NullPointerException @ validation interceptor

[tyte kyat]

Hi there I got a Null pointer Exception when trying to save an obj...
what actually happen is when I implemented validation interceptor while inserting customer obj into DB, I got the NPE .
if I remove that interceptor, it works fine.

But, I need validation implemented. so, how can i bypass?

thanks.

java.lang.NullPointerException
	at com.myauk.dao.CustomerDAOImpl.addCustomer(CustomerDAOImpl.java:21)
	at com.myauk.action.CustomerAction.add(CustomerAction.java:30)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:453)
	at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)
	at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
	at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
	at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
	at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:510)
	at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
	at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
java.lang.NullPointerException
	at com.myauk.dao.CustomerDAOImpl.addCustomer(CustomerDAOImpl.java:24)
	at com.myauk.action.CustomerAction.add(CustomerAction.java:30)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:453)
	at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)
	at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
	at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
	at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
	at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:510)
	at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
	at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

the following is my action class

package com.myauk.action;


import java.util.ArrayList;
import java.util.List;

import com.myauk.dao.CustomerDAO;
import com.myauk.dao.CustomerDAOImpl;
import com.myauk.model.Customer;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;

public class CustomerAction extends ActionSupport implements ModelDriven<Customer> {

	
	
	private static final long serialVersionUID = 1L;
	private Customer customer=new Customer();
	private CustomerDAO customerdao=new CustomerDAOImpl();
	private List<String> mtype=new ArrayList<String>();	
	
	@Override
	public Customer getModel() {
		
		return customer;
	}
	
	public String add(){
		try{
		customerdao.addCustomer(customer);
		}catch (Exception e) {
			e.printStackTrace();
		}
		return "success";
	}

	public Customer getCustomer() {
		return customer;
	}

	public void setCustomer(Customer customer) {
		this.customer = customer;
	}
	
	public List<String> getMtype() {
		return mtype;
	}
	
	public String populate(){
		
		mtype.add("Platinum");
		mtype.add("Gold");
		mtype.add("Lead");
		return "success";
	}
}

and this is my struts.xml file

<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
	<constant name="devMode" value="true"></constant>
	<package name="default" extends="hibernate-default">
	
		<interceptors>
    		<interceptor name="LoginInterceptor" class="com.myauk.interceptor.LoginInterceptor"></interceptor>
    		<interceptor-stack name="mystack">
    			<interceptor-ref name="LoginInterceptor"></interceptor-ref>
    		</interceptor-stack>   
   		</interceptors>
   		
   			
		<action name="addCustomer" class="com.myauk.action.CustomerAction" method="add" >	
			<interceptor-ref name="validation"></interceptor-ref>
			<result name="success">/register_success.jsp</result>
			<result name="input">/register.jsp</result>
		</action>
		
		<action name="prepRegister" class="com.myauk.action.CustomerAction" method="populate">
			<result name="success">/register.jsp</result>
		</action>
		
		<action name="login" class="com.myauk.action.LoginAction" method="login">			
			<result name="success">/login_success.jsp</result>
			<result name="input">/login_error.jsp</result>
		</action>
		
		<action name="RegisterFacility" class="com.myauk.action.FacilityAction" method="facilityadd">
			<result name="success">/facilityregister_success.jsp</result>
		</action>
		
		<action name="viewslot" class="com.myauk.action.ListFacilityAction" method="viewfacilitylist" >
			<interceptor-ref name="mystack"></interceptor-ref>
			<result name="success">/booking.jsp</result>
			<result name="input">/login.jsp</result>
		</action>
		
	</package>
</struts>

My dao class is as follow

package com.myauk.dao;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.googlecode.s2hibernate.struts2.plugin.annotations.SessionTarget;
import com.googlecode.s2hibernate.struts2.plugin.annotations.TransactionTarget;
import com.myauk.model.Customer;

public class CustomerDAOImpl implements CustomerDAO {
	
	@SessionTarget
	Session session;
	
	@TransactionTarget
	Transaction transaction;

	@Override
	public void addCustomer(Customer customer) {
		try {
			session.save(customer);
		} catch (Exception e) {
			e.printStackTrace();
			transaction.rollback();
		}
		
	}

}

my validation xml is as follow

<!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator 1.0.2//EN"
       "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">
       
<validators>
	<field name="name">
		<field-validator type="requiredstring">
			<message>Name should not be blank.</message>
		</field-validator>
	</field>
	
	<field name="email">
		<field-validator type="requiredstring">
			<message>Email should not be blank.</message>
		</field-validator>
		
		<field-validator type="email">
			<message>The email address you entered is not valid.</message>
		</field-validator>
	</field>
	
	<field name="address">
		<field-validator type="requiredstring">
			<message>Address should not be blank.</message>
		</field-validator>
	</field>
	
	<field name="telephone">
		<field-validator type="requiredstring">
			<message>Telephone should not be blank.</message>
		</field-validator>
		
		<field-validator type="regex">
			<param name="expression"><![CDATA[\d{11}]]></param>
			<message>Phone number must be 11.</message>
		</field-validator>
	</field>
	
	<field name="password">
		<field-validator type="requiredstring">
			<message>Password should not be blank.</message>
		</field-validator>
	</field>
</validators>

[James Boswell]

How is the member variable session set in your DAO? I suspect your @SessionTarget annotation is not working and session is null when the code tries to add a customer.

