Class ObjectInputStream

protected ObjectInputStream()
            throws IOException,
                   SecurityException

Protected constructor that allows subclasses to override deserialization. This constructor should be called by subclasses that wish to override readObject (Object). This method does a security check NOTE: currently not implemented, then sets a flag that informs readObject (Object) to call the subclasses readObjectOverride (Object) method.

See Also:

readObjectOverride()

public ObjectInputStream(InputStream in)
            throws IOException,
                   StreamCorruptedException

Creates a new ObjectInputStream that will do all of its reading from in. This method also checks the stream by reading the header information (stream magic number and stream version).

Throws:

IOException - Reading stream header from underlying stream cannot be completed.

StreamCorruptedException - An invalid stream magic number or stream version was read from the stream.

See Also:

readStreamHeader()

public int available()
            throws IOException

This method returns the number of bytes that can be read without blocking.

Specified by:

available in interface ObjectInput

Overrides:

available in interface InputStream

Returns:

The number of bytes available before blocking

Throws:

IOException - If an error occurs

public void close()
            throws IOException

This method closes the input source

Specified by:

close in interface ObjectInput

close in interface AutoCloseable

close in interface Closeable

Overrides:

close in interface InputStream

Throws:

IOException - If an error occurs

public void defaultReadObject()
            throws ClassNotFoundException,
                   IOException,
                   NotActiveException

Reads the current objects non-transient, non-static fields from the current class from the underlying output stream. This method is intended to be called from within a object's private void readObject (ObjectInputStream) method.

Throws:

ClassNotFoundException - The class that an object being read in belongs to cannot be found.

NotActiveException - This method was called from a context other than from the current object's and current class's private void readObject (ObjectInputStream) method.

IOException - Exception from underlying OutputStream.

protected boolean enableResolveObject(boolean enable)
            throws SecurityException

If enable is true and this object is trusted, then resolveObject (Object) will be called in subsequent calls to readObject (Object). Otherwise, resolveObject (Object) will not be called.

Throws:

SecurityException - This class is not trusted.

public int read()
            throws IOException

This method reading a byte of data from a stream. It returns that byte as an int. This method blocks if no data is available to be read.

Specified by:

read in interface ObjectInput

Overrides:

read in interface InputStream

Returns:

The byte of data read

Throws:

IOException - If an error occurs

public int read(byte[] data,
                int offset,
                int length)
            throws IOException

This method reads raw bytes and stores them in a byte array buffer buf starting at position offset into the buffer. A maximum of len bytes will be read. Note that this method blocks if no data is available, but will not necessarily block until it can read len bytes of data. That is, a "short count" is possible.

Specified by:

read in interface ObjectInput

Overrides:

read in interface InputStream

Parameters:

offset - The offset into buf to start storing data

Returns:

The actual number of bytes read or -1 if end of stream

Throws:

IOException - If an error occurs

public boolean readBoolean()
            throws IOException

This method reads a Java boolean value from an input stream. It does so by reading a single byte of data. If that byte is zero, then the value returned is false. If the byte is non-zero, then the value returned is true.

This method can read a boolean written by an object implementing the writeBoolean() method in the DataOutput interface.

Specified by:

readBoolean in interface DataInput

Returns:

The boolean value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeBoolean(boolean)

public byte readByte()
            throws IOException

This method reads a Java byte value from an input stream. The value is in the range of -128 to 127.

This method can read a byte written by an object implementing the writeByte() method in the DataOutput interface.

Specified by:

readByte in interface DataInput

Returns:

The byte value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeByte(int)

public char readChar()
            throws IOException

This method reads a Java char value from an input stream. It operates by reading two bytes from the stream and converting them to a single 16-bit Java char. The two bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering.

As an example, if byte1 and byte2 represent the first and second byte read from the stream respectively, they will be transformed to a char in the following manner:

(char)((byte1 << 8) + byte2)

This method can read a char written by an object implementing the writeChar() method in the DataOutput interface.

Specified by:

readChar in interface DataInput

Returns:

The char value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeChar(int)

protected ObjectStreamClass readClassDescriptor()
            throws ClassNotFoundException,
                   IOException

This method reads a class descriptor from the real input stream and use these data to create a new instance of ObjectStreamClass. Fields are sorted and ordered for the real read which occurs for each instance of the described class. Be aware that if you call that method you must ensure that the stream is synchronized, in the other case it may be completely desynchronized.

Returns:

A new instance of ObjectStreamClass containing the freshly created descriptor.

Throws:

ClassNotFoundException - if the required class to build the descriptor has not been found in the system.

IOException - An input/output error occured.

public double readDouble()
            throws IOException

This method reads a Java double value from an input stream. It operates by first reading a long value from the stream by calling the readLong() method in this interface, then converts that long to a double using the longBitsToDouble method in the class java.lang.Double.

This method can read a double written by an object implementing the writeDouble() method in the DataOutput interface.

