A Bytecode Example Though you may not realize it, you have already seen an example of bytecode or at least its human readable format. The output generated by the javap command when we ran it with the -c flag contained a disassembly of each of the methods in the class file. Let’s consider now the … Read more
We said that the constant pool contains a great deal of information. In fact it contains an interesting mixture of items. The constant pool combines the function of a symbol table for linking purposes as well as a repository for constant values and string literals present in the source code. It may be considered as … Read more
The class file contains a lot more information than its cousin, the executable file. Of course, it still contains the same type of information: program requirements, an identifier indicating that this is a program and executable code (bytecode, in this case). However, it also contains some very rich information about the original source code. The … Read more
Moving back to the world of Java, we see that it is a high-level programming language and that bytecode is the low-level machine language of the JVM. Java is an object-oriented language; that is, it deals primarily with objects and their interrelationships. Objects are best thought of in this context as a collection of data … Read more
The class loading mechanism plays a critical role in Java security since the class loader is responsible for locating and fetching the class files, consulting the security policy, and defining the appropriate permissions associated with the class object. In JDK 1.1, local code and correctly signed remote code were generally trusted to have full access … Read more
A protection domain can be scoped by a set of objects that are currently directly accessible by a principal, where a principal is an entity in the computer system to which permissions are granted. A principal can access objects in the protection domain by virtue of the permissions it enjoys over the objects in the … Read more
The Need for Java Security From its inception, Java has shown that it was designed for the net. Java brought about, for the first time on a large scale, the concept of dynamic loading of code from a source outside the system. Though this is very powerful, and adds several features to the system using … Read more
There are a number of different components to Java: 1. Development environment The Java 2 SDK contains the tools and executable code needed to compile and test Java programs. However, unlike a normal language, the Java 2 SDK includes object frameworks for creating graphical user interfaces, for networking and for complex I/O. Normally, in other … Read more