java - Struts2 interceptor session get null value when authenticate login page -

i beginner in struts2 , i'm trying scenario on own web project :

• when user access login page, server authenticate whether he/she has login "admin" / "user" accessing session using interceptor, if user has no privilege data (it's null) inside session, passed login page.
• if user has login "admin", user redirected "admin" page.
• if user has login "user", user redirected "user" page.

i trying these codes, if don't use interceptor, can access session, if use interceptor is, session still null , giving error 500 instead npe. don't know wrong it.

thanks of me.

struts.xml

<struts>     <constant name="struts.action.extension" value=","/>     <constant name="struts.custom.i18n.resources" value="global" />     <constant name="struts.devmode" value="true" />     <!-- configuration default package. -->     <include file="strutsconf/struts-user.xml"/>  </struts> 

struts-pageauth.xml

<struts>     <package name="struts-pageauth" namespace="/" extends="struts-default">         <interceptors>              <interceptor name="loginpageauth" class="control.intercept.userauthenticationlogin"/>              <interceptor-stack name="loginauth">                 <interceptor-ref name="createsession"/>                 <interceptor-ref name="loginpageauth"/>                 <interceptor-ref name="defaultstack"/>             </interceptor-stack>          </interceptors>     </package> </struts> 

strusts-user.xml

<struts>     <constant name="struts.custom.i18n.resources" value="prop-user" />      <include file="strutsconf/struts-pageauth.xml"/>      <package name="struts-user" namespace="/" extends="struts-default, struts-pageauth">          <action name="login" method="login" class="control.action.login">              <interceptor-ref name="loginauth"/>             <result name="admin">/main/admin/admin.jsp</result>             <result name="user">/main/user/user.jsp</result>             <result name="error">/login.jsp</result>         </action>          <action name="logout" method="logout" class="control.action.login">             <result name="success">/login.jsp</result>             <result name="error">/login.jsp</result>         </action>      </package> </struts> 

userauthenticationlogin.java

/*  * change template, choose tools | templates  * , open template in editor.  */ package control.intercept;  import com.opensymphony.xwork2.actioninvocation; import com.opensymphony.xwork2.actionsupport; import com.opensymphony.xwork2.interceptor.interceptor; import java.util.map; import org.apache.struts2.interceptor.sessionaware;  public class userauthenticationlogin extends actionsupport implements sessionaware, interceptor {      public void setsession(map<string, object> map) {         this.sessionmap = map;     }      public void destroy() {         system.out.println("userauthentication interceptor destroy() called");     }      public void init() {         system.out.println("userauthentication interceptor init() called");     }      public string intercept(actioninvocation ai) throws exception {         system.out.println("=========================debug========================");         system.out.println("userauthentication interceptor intercept() called");         system.out.println(gettext("auth.privilage")); // can access properties         system.out.println(this.sessionmap); // gets null ?? //        system.out.println(this.sessionmap.get(gettext("auth.privilage")));         if(this.sessionmap.get(gettext("auth.privilage"))==null) {             return ai.invoke();         }         else if(this.sessionmap.get(gettext("auth.privilage")).equals("admin")) {             return "admin";         }         else if(this.sessionmap.get(gettext("auth.privilage")).equals("user")) {             return "user";         }         else {             return "login";         }     }      private string id;     private string password;     private string admin;     private map<string, object> sessionmap;      public string getid() {         return id;     }      public void setid(string id) {         this.id = id;     }      public string getpassword() {         return password;     }      public void setpassword(string password) {         this.password = password;     }      public string getadmin() {         return admin;     }      public void setadmin(string admin) {         this.admin = admin;     }      public map<string, object> getsessionmap() {         return sessionmap;     }      public void setsessionmap(map<string, object> sessionmap) {         this.sessionmap = sessionmap;     } } 

login.java

/*  * change template, choose tools | templates  * , open template in editor.  */ package control.action;  import com.opensymphony.xwork2.actionsupport; import java.util.map; import org.apache.struts2.interceptor.sessionaware;  public class login extends actionsupport implements sessionaware {      public void setsession(map<string, object> map) {         this.sessionmap = map;     }      public string login() throws exception {         if(id.equals("admin") && password.equals("admin")) {             this.sessionmap.put("id", "admin");             this.sessionmap.put("priv", "admin");             return "admin";         }         if(id.equals("user") && password.equals("user")) {             this.sessionmap.put("id", "user");             this.sessionmap.put("priv", "user");             return "user";         }         else {             seterr_msg(super.gettext("error.login"));             return super.error;         }     }      public string logout() throws exception {         this.sessionmap.remove("id");         this.sessionmap.remove("priv");         return super.success;     }      private string id;     private string password;     private string err_msg;     private string admin;     private map<string, object> sessionmap;      public map<string, object> getsessionmap() {         return sessionmap;     }      public void setsessionmap(map<string, object> sessionmap) {         this.sessionmap = sessionmap;     }      public string getadmin() {         return admin;     }      public void setadmin(string admin) {         this.admin = admin;     }      public string getid() {         return id;     }      public void setid(string id) {         this.id = id;     }      public string getpassword() {         return password;     }      public void setpassword(string password) {         this.password = password;     }      public string geterr_msg() {         return err_msg;     }      public void seterr_msg(string err_msg) {         this.err_msg = err_msg;     }  } 

the sessionmap injected servletconfiginterceptor in actions implementing sessionaware interface, not interceptors.

the right way session map in interceptor is:

map<string, object> session = actioncontext.getcontext().getsession(); 

_{note: careful in messing actions , interceptors together: it's strange see interceptor implementing actionsupport... it's not problem code because using declarative xml configuration, convention plugin scan packages (luckily have package unmatching name) classes extending actionsupport , detect action, making threadlocal, not interceptor has meant be. have remember careful upgrading code in future avoid unexpected result.}