Spring 在Web中的应用

Spring 在Web中的应用

　　在web项目开发中，不会直接实例化ApplicationContext对象，如果想用到ApplicationContext,一般的步骤：

1. 配置一个监听器ContextLoaderListener，这个监听器是ServletContext的监听器

   <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>

2. 可选的，设定你的xml配置文件的路径

   1. 如果文件在web-info 下面，并且名字为applicationContext.xml,就不需要再额外配置

   2. 如果文件不符合上面的规则，就需要配置context-param、

3. 利用一个WebApplicationContextUtils来读取第二部创建的ApplicationContext对象

---

导相关依赖包

 <?xml version="1.0" encoding="UTF-8"?>
 <project xmlns="http://maven.apache.org/POM/4.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>

     <groupId>com</groupId>
     <artifactId>spring-demo</artifactId>
     <version>1.0-SNAPSHOT</version>
     <packaging>war</packaging>

     <dependencies>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-core</artifactId>
             <version>5.0.2.RELEASE</version>
         </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-context</artifactId>
             <version>5.0.2.RELEASE</version>
         </dependency>

         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-jdbc</artifactId>
             <version>5.0.2.RELEASE</version>
         </dependency>
         <dependency>
             <groupId>com.microsoft.sqlserver</groupId>
             <artifactId>mssql-jdbc</artifactId>
             <version>6.2.1.jre8</version>
         </dependency>

         <!-- hibernate -->

         <dependency>
             <groupId>org.hibernate</groupId>
             <artifactId>hibernate-core</artifactId>
             <version>5.2.10.Final</version>
         </dependency>

         <!-- 下面的依赖里面至少有LocalSessionFactoryBean -->
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-orm</artifactId>
             <version>5.0.2.RELEASE</version>
         </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-beans</artifactId>
             <version>5.0.2.RELEASE</version>
         </dependency>
         <!--Web依赖-->
         <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
         <dependency>
             <groupId>javax.servlet</groupId>
             <artifactId>javax.servlet-api</artifactId>
             <version>3.1.0</version>
             <scope>provided</scope>
         </dependency>
         <!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-web</artifactId>
             <version>5.0.1.RELEASE</version>
         </dependency>

     </dependencies>
     <build>
         <plugins>
             <plugin>
                 <artifactId>maven-war-plugin</artifactId>
                 <version>2.2</version>
                 <configuration>
                     <warSourceDirectory>web</warSourceDirectory>
                 </configuration>
             </plugin>
         </plugins>
     </build>
 </project>

　　配置web.xml文件

     <listener>
         <!--配置一个监听器ContextLoaderListener，这个监听器是ServletContext的监听器-->
         <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
     </listener>

     <context-param>
         <!--spring的配置文件路径-->
         <param-name>contextConfigLocation</param-name>
         <param-value>classpath:Springweb.xml</param-value>
     </context-param>

　　配置Spring的依赖注入：SpringWeb.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

     <bean id="dao" class="web.UserDaoImpl"></bean>
     <bean id="service" class="web.Service">
         <property name="userDao" ref="dao"></property>
     </bean>
 </beans>

　　dao接口

 public interface UserDao {
     void add();
 }

　　dao实现

 public class UserDaoImpl implements UserDao
 {
     public void add() {
         System.out.println("aaaaaaaa");
     }
 }

　　service

 public class Service {
     private UserDao userDao;

     public UserDao getUserDao() {
         return userDao;
     }

     public void setUserDao(UserDao userDao) {
         this.userDao = userDao;
     }
     public void insert(){
         userDao.add();
     }
 }

　　servlet

 @WebServlet("/fist")
 public class Servlet extends HttpServlet {
     @Override
     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /* ApplicationContext applicationContext = new ClassPathXmlApplicationContext("Springweb.xml");
         Service service = applicationContext.getBean("service",Service.class);
         service.insert();*/
         ApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(req.getServletContext());
         Service service = applicationContext.getBean("service",Service.class);
         service.insert();
     }
 }