Java Reference
In-Depth Information
What Is HTTP Tunneling?
HTTP tunneling is a method of reading and writing serialized objects using an HTTP connec-
tion. You are creating a sub-protocol inside the HTTP protocol—that is, “tunneling” inside
another protocol. This relieves you from the hassles of dealing with the actual transport layer.
Object Serialization
Before you can get started with HTTP tunneling, you need to understand object serialization.
Object serialization is a feature introduced in the Java Development Kit version 1.1. It enables
you to create objects that are persistent across several media. An exceptionally convenient
characteristic of serialization is that it not only serializes your object, it also unwinds and seri-
alizes all the objects that are referenced by your object.
To make an object serializable, it must implement the Serializable interface. This interface is
found in the package. The entire Serializable interface is listed as follows:
public interface Serializable {
static final long serialVersionUID = 1196656838076753133L;
As you can see, there is not much to this interface. Its only purpose is to signify that an object
can be serialized.
The steps involved in serializing an object are as follows:
Create an OutputStream object. This can be a stream to a file, a TCP/IP connection, or
most any other target.
Create an ObjectOutputStream and pass to its constructor the OutputStream created in
Step 1.
Call the ObjectOutputStream 's writeObject() method and pass to it the object that
implements the Serializable interface.
The equivalent steps involved in reading a serialized object are as follows:
Create an InputStream object that points to the location of the serialized object.
Create an ObjectInputStream and pass to its constructor the InputStream created in
Step 1.
Call the ObjectInputStream 's readObject() method.
The readObject() method returns an upcasted Object that must be downcasted back to
your original object's type.
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