Web Programming Chapter 3

Study Notes

Web Programming - Chapter 3

A web application is a collection of web pages dynamically generated in response to user requests. Examples include search engines, online stores, auctions, and discussion forums.
Web applications are client/server applications. Components are stored either on the client or server computer.
The web application itself is located on the server. This server utilizes web server software to send web pages to browsers. Apache HTTP Server is a common choice, especially for Java web applications.
Most web applications use a database (DBMS) for storing data. Popular choices for Java development include Oracle and MySQL.
Static web pages display the same information each time they are viewed. Their content isn't affected by user input, akin to news articles.
HTML, the Hypertext Markup Language, is the language used to create the structure and content of web pages. Web browsers display these pages.
The web page viewing process starts when a user enters an address or clicks a link in a web browser. The browser uses HTTP, the Hypertext Transfer Protocol, to request the page from the web server.
Dynamic web pages change in response to user choices or customized settings, like parameters sent via web applications to web servers.
The server generates the dynamic page and returns the HTML to the browser. This process determines if the page is truly dynamic.
For a Java web application, the server needs additional software, a Servlet/JSP engine (or container). This allows the web server to run servlets and JSPs.
Sun's Java Enterprise Edition (Java EE) outlines how the servlet/JSP engine interacts with the web server.
Tomcat, a free and open-source servlet/JSP engine, is based on the Apache Software Foundation's Jakarta project. It is typically used to implement servlet/JSP specifications.
For proper function, the servlet/JSP engine needs access to the Java Development Kit (JDK), which includes the Java compiler and runtime environment.
JSP (Java Server Pages) combines static HTML with dynamically generated content from servlets. This is important because it allows creating interactive web pages.
JSPs are converted to servlets before execution. For repeated use of a JSP, the JSP engine does not repeat the conversion to a servlet. It just re-uses the compiled servlet code.
Servlets are Java classes running on a server to handle dynamic content for web pages, typically implemented by programmers, not web designers.
Servlets employ the println method with an out object to send HTML output to the browser.
The servlet life cycle has three primary methods (Init(), Service(), Destroy()). Inside the Servie method, two crucial methods (doGet() and doPost()) handle specific request types.
Model-View-Controller (MVC) is a pattern that organizes web applications into three layers (Model, View, Controller). The model handles business logic, the view displays information, and the controller manages the interaction between the two.
The Model is primarily implemented with JavaBeans, the business logic layer. This logic is responsible for processing data.
The View presents data to the user, typically via HTML documents generated by servlets or JSPs depending on the implementation.
The Controller manages the flow of the application, usually through servlets that handle incoming requests, update the model (data) if necessary, and present data to the view. It is done through handling user requests and sending information back to the view.
The advantage of JSP over other web technologies is its robust dynamic data handling features and general portability.
JSPs' integration with HTML allows for dynamic data insertion, a technique that static HTML cannot replicate seamlessly.
SSI (Server-Side Includes) is a similar technology but JSP usually offers more flexibility.