I have created a servlet based web application and I want to used Spring beans in it. So how do I do this in my servlet. Well, it simple enough to do this. First of all I have to obtain the Spring’s WebApplicationContext, from where I can grab the required bean by my servlet.

Let’s see some lines of code on how to do it, here we go:

package org.kodejava.example.servlet;

import org.kodejava.example.servlet.dao.UserDao;
import org.kodejava.example.servlet.model.User;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class SpringBeanServletExample extends HttpServlet {
    protected void doGet(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {
        ServletContext context = getServletContext();
        WebApplicationContext ctx =
                WebApplicationContextUtils
                        .getWebApplicationContext(context);
        UserDao dao = ctx.getBean("userDao", UserDao.class);

        Long userId = Long.valueOf(req.getParameter("user_id"));
        User user = dao.getUser(userId);

        res.setContentType("text/html");
        PrintWriter pw = res.getWriter();
        pw.print("User Details: " + user.toString());
        pw.flush();
    }
}

Inside the Java Servlet doGet() method above I get the ServletContext, next the WebApplicationContextUtils help me to get Spring’s WebApplicationContext. With this object in my hand I can get my UserDao implementation and do a query from database.

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Wayan

Programmer, runner, recreational diver, live in the island of Bali, Indonesia. Mostly programming in Java, Spring Framework, Hibernate / JPA.

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