NullPointerException when using interceptor in struts2

Question

My problem is that , when i am tying to log to my webapp using Struts2 and hibernate a null pointer exception is given My tomcat server gives exception is as follow:

INFOS: Server startup in 10968 ms
inside execute
inside find
java.lang.NullPointerException
Nameeee   admin passwordddd   admin
session getuser  null
    at com.inwi.dao.UserDAOImpl.find(UserDAOImpl.java:43)
    at com.inwi.action.LoginAction.execute(LoginAction.java:43)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

LoginAction :

public class LoginAction extends ActionSupport implements SessionAware, ModelDriven<User>{

    private static final long serialVersionUID = -3369875299120377549L;

    private User                         user = new User();
    private SessionMap<String, Object>   sessionAttributes = null;
    private List<User>                   userList = new ArrayList<User>();
    private UserDAO                      userDAO  = new UserDAOImpl();


    @Override
    public String execute(){
        System.out.println("inside execute");
        if(userDAO.find(user.getName(),user.getPassword())){
        //if(user.getName().equals(user.getName()) && user.getName().equals(user.getPassword())){
            System.out.println("ggggggggggggg");
            sessionAttributes.put("USER", user);
            return SUCCESS;
        }
        return INPUT;
    }
    @Override
    public void setSession(Map<String, Object> sessionAttributes) {
        this.sessionAttributes = (SessionMap<String, Object>)sessionAttributes;
    }

    @Override
    public User getModel() {
        return user;
    }

UserDaoImpl class :

public class UserDAOImpl implements SessionAware,UserDAO {

    @SessionTarget
    Session session;

    @TransactionTarget
    Transaction transaction;

    private Map<String, Object> sessionAttributes = null;

    @Override
    public void setSession(Map<String, Object> sessionAttributes) {
        this.session = (Session) sessionAttributes;
    }

    @SuppressWarnings("unchecked")
    public boolean find(String name, String password) {
        System.out.println("inside find");
        System.out.println("Nameeee   "+name   +" passwordddd   "+password);
        boolean result = false;
        List<User> user = null;
        try {
            System.out.println("session getuser  "+session);
            String hql = "from User u where u.name = : name and u.password = : password";
            user = session.createQuery(hql).list();

            while (!user.isEmpty()) {  
             result = true;  
            }  
         } catch (Exception e) {  
             e.printStackTrace();
         }  
        return result;
    }

AuthenticationInterceptor class :

public class AuthenticationInterceptor implements Interceptor {

    private static final long serialVersionUID = -5011962009065225959L;

    @Override
    public void destroy() {
        //release resources here
    }

    @Override
    public void init() {
        // create resources here
    }

    @Override
    public String intercept(ActionInvocation actionInvocation)
            throws Exception {
        System.out.println("inside auth interceptor");
        Map<String, Object> sessionAttributes = actionInvocation.getInvocationContext().getSession();

        User user = (User) sessionAttributes.get("USER");

        if(user == null){
            return Action.LOGIN;
        }else{
            Action action = (Action) actionInvocation.getAction();
            if(action instanceof UserAware){
                ((UserAware) action).setUser(user);
            }
            return actionInvocation.invoke();
        }
    }

}

Welcome Action class :

public class WelcomeAction extends ActionSupport implements UserAware, ModelDriven<User> {

    private static final long serialVersionUID = 8111120314704779336L;

    @Override
    public String execute(){
        return SUCCESS;
    }

    private User user;
    @Override
    public void setUser(User user) {
        this.user=user;
    }

    public User getUser(User user){
        return this.user;
    }

    @Override
    public User getModel() {
        return this.user;
    }
}

Struts.xml

<struts>
    <constant name="struts.mapper.action.prefix.enabled" value="true" />
    <constant name="struts.enable.DynamicMethodInvocation" value="false" />
    <constant name="struts.devMode" value="false" />
    <!-- <constant name="struts.ui.theme" value="simple" /> -->
    <package  name="default"  extends="hibernate-default">

       <interceptors>
            <interceptor name="authentication"
                class="com.inwi.interceptors.AuthenticationInterceptor"></interceptor>
            <interceptor-stack name="authStack">
                <interceptor-ref name="authentication"></interceptor-ref>
                <interceptor-ref name="defaultStackHibernate"></interceptor-ref>
            </interceptor-stack>
        </interceptors>

        <default-interceptor-ref name="authStack"></default-interceptor-ref>

        <global-results>
            <result name="loginAction" type="redirect">/home.action</result>
        </global-results>

        <action name="home">
            <interceptor-ref name="defaultStackHibernate"></interceptor-ref>
            <result>/login.jsp</result>
        </action>

        <action name="loginAction" class="com.action.LoginAction">
            <interceptor-ref name="defaultStack"></interceptor-ref>
            <result name="success">/dashboard.jsp</result>
            <result name="input">/loginError.jsp</result>
        </action>
        <action name="welcome" class="com.action.WelcomeAction">
            <result name="success">/dashboard.jsp</result>
            <!-- <result name="success">/siteMain.jsp</result> -->
        </action>

        <action     name="logOut"    method="logout" class="com.action.LoginAction">
            <result name="success" type="redirect">/</result>
        </action>

Login jsp :

<form action="loginAction" method="post" id="login_form">
<s:textfield id="username" name="name" placeholder="Username"  required="required"/>
<s:password id="password" name="password" placeholder="Password"  required="required"  />
<button  type="submit">Se connecter</button>
    </form>

Edite 1 :

java.lang.NullPointerExceptioninside execute
inside find
Nameeee   admin passwordddd   admin
session getuser  null

    at com.inwi.dao.UserDAOImpl.find(UserDAOImpl.java:43)
    at com.inwi.action.LoginAction.execute(LoginAction.java:30)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:870)

Answer 1

I was solve that by editing the folling code in sruts.xml

<action name="loginAction" method="executee" class="com.inwi.action.LoginAction">
            <interceptor-ref name="defaultStackHibernate"></interceptor-ref>
            <result name="success">/dashboard.jsp</result>
            <result name="input">/loginError.jsp</result>
        </action>*

And in the LoginAction i change the name of the method execute to executee.

Answer 2

Judging by the responses you have given, the problem is on this line:

Query q = session.createQuery(hql);

As session is null, you get a NullPointerException.

Looking at your setter for session:

@Override
public void setSession(Map<String, Object> sessionAttributes) {
    this.session = (Session) sessionAttributes;
}

I am not sure how you expect to cast a Map to a Session object.

Answer 3

your SESSION can be null and another things you have not assigned values to parameters.check both things

user = session.createQuery(hql).list();  
List result = session.createQuery(hql).setParameter("name","ARUN")..setParameter("password", "124").list();