Reading Initialization Parameters
Example 4
A
part from Request Parameters, we can also pass parameters using deployment
descriptor file web.xml. These are called as Init Parameters and these
available/scoped with in that Servlet alone and we can retrieve them using
init() method so the reason they are called as Init Parameters.
- Create following files in a folder (Please check next slide for code)
- Java File ReadInitParamsServlet.java Contains logic to get the params details.
- DD web.xml Deployment Descriptor
- Compile the Java File as you did in earlier example
- Create below structure with files that you created above
- Folder "ReadParamsServlet" contains
- I__"WEB-INF" Folder
- I__"WEB-INF" Folder contains "classes" Folder and web.xml File
- I__"classes" Folder contains "ReadInitParamsServlet.class" File
- Deploy the ReadInitParamsServlet folder inside webapps folder of Tomcat
- Bounce the Server
- Send request using "http://localhost:8550/ReadInitParamsServlet/getDetails"
ReadInitParamsServlet.java
: This prepares the response as HTML file that display init request parameters
that are provided in servlet
import java.io.x;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class
ReadlnitParamsServlet extends HttpServlet {
private Map
initParamsCollection = new HashMap();
public void init() throws
ServletException {
Enumeration<String>
initParams = getServletConfig().getInitParameterNames();
System.out.println(initParams
+ " initParams");
while (initParams.hasMoreElements())
{
String initParamName =
initParams.nextElement();
String initParamValue =
getServletConfig().getInitParameter(initParamName);
initParamsCollection.put(initParamName,
initParamValue);
}
}
PrintWriter out =
response.getWriter();
response.setContentType("text/html");
outprintln("<htmi>");
out.println("<head>");
out.println("<title>InitParams!</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Init
Params from Servlet!</h1>");
Iterator<Map.Entry> iter
= initParamsCollection.entrySet().iterator();
while (iter.hasNext()) {
Map.Entry entry = iter.next();
String key =
(String)entry.getKey();
String value =
(String)entry.getValue();
out.println("InitParameter
:" +key +" Its Value:"+value+…….");
}
out. println ("</body>");
out.println("</html>");
out.close();
}
}
- web.xml
o <servlet>
tag maps your servlet class with internal name
o <servlet-mapping>
tag maps internal name with url-pattern that your invoke
<web-app>
<servlet>
<servlet-name>initparamsservlet</servlet-name>
<servlet-class>ReadInitParamsServlet</servlet-class>
<init-param>
<param-name>FirstInitParam</param-name>
<param-value>Trainer</param-value>
</init-param>
<init-param>
<param-name>SecondlnitParam</param-name>
<param-value>
Learner</param-value>
</init-param>
</servlet>
<servlet-mapping>
<serviet-name>initparamsservlet</servlet-name>
<url-pattern>/getDetails</url-pattern>
</servlet-mapping>
</web-app>
