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：

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>

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

导相关依赖包

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0"
 3          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 5     <modelVersion>4.0.0</modelVersion>
 6 
 7     <groupId>com</groupId>
 8     <artifactId>spring-demo</artifactId>
 9     <version>1.0-SNAPSHOT</version>
10     <packaging>war</packaging>
11 
12 
13     <dependencies>
14         <dependency>
15             <groupId>org.springframework</groupId>
16             <artifactId>spring-core</artifactId>
17             <version>5.0.2.RELEASE</version>
18         </dependency>
19         <dependency>
20             <groupId>org.springframework</groupId>
21             <artifactId>spring-context</artifactId>
22             <version>5.0.2.RELEASE</version>
23         </dependency>
24 
25         <dependency>
26             <groupId>org.springframework</groupId>
27             <artifactId>spring-jdbc</artifactId>
28             <version>5.0.2.RELEASE</version>
29         </dependency>
30         <dependency>
31             <groupId>com.microsoft.sqlserver</groupId>
32             <artifactId>mssql-jdbc</artifactId>
33             <version>6.2.1.jre8</version>
34         </dependency>
35 
36         <!-- hibernate -->
37 
38         <dependency>
39             <groupId>org.hibernate</groupId>
40             <artifactId>hibernate-core</artifactId>
41             <version>5.2.10.Final</version>
42         </dependency>
43 
44         <!-- 下面的依赖里面至少有LocalSessionFactoryBean -->
45         <dependency>
46             <groupId>org.springframework</groupId>
47             <artifactId>spring-orm</artifactId>
48             <version>5.0.2.RELEASE</version>
49         </dependency>
50         <dependency>
51             <groupId>org.springframework</groupId>
52             <artifactId>spring-beans</artifactId>
53             <version>5.0.2.RELEASE</version>
54         </dependency>
55         <!--Web依赖-->
56         <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
57         <dependency>
58             <groupId>javax.servlet</groupId>
59             <artifactId>javax.servlet-api</artifactId>
60             <version>3.1.0</version>
61             <scope>provided</scope>
62         </dependency>
63         <!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
64         <dependency>
65             <groupId>org.springframework</groupId>
66             <artifactId>spring-web</artifactId>
67             <version>5.0.1.RELEASE</version>
68         </dependency>
69 
70 
71     </dependencies>
72     <build>
73         <plugins>
74             <plugin>
75                 <artifactId>maven-war-plugin</artifactId>
76                 <version>2.2</version>
77                 <configuration>
78                     <warSourceDirectory>web</warSourceDirectory>
79                 </configuration>
80             </plugin>
81         </plugins>
82     </build>
83 </project>

　　配置web.xml文件

 1     <listener>
 2         <!--配置一个监听器ContextLoaderListener，这个监听器是ServletContext的监听器-->
 3         <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
 4     </listener>
 5 
 6     <context-param>
 7         <!--spring的配置文件路径-->
 8         <param-name>contextConfigLocation</param-name>
 9         <param-value>classpath:Springweb.xml</param-value>
10     </context-param>

　　配置Spring的依赖注入：SpringWeb.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
 5 
 6 
 7 
 8     <bean id="dao" class="web.UserDaoImpl"></bean>
 9     <bean id="service" class="web.Service">
10         <property name="userDao" ref="dao"></property>
11     </bean>
12 </beans>

　　dao接口

1 public interface UserDao {
2     void add();
3 }

　　dao实现

1 public class UserDaoImpl implements UserDao
2 {
3     public void add() {
4         System.out.println("aaaaaaaa");
5     }
6 }

　　service

 1 public class Service {
 2     private UserDao userDao;
 3 
 4     public UserDao getUserDao() {
 5         return userDao;
 6     }
 7 
 8     public void setUserDao(UserDao userDao) {
 9         this.userDao = userDao;
10     }
11     public void insert(){
12         userDao.add();
13     }
14 }

　　servlet

 1 @WebServlet("/fist")
 2 public class Servlet extends HttpServlet {
 3     @Override
 4     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 5        /* ApplicationContext applicationContext = new ClassPathXmlApplicationContext("Springweb.xml");
 6         Service service = applicationContext.getBean("service",Service.class);
 7         service.insert();*/
 8         ApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(req.getServletContext());
 9         Service service = applicationContext.getBean("service",Service.class);
10         service.insert();
11     }
12 }