JSP
What is page directive?
Nov 26th
• A page directive is to inform the JSP engine about the headers or facilities that page should get from the environment. • Typically, the page directive is found at the top of almost all of our JSP pages. • There can be any number of page directives within a JSP page (although the attribute – value pair must be unique). • The syntax of the include directive is: • Example:
What are the attributes of page directive?
Nov 26th
There are thirteen attributes defined for a page directive of which the important attributes are as follows: • import: It specifies the packages that are to be imported. • session: It specifies whether a session data is available to the JSP page. • contentType: It allows a user to set the content-type for a page. • isELIgnored: It specifies whether the EL expressions are ignored when a JSP is translated to a servlet.
How can I override the jspInit() and jspDestroy() methods within a JSP page?
Nov 26th
The jspInit() and jspDestroy() methods are each executed just once during the lifecycle of a JSP page and are typically declared as JSP declarations:
<%!public void jspInit() {. . .}%><%!public void jspDestroy() {. . .}%>
What are implicit objects in JSP?
Nov 26th
Implicit objects in JSP are the Java objects that the JSP Container makes available to developers in each page. These objects need not be declared or instantiated by the JSP author. They are automatically instantiated by the container and are accessed using standard variables; hence, they are called implicit objects.The implicit objects available in JSP are as follows: • request • response • pageContext • session • application • out • config • page • exception The implicit objects are parsed by the container and inserted into the generated servlet code. They are available only within the jspService method and More >
What is the _jspService() method?
Nov 26th
The _jspService() method of the javax.servlet.jsp.HttpJspPage interface is invoked every time a new request comes to a JSP page. This method takes the HttpServletRequest and HttpServletResponse objects as its arguments. A page author cannot override this method, as its implementation is provided by the container.
What JSP lifecycle methods can I override?
Nov 26th
You cannot override the _jspService() method within a JSP page. You can however, override the jspInit() and jspDestroy() methods within a JSP page. jspInit() can be useful for allocating resources like database connections, network connections, and so forth for the JSP page. It is good programming practice to free any allocated resources within jspDestroy().
What is the life-cycle of JSP?
Nov 26th
When a request is mapped to a JSP page for the first time, it translates the JSP page into a servlet class and compiles the class. It is this servlet that services the client requests. A JSP page has seven phases in its lifecycle, as listed below in the sequence of occurrence:
- Translation
- Compilation
- Loading the class
- Instantiating the class
- jspInit() invocation
- _jspService() invocation
- jspDestroy() invocation
What is the jspInit() method?
Nov 26th
The jspInit() method of the javax.servlet.jsp.JspPage interface is similar to the init() method of servlets. This method is invoked by the container only once when a JSP page is initialized. It can be overridden by a page author to initialize resources such as database and network connections, and to allow a JSP page to read persistent configuration data.
What are the advantages of JSP over Servlet?
Nov 26th
JSP is a serverside technology to make content generation a simple appear.The advantage of JSP is that they are document-centric. Servlets, on the other hand, look and act like programs. A Java Server Page can contain Java program fragments that instantiate and execute Java classes, but these occur inside an HTML template file and are primarily used to generate dynamic content. Some of the JSP functionality can be achieved on the client, using JavaScript. The power of JSP is that it is server-based and provides a framework for Web application development.
