JavaServer Pages facts for kids

JavaServer Pages (JSP) is a special way to build websites that can change and show different things to different people. Imagine a website that always shows you the latest news or your personal profile – that's what JSP helps create! It's like a recipe for making dynamic web pages.

JSP was created by a company called Sun Microsystems. To make JSP work, you need a special computer program called a server (like Apache Tomcat) that helps deliver web pages to your computer or phone.

What are JavaServer Pages?

Think of most websites as being made of HTML. HTML tells your web browser what to show, like text, pictures, and links. But what if you want the website to show something different every time someone visits, or to show information from a database? That's where JSP comes in!

JSP lets web developers mix regular HTML with special Java code. This Java code runs on the web server before the page is sent to your browser. This means the server can do things like:

• Look up information from a database.
• Show different content based on who is visiting the site.
• Process forms you fill out.
• Create parts of a web page on the fly.

So, instead of just sending a fixed HTML page, the server uses JSP to build a unique HTML page for each visitor or situation.

How JSP Works

When you type a website address into your browser, here's a simplified idea of what happens if that website uses JSP:

• Step 1: You ask for a page. Your web browser sends a request to the web server for a specific JSP page.
• Step 2: The server gets ready. The first time someone asks for that JSP page, the web server "translates" the JSP code into a special Java program called a Servlet. Think of a Servlet as a powerful Java program that knows how to handle web requests.
• Step 3: The Servlet runs. This Servlet then runs on the server. It uses the Java code inside the JSP to do whatever is needed, like getting data or making calculations.
• Step 4: HTML is created. The Servlet then creates a regular HTML page based on its work and the original JSP template.
• Step 5: You see the page. This newly created HTML page is sent back to your web browser, and you see the finished result!

If someone asks for the same JSP page again, the server usually doesn't need to translate it again. It just uses the Servlet that was already created, making things faster.

Why Use JSP?

JSP is popular for building dynamic websites because it offers several benefits:

• Easy to mix code and design: Developers can easily combine HTML (for how the page looks) with Java code (for how the page works). This makes it simpler to build web pages that change.
• Powerful Java features: Since JSP uses Java, developers can use all the powerful tools and libraries that Java offers. This means they can build very complex and secure web applications.
• Reusable components: You can create reusable parts of a web page using JSP. For example, a common header or footer can be made once and included on many pages.
• Platform independent: Like Java, JSP can run on many different types of computer systems, which makes it very flexible.

Key Parts of JSP

JSP pages have special parts that tell the server what to do:

• Directives: These are instructions for the JSP engine (the part of the server that handles JSP). They might tell the server to include another file or set up certain things for the page.
• Scriptlets: These are blocks of Java code that run when the page is processed. Developers can write Java logic here, like loops or if-statements.
• Expressions: These are small pieces of Java code that calculate a value, and that value is then directly put into the HTML output.
• Actions: These are special XML-like tags that perform common tasks, like including other files or working with Java objects.

JSP and Other Web Technologies

JSP doesn't work alone. It's usually part of a bigger team of technologies that build a website:

• HTML: JSP creates HTML, which is the basic language for web pages.
• CSS: CSS (Cascading Style Sheets) is used to make the HTML look good, controlling colors, fonts, and layout.
• JavaScript: This language runs in your web browser and makes pages interactive, like showing pop-up messages or checking forms before they are sent. JSP handles things on the server, while JavaScript handles things in your browser.
• Databases: JSP often connects to databases (like MySQL or Oracle Database) to store and retrieve information, such as user profiles or product lists.

History of JSP

JSP was first released by Sun Microsystems in 1999. It was created to make it easier for developers to build dynamic web pages using the Java programming language. Before JSP, developers often used Servlets directly, which could be more complex for creating the visual parts of a web page. JSP helped separate the design (HTML) from the logic (Java code), making web development more organized and efficient. Over the years, JSP has been updated and improved, remaining an important tool for many web applications.

See also

In Spanish: JavaServer Pages para niños