Error in Select box - struts2

Question

This is my Assignemployee.jsp file code
<s:form action="AssignEmployee" name="myForm">
<s:select name="pname" list="projectlist" headerKey="0" label="Select a country" />
<s:submit/>
</s:form>
This is my projectlist.java action file
package myPack;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.apache.struts2.interceptor.ApplicationAware;
import org.apache.struts2.interceptor.ServletRequestAware;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.Preparable;
public class projectlist extends ActionSupport implements ServletRequestAware {
private static final long serialVersionUID = 1L;
HttpServletRequest request;
private List<String> projectlist;
public List<String> getProjectlist() {
return projectlist;
}
public void setProjectlist(List<String> projectlist) {
this.projectlist = projectlist;
}
public void setServletRequest(HttpServletRequest request)
{
this.request = request;
}
public HttpServletRequest getServletRequest(){
return request;
}
public String getDefaultSearchEngine() {
return "yahoo.com";
}
public projectlist()
{
try
{
Class.forName("com.mysql.jdbc.Driver");
java.sql.Connection con=DriverManager.getConnection("jdbc:mysql:///pmt","root","shree");
ps=con.prepareStatement("select * from addproject");
ResultSet res = ps.executeQuery();
while(res.next())
{
projectlist = new ArrayList<String>();
projectlist.add(res.getString("pname"));
}
ps.close();
con.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
public String execute()throws Exception
{
return SUCCESS;
}
public String display() {
return NONE;
}
}
And This is struts.xml
<action name="AssignEmployee" class="myPack.projectlist" method="display">
<result name="success">assignemployee.jsp</result>
</action>
When i am running application i get an error like
SEVERE: Servlet.service() for servlet [jsp] in context with path [/PTMS] threw exception [tag 'select', field 'list', name 'pname': The requested list key 'projectlist' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or people.{name} - [unknown location]] with root cause
tag 'select', field 'list', name 'pname': The requested list key 'projectlist' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or people.{name} - [unknown location]
How to solve this error?

Answer 1

There are two problems:
Project list creation is broken, and
The first access to the form is broken.
1) You're creating a new list for every row in the result set:
while (res.next()) {
projectlist = new ArrayList<String>();
projectlist.add(res.getString("pname"));
}
This should look closer to:
projectlist = new ArrayList<String>();
while (res.next()) {
projectlist.add(res.getString("pname"));
}
It also appears you never actually call this method, although it's difficult to tell since the code is essentially illegible without indentation or any valuable whitespace. Where you call it is open to some debate; it could be in the getter itself, a prepare() method (and the action would implement Prepareable), the execute() method, etc.
These kinds of things should likely go into a service, however, as a testability aid.
2) I'm not convinced your initial visit to the JSP is being handled correctly. It should:
a) Go through a Struts 2 action,
b) Call the projectlist initializer, and
c) Forward to the JSP with the form.
If all those criteria are met, you will not get that error.