Spring - 10集成Web

Spring - 10集成Web环境

（1）搭建Spring集成Web环境

（1.1）项目添加webapp

IDEA工具： File ->  Project Structure -> Modules -> 点击"+"号 -> 选择"Web"

               -> 填写文件夹名称 -> 填写项目的web.xml文件路径 -> 填写WebResourceDirectory 

（1.2）编写基础代码

public class UserDaoImpl implements UserDao {
    public void save() {
        System.out.println("save running......");
    }
}
//---------------------------------------------
public class UserServiceImpl implements UserService  {
    private UserDao userDao;
    public void setUserDao(UserDao userDao){
       this.userDao = userDao;
    }
    public void save() {
        userDao.save();
    }
}

（1.3）配置文件

    <context:property-placeholder location="classpath:jdbc.properties"/>

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${jdbc.driver}"/>
        <property name="jdbcUrl" value="${jdbc.url}"/>
        <property name="user" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>

    <bean id="userDao" class="com.bearpx.spring.mvc.dao.impl.UserDaoImpl"/>

    <bean id="userService" class="com.bearpx.spring.mvc.service.impl.UserServiceImpl">
        <property name="userDao" ref="userDao"/>
    </bean>

（1.4）引入坐标 javax.servlet-api, javax.servlet.jsp-api

       <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.2.1</version>
            <scope>provided</scope>
        </dependency>

（1.5）配置自定义Servlet

public class UserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = app.getBean(UserService.class);
        userService.save();
    }
}

（1.6）配置web.xml

    <servlet>
        <servlet-name>UserServlet</servlet-name>
        <servlet-class>com.bearpx.spring.mvc.web.UserServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>UserServlet</servlet-name>
        <url-pattern>/userServlet</url-pattern>
    </servlet-mapping>

（1.7）配置Tomcat，启动项目

先要在项目工程中，加入Tomcat，然后把项目添加到Tomcat中

 

 

（2）ApplicationContext应用上下文获取方式 

应用上下文对象是通过new ClasspathXmlApplicationContext(spring配置文件)方式获取的，但是每次从容器中获得Bean时

都要编写new ClasspathXmlApplicationContext(spring配置文件)，这样的弊端是配置文件加载多次，应用上下文对象创建多次。

 

在Web项目中，可以使用ServletContextListener监听Web应用的启动，可以在Web应用启动时，就加载Spring的配置文件，创建应用上下文对象ApplicationContext，

再将其保存到最大的域servletContext域中，这样就可以在任意位置从域中获得应用上下文ApplicationContext对象了。

（2.1）实现ServletContextListener

public class ContextLoaderListener implements ServletContextListener {
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        ServletContext servletContext = servletContextEvent.getServletContext();
        servletContext.setAttribute("app",app);  // 将Spring的应用上下文对象存储到ServletContext域中
        System.out.println("spring容器创建完毕......");
    }

    public void contextDestroyed(ServletContextEvent servletContextEvent) {}
}

在web.xml 配置监听器

    <listener>
        <listener-class>com.bearpx.spring.mvc.listener.ContextLoaderListener</listener-class>
    </listener>

改进Servlet

public class UserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        ServletContext servletContext = this.getServletContext();
        ApplicationContext app = (ApplicationContext) servletContext.getAttribute("app");
        UserService userService = app.getBean(UserService.class);
        userService.save();
    }
}

（2.2）将配置文件的使用从代码中去掉，改成引用配置文件

在web.xml 设置 全局初始化参数

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>applicationContext.xml</param-value>
    </context-param>

读取初始化参数

    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();

        // 读取web.xml 中的全局参数
        String contextConfigLocation = servletContext.getInitParameter("contextConfigLocation");
        ApplicationContext app = new ClassPathXmlApplicationContext(contextConfigLocation);

        // 将Spring的应用上下文对象存储到ServletContext域中
        servletContext.setAttribute("app",app);
        System.out.println("spring容器创建完毕......");
    }

自定义获取应用上下文的工具

public class WebApplicationContextUtils {
    public static ApplicationContext getWebApplicationContext(ServletContext servletContext){
        return (ApplicationContext) servletContext.getAttribute("app");
    }
}

改进UserServlet

public class UserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        ServletContext servletContext = this.getServletContext();
//        ApplicationContext app = (ApplicationContext) servletContext.getAttribute("app");
        // 使用工具类，获取ApplicationContext
        ApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(servletContext);
        UserService userService = app.getBean(UserService.class);
        userService.save();
    }
}

（2.3）Spring提供获取应用上下文工具

Spring提供了一个监听器ContextLoaderListener就是对上述功能的封装，

该监听器内部加载Spring配置文件，创建应用上下文对象，并存储到ServletContext域中，

并提供了一个客户端工具WebApplicationContextUtils供使用者获得应用上下文对象。

导入spring-web坐标

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.0.10.RELEASE</version>
        </dependency>

在web.xml中配置ContextLoadListener监听器

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

使用WebApplicationContextUtils获取应用上下文对象 ApplicationContext

public class UserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        ApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(servletContext);
        UserService userService = app.getBean(UserService.class);
        userService.save();
    }
}