[tyte kyat]

Thanks
James..

It turns out that it is not because of Session, it is somewhere @ value stack or at struts.xml file.

when I implement the following code in my struts.xml file (without validation interceptor)

<action name="addCustomer" class="com.myauk.action.CustomerAction" method="add" >	
									
			
			<result name="success">/register_success.jsp</result>
			<result name="input">/register.jsp</result>
		</action>

and insert customer as named "p". I got the following at concole meaning that it is working perfectly.

valuestack size = 3
p
p
Hibernate: insert into CUSTOMER (ADDRESS, EMAIL, NAME, PASSWORD, TELEPHONE, TYPE) values (?, ?, ?, ?, ?, ?)

and in my debug mode at my jsp page. I got the following information.

Object    Property Name     Property Value 
com.myauk.model.Customer     id                10 
                                              email            [e-mail] 
                                              address         paddress 
                                              name           p 
                                              type             Platinum 
                                              telephone     [phone] 
                                              password      pass 

Now, what i believe is , due the implementation of "validation" interceptor, my value stack become empty or having null.
why is that so?

[James Boswell]

<interceptor-ref name="validation">

Where is the interceptor called validation defined?

[tyte kyat]

I am using predefine interceptor .

[tyte kyat]

I got it working...
and I have to change my struts.xml file as follow

<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>
	<constant name="devMode" value="true"></constant>
	<package name="default" extends="hibernate-default">
	
		<interceptors>
    		<interceptor name="LoginInterceptor" class="com.myauk.interceptor.LoginInterceptor"></interceptor>
    		<interceptor-stack name="mystack">
    			<interceptor-ref name="LoginInterceptor"></interceptor-ref>
    			<interceptor-ref name="defaultStackHibernate"></interceptor-ref> <--------(1)
    		</interceptor-stack> 
    		
    		<interceptor-stack name="teststack">    		  
    			<interceptor-ref name="logger"></interceptor-ref>
    			<interceptor-ref name="timer"></interceptor-ref>
    			<interceptor-ref name="modelDriven"/>    <---------(2)
    			<interceptor-ref name="params"/>           <---------(3)
    			<interceptor-ref name="validation">         <---------(4)
    				<param name="excludeMethods">input,back,cancel,browse</param>
    			</interceptor-ref>
    			<interceptor-ref name="workflow"/>
    			<interceptor-ref name="defaultStackHibernate"></interceptor-ref>  <----------(5)
    		</interceptor-stack>  
   		</interceptors>
   		
   		   					
		<action name="addCustomer" class="com.myauk.action.CustomerAction" method="add" >
			<interceptor-ref name="teststack"></interceptor-ref>				
			<result name="success">/register_success.jsp</result>
			<result name="input">/register.jsp</result>
		</action>
		
		<action name="prepRegister" class="com.myauk.action.CustomerAction" method="populate">
			<result name="success">/register.jsp</result>
		</action>
		
		<action name="login" class="com.myauk.action.LoginAction" method="login">	
			<interceptor-ref name="teststack"></interceptor-ref>
			<result name="success">/login_success.jsp</result>
			<result name="input">/login.jsp</result>
		</action>
		
		<action name="RegisterFacility" class="com.myauk.action.FacilityAction" method="facilityadd">
			<result name="success">/facilityregister_success.jsp</result>
		</action>
		
		<action name="viewslot" class="com.myauk.action.ListFacilityAction" method="viewfacilitylist" >
			<interceptor-ref name="mystack"></interceptor-ref> 
			<result name="success">/booking.jsp</result>
			<result name="input">/login.jsp</result>
		</action>
		
	</package>
</struts>

This is intend for those who are like me(newbie) in Struts and Hibernate...

You see no 1 and 5 is required as I am using full hibernate plugin. And according to the rule, there should be basic stack or default stack in your newly created stack.
without that you will get nullPointerException.

you see no 2 is required this is because ( you might need to go above of this page and look for "CustomerAction", which is implemented using modeldriven.)
for that reason you need it. again if you do not turn on ModelDriven Interceptor, you will get NullPointerException.

you see no 3 is required this is because somewhere in my application (which you can not have a reference here), username and password is required and that params interceptor is required for that reason.
without that again NPE.

and No 4 is the validation which is required to validate against user input.
that is all ...


(if i state something wrong here, I will happily take any suggestion and improvement.)
Thanks...