Issue
Can I call a servlet from JSP file without using a HTML form?
For example, to show results from database in a HTML table during page load.
Solution
You can use the href="http://docs.oracle.com/javaee/7/api/javax/servlet/http/HttpServlet.html#doGet%28javax.servlet.http.HttpServletRequest,%20javax.servlet.http.HttpServletResponse%29" rel="nofollow noreferrer">doGet() method of the servlet to preprocess a request and forward the request to the JSP. Then just point the servlet URL instead of JSP URL in links and browser address bar.
E.g.
@WebServlet("/products")
public class ProductsServlet extends HttpServlet {
@EJB
private ProductService productService;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
List<Product> products = productService.list();
request.setAttribute("products", products);
request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
}
}
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
...
<table>
<c:forEach items="${products}" var="product">
<tr>
<td>${product.name}</td>
<td>${product.description}</td>
<td>${product.price}</td>
</tr>
</c:forEach>
</table>
Note that the JSP file is placed inside /WEB-INF folder to prevent users from accessing it directly without calling the servlet.
Also note that @WebServlet is only available since Servlet 3.0 (Tomcat 7, etc), see also @WebServlet annotation with Tomcat 7. If you can't upgrade, or when you for some reason need to use a web.xml which is not compatible with Servlet 3.0, then you'd need to manually register the servlet the old fashioned way in web.xml as below instead of using the annotation:
<servlet>
<servlet-name>productsServlet</servlet-name>
<servlet-class>com.example.ProductsServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>productsServlet</servlet-name>
<url-pattern>/products</url-pattern>
</servlet-mapping>
Once having properly registered the servlet by annotation or XML, now you can open it by http://localhost:8080/context/products where /context is the webapp's deployed context path and /products is the servlet's URL pattern. If you happen to have any HTML <form> inside it, then just let it POST to the current URL like so <form method="post"> and add a doPost() to the very same servlet to perform the postprocessing job. Continue the below links for more concrete examples on that.
See also
- Our Servlets wiki page
- doGet and doPost in Servlets
- How to avoid Java code in JSP
- Servlet returns "HTTP Status 404 The requested resource (/servlet) is not available"
Answered By - BalusC
Answer Checked By - Marilyn (JavaFixing Volunteer)
