JSP – Invoking Java Scriptlet Using HTML

javajspscriptletservlets

I am trying to find a way to invoke a piece of java code within the JSP using HTML form

  <form method="get" action="invokeMe()">

       <input type="submit" value="click to submit" />

  </form>


  <%
     private void invokeMe(){
       out.println("He invoked me. I am happy!");   
     }
  %>

the above code is within the JSP. I want this run the scriptlet upon submit

I know the code looks very bad, but I just want to grasp the concept… and how to go about it.

thanks

Best Answer

You can use Ajax to submit form to servlet and evaluate java code, but stay on the same window.

<form method="get" action="invokeMe()" id="submit">

       <input type="submit" value="click to submit" />

</form>

<script>
    $(document).ready(function() {
        $("#submit").submit(function(event) {
            $.ajax({
                type : "POST",
                url : "your servlet here(for example: DeleteUser)",
                data : "id=" + id,
                success : function() {
                    alert("message");
                }
            });
            $('#submit').submit(); // if you want to submit form
        });
    });
</script>

Related Solutions

JavaScript – How to Use Scriptlet Inside JavaScript

That line of code has to be placed in a HTML <script> tag in a .jsp file. This way the JspServlet will process the scriptlets (and other JSP/EL specific expressions).

<script>var myVar = '<%= request.getContextPath() %>';</script>

Note that <%= %> is the right syntax to print a variable, the <% %> doesn't do that.

Or if it is intended to be served in a standalone .js file, then you need to rename it to .jsp and add the following to top of the file (and change the <script src> URL accordingly):

<%@page contentType="text/javascript" %>
...
var myVar = '<%= request.getContextPath() %>';

This way the JspServlet will process it and the browser will be instructed to interpret the JSP response body as JavaScript instead of HTML.

Unrelated to the concrete problem, note that scriptlets are considered poor practice. Use EL.

var myVar = '${pageContext.request.contextPath}';

JSP Servlets – How to Call Servlet Through JSP Page

First put the JSP page anywhere in /WEB-INF folder so that it's impossible to accidentally open the JSP page individually without invoking the Servlet first. E.g. /WEB-INF/result.jsp.

Then create a Servlet which does something like following in doGet() method.

request.setAttribute("result", "This is the result of the servlet call");
request.getRequestDispatcher("/WEB-INF/result.jsp").forward(request, response);

And put this line in /WEB-INF/result.jsp.

<p>The result is ${result}</p>

Now call the Servlet by the URL which matches the URL pattern as defined in its @WebServlet annotation or in its <url-pattern> configuration in web.xml, e.g. /servletURL: http://example.com/contextname/servletURL.

If your actual question is "How to submit a form to a servlet?" then you just have to specify the servlet URL in the HTML form action.

<form action="servletURL" method="post">

Its doPost() method will then be called.

Best Answer

Related Solutions

JavaScript – How to Use Scriptlet Inside JavaScript

JSP Servlets – How to Call Servlet Through JSP Page

See also:

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