单击按钮将ArrayList发送到另一个页面

Question

I want to send an ArrayList to another page after a button is clicked.

function gotosave(){
<% 
request.setAttribute("list", ar);
request.getRequestDispatcher("savecard.jsp").forward(request,response);
%>
}

<button type="submit" name="save" style="float:right;" class="btn btn-info" 
 onclick="gotosave()">SAVE</button> 

"ar" is my array list.

This is my First Question here so if i have missed the correct format then don't mind.

Answer 1

You're trying to mix Java and JavaScript here. It won't work. In JSP (or any similar backend rendering technology) first Java code will be executed, then the page will be rendered by your browser, and only then JavaScript code will execute.

What happens now: First this code is executed:

<% 
request.setAttribute("list", ar);
request.getRequestDispatcher("savecard.jsp").forward(request,response);
%>

Then JavaScript function is generated, and it looks like this:

function gotosave(){
}

And if you haven't been forwarded yet, when you click the button, nothing will happen.

Another problem with your code is that you're forwarding to JSP, and not to your servlet. Especially if you want to pass some parameters, that shouldn't be the case.

What I would suggest in your case: Remove JS function, and wrap everything in a form. Then specify action of this form, and point it to your servlet (or JSP, if you insist)

<form method = "POST" action = "./savecard.jsp"> 
   <input type = 'hidden' name = 'list' value = '${ar}' /> 
   <button type="submit" name="save" style="float:right;" class="btn btn-info">SAVE</button>  
</form>

Answer 2

OK you can achieve this objective using two ways . Ones is using a hidden field. That is the traditional and efficient way of doing it.

<input type="hidden" name="userId" value="<your array list>"> 

Another option is to use a session variable. Using a session storage , you can access your arraylist on any jsp within the project as long as you dont clear the session.

Set your attribute in the current jsp like this

session.setAttribute("arraylist", <your arraylist variable>);

In your other JSP use this

int arraylist = session.getAttribute("arraylist");