jrun.jms.core.message
Class StreamMessageImpl

jrun.jms.core.message.StreamMessageImpl

public final class StreamMessageImpl

This class implements the StreamMessage interface

A StreamMessage is used to send a stream of Java primitives. It is filled and read sequentially. It inherits from Message and adds a stream message body. It's methods are based largely on those found in java.io.DataInputStream and java.io.DataOutputStream.

The primitive types can be read or written explicitly using methods for each type. They may also be read or written generically as objects. For instance, a call to StreamMessage.writeInt(6) is equivalent to StreamMessage.writeObject(new Integer(6)). Both forms are provided because the explicit form is convenient for static programming and the object form is needed when types are not known at compile time.

When the message is first created, and when clearBody() is called, the body of the message is in write-only mode. After the first call to reset() has been made, the message body is in read-only mode. When a message has been sent, by definition, the provider calls reset in order to read it's content, and when a message has been received, the provider has called reset so that the message body is in read-only mode for the client.

If clearBody is called on a message in read-only mode, the message body is cleared and the message body is in write-only mode.

If a client attempts to read a message in write-only mode, a MessageNotReadableException is thrown.

If a client attempts to write a message in read-only mode, a MessageNotWriteableException is thrown.

Stream messages support the following conversion table. The marked cases must be supported. The unmarked cases must throw a JMSException. The String to primitive conversions may throw a runtime exception if the primitives valueOf() method does not accept it as a valid String representation of the primitive.

A value written as the row type can be read as the column type.

 |        | boolean byte short char int long float double String byte[]
 |----------------------------------------------------------------------
 |boolean |    X                                            X
 |byte    |          X     X         X   X                  X
 |short   |                X         X   X                  X
 |char    |                     X                           X
 |int     |                          X   X                  X
 |long    |                              X                  X
 |float   |                                    X     X      X
 |double  |                                          X      X
 |String  |    X     X     X         X   X     X     X      X
 |byte[]  |                                                        X
 |----------------------------------------------------------------------
 

Attempting to read a null value as a Java primitive type must be treated as calling the primitive's corresponding valueOf(String) conversion method with a null value. Since char does not support a String conversion, attempting to read a null value as a char must throw NullPointerException.

Version:

$Revision: 1.9 $ $Date: 2001/08/06 03:00:36 $

Author:

Jim Mourikis, Tim Anderson

See Also:

StreamMessage

Constructor Summary

StreamMessageImpl()
Construct a new StreamMessage.

Method Summary

void	clearBody() Overide the super class method to reset the streams, and put the message body in write only mode
java.lang.Object	clone() Clone an instance of this object
boolean	readBoolean() Read a boolean from the bytes message stream
byte	readByte() Read a byte value from the stream message
int	readBytes(byte[] value) Read a byte array field from the stream message into the specified byte[] object (the read buffer).
char	readChar()
double	readDouble() Read a double from the stream message
void	readExternal(java.io.ObjectInput in) Serialize in this message's data
float	readFloat() Read a float from the stream message
int	readInt()
long	readLong()
java.lang.Object	readObject() Read a Java object from the stream message
short	readShort() Read a 16-bit number from the stream message.
java.lang.String	readString() Read in a string from the stream message
void	reset() Put the message body in read-only mode, and reposition the stream to the beginning
void	setReadOnly(boolean readOnly) Set the read-only mode of the message.
void	writeBoolean(boolean value) Write a boolean to the stream message.
void	writeByte(byte value) Write out a byte to the stream message
void	writeBytes(byte[] value) Write a byte array field to the stream message
void	writeBytes(byte[] value, int offset, int length) Write a portion of a byte array as a byte array field to the stream message
void	writeChar(char value) Write a char to the stream message
void	writeDouble(double value) Write a double to the stream message
void	writeExternal(java.io.ObjectOutput out) Serialize out this message's data
void	writeFloat(float value) Write a float to the stream message
void	writeInt(int value) Write an int to the stream message
void	writeLong(long value) Write a long to the stream message
void	writeObject(java.lang.Object value) Write a Java object to the stream message
void	writeShort(short value) Write a short to the stream message
void	writeString(java.lang.String value) Write a string to the stream message

Constructor Detail

StreamMessageImpl

public StreamMessageImpl()
                  throws javax.jms.JMSException

Construct a new StreamMessage. When first created, the message is in write-only mode.

