The JSP API

The JSP API

• The JSP API consists of two packages:
• javax.servlet.jsp
• javax.servlet.jsp.tagext

• javax.servlet.jsp package
• The javax.servlet.jsp package has two interfaces and classes.
• The two interfaces are as follows:

• JspPage
• HttpJspPage
• The classes are as follows:

• JspWriter
• PageContext
• JspFactory
• JspEngineInfo
• JspException
• JspError

The JspPage interface

• According to the JSP specification, all the generated servlet classes must implement the JspPage interface. It extends the Servlet interface. It provides two life cycle methods.

Methods of JspPage interface

public void jspInit(): 

• It is invoked only once during the life cycle of the JSP when JSP page is requested firstly. 
• It is used to perform initialization. 
• It is same as the init() method of Servlet interface.

public void jspDestroy(): 

• It is invoked only once during the life cycle of the JSP before the JSP page is destroyed. 
• It can be used to perform some clean up operation.

The HttpJspPage interface

• The HttpJspPage interface provides the one life cycle method of JSP. It extends the JspPage interface.

Method of HttpJspPage interface:

public void _jspService(): 

• It is invoked each time when request for the JSP page comes to the container. 
• It is used to process the request. 
• The underscore _ signifies that you cannot override this method.