Specified by:

readDouble in interface DataInput

Returns:

The double value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeDouble(double), Double.longBitsToDouble(long)

public ObjectInputStream.GetField readFields()
            throws IOException,
                   ClassNotFoundException,
                   NotActiveException

This method should be called by a method called 'readObject' in the deserializing class (if present). It cannot (and should not)be called outside of it. Its goal is to read all fields in the real input stream and keep them accessible through the ObjectInputStream.GetField class. Calling this method will not alter the deserializing object.

Returns:

A valid freshly created 'GetField' instance to get access to the deserialized stream.

Throws:

IOException - An input/output exception occured.

ClassNotFoundException -

NotActiveException -

public float readFloat()
            throws IOException

This method reads a Java float value from an input stream. It operates by first reading an int value from the stream by calling the readInt() method in this interface, then converts that int to a float using the intBitsToFloat method in the class java.lang.Float.

This method can read a float written by an object implementing the writeFloat() method in the DataOutput interface.

Specified by:

readFloat in interface DataInput

Returns:

The float value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeFloat(float), Float.intBitsToFloat(int)

public void readFully(data[] )
            throws IOException

public void readFully(data[] ,
                      int offset,
                      int size)
            throws IOException

public int readInt()
            throws IOException

This method reads a Java int value from an input stream It operates by reading four bytes from the stream and converting them to a single Java int. The bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering.

As an example, if byte1 through byte4 represent the first four bytes read from the stream, they will be transformed to an int in the following manner:

(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) + ((byte3 & 0xFF)<< 8) + (byte4 & 0xFF)))

The value returned is in the range of -2147483648 to 2147483647.

This method can read an int written by an object implementing the writeInt() method in the DataOutput interface.

Specified by:

readInt in interface DataInput

Returns:

The int value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeInt(int)

public String readLine()
            throws IOException

Deprecated.

Specified by:

readLine in interface DataInput

See Also:

()

public long readLong()
            throws IOException

This method reads a Java long value from an input stream It operates by reading eight bytes from the stream and converting them to a single Java long. The bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering.

As an example, if byte1 through byte8 represent the first eight bytes read from the stream, they will be transformed to an long in the following manner:

(long)(((byte1 & 0xFF) << 56) + ((byte2 & 0xFF) << 48) + ((byte3 & 0xFF) << 40) + ((byte4 & 0xFF) << 32) + ((byte5 & 0xFF) << 24) + ((byte6 & 0xFF) << 16) + ((byte7 & 0xFF) << 8) + (byte8 & 0xFF)))

The value returned is in the range of -9223372036854775808 to 9223372036854775807.

This method can read an long written by an object implementing the writeLong() method in the DataOutput interface.

Specified by:

readLong in interface DataInput

Returns:

The long value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeLong(long)

public final Object readObject()
            throws ClassNotFoundException,
                   IOException

Returns the next deserialized object read from the underlying stream. This method can be overriden by a class by implementing private void readObject (ObjectInputStream). If an exception is thrown from this method, the stream is left in an undefined state. This method can also throw Errors and RuntimeExceptions if caused by existing readResolve() user code.

Specified by:

readObject in interface ObjectInput

Returns:

The object read from the underlying stream.

Throws:

ClassNotFoundException - The class that an object being read in belongs to cannot be found.

IOException - Exception from underlying InputStream.

protected Object readObjectOverride()
            throws ClassNotFoundException,
                   IOException,
                   OptionalDataException

This method allows subclasses to override the default de serialization mechanism provided by ObjectInputStream. To make this method be used for writing objects, subclasses must invoke the 0-argument constructor on this class from their constructor.

See Also:

ObjectInputStream()

public short readShort()
            throws IOException

This method reads a signed 16-bit value into a Java in from the stream. It operates by reading two bytes from the stream and converting them to a single 16-bit Java short. The two bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering.

As an example, if byte1 and byte2 represent the first and second byte read from the stream respectively, they will be transformed to a short in the following manner:

(short)(((byte1 & 0xFF) << 8) + (byte2 & 0xFF))

The value returned is in the range of -32768 to 32767.

This method can read a short written by an object implementing the writeShort() method in the DataOutput interface.

Specified by:

readShort in interface DataInput

Returns:

The short value read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeShort(int)

protected void readStreamHeader()
            throws IOException,
                   StreamCorruptedException

Reads stream magic and stream version information from the underlying stream.

Throws:

IOException - Exception from underlying stream.

StreamCorruptedException - An invalid stream magic number or stream version was read from the stream.

public String readUTF()
            throws IOException

This method reads a String from an input stream that is encoded in a modified UTF-8 format. This format has a leading two byte sequence that contains the remaining number of bytes to read. This two byte sequence is read using the readUnsignedShort() method of this interface. After the number of remaining bytes have been determined, these bytes are read an transformed into char values. These char values are encoded in the stream using either a one, two, or three byte format. The particular format in use can be determined by examining the first byte read.

If the first byte has a high order bit of 0, then that character consists on only one byte. This character value consists of seven bits that are at positions 0 through 6 of the byte. As an example, if byte1 is the byte read from the stream, it would be converted to a char like so:

(char)byte1

If the first byte has 110 as its high order bits, then the character consists of two bytes. The bits that make up the character value are in positions 0 through 4 of the first byte and bit positions 0 through 5 of the second byte. (The second byte should have 10 as its high order bits). These values are in most significant byte first (i.e., "big endian") order.

