Class FormatIdOutputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.io.DataOutput, java.io.Flushable, java.io.ObjectOutput, java.lang.AutoCloseable, ErrorInfo

    public class FormatIdOutputStream
    extends java.io.DataOutputStream
    implements java.io.ObjectOutput, ErrorInfo
    A stream for serializing objects with format id tags.

    An ObjectOutput (henceforth 'out') preceeds objects it writes with a format id. The companion FormatIdInputStream (henceforth 'in') uses these format ids in parsing the stored data. The stream can be thought of as containing a sequence of (formatId,object) pairs interspersed with other data. The assumption is that out.writeObject() produces these pairs and in.readObject() uses the format ids to construct objects from the pairs that out.writeObject produced. The description below describes each supported pair and how in.readObject() processes it.

    1. (NULL_FORMAT_ID, nothing) in.readObject() returns null.
    2. (SRING_FORMAT_ID, UTF8 encoded string)in.readObject reads and returns this string.
    3. (SERIALIZABLE_FORMAT_ID,serialized object) in.readObject() reads the object using java serialization and returns it.
    4. (A format id for a Storable, isNull flag and object if isNull == false) (see note 1) in.readObject() reads the boolean isNull flag. If is null is true, in.readObject() returns a Storable object of the correct class which is null. If ifNull is false, in.readObject() restores the object using its readExternal() method.
    5. (A format id for a Formatable which is not Storable, the stored object) (see note 1) in.readObject restores the object using its readExternal() method.

    Note 1: The FormatIdInputStream uses Monitor.newInstanceFromIdentifier(format id) to get the class.

    Note 2: An object may support more than one of the following interfaces Storable, Formatable, Serializable. In this case out.writeObject use the first of these interfaces which the object supports (based on the order listed here) to determine how to write the object.

    • Field Summary

      • Fields inherited from class java.io.DataOutputStream

        written
      • Fields inherited from class java.io.FilterOutputStream

        out
    • Constructor Summary

      Constructors 
      Constructor Description
      FormatIdOutputStream​(java.io.OutputStream out)
      Constructor for a FormatIdOutputStream
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.String getErrorInfo()  
      java.lang.Exception getNestedException()  
      void setOutput​(java.io.OutputStream out)
      Set the OutputStream for this FormatIdOutputStream to the stream provided.
      void writeObject​(java.lang.Object ref)
      Write a format id for the object provied followed by the object itself to this FormatIdOutputStream.
      • Methods inherited from class java.io.DataOutputStream

        flush, size, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF
      • Methods inherited from class java.io.FilterOutputStream

        close, write
      • Methods inherited from class java.io.OutputStream

        nullOutputStream
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
      • Methods inherited from interface java.io.DataOutput

        writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF
      • Methods inherited from interface java.io.ObjectOutput

        close, flush, write, write, write
    • Constructor Detail

      • FormatIdOutputStream

        public FormatIdOutputStream​(java.io.OutputStream out)
        Constructor for a FormatIdOutputStream
        Parameters:
        out - output goes here.
    • Method Detail

      • writeObject

        public void writeObject​(java.lang.Object ref)
                         throws java.io.IOException
        Write a format id for the object provied followed by the object itself to this FormatIdOutputStream.
        Specified by:
        writeObject in interface java.io.ObjectOutput
        Parameters:
        ref - a reference to the object.
        Throws:
        java.io.IOException - the exception.
      • setOutput

        public void setOutput​(java.io.OutputStream out)
        Set the OutputStream for this FormatIdOutputStream to the stream provided. It is the responsibility of the caller to flush or close (as required) the previous stream this class was attached to.
        Parameters:
        out - The new output stream.
      • getErrorInfo

        public java.lang.String getErrorInfo()
        Specified by:
        getErrorInfo in interface ErrorInfo