015

OptionalDataException

java.io.OptionalDataException

OptionalDataException is described in the javadoc comments as:

Exception indicating the failure of an object read operation due to unread primitive data, or the end of data belonging to a serialized object in the stream. This exception may be thrown in two cases:
  • An attempt was made to read an object when the next element in the stream is primitive data. In this case, the OptionalDataException's length field is set to the number of bytes of primitive data immediately readable from the stream, and the eof field is set to false.
  • An attempt was made to read past the end of data consumable by a class-defined readObject or readExternal method. In this case, the OptionalDataException's eof field is set to true, and the length field is set to 0.

author: unascribed version: 1.18, 01/12/04 since: JDK1.1

Where is this exception thrown?

Following, is a list of exception messages cross-referenced to the source code responsible for throwing them. Click on the method link to view the code and see how the exception is thrown.

How is this exception thrown?

The following sub-sections identify where this exception is thrown, and how (or why) the code is throwing the exception.

Any source code quoted in this section is subject to the Java Research License unless stated otherwise.

java.io.ObjectInputStream.readObject0(boolean)

/**
     * Underlying readObject implementation.
     */
private Object readObject0(boolean unshared) throws IOException {
    boolean oldMode = bin.getBlockDataMode();
    if (oldMode) {
        int remain = bin.currentBlockRemaining();
        if (remain > 0) {
            throw new OptionalDataException(remain);
        } else if (defaultDataEnd) {
            throw new OptionalDataException(true);
        }
        bin.setBlockDataMode(false);
    }
    byte tc;
    while ((tc = bin.peekByte()) == TC_RESET) {
        bin.readByte();
        handleReset();
    }
    depth++;
    try {
        switch(tc) {
            case TC_NULL:
                return readNull();
            case TC_REFERENCE:
                return readHandle(unshared);
            case TC_CLASS:
                return readClass(unshared);
            case TC_CLASSDESC:
            case TC_PROXYCLASSDESC:
                return readClassDesc(unshared);
            case TC_STRING:
            case TC_LONGSTRING:
                return checkResolve(readString(unshared));
            case TC_ARRAY:
                return checkResolve(readArray(unshared));
            case TC_ENUM:
                return checkResolve(readEnum(unshared));
            case TC_OBJECT:
                return checkResolve(readOrdinaryObject(unshared));
            case TC_EXCEPTION:
                IOException ex = readFatalException();
                throw new WriteAbortedException('writing aborted', ex);
            case TC_BLOCKDATA:
            case TC_BLOCKDATALONG:
                if (oldMode) {
                    bin.setBlockDataMode(true);
                    bin.peek();
                    throw new OptionalDataException(bin.currentBlockRemaining());
                } else {
                    throw new StreamCorruptedException('unexpected block data');
                }
            case TC_ENDBLOCKDATA:
                if (oldMode) {
                    throw new OptionalDataException(true);
                } else {
                    throw new StreamCorruptedException('unexpected end of block data');
                }
            default:
                throw new StreamCorruptedException();
        }
    } finally {
        depth--;
        bin.setBlockDataMode(oldMode);
    }
}

Source: "Java SE Downloads: Java SE 6 JDK Source Code", at: http://www.oracle.com/technetwork/java/javase/downloads/index.html

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