JSP config Object is implicitly available to the developer on Java Server Pages. Config object is useful in getting application configuration values to JSP from web.xml file. Config object has a scope of application.
following is the list of applicable methods.
- getInitParameter ( )
- getInitParameterNames()
- getServlerName()
JSP config Object Example:
web.xml:
<?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>Test</display-name> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>ConfigObjectTest</servlet-name> <jsp-file>/configTest.jsp</jsp-file> <init-param> <param-name>name</param-name> <param-value>Dinesh</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>ConfigObjectTest</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> </web-app>
JSP File(configTest.jsp):
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>JSP Application Object Example</title>
</head>
<body>
Config Value for Parameter 'name' is: <%= config.getInitParameter("name")%>
</body>
</html>
As you can see above, web.xml has a configuration settings for Servlet named as ConfigObjectTest.
This configuration is defined within <servlet> and </servlet> tag.
The name of the servlet is defined within tag <servlet-name> and </servlet-name>
This Servlet specifies the JSP File within <jsp-file> and </jsp-file> tag.
Init Parameter is defined within tag <init-param> and </init-param>
Parameter name is defined within tag <param-name> and </param-name>
Parameter value is defined within tag <param-value> and </param-value>
The Servlet defined above is mapped with Url Pattern. Mapping is done using <servlet-mapping> and </servlet-mapping> tags. Within these tags, servlet is identified using <servlet-name> and </servlet-name>. It must match with the servlet name defined withing <servlet> and </servlet> tag.
Url Pattern is defined within <url-pattern> and <url-pattern> tag.
Once web.xml configuration is completed, the configuration parameters can be accessed in the JSP using config object. Init Parameters can be accessed using getInitParameters method of config object by passing parameter name as an argument.
Other useful methods available to config object are getServletName, getServletcontext and getInitParameterNames.
