SpringMVC 温习笔记(一)服务器启动和组件解析

末蓝、 2022-10-25 01:00 49阅读 0赞

## spring 组件扫描解析 ##

首先小猿先引入一张图片，该图片可以全面的诠释自定义组件的全部运行过程：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h1ZXNoYW5mZWl0aWFu_size_16_color_FFFFFF_t_70]  
整个过程中最为核心的思想就是tomcat服务器启动的时候可以直接通过监听器去加载spring配置文件applicationContext.xml文件，以这种方式，我们可以借助tomcat服务器加载监听器的过程，可将service层，dao层的各类bean纳入到spring容器中来进行管理，这样就使得整个启动过程变得非常完美，总之自定义监听类的本质作用是**将tomcat容器初始化和spring容器初始化紧密的链接在了一起**。  
下面小猿将整个小案例的代码附在下面。

### 项目依赖 ###

<dependency>
           <groupId>mysql</groupId>
           <artifactId>mysql-connector-java</artifactId>
           <version>5.1.32</version>
       </dependency>
       <dependency>
           <groupId>c3p0</groupId>
           <artifactId>c3p0</artifactId>
           <version>0.9.1.2</version>
       </dependency>
       <dependency>
           <groupId>com.alibaba</groupId>
           <artifactId>druid</artifactId>
           <version>1.1.10</version>
       </dependency>
       <dependency>
           <groupId>junit</groupId>
           <artifactId>junit</artifactId>
           <version>4.12</version>
           <scope>test</scope>
       </dependency>
       <dependency>
           <groupId>commons-fileupload</groupId>
           <artifactId>commons-fileupload</artifactId>
           <version>1.3.3</version>
       </dependency>
    
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-context</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-test</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-web</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-webmvc</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>javax.servlet</groupId>
           <artifactId>javax.servlet-api</artifactId>
           <version>3.0.1</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>

### dao 层 ###

接口

public interface UserDao { 
        public void save();
    }

实现类

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

### service层 ###

接口

public interface UserService { 
        public void save();
    }

实现类

public class UserServiceImpl implements UserService { 
        private UserDao userDao;
        public void setUserDao(UserDao userDao) { 
            this.userDao = userDao;
        }
        public void save() { 
            userDao.save();
        }
    }

### 自定义监听类和工具类 ###

监听类

public class  ContextLoaderListener implements ServletContextListener{ 
        public void contextInitialized(ServletContextEvent sce) { 
            ServletContext servletContext = sce.getServletContext();
            String contextConfigLocation = servletContext
                    .getInitParameter("contextConfigLocation");
            ApplicationContext applicationContext = new
                    ClassPathXmlApplicationContext(contextConfigLocation);
            servletContext.setAttribute("applicationContext",applicationContext);
            System.out.println("容器已经创建完毕。。。。。。");
        }
        public void contextDestroyed(ServletContextEvent sce) { 
        }
    }

工具类

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

### applicationContext.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" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    
        
        <context:property-placeholder location="classpath:jdbc.properties"/>
        
        <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
            <property name="driverClass" value="${jdbc.driver}"></property>
            <property name="jdbcUrl" value="${jdbc.url}"></property>
            <property name="user" value="${jdbc.username}"></property>
            <property name="password" value="${jdbc.password}"></property>
        </bean>
        
        <bean id="userDao" class="com.feitian.component.dao.impl.UserDaoImpl"></bean>
    
        
        <bean id="userService" class="com.feitian.component.servicce.impl.UserServiceImpl">
            <property name="userDao" ref="userDao"/>
        </bean>
    
    </beans>

当然此处配置的数据库暂时没有用。

### web.xml ###

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0">
    
        
        <context-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:applicationContext.xml</param-value>
        </context-param>
        
        <listener>
            <listener-class>com.feitian.component.web.listener.ContextLoaderListener</listener-class>
        </listener>
        
        <servlet>
            <servlet-name>UserServlet</servlet-name>
            <servlet-class>com.feitian.component.web.servlet.UserServlet</servlet-class>
        </servlet>
        
        <servlet-mapping>
            <servlet-name>UserServlet</servlet-name>
            <url-pattern>/userServlet</url-pattern>
        </servlet-mapping>
    </web-app>

### web层 ###

public class UserServlet extends HttpServlet { 
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException { 
            ServletContext servletContext = this.getServletContext();
            ApplicationContext applicationContext =
                    WebApplicationContextUtils.getAttribute(servletContext);
            UserService userService = applicationContext.getBean(UserService.class);
            userService.save();
        }
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException { 
            this.doGet(req,resp);
        }
    }

上述案例基本上完整的演绎了整个tomcat服务器启动并加载spring容器的过程，从下节小猿正式开始复习springMVC。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h1ZXNoYW5mZWl0aWFu_size_16_color_FFFFFF_t_70]: /images/20221024/6925829cef784360bbe2671e3338bbd8.png