getting servlet parameters in one file to reuse it

[Farakh khan]

Hello,

Can I get parameters from HTML file to my servlet and to reuse these parameters by inheriting this class to other servlet classes?

Best regards

[Miku Ranjan]

Hi,
Can you describe your question bit more clearly , I could not get what you want.

[hemantha kumar k]

one way you can do this,

1. get the all parameter names from html using getParameterNames() method from the Request Object

2. use the getParmeter() to get the values of the html parameter by passing the names you got it from getParameterNames() method and store it any other class for further use.

[Farakh khan]

For example I have a servlet name HTMLParameters.java where I am getting parameters like: String name = request.getParamter("name");

then I want to use this parameter in another class e.g. DisplayRecords.java to show some records on basis of the parameters got in HTMLParameters.java??

regards

[Matthew Freake]

I may be misunderstanding you, but can't you just pass the name in as a parameter to a method in your other class? So, something like:

    // within HTMLParameters.java
   void doGet(HttpServletRequest req, HttpServletResponse resp) {
       String name = req.getParamter("name");
       DisplayRecords displayRecord = new DisplayRecord();
       displayRecord.doSomeWork(name);
       ...
   }

   //within DisplayRecords.java
   void doSomeWork(String name) {
        // do something with name here
   }
   

[Farakh khan]

I mean like this code:

    // within HTMLParameters.java
   void doGet(HttpServletRequest req, HttpServletResponse resp) {
       String name = req.getParamter("name");
       ...
   }

   //within DisplayRecords.java
   void doSomeWork(HTMLParameters hp) {
       MyMethod m= new MyMethod();
       MyDAO md = new MyDAO();
     
      m.show(hp.name);
     md.insertToDB(hp.name);
   }
   

and this HTMLParameters.java may be called to many methods from different classes

[Steven Walkling]

Hi Farakh!
It looks like you're trying to pass an instance of the Servlet class (HTMLParameters.java) into a function in another class (DisplayRecords.java) in your code. I'm not sure if that would work for what you're trying to accomplish. If I'm reading your code right, what you have won't work because "name" isn't class variable for HTMLParameters.

Since the parameters are contained on the request object, what you could do is pass the request object to the class that needs those values.

//SomeServlet
void doGet(HttpServletRequest req, HttpServletResponse resp)
{
DisplayRecords.doSomeWork(req);
}

//DisplayRecords.java
void doSomeWork(HttpServletRequest req)
{
MyMethod m= new MyMethod();   
MyDAO md = new MyDAO();
String name = req.getParameter("name");

m.show(name);   
md.insertToDB(name);   
}

Or you create a class that can contains all of the parameter values you'll need (I'll call it ParameterKey), and pass an instance of that class to the classes that need it.

//ParameterKey.java
public ParameterKey(HttpServletRequest req)
{
//assign values from req.getParameter().
}

//SomeServlet.java
void doGet(HttpServletRequest req, HttpServletResponse resp)
{
ParameterKey paramKey = new ParameterKey(req);
DisplayRecords.doSomeWork(paramKey);
}

//within DisplayRecords.java   
void doSomeWork(ParameterKey paramKey) 
{   
 MyMethod m= new MyMethod();   
 MyDAO md = new MyDAO();   
        
 m.show(paramKey.name);   
 md.insertToDB(paramKey.name);   
 }   

This is a newbie answer to an admittedly limited understanding of your question, but it's my best shot!

Let us know if it helps!

Update: Mixed UBB code with Not-UBB code. Embarrassing! And fixed!

[Farakh khan]

Thanks for giving me your precious time

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

class Hello extends HttpServlet {
                	
  public void doGet(HttpServletRequest req, HttpServletResponse res)throws IOException,ServletException{

	res.setContentType("text/html");
	PrintWriter out=res.getWriter();

	ParameterKey paramKey = new ParameterKey(req);   
	}
}

--------------------------

import javax.servlet.http.*;

class ParameterKey{

	public ParameterKey(HttpServletRequest req){   
	String name 	= req.getParameter("name");
	String rollNo 	= req.getParameter("rollNo");

	System.out.println(name+"\n"+rollNo);
	}   
}

By sending form data it throws the following error:
http://127.0.0.1:7070/servlet/Hello?name=Hello+World&rollNo=12

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Error instantiating servlet class Hello
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
	org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
	org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	java.lang.Thread.run(Thread.java:619)

root cause

java.lang.IllegalAccessException: Class org.apache.catalina.core.StandardWrapper can not access a member of class Hello with modifiers ""
	sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
	java.lang.Class.newInstance0(Class.java:349)
	java.lang.Class.newInstance(Class.java:308)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
	org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
	org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	java.lang.Thread.run(Thread.java:619)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.

When am trying like this:

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

class Hello extends HttpServlet {
                	
  public void doGet(HttpServletRequest req, HttpServletResponse res)throws IOException,ServletException{

	res.setContentType("text/html");
	PrintWriter out=res.getWriter();

	ParameterKey paramKey = new ParameterKey(req); 

	DisplayRecords dr = new DisplayRecords();	  
	dr.doSomeWork(paramKey);   
	}
}

--------------------------

import javax.servlet.http.*;

class ParameterKey{

	public ParameterKey(HttpServletRequest req){   
	String name 	= req.getParameter("name");
	String rollNo 	= req.getParameter("rollNo");

	System.out.println(name+"\n"+rollNo);
	}   
}

--------------------------

class DisplayRecords{
               
	public DisplayRecords(){

	} 	
	
  void doSomeWork(ParameterKey paramKey){      
 	System.out.println(paramKey.name);      
 	System.out.println(paramKey.name);      
 }     

}

C:\Program Files (x86)\Java\Tomcat7.2\webapps\ROOT\WEB-INF\classes>javac Hello.j
ava
.\DisplayRecords.java:8: cannot find symbol
symbol : variable name
location: class ParameterKey
System.out.println(paramKey.name);
^
.\DisplayRecords.java:9: cannot find symbol
symbol : variable name
location: class ParameterKey
System.out.println(paramKey.name);
^
2 errors

[/code]

thanks again

regards

[Louis Bros]

Hi, It looks like 'name' and 'rollNo' only exist within the constructor scope of ParameterKey.

Also rather than allow direct access to variables you should use getter and setter methods.

[Pete Nelson]

I am pretty sure the cause of the error is on line #5 of your servlet code:

class Hello extends HttpServlet {  

You would need to make that a public class for the servlet container to access it.

Another thing to consider - use the ServletRequest's getParameterMap() method, and pass a Map to your constructor, rather than the full request object. Then your data class has no need to know anything of servlets.

[Farakh khan]

Pete Nelson wrote:I am pretty sure the cause of the error is on line #5 of your servlet code:

class Hello extends HttpServlet {  

You would need to make that a public class for the servlet container to access it.

You are very well right. I changed the class to public and it start working

Thanks for helping but still this part of question is not working

DisplayRecords dr = new DisplayRecords();	  
	dr.doSomeWork(paramKey);   

[Farakh khan]

Thanks to all from the bottom of my heart to helping me out