Throws:

JMSException - if the message type can't be set, or an I/O error occurs

Method Detail

clone

public final java.lang.Object clone()
                             throws java.lang.CloneNotSupportedException

Clone an instance of this object

Returns:

a copy of this object

Throws:

java.lang.CloneNotSupportedException - if object or attributes aren't cloneable

writeExternal

public final void writeExternal(java.io.ObjectOutput out)
                         throws java.io.IOException

Serialize out this message's data

Parameters:

out - the stream to serialize out to

Throws:

java.io.IOException - if any I/O exceptions occurr

readExternal

public final void readExternal(java.io.ObjectInput in)
                        throws java.lang.ClassNotFoundException,
                               java.io.IOException

Serialize in this message's data

Parameters:

in - the stream to serialize in from

Throws:

java.lang.ClassNotFoundException - if the class for an object being restored cannot be found.

java.io.IOException - if any I/O exceptions occur

readBoolean

public final boolean readBoolean()
                          throws javax.jms.JMSException,
                                 javax.jms.MessageEOFException,
                                 javax.jms.MessageFormatException,
                                 javax.jms.MessageNotReadableException

Read a boolean from the bytes message stream

Returns:

the boolean value read

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readByte

public final byte readByte()
                    throws javax.jms.JMSException,
                           javax.jms.MessageEOFException,
                           javax.jms.MessageFormatException,
                           javax.jms.MessageNotReadableException

Read a byte value from the stream message

Returns:

the next byte from the stream message as a 8-bit byte

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readShort

public final short readShort()
                      throws javax.jms.JMSException,
                             javax.jms.MessageEOFException,
                             javax.jms.MessageFormatException,
                             javax.jms.MessageNotReadableException

Read a 16-bit number from the stream message.

Returns:

a 16-bit number from the stream message

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readChar

public final char readChar()
                    throws javax.jms.JMSException,
                           javax.jms.MessageEOFException,
                           javax.jms.MessageFormatException,
                           javax.jms.MessageNotReadableException

readInt

public final int readInt()
                  throws javax.jms.JMSException,
                         javax.jms.MessageEOFException,
                         javax.jms.MessageFormatException,
                         javax.jms.MessageNotReadableException

readLong

public final long readLong()
                    throws javax.jms.JMSException,
                           javax.jms.MessageEOFException,
                           javax.jms.MessageFormatException,
                           javax.jms.MessageNotReadableException

readFloat

public final float readFloat()
                      throws javax.jms.JMSException,
                             javax.jms.MessageEOFException,
                             javax.jms.MessageFormatException,
                             javax.jms.MessageNotReadableException

Read a float from the stream message

Returns:

a float value from the stream message

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readDouble

public final double readDouble()
                        throws javax.jms.JMSException,
                               javax.jms.MessageEOFException,
                               javax.jms.MessageFormatException,
                               javax.jms.MessageNotReadableException

Read a double from the stream message

Returns:

a double value from the stream message

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readString

public final java.lang.String readString()
                                  throws javax.jms.JMSException,
                                         javax.jms.MessageEOFException,
                                         javax.jms.MessageFormatException,
                                         javax.jms.MessageNotReadableException

Read in a string from the stream message

Returns:

a Unicode string from the stream message

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readBytes

public final int readBytes(byte[] value)
                    throws javax.jms.JMSException,
                           javax.jms.MessageEOFException,
                           javax.jms.MessageFormatException,
                           javax.jms.MessageNotReadableException

Read a byte array field from the stream message into the specified byte[] object (the read buffer).

To read the field value, readBytes should be successively called until it returns a value less than the length of the read buffer. The value of the bytes in the buffer following the last byte read are undefined.

If readBytes returns a value equal to the length of the buffer, a subsequent readBytes call must be made. If there are no more bytes to be read this call will return -1.

If the bytes array field value is null, readBytes returns -1.

If the bytes array field value is empty, readBytes returns 0.

Once the first readBytes call on a byte[] field value has been done, the full value of the field must be read before it is valid to read the next field. An attempt to read the next field before that has been done will throw a MessageFormatException.

To read the byte field value into a new byte[] object, use the readObject() method.

Parameters:

value - the buffer into which the data is read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the byte field has been reached.

