Spring基础知识（4）

亦凉 2022-08-22 03:55 200阅读 0赞

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");
    	}
    }

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

<listener>
        	<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
        </listener>
        
        <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

![Center][]  
      当再次访问web容器时，不再重复加载spring配置

![Center 1][]

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();
    	}
    }

[Center]: /images/20220724/7753c872b8924525ac56cc79626d14e2.png
[Center 1]: /images/20220724/91724121f4e14c6f94d73a73b16bf1ef.png