Lecture 14 Advanced Features of Java

1. Lecture 14Advanced Features of Java Jaeki Song

2. Software Development using Components • The ideal situation in application development • Run on any platform • Work with any operating systems • Interface with any language • Java has many features that aid in multisystem approach to application development • Java Beans, RMI, COBRA, etc.

3. Java Beans • Java Bean generally refers to components written to extend the Java language • Components that can add to applet or applications • Many components are visual; others are not • You define Java Bean as a class, which can include data fields or properties, methods, events, and storage

4. Java Bean • A property is a data field that contains a value • E.g., color, size, position, etc. • A method refers to the actions • Send message between two components • Event transmission • The communication between components is called • Event source • A component that fires an event • Event listener • The components that catches the event

5. Client/Server Applications • Remote Method Invocation (RMI) • Common Object Request Broker Architecture (COBRA) • Distributed Common Object Model (DCOM) • Java Native Interface (JNI) • Java Servlets

6. RMI • Allows you to use an object that exists on a different computer • The remote system can even call the methods of the object, just as if the object existed on the local machine • This technique is used extensively in client/server applications • Java.rmi package

7. CORBA • The basis of CORBA relies on an Object Request Broker (ORB) • The ORB can call methods from objects in any language that has an Interface Design Language (IDL) • Since objects can be remote, a system can create objects from a class defined on another system • With ORB, the programmer does not need to know the actual location of the class declaration or the language used to create the class

8. DCOM • DCOM is Microsoft’s component architecture • At time you may need to use CORBA to work with a system that uses DCOM • You can connect a DCOM client to communicate with a CORBA server by suing the Microsoft’s DCOM-to-CORBA bridge

9. JNI • JNI allows Java programs to use methods that were created in another programming language • Advantage • Use existing code (legacy code) regardless of the format in which it exists • Interface with other system also is enhanced

10. Java Servlets • Provides a way to create interactive Web applications • A servlet is like an applet that runs on the server side and is platform independent

11. Security • Security includes • The validity of classes • The resource restrictions placed on applet running in a browser, such as access local files and printers • Security in JVM contains a verifier and class loader • The goal is to determine that a hostile complier cannot generate dangerous byte code • The class loader locates all classes used by applet • A verifier tests classes so that only appropriate classes are loaded

12. Security • The security package in Java allows a program to check a digital signature from a developer • Determines that the program has not been altered and does not contains any viruses or malicious operation • Also, Java API contains a Security Manager class for defining the tasks that an application can perform