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if an end of message stream

MessageFormatException - if this type conversion is invalid

MessageNotReadableException - if message is in write-only mode

readObject

public final java.lang.Object readObject()
                                  throws javax.jms.JMSException,
                                         javax.jms.MessageEOFException,
                                         javax.jms.MessageNotReadableException

Read a Java object from the stream message

Note that this method can be used to return in objectified format, an object that had been written to the stream with the equivalent writeObject method call, or it's equivalent primitive write method.

Note that byte values are returned as byte[], not Byte[].

Returns:

a Java object from the stream message, in objectified format (eg. if it set as an int, then a Integer is returned).

Throws:

JMSException - if JMS fails to read message due to some internal JMS error

MessageEOFException - if end of message stream

MessageNotReadableException - if message is in write-only mode

writeBoolean

public final void writeBoolean(boolean value)
                        throws javax.jms.JMSException,
                               javax.jms.MessageNotWriteableException

Write a boolean to the stream message. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0.

Parameters:

value - the boolean value to be written.

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeByte

public final void writeByte(byte value)
                     throws javax.jms.JMSException,
                            javax.jms.MessageNotWriteableException

Write out a byte to the stream message

Parameters:

value - the byte value to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeShort

public final void writeShort(short value)
                      throws javax.jms.JMSException,
                             javax.jms.MessageNotWriteableException

Write a short to the stream message

Parameters:

value - the short to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeChar

public final void writeChar(char value)
                     throws javax.jms.JMSException,
                            javax.jms.MessageNotWriteableException

Write a char to the stream message

Parameters:

value - the char value to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeInt

public final void writeInt(int value)
                    throws javax.jms.JMSException,
                           javax.jms.MessageNotWriteableException

Write an int to the stream message

Parameters:

value - the int to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeLong

public final void writeLong(long value)
                     throws javax.jms.JMSException,
                            javax.jms.MessageNotWriteableException

Write a long to the stream message

Parameters:

value - the long to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeFloat

public final void writeFloat(float value)
                      throws javax.jms.JMSException,
                             javax.jms.MessageNotWriteableException

Write a float to the stream message

Parameters:

value - the float value to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeDouble

public final void writeDouble(double value)
                       throws javax.jms.JMSException,
                              javax.jms.MessageNotWriteableException

Write a double to the stream message

Parameters:

value - the double value to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeString

public final void writeString(java.lang.String value)
                       throws javax.jms.JMSException,
                              javax.jms.MessageNotWriteableException

Write a string to the stream message

Parameters:

value - the String value to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeBytes

public final void writeBytes(byte[] value)
                      throws javax.jms.JMSException,
                             javax.jms.MessageNotWriteableException

Write a byte array field to the stream message

The byte array value is written as a byte array field into the StreamMessage. Consecutively written byte array fields are treated as two distinct fields when reading byte array fields.

Parameters:

value - the byte array to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeBytes

public void writeBytes(byte[] value,
                       int offset,
                       int length)
                throws javax.jms.JMSException,
                       javax.jms.MessageNotWriteableException

Write a portion of a byte array as a byte array field to the stream message

The a portion of the byte array value is written as a byte array field into the StreamMessage. Consecutively written byte array fields are treated as two distinct fields when reading byte array fields.

Parameters:

value - the byte array value to be written

offset - the initial offset within the byte array

length - the number of bytes to write

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageNotWriteableException - if message in read-only mode

writeObject

public void writeObject(java.lang.Object value)
                 throws javax.jms.JMSException,
                        javax.jms.MessageFormatException,
                        javax.jms.MessageNotWriteableException

Write a Java object to the stream message

Note that this method only works for the objectified primitive object types (Integer, Double, Long ...), String's and byte arrays.

Parameters:

value - the Java object to be written

Throws:

JMSException - if JMS fails to write message due to some internal JMS error

MessageFormatException - if the object is invalid

MessageNotWriteableException - if message in read-only mode

reset

public void reset()
           throws javax.jms.JMSException

Put the message body in read-only mode, and reposition the stream to the beginning

Throws:

JMSException - if JMS fails to reset the message due to some internal JMS error

clearBody

public void clearBody()
               throws javax.jms.JMSException

Overide the super class method to reset the streams, and put the message body in write only mode

Throws:

JMSException - if JMS fails to reset the message due to some internal JMS error.

setReadOnly

public final void setReadOnly(boolean readOnly)
                       throws javax.jms.JMSException

Set the read-only mode of the message.

Parameters:

readOnly - if true, make the message body and properties read-only, and invoke reset()

Throws:

JMSException - if the read-only mode cannot be changed