JSP

Introduction:

• JSP technology is used to create dynamic web applications. 
• JSP pages are easier to maintain then a Servlet. 
• JSP pages are opposite of Servlets as a servlet adds HTML code inside Java code, while JSP adds Java code inside HTML using JSP tags. 
• Everything a Servlet can do, a JSP page can also do it.

• JSP enables us to write HTML pages containing tags, inside which we can include powerful Java programs. 
• JSP becomes a Servlet
• JSP pages are converted into Servlet by the Web Container.
• The Container translates a JSP page into a servlet class source(.java) file and then compiles into a Java Servlet class.
  
  
  

Why JSP is preferred over servlets?

• JSP provides an easier way to code dynamic web pages.
• JSP does not require additional files like java class files, web.xml, etc
• Any change in the JSP code is handled by Web Container(Application server like tomcat) and doesn't require recompilation.
• JSP pages can be directly accessed, and web.xml mapping is not required like in servlets.

Advantage of JSP

• Easy to maintain and code.
• High Performance and Scalability.
• JSP is built on Java technology, so it is platform-independent.

Lifecycle of JSP

• A JSP page is converted into Servlet in order to service requests. 
• The translation of a JSP page to a Servlet is called Lifecycle of JSP. JSP Lifecycle is precisely the same as the Servlet Lifecycle, with one additional first step, which is, translation of JSP code to Servlet code. 
  
  
  
• Following are the JSP Lifecycle steps:
• Translation of JSP to Servlet code.
• Compilation of Servlet to bytecode.
• Loading Servlet class.
• Creating a servlet instance.
• Initialization by calling jspInit() method
• Request Processing by calling _jspService() method
• Destroy by calling jspDestroy() method

Example:
in head tag
    <%
       int count = 0;
    %>
in body tag
        Page Count is: 
        <% out.println(++count); %>