Null pointer exception (implementing session on Struts2)

Question

I followed many examples on how to use SessionAware in a Struts 2 project and I always get a NullPointerException when I want to put data in the session. Why?

public class UserService extends ActionSupport implements SessionAware {

private Map<String,Object> sessionmap;

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

public String execute() {
    sessionmap.put("id", iduser);
    return SUCCESS;
}

Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — fantaghirocco, Mar 06 '20 at 11:07
No, the problem is that the session doesn't want to make put — AlexWallcott, Mar 06 '20 at 11:14
The problem is that the sessionmap is null. You can't call a method on a object that is null. In short, it means that the setter was never called. Put a breakpoint in your code and you'll see. — Wesley De Keirsmaeker, Mar 06 '20 at 11:19

score -1 · Accepted Answer · answered Mar 06 '20 at 11:34

-1

As Wesley said the problem is that session map is null thats why you get null pointer eception, the solution is to add this this.sessionmap = ActionContext.getContext().getSession(); before the put in the execute method like this

public String execute(){
        this.sessionmap = ActionContext.getContext().getSession();
        sessionmap.put("id", iduser);
    return SUCCESS;
}

answered Mar 06 '20 at 11:34

mohameddrira

82
6

1

No, this isn't the answer. This is *an* answer, but is almost always the wrong one--the reason `SessionAware` exists is to help S2 actions be as POJO-like as possible, which is an aid in testing. Reaching into `ActionContext` directly breaks that abstraction and makes testing (in particular) more difficult than necessary. – Dave Newton Mar 06 '20 at 21:19

Null pointer exception (implementing session on Struts2)

1 Answers1