Spring DI in servlet

Today, I'll show you how can inject a bean into your servlet.

1. Using ServletContextListener

The ServletContextListener will enable your servlets to access the Spring ApplicationContext.

	package com.vedrax.servlet;
	import org.springframework.context.ApplicationContext;
	import org.springframework.web.context.support.WebApplicationContextUtils;
	import javax.servlet.ServletContextEvent;
	import javax.servlet.ServletContextListener;
	import javax.servlet.annotation.WebListener;
	@WebListener
	public class SpringApplicationContextListener implements ServletContextListener {
	@Override
	public void contextInitialized(ServletContextEvent servletContextEvent) {
	//we get the Spring application context
	ApplicationContext applicationContext = WebApplicationContextUtils
	.getWebApplicationContext(servletContextEvent.getServletContext());
	//make accessible the application context via an attribute
	servletContextEvent.getServletContext()
	.setAttribute("applicationContext", applicationContext);
	}
	@Override
	public void contextDestroyed(ServletContextEvent servletContextEvent) {
	}
	}

view raw springApplicationContextListener hosted with ❤ by GitHub

In your servlet :

	package com.vedrax.servlet;
	import com.vedrax.core.clientproduct.ExpiredClientProductVO;
	import com.vedrax.service.ClientProductService;
	import org.springframework.context.ApplicationContext;
	import javax.servlet.ServletConfig;
	import javax.servlet.ServletException;
	import javax.servlet.annotation.WebServlet;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;
	import java.io.IOException;
	import java.util.List;
	@WebServlet(
	name = "SurveyScheduler",
	description = "Create survey automatically",
	urlPatterns = "/admin/survey-scheduler"
	)
	public class SurveyScheduler extends HttpServlet {
	private ClientProductService clientProductService;
	public void init(ServletConfig config) throws ServletException {
	super.init(config);
	ApplicationContext applicationContext = (ApplicationContext) config
	.getServletContext()
	.getAttribute("applicationContext");
	this.clientProductService = applicationContext.getBean("ClientProductService", ClientProductService.class);
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {
	//1. get expired client products (next month)
	List<ExpiredClientProductVO> expiredClientProducts = clientProductService.findExpiredProducts();
	}
	}

view raw SurveyScheduler hosted with ❤ by GitHub

2. Using the SpringBeanAutowiringSupport

I personally prefer the following solution :

	package com.vedrax.servlet;
	import com.vedrax.core.clientproduct.ExpiredClientProductVO;
	import com.vedrax.service.ClientProductService;
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.web.context.support.SpringBeanAutowiringSupport;
	import javax.servlet.ServletConfig;
	import javax.servlet.ServletException;
	import javax.servlet.annotation.WebServlet;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;
	import java.io.IOException;
	import java.util.List;
	@WebServlet(
	name = "SurveyScheduler",
	description = "Create survey automatically",
	urlPatterns = "/admin/survey-scheduler"
	)
	public class SurveyScheduler extends HttpServlet {
	@Autowired
	private ClientProductService clientProductService;
	public void init(ServletConfig config) throws ServletException {
	super.init(config);
	SpringBeanAutowiringSupport.processInjectionBasedOnServletContext(this,
	config.getServletContext());
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {
	//1. get expired client products (next month)
	List<ExpiredClientProductVO> expiredClientProducts = clientProductService.findExpiredProducts();
	}
	}

view raw SurveyScheduleWithAutowiringSupport hosted with ❤ by GitHub

thanks for sharing...