As an example, if byte1 and byte2 are the first two bytes read respectively, and the high order bits of them match the patterns which indicate a two byte character encoding, then they would be converted to a Java char like so:

(char)(((byte1 & 0x1F) << 6) + (byte2 & 0x3F))

If the first byte has a 1110 as its high order bits, then the character consists of three bytes. The bits that make up the character value are in positions 0 through 3 of the first byte and bit positions 0 through 5 of the other two bytes. (The second and third bytes should have 10 as their high order bits). These values are in most significant byte first (i.e., "big endian") order.

As an example, if byte1, byte2, and byte3 are the three bytes read, and the high order bits of them match the patterns which indicate a three byte character encoding, then they would be converted to a Java char like so: (char)(((byte1 & 0x0F) << 12) + ((byte2 & 0x3F) + (byte3 & 0x3F)) Note that all characters are encoded in the method that requires the fewest number of bytes with the exception of the character with the value of \<llll>u0000 which is encoded as two bytes. This is a modification of the UTF standard used to prevent C language style NUL values from appearing in the byte stream.

This method can read data that was written by an object implementing the writeUTF() method in DataOutput.

Specified by:

readUTF in interface DataInput

Returns:

The String read

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeUTF(String)

public Object readUnshared()
            throws IOException,
                   ClassNotFoundException

Returns the next deserialized object read from the underlying stream in an unshared manner. Any object returned by this method will not be returned by subsequent calls to either this method or readObject().

This behaviour is achieved by:

• Marking the handles created by successful calls to this method, so that future calls to readObject() or readUnshared() will throw an ObjectStreamException rather than returning the same object reference.
• Throwing an ObjectStreamException if the next element in the stream is a reference to an earlier object.

Returns:

a reference to the deserialized object.

Throws:

ClassNotFoundException - if the class of the object being deserialized can not be found.

IOException - if an I/O error occurs from the stream.

Since:

1.4

See Also:

readObject()

public int readUnsignedByte()
            throws IOException

This method reads 8 unsigned bits into a Java int value from the stream. The value returned is in the range of 0 to 255.

This method can read an unsigned byte written by an object implementing the writeByte() method in the DataOutput interface.

Specified by:

readUnsignedByte in interface DataInput

Returns:

The unsigned bytes value read as a Java int.

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeByte(int)

public int readUnsignedShort()
            throws IOException

This method reads 16 unsigned bits into a Java int value from the stream. It operates by reading two bytes from the stream and converting them to a single Java int. The two bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering.

As an example, if byte1 and byte2 represent the first and second byte read from the stream respectively, they will be transformed to an int in the following manner:

(int)(((byte1 0xFF) << 8) + (byte2 & 0xFF))

The value returned is in the range of 0 to 65535.

This method can read an unsigned short written by an object implementing the writeShort() method in the DataOutput interface.

Specified by:

readUnsignedShort in interface DataInput

Returns:

The unsigned short value read as a Java int.

Throws:

IOException - If any other error occurs

See Also:

DataOutput.writeShort(int)

public void registerValidation(ObjectInputValidation validator,
                               int priority)
            throws InvalidObjectException,
                   NotActiveException

Registers a ObjectInputValidation to be carried out on the object graph currently being deserialized before it is returned to the original caller of readObject (). The order of validation for multiple ObjectInputValidations can be controled using priority. Validators with higher priorities are called first.

Throws:

InvalidObjectException - validator is null

NotActiveException - an attempt was made to add a validator outside of the readObject method of the object currently being deserialized

See Also:

ObjectInputValidation

protected Class resolveClass(ObjectStreamClass osc)
            throws ClassNotFoundException,
                   IOException

Called when a class is being deserialized. This is a hook to allow subclasses to read in information written by the annotateClass (Class) method of an ObjectOutputStream. This implementation looks up the active call stack for a ClassLoader; if a ClassLoader is found, it is used to load the class associated with osc, otherwise, the default system ClassLoader is used.

Throws:

IOException - Exception from underlying OutputStream.

See Also:

(java.lang.Class)

protected Object resolveObject(Object obj)
            throws IOException

Allows subclasses to resolve objects that are read from the stream with other objects to be returned in their place. This method is called the first time each object is encountered. This method must be enabled before it will be called in the serialization process.

Throws:

IOException - Exception from underlying OutputStream.

See Also:

enableResolveObject(boolean)

protected Class resolveProxyClass(String[] intfs)
            throws IOException,
                   ClassNotFoundException

public int skipBytes(int len)
            throws IOException

This method skips and discards the specified number of bytes in an input stream. Note that this method may skip less than the requested number of bytes. The actual number of bytes skipped is returned. No bytes are skipped if a negative number is passed to this method.

Specified by:

skipBytes in interface DataInput

Parameters:

Returns:

The number of bytes actually skipped, which will always be numBytes

Throws:

IOException - If any other error occurs