ServletContext InitParameter Problem

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posted 19 years ago

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Hello All,
Can you tell me what is the use of context.getInitParameter() or context.getInitParameterNames() . where we should define init parameters for Context. (Referring to text in bold context is of type ServletContext.)
What is the difference between context.getAttribute() or context.getAttributeNames() & getInitparameter() & getInitParameterNames()?
when i am using the following code on Tomcat 5.0 it shows the outputas given below:

Context_Servlet.java
//Servlet
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
 
public class Context_Servlet extends GenericServlet {
 
ServletContext context;
 
public void init(ServletConfig config) throws ServletException {
 
super.init(config);
 
// getting the current context...
context = getServletContext();
 
// setting context attributes...
context.setAttribute("companyName", "Seed Infotech Pvt. Ltd. Pune");
context.setAttribute("loginName", "Seed");
context.setAttribute("password", "pune");
System.out.println("Context Attribute are set...");
}
 
public void service(ServletRequest request, ServletResponse response) throws IOException, ServletException {
 
Enumeration enums;
 
response.setContentType("text/html");
PrintWriter out = response.getWriter();
 
out.println("<HTML>");
out.println("<HEAD>");
out.println("<TITLE>Context_Servlet...</TITLE>");
out.println("</HEAD>");
out.println("<BODY>");
out.println("");
 
out.println("Printing context-param elements from web.xml..." + " ");
enums = context.getInitParameterNames();
while(enums.hasMoreElements()) {
String name = (String) enums.nextElement();
String value = context.getInitParameter(name);
System.out.println(name + " : " + value);
out.println(name + " : " + value + " ");
}
 
/*out.println("Printing context attributes..."+" ");
enums = context.getAttributeNames();
while(enums.hasMoreElements()) {
String name = (String) enums.nextElement();
String value = (String) context.getAttribute(name);
System.out.println(name + " : " + value);
out.println(name + " : " + value + " ");
}*/
 
// updating companyName and removing password, context parameters...
String sCompanyName = (String) context.getAttribute("companyName");
context.setAttribute("companyName", sCompanyName.toUpperCase());
context.removeAttribute("password");
 
out.println("Printing after manipulating the Context Prameters..."+" ");
out.println("Company Name : " + (String) context.getAttribute("companyName") + " ");
out.println("Login Name : " + (String) context.getAttribute("loginName") + " ");
out.println("Password : " + (String) context.getAttribute("password") + " ");
 
out.println("</BODY>");
out.println("</HTML>");
}
}
 
 
//======================================================================
web.xml
//======================================================================
<?xml version="1.0" ?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
 
<web-app>
 

<servlet>
<servlet-name>Generic_Servlet</servlet-name>
<servlet-class>Generic_Servlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Generic_Servlet</servlet-name>
<url-pattern>/Generic_Servlet</url-pattern>
</servlet-mapping>
 

<servlet>
<servlet-name>Config_Servlet</servlet-name>
<servlet-class>Config_Servlet</servlet-class>
<init-param>
<param-name>DB_Driver</param-name>
<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
</init-param>
<init-param>
<param-name>DB_URL</param-name>
<param-value>jdbc :-o	 dbc:MyDataSource</param-value>
</init-param>
<init-param>
<param-name>DB_UserName</param-name>
<param-value>scott</param-value>
</init-param>
<init-param>
<param-name>DB_Password</param-name>
<param-value>tiger</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Config_Servlet</servlet-name>
<url-pattern>/Config_Servlet</url-pattern>
</servlet-mapping>

<servlet>
<servlet-name>Context_Servlet</servlet-name>
<servlet-class>Context_Servlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Context_Servlet</servlet-name>
<url-pattern>/Context_Servlet</url-pattern>
</servlet-mapping>
 
<context-param>
<param-name>DB_Driver</param-name>
<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
</context-param>
<context-param>
<param-name>DB_URL</param-name>
<param-value>jdbc :-o	 dbc:MyDataSource</param-value>
</context-param>
<context-param>
<param-name>DB_UserName</param-name>
<param-value>scott</param-value>
</context-param>
<context-param>
<param-name>DB_Password</param-name>
<param-value>tiger</param-value>
</context-param>
 
</web-app>

//====================================================================
OUTPUT in web browser
//====================================================================
Printing context-param elements from web.xml...

DB_Driver : sun.jdbc.odbc.JdbcOdbcDriver
DB_UserName : scott
DB_URL : jdbc

dbc:MyDataSource
DB_Password : tiger
Printing after manipulating the Context Prameters...

Company Name : SEED INFOTECH PVT. LTD. PUNE
Login Name : Seed
Password : null
//=========================================================================

It is not showing me any initparameter in the output can you help me to understand hoe init parametres can be specified & what would be its use?

Thanx in Advance
Shrinivas Mujumdar

[Code tags fixed]
[ August 27, 2005: Message edited by: David O'Meara ]

te zhang

Greenhorn

Posts: 6

posted 19 years ago

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if you want to get the InitParameter
since the initparameters are configued in the configuration file.
the web.xml, so the config object must be getten.
javax.servlet.ServletConfig
using the above class generate the config object ,you can

Ben Souther

Sheriff

Posts: 13411

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posted 19 years ago

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All the answers to your questions can be found in the API:
http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletContext.html

If you would like an example app that uses context init params I have one on
http://simple.souther.us.
There is also one for servlet init-params.

Java API J2EE API Servlet Spec JSP Spec How to ask a question... Simple Servlet Examples jsonf

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