Spring基础知识（4）

一、在web项目中集成Spring

1、直接在Servlet 加载Spring 配置文件

package lsq.service;

public class HelloService {
	public void sayHello(){
		System.out.println("hello,Spring web");
	}
}

package lsq.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

import lsq.service.HelloService;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class HelloServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//通过spring容器获得HelloService对象
		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
		HelloService helloService = (HelloService) applicationContext.getBean("helloService");
		helloService.sayHello();
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

      这种做法存在的问题：每次请求都会加载Spring环境，初始化所有Bean ，性能问题 ！！！

17:02:45,316  INFO ClassPathXmlApplicationContext:510 - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3d94cc41: startup date [Wed May 11 17:02:45 CST 2016]; root of context hierarchy
17:02:45,317  INFO XmlBeanDefinitionReader:315 - Loading XML bean definitions from class path resource [applicationContext.xml]
17:02:45,329  INFO DefaultListableBeanFactory:577 - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@5c127549: defining beans [helloService]; root of factory hierarchy
hello,Spring web
17:08:36,682  INFO ClassPathXmlApplicationContext:510 - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@35757617: startup date [Wed May 11 17:08:36 CST 2016]; root of context hierarchy
17:08:36,684  INFO XmlBeanDefinitionReader:315 - Loading XML bean definitions from class path resource [applicationContext.xml]
17:08:36,698  INFO DefaultListableBeanFactory:577 - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@611943bf: defining beans [helloService]; root of factory hierarchy
hello,Spring web

      解决方案：
      方案一 ： 将代码放入Servlet init 中 ， 无法保证所有Servlet都能使用 ApplicationContext 

      方案二 ： ServletContext ----- tomcat启动时， 加载Spring配置文件，获得对象 ，放入ServletContext 
                        最适合写这个代码的是：
                       * ServletCointextListener

2、导入spring-web.jar

      保存 ContextLoaderListener 完成在Servlet初始化阶段，加载Spring配置文件，将工厂对象放入 ServletContext

3、配置web.xml

      ☆注意：* 默认读取 WEB-INF/applicationContext.xml 
                        配置 全局参数 contextConfigLocation 指定 配置文件位置

    <!-- 配置spring监听器 -->
    <listener>
    	<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!-- 配置spring配置文件所在位置 -->
    <context-param>
    	<param-name>contextConfigLocation</param-name>
    	<param-value>classpath:applicationContext.xml</param-value>
    </context-param>

4、修改Servlet代码

package lsq.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

import lsq.service.HelloService;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

public class HelloServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//通过spring容器获得HelloService对象
//		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
		
		//从ServletContext中获取Spring工厂
		//第一种方法：
//		WebApplicationContext applicationContext = (WebApplicationContext) getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
		//第二种方法：
		WebApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		
		HelloService helloService = (HelloService) applicationContext.getBean("helloService");
		helloService.sayHello();
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

      修改后的效果：

      web容器初始化的时候，加载spring配置

      当再次访问web容器时，不再重复加载spring配置

      

二、Spring 整合 junit4 测试 

      1）导入spring-test.jar

      2）编写测试用例 

package lsq.test;

import lsq.service.HelloService;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml") //☆:指定配置文件的位置
public class HelloServiceTest {
	@Autowired
	private HelloService helloService;   //注入需要测试的对象
	
	@Test
	public void demo2(){
		helloService.sayHello();   //调用测试方法
	}
	
	@Test
	//没有整合spring的测试
	public void demo1(){
		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
		HelloService helloService = (HelloService) applicationContext.getBean("helloService");
		helloService.sayHello();
	}
}