System for modifying object oriented code

Details System for modifying object oriented code System for modifying object oriented code

1998-08-20

2001-07-10

Powell, Mark R. (Department: 2122)

Data processing: software development, installation, and managem

Software program development tool

Translation of code

Reexamination Certificate

active

06260187

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a system for modifying object oriented code.
2. Description of the Related Art
Java is an object oriented programming language that contains built-in support for the Internet, freeing the programmer from the burden of designing ad hoc solutions to common Internet problems. Java generates extremely small executables to facilitate faster loading over potentially slow communication lines. Additionally, Java is machine independent. That is, the same executable program should be capable of being executed on a PC, a Mac or even a UNIX machine. Because of these features, software developers worldwide are adopting Java technology at a compelling rate. For example, many web pages on the Internet include Java applets in addition to HIM instructions. Furthermore, many software systems are being written in Java in an attempt to allow the code to operate across many platforms.
While Java provides many new features useful to both programmers and users, Java also brings with it a new set of problems. One feature of Java discussed above is that it can easily be used on the Internet. Thus, rather than shrink wrap software to sell in stores, many software programs are sold on the Internet. This will allow any person anywhere in the world to download a computer program that should run on almost any platform. However, different people and different cultures may have different needs for their computer program. For example, since different languages are spoken in different parts of the world, it is desirable to have the user interface of the computer program be tailored for the local culture. Furthermore, certain people have special needs, such as color blind people may prefer gray scale user interfaces rather than color interfaces. This problem has previously been taken care of by creating different versions of a particular executable and only allowing the relevant versions to be available in stores in the local communities. With the distribution of software on the Internet, it is harder to direct the right executable to the right people. Thus, it would be useful to be able to modify software downloaded from the internet in order to add features needed by corporations, local communities and other special interests groups. Some software may need modifications (to accommodate users) that the manufacturer did not anticipate. Furthermore, rather than design and ship multiple versions of a software product it may be more cost effective to ship one version of the software and let the different user groups modify the software to meet their needs.
Because Java code can be run on different platforms and can be downloaded from web pages, computer users with access to the Internet or other networks can easily find and download new Java programs and install these programs on their computer. In a local area network (e.g. an office), it will be difficult to monitor all new programs being downloaded and installed. Many of these programs could wreak havoc on the network Managers of networks have no easy way to monitor, track profile or otherwise provide some means for understanding what users on the network are doing. A network manager would benefit from the ability to modify Java programs that are downloaded from the Internet to add functionality that profiled the downloaded code, alerted the network manager of the new program or added other security features.
Although Java is intended to be platform independent, different entities have implemented the Java Virtual Machine in different ways. Therefore, a Java applet may not necessarily run in the same manner on all virtual machines. In fact, some applets may not run at all on certain virtual machines. Debugging Java code to figure out why it works in some machines and not others can be very difficult. Furthermore, nobody may be aware that a certain applet does not work on a certain virtual machine until the user is attempting to execute the applet. Software developers and software users would benefit from a tool that could add functionality to an existing Java executable to add debugging tools to Java code or, to add functionality, features or bug fixes that are specific to a particular virtual machine.
The above discussion demonstrates a need to modify Java programs after they have been completed by the developer. Most previous attempts to modify code attempt to do so at the source code level. That is, source code is run through a compiler that can add additional instructions for profiling, debugging, etc. Since most Java code available for downloading on the web or purchasing at a store is not source code, it is not practical to modify the source code of a Java program. Most Java code downloaded or sold is object code. Object code is code that has been compiled, as distinguished from source code. Some systems can execute object code. For Java, object code is executable code. Furthermore, previous attempts to modify code have not taken into account nor taken advantage of the object oriented paradigm of Java.
System Object Model (SOM) is an object technology developed by IBM. SOM provides the ability at run time to replace the use of one class for another class, but does not make special provisions for a final class and it does not provide for the substitution of static fields. Furthermore, because SOM operates at run time, any changes made are not permanent. Thus, after execution is complete, the user is left with the original program rather than a modified version that can be shipped to other users. Furthermore, SOM does not work with Java and in order to use SOM the source code must be written to utilize the SOM API. It would be desirable to have a system that can modify an executable, with no preparation for the modification made in the source, and allow the modification to be permanent for distribution.
Thus, there is a need for a tool that can modify Java or other object oriented code to add new functionality to the existing code.
SUMMARY OF THE INVENTION
The present invention, roughly described, includes a code modifier that receives three sets of inputs: program class definitions, a set of rules, and additional class definitions to be merged with the original class definitions. There are three types of rules: the first rule is used to substitute the allocation of an object of a new class for the allocation of the object based on an original class; the second rule is used to change code that allocates an object of an original class to code that calls a static method in another class that allocates the object of the original class; and the third rule is used to a replace a new static field for an original static field. The system reads the program class definitions into a class data structure and performs the modifications to the class data structure according to the set of rules. In one embodiment the system for modifying object oriented code performs the steps of reading a rule defining a change to object code defining an object oriented class, modifying the object code based on the rule, and writing the modified object code to a stream.
The system of the present invention can be implemented using software that is stored on a processor readable storage medium and executed using a processor. For example, the code modifier described below can be implemented in software and run on a general purpose computer. Alternatively, the invention can be implemented in specific hardware, or a combination of specific hardware and software, designed to carry out the methods described herein.
The code modifier of the present invention may be used change a user interface or add features specific to a particular virtual machine. The code modifier may also be used to modify existing applets used on a network to generate diagnostic or security information about the applets and send that diagnostic information to a server for presentation to a network administrator. Additionally, the code modifier can also be used to enable applets to communicate with a server on the Internet from behi

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