Question

I am trying to add an object into an ArrayList stored in the session.

The object doesn’t seem to be added.

Please check my below code and suggest me a correct answer for this.

While debugging my debugger goes till this code books.add(book); and then it skips the remaining code. I know problem is here books.add(book); . Book detail is not adding into my arraylist books.

AddBookToSession.java

    public class AddBookToSession extends ActionSupport {
         Bookdetails book=new Bookdetails();
            List<Bookdetails> books = new ArrayList<Bookdetails>();

            BookdetailsDAO dao = new BookdetailsDAO(); 
      Map session = ActionContext.getContext().getSession();

        public String execute()
        { 
            HttpServletRequest request = ServletActionContext.getRequest();  
            String bookid = request.getParameter("bid");    
            books = (List) session.get( BillTransactionBooksConstants.BOK ); 
          for(int i=1;i<=1;i++)
        {
          book = dao.listBookDetailsById(Integer.parseInt(bookid));    
          books.add(book); //problem is here obj book is not adding into books list

          books = new ArrayList<Bookdetails>();

          System.out.println("---------------Bookid-"+book); 
        }
        ....................
                ...............

struts.xml

        <package name="testwithrowselect" extends="struts-default" >  
                    <action name="InsertbooksToSession" class="v.esoft.actions.booktransaction.AddBookToSession">
                        <result name="success">/jspHomepage/bookstransaction/shortBill.jsp</result>  
                    </action>
         </package>

Answer 1

You add a new, empty list to session:

for (int i = 1; i <= 1; i++) {
    book = dao.listBookDetailsById(Integer.parseInt(bookid));    
    books.add(book);
    books = new ArrayList<Bookdetails>(); // <-- Now it's a new, empty list?!
}
session.put(BillTransactionBooksConstants.BOK, books);

That said, your action code should look something closer to this (untested):

public class AddBookToSession extends ActionSupport implements SessionAware {

    private Integer bid;
    private Map<String, Object> session;

    private BookdetailsDAO dao = new BookdetailsDAO(); 

    public String execute() { 
        BookDetails book = dao.listBookDetailsById(Integer.parseInt(bookid));
        if (book != null) {
            List<Bookdetails> books = sessionBooks();
            books.add(book);
        }

        return SUCCESS;
    } 

    private List<Bookdetails> sessionBooks() {
        List<Bookdetails> books = (List) session.get(BillTransactionBooksConstants.BOK);
        if (books == null) {
            books = new ArrayList<BookDetails>();
            session.put(BillTransactionBooksConstants.BOK, books);
        }
        return books;
    }

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

    public Integer getBid() {
        return this.bid;
    }

    public void setBid(Integer bid) {
        this.bid = bid;
    }
}

Note that instantiating a book DAO like this may make testing a bit more difficult than necessary.