spring get bean test

package com.jayway.springsessionexample;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Optional;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.servlet.support.RequestContextUtils;
/**
 * webTest in subcontainer
 * webTest2 in parent container
 * @author root
 *
 */
public class HelloServlet extends HttpServlet {

    private static final String NAME = "name";

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
    	
    	
    	
    	/*
    	 * 1.ApplicationContextAware can get the parent container
    	 * WebTest webTest = (WebTest) SpringContextHelper.getBean("webTest2");
    	System.out.println("webTest2 :"+webTest);
    	
    	
    	WebTest webTest2 = (WebTest) SpringContextHelper.getBean("webTest");
    	System.out.println("webTest :"+webTest2);*/
    	
    	//2. Only get the parent container,
    	/*WebTest webTest = (WebTest) ContextLoader.getCurrentWebApplicationContext().getBean("webTest2");
    	System.out.println("webTest :"+webTest);
    	
    	
    	WebTest webTest2 = (WebTest) ContextLoader.getCurrentWebApplicationContext().getBean("webTest");
    	System.out.println("webTest2 :"+webTest2);*/
    	
    	//3. Only the parent container can be obtained,
    	/*WebTest webTest = (WebTest) WebApplicationContextUtils.getWebApplicationContext(req.getServletContext()).getBean("webTest2");
    	System.out.println("webTest :"+webTest);
    	
    	
    	WebTest webTest2 = (WebTest) WebApplicationContextUtils.getWebApplicationContext(req.getServletContext()).getBean("webTest");
    	System.out.println("webTest2 :"+webTest2);*/
    	
    	
    /*	4.
     *  WebTest webTest = (WebTest) RequestContextUtils.getWebApplicationContext(req).getBean("webTest2");
    	System.out.println("webTest :"+webTest);
    	
    	
    	WebTest webTest2 = (WebTest) RequestContextUtils.getWebApplicationContext(req).getBean("webTest");
    	System.out.println("webTest2 :"+webTest2);*/
    	
    	
    	/*// 5.WebApplicationObjectSupport can get the parent container
    	 WebTest webTest = (WebTest) ApplicationContextUtils.getBean("webTest2");
    	System.out.println("webTest2 :"+webTest);
    	
    	
    	WebTest webTest2 = (WebTest) ApplicationContextUtils.getBean("webTest");
    	System.out.println("webTest :"+webTest2);*/
    	
    	
    	
        String name = Optional.ofNullable(req.getSession(false))
                .map(session -> (String) session.getAttribute(NAME))
                .orElse("World");
        String greeting = String.format("Hello %s!", name);
        System.out.println("get====greeting  "+greeting);
        try (ServletOutputStream out = resp.getOutputStream()) {
            out.write(greeting.getBytes(StandardCharsets.UTF_8));
            out.flush();
        } catch (IOException e) {
            e.printStackTrace ();
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        String name = req.getParameter(NAME);
        System.out.println("post===="+name);
        req.getSession().setAttribute(NAME, name);
    }
}