Saturday, March 20, 2010

Java Virtual Machine Feature

The following section provides a more comprehensive discussion of the three main task performed by the Java Virtual Machine.

• Code Lode by class loader

The class Loader loads all classes needed for the execution of a program. The class loader adds security by separating the namespaces for the classes of the local file system from those imported from network sources. This limits any Torjan Horse application, because local classes are always loaded first.

• Verifier Code by Bytecode Verifier

Java software codes passes several tests before running on your machine. The JVM puts the code through a bytecode verifier that tests the format of code fragments and checks code fragments for illegal code, which is code that gorges pointers, violates access rights on objects, or attempts to change object type.

* Verification Process-

The bytecode verifier makes four passes on the code in a program. It ensures that the code adhere to the JVM specifications and does not violates system integrity. If the verifier completes all four passes without returning an error message, the following is ensured:

The classes adhere to the class file format of the JVM specification.

There are no access restriction violations.

The code causes no operand stack overflows or underflows.

The types of parameters for all operational codes are correct.

No illegal data conversions, such as converting integers to object

references, have occurred.