Swarnalatha Ashok

Java Database Connectivity

Applications that require complex manipulation of data will need to use a database to store information. Many Java applications fall into this category. Although many database vendors provide Java APIs, they are proprietary to their database implementations. Therefore, it becomes very difficult to port applications from one database to another. Java Database Connectivity (JDBC) APIs provide a simplified and uniform access to the database management systems from different vendors. In this chapter you will learn the essential classes and techniques to use JDBC APIs.

Implementation in Java

In Chapter 3, we demonstrated how object-oriented concepts can be implemented via notations in the Java programming language. For validation purposes, these concepts allow objects in our system to be operational. We now proceed to see how they are practically applied to example problems as typical programs.

Applets and Loaders

We have learned that Java is an interpreted language. A Java compiler (javac in JDK) translates source code to Java bytecodes so that it may execute as long as a Java Virtual Machine (java in JDK) is implemented to run on the underlying hardware. As such, Java is described as platform independent. In fact, the Java Virtual Machine not only allows Java to be source-code compatible, but object-code compatible as well. Object-code derived from compilation on one machine will execute unmodified on another.

Input and Output Operations

We have covered all the basic mechanisms of Java, but not much has been said about input and output operations such as reading from and writing to files. In fact, the Java programming language excludes any description of performing such operations. Instead, this critical functionality is implemented by standard libraries.

Object, Class, Message and Method

We had our first introduction to objects, message and method in Chapter 1. Another concept closely associated with the concept of objects is class. In object-oriented programming, a class is a definition template for structuring and creating objects. In this chapter, we will discuss the concept of object, message, method and class and how these concepts are used in a computer model.

Classification, Generalization, and Specialization

Objects with similar definitions have been grouped and defined into classes. The act of identifying and categorizing similar objects into classes is known as classification in object-oriented modeling. In this chapter, we will examine how objects are grouped into classes and how the relationships of classes can be organized into a class hierarchy using abstraction mechanisms generalization and specialization. In addition, we will discuss the concept of superclass and subclass as a prelude to discussing generalization and specialization.

Graphical Interfaces and Windows

In the earlier chapters, we previewed the Java API for input and output mechanisms, networking, and multithreading. In this chapter, we proceed to look at the facilities for incorporating graphical user interfaces. With the availability of powerful and cheap hardware, and widespread and diverse use of computers, easy and intuitive interfaces have become an important aspect to developers.

Networking and Multithreading

In Chapter 10, we previewed the Java API for input and output facilities, especially those associated with files requiring different formatting. The framework used to maximize code reusability was also discussed. In this chapter, we will go beyond the local machine by looking at networking facilities in the Java API. Since the abstraction for networking primitives turns out to be byte streams, there is indeed much reuse of the classes seen in the previous chapter.

A Quick Tour of Java

Earlier, we introduced key object-oriented concepts such as objects, methods and classes and how these may be ultimately used in a computer model. In this chapter, we see how the Java programming language is used to construct our object model of the problem domain. This approach is advantageous in that it allows our model to operate or “come alive” under computer control.

Object Serialization and Remote Method Invocation

Almost every application requires some means of keeping data across program runs. Most applications use a file or database for the storage or persistence of data. However, databases are not typically used to store objects, particularly Java objects. On the other hand, flat files alone do not cope well with object structure. What is required is some means to preserve the state of a Java object so that it may be easily stored and subsequently restored to its original state.