How do I get a spring’s bean from a servlet?

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.

Spring Bean Servlet Example

Spring Bean Servlet Example

Wayan Saryada

Programmer, runner, recreational diver, currently living in the island of Bali, Indonesia. Mostly programming in Java, creating web based application with Spring Framework, Hibernate / JPA.

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