With this example we are going to demonstrate how to compress and expand an Object. We have implemented the ObjectCompressionUtil Class, that extends the Serializable class and has a parameter that is the generic type of the serializable object to be compressed. The class consists of two methods.

The compressObject(final T objectToCompress, final OutputStream outstream) takes the object to compress and an OutputStream and returns the compressed object, as described below:
• Creates a new GZIPOutputStream with a default buffer size.
• Creates an ObjectOutputStream that writes to the specified GZIPOutputStream. 
• Writes the specified object to be compressed to the ObjectOutputStream and flush it, using writeObject(Object obj) and flush() API methods of ObjectOutputStream.
• Closes both the GZIPOutputStream and the ObjectOutputStream, using their close() API methods.

The expandObject(final T objectToExpand, final InputStream instream) method takes the object to expand and an InputStream and returns the expanded object, as shown below:
• Creates a new GZIPInputStream with a default buffer size.
• Creates an ObjectInputStream that reads from the specified GZIPInputStream.
• Reads the object to expand from the ObjectInputStream, with readObject() API method of ObjectInputStream.
• Returns the expanded object and closes both the GZIPInputStream and the ObjectInputStream, using their close() API methods.

Let’s take a look at the code snippet that follows:  

package javaitzen.blog;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
 
/**
 * The Class ObjectCompressionUtil.
 * 
 * @param <T> the generic type of the serializable object to be compressed
 */
public class ObjectCompressionUtil<T extends Serializable> {
 
 /**
  * Compress object.
  * 
  * @param objectToCompress the object to compress
  * @param outstream the outstream
  * @return the compressed object
  * @throws IOException Signals that an I/O exception has occurred.
  */
 public T compressObject(final T objectToCompress, final OutputStream outstream) throws IOException {
 
  final GZIPOutputStream gz = new GZIPOutputStream(outstream);
  final ObjectOutputStream oos = new ObjectOutputStream(gz);
   
  try {
  oos.writeObject(objectToCompress);
  oos.flush();
  return objectToCompress;
  }finally {
   oos.close();
   outstream.close();
  }
 
 }
 
 /**
  * Expand object.
  * 
  * @param objectToExpand the object to expand
  * @param instream the instream
  * @return the expanded object
  * @throws IOException Signals that an I/O exception has occurred.
  * @throws ClassNotFoundException the class not found exception
  */
 public T expandObject(final T objectToExpand, final InputStream instream) throws IOException,
   ClassNotFoundException {
  final GZIPInputStream gs = new GZIPInputStream(instream);
  final ObjectInputStream ois = new ObjectInputStream(gs);
 
  try {
   @SuppressWarnings("unchecked")
   T expandedObject = (T) ois.readObject();
   return expandedObject;
  } finally {
   gs.close();
   ois.close();
  }
 }
 
}

Related Article:

• Java Compression

Reference: Java Compression from our JCG partner Brian at Zen in the art of IT

  
This was an example of how to compress and expand an Object in Java.