Class FormatIdOutputStream
- java.lang.Object
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- java.io.OutputStream
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- java.io.FilterOutputStream
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- java.io.DataOutputStream
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- org.apache.derby.iapi.services.io.FormatIdOutputStream
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- 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.
- (NULL_FORMAT_ID, nothing) in.readObject() returns null.
- (SRING_FORMAT_ID, UTF8 encoded string)in.readObject reads and returns this string.
- (SERIALIZABLE_FORMAT_ID,serialized object) in.readObject() reads the object using java serialization and returns it.
- (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.
- (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.
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Constructor Summary
Constructors Constructor Description FormatIdOutputStream(java.io.OutputStream out)
Constructor for a FormatIdOutputStream
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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
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Method Detail
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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 interfacejava.io.ObjectOutput
- Parameters:
ref
- a reference to the object.- Throws:
java.io.IOException
- the exception.
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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.
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getErrorInfo
public java.lang.String getErrorInfo()
- Specified by:
getErrorInfo
in interfaceErrorInfo
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getNestedException
public java.lang.Exception getNestedException()
- Specified by:
getNestedException
in interfaceErrorInfo
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