How to call servlet through a JSP page

I would like to call a Servlet through a JS开发者_运维问答P page. What is the method to call?

You could use <jsp:include> for this.

<jsp:include page="/servletURL" />

It's however usually the other way round. You call the servlet which in turn forwards to the JSP to display the results. 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 in /WEB-INF/result.jsp

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

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

Do note that the JSP file is explicitly placed in /WEB-INF folder. This will prevent the user from opening the JSP file individually. The user can only call the servlet in order to open the JSP file.

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.

See also:

• Servlets info page - Contains a hello world
• How to call servlet class from HTML form
• How do I pass current item to Java method by clicking a hyperlink or button in JSP page?
• Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern
• Design Patterns web based applications

You can use RequestDispatcher as you usually use it in Servlet:

<%@ page contentType="text/html"%>
<%@ page import = "javax.servlet.RequestDispatcher" %>
<%
     RequestDispatcher rd = request.getRequestDispatcher("/yourServletUrl");
     request.setAttribute("msg","HI Welcome");
     rd.forward(request, response);
%>

Always be aware that don't commit any response before you use forward, as it will lead to IllegalStateException.

there isn't method to call Servlet. You should make mapping in web.xml and then trigger this mapping.

Example: web.xml:

  <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>test.HelloServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>

This mapping means that every call to http://yoursite/yourwebapp/hello trigger this servlet For example this jsp:

<jsp:forward page="/hello"/> 

Why would you want to do this? You shouldn't be executing controller code in the view, and most certainly shouldn't be trying to pull code inside of another servlet into the view either.

Do all of your processing and refactoring of the application first, then just pass off the results to a view. Make the view as dumb as possible and you won't even run into these problems.

If this kind of design is hard for you, try Freemarker or even something like Velocity (although I don't recommend it) to FORCE you to do this. You never have to do this sort of thing ever.

To put it more accurately, the problem you are trying to solve is just a symptom of a greater problem - your architecture/design of your servlets.

You can submit your jsp page to servlet. For this use <form> tag.

And to redirect use:

response.sendRedirect("servleturl")

You can either post HTML form to URL, which is mapped to servlet or insert your data in HttpServletRequest object you pass to jsp page.