com.xavax.xstore.tools
Class ProxyBuilder

Object
  ProxyBuilder

public class ProxyBuilder

extends Object

ProxyBuilder is a tool for building proxy classes for persistent objects. The Proxy pattern is essential to implementing demand- loading of persistent objects which is a fundamental concept of the persistence framework. When the client performs a query, what is returned is a collection of proxies for persistent objects. The first attempt to use a proxy object will result in loading the persistent object if it is not already in the object cache. When the client creates a new proxy object, the persistence framework creates the actual persistent object and registers it with the object directory of the current persistence context.

Before using ProxyBuilder, one must separate the interface from the implementation of the class to be persisted. Typically, the original class is renamed to become the implementation class and an interface is defined using the old name. The generated proxy class implements this interface; therefore, a proxy can be cast as the interface, thereby reducing the need for changes to code which used the old class name. The only lines of code which must change are those which create new objects. For example: the class User is renamed to UserImpl and an interface named User is created. Since a UserProxy is a User, the proxy can be cast as a User and passed to any code which previously used the old User class. Instances of "new User(...)" must change to "new UserProxy(...)".

The generated proxy class extends AbstractProxy and implements all methods defined by the interface and any superinterfaces. The proxy contains a reference to a Link which is an object directory entry. All methods delegate to methods in the implementation class which are accessed via the link. The proxy class defines a constructor with the same signature as each constructor defined by the implementation class. Defining constructors allows the creation of new proxy objects using the same parameters used to create instances of the old class. The proxy constructors delegate to implementation class constructors to create the implementation object, then register the object in the object directory of the current persistence context.

ProxyBuilder uses reflection to determine the methods defined by the interface and any superinterfaces, and the constructors defined by the implementation class. For this reason, it is essential for these classes to appear in the classpath when running ProxyBuilder.

ProxyBuilder expects 4 command line parameters: the package name, interface name, implementation class name, and proxy class name. The interface and class names are unqualified and all must belong to the specified package. ProxyBuilder is a Java application and can be executed as follows.

TOOLS=com.xavax.xstore.tools
java ${TOOLS}.ProxyBuilder package interface implementation proxy [factory]

It is recommended that ProxyBuilder be invoked from a makefile or Ant build file with automatic dependency rules that rebuild the proxy class if the interface or implementation changes. See the demo package for examples.

Method Summary

static void

main(String[] args) Run the ProxyBuilder and generate a proxy class.

Methods inherited from class Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

main

public static void main(String[] args)

Run the ProxyBuilder and generate a proxy class.

Parameters:

args - the command line arguments.

args[0]	The package name.
args[1]	The interface name.
args[2]	The implementation class name.
args[3]	The proxy class name.
args[4]	The factory class name (optional).