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();
    }
}