Web Applications with Java: Servlets, JSP, and JDBC
Web Applications with Java
Objective
Java technologies have revolutionized computer system development, enabling the creation of high-performance and complex systems. Web applications, particularly those involving database management and dynamic content generation, have experienced significant growth. By combining JSP and JDBC, developers can create diverse online services, including catalogs, portals, storefronts, e-commerce tools, and any system requiring web-based information handling. These Java-based technologies offer efficient resource consumption, rapid development times, and reliable final products.
Technologies for Generating Dynamic Pages
What is a Servlet?
Servlets are Java classes that extend web server functionality by generating dynamic web pages. A servlet engine manages servlet loading and unloading, collaborating with the HTTP web server to direct client requests to the servlet and send responses. Introduced in 1997, servlets have become the dominant Java server programming environment. They address limitations of applets, such as restricted access to servers other than the host, limited access to server services, and security vulnerabilities (e.g., reverse engineering).
Features of Servlets
Servlets offer several advantages:
- Platform independence due to being 100% pure Java.
- Object-oriented nature, inheriting all associated benefits.
- Utilization of all Java technologies (e.g., storage classes, threads, database access, I/O streams, RMI, network access).
- Efficient server resource usage by creating a single process for the servlet upon the first request and subsequent execution threads for later requests.
- Superior speed compared to CGI due to precompilation and non-independent results for each URL request.
- Enhanced security through the Java Security Manager.
- Simplified communication with other servlets.
- Easy error handling through exception management.
What is JSP?
JSP (Java Server Pages) is a web page template using Java code to dynamically generate HTML. A JSP container translates JSP into equivalent Java servlets. Therefore, JSP offers the same advantages as servlets.
JSP or Servlets?
Both Servlets and JSP offer advantages over CGI:
- Improved performance and adaptability due to in-memory operation and multithreading.
- No special client configuration required.
- Support for HTTP sessions, enabling application planning.
- Access to Java technologies (threads, networking, database connectivity) without applet limitations.
Advantages of JSP over Servlets:
- Automatic compilation as needed.
- Easier location due to placement within the web server’s document directory.
- HTML-like structure, enhancing compatibility with web development tools.
JDBC Technology
JDBC enables Java and JSP programs to connect to databases and execute SQL queries. More details are available at: http://java.sun.com/jdbc/.
The JDBC API
The JDBC API, a standard technology by Sun, allows Java and JSP developers to access any database engine. Key features include:
- SQL (Structured Query Language) support.
- Easy access to all SQL features.
- Object-based treatment of SQL results, enabling exception handling for errors.
Sun’s JDBC API is inspired by Microsoft’s ODBC (Open Database Connectivity) standard, aiming to create a standard for database access using Java. The JDBC-ODBC bridge converts JDBC calls to ODBC transparently for the programmer. However, this conversion process can lead to performance issues in applications with extensive database queries.