1.Spring integrated with the Web environment
1.1 Custom Spring listeners will be integrated into the web environment
1_ demand: the spring integrated into web development environment, will create all of the bean object to spring, in addition to servlet, servlet can be understood as a test class ApplicationContext get in a servlet, to obtain the corresponding bean.
Environment to build, this is a step by step to take themselves to achieve, in fact, spring has provided a simple way to complete the operation 1.1
<!--在pom文件中引入所需的依赖-->
<!--Spring坐标-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.0.5.RELEASE</version>
</dependency>
<!--SpringMVC坐标-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.0.5.RELEASE</version>
</dependency>
<!--Servlet坐标-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
<!--Jsp坐标-->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.0</version>
</dependency>
//1.创建dao层接口和实现类
//dao接口 IUserDao
public interface IUserDao{
void save();
}
//UserDaoImpl实现类
public class UserDaoImpl implements IUserDao{
@Override
public void save(){
System.out.printLn("正在保存...");
}
}
//2.创建service业务层接口和实现类
public interface IUserService{
void save();
}
//UserServletImpl实现类
public class UserServiceImpl implements IUserService{
private IUserDao userDao;
//为依赖注入提供set方法
public void setUserDao(IUserDao userDao){this userDao=userDao;}
@Override
public void save(){
userDao.save();
}
}
<!--applicationContext.xml文件中配置Dao,service交给spring管理-->
<?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">
<!--配置Dao-->
<bean class="cn.ppvir.dao.impl.UserDaoImpl" id="userDao"></bean>
<!--配置service-->
<bean class="cn.ppvir.service.impl.UserServiceImpl" id="userService">
<property name="userDao" ref="userDao"></property>
</bean>
</beans>
/*web包下创建UserServlet类 内部功能:调Spring容器,创建service对象,调sava()方法*/
public class UserServlet extends HttpServlet{
@Override//复写doGet方法
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{
//通过配置文件获取上下文
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
//获取bean,因为只有一个UserServiceImpl,可以使用字节码的方法获取
UserServiceImpl userService = context.getBean(UserServiceImpl.class);
//调用save方法
userService.save();
}
}
<!--在web.xml中配置 servlet-->
<servlet>
<servlet-name>userServlet</servlet-name>
<servlet-class>cn.ppvir.web.UserServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>userServlet</servlet-name>
<url-pattern>/userServlet</url-pattern>
</servlet-mapping>
Finally configure tomcat, start the test
http: // localhost: 80 / userServlet
2_ Description of the problem:
the Spring in a web development environment, each servlet needs new ClassPathXmlApplicationContext("applicationContext.xml")
because the configuration file is loaded several times, it will cause the performance of waste
3_ improve one:
the creation ApplicationContext object to create a listener, the listener will create good domain objects stored in the ServletContext object, to acquire the object directly in the servlet.
- Listeners write the code
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class ContextLoaderListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
//获取上下文
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
//将spring获取到的应用上下文,保存到servletContext域中
ServletContext servletContext = servletContextEvent.getServletContext();
servletContext.setAttribute("context",context);
//之后去web.xml配置listener监听器和改写servlet代码
}
- Listener configuration
web.xml
<!--配置servlet-->
<!--配置自己实现的监听器-->
<listener>
<listener-class>cn.ppvir.listener.ContextLoaderListener</listener-class>
</listener>
- servlet code rewrite
public class UserServlet extends HttpServlet {
/**
* 改进一:
* 将ApplicationContext对象的创建交给监听器创建,监听器将创建好的对象存入ServletContext域对象中,在servlet中直接取该对象即可
*
* @param req
* @param resp
* @throws ServletException
* @throws IOException
*/
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取servletContext域对象
ServletContext servletContext = this.getServletContext();
//从ServletContext域对象中,获取监听器创建的应用上下文,强转为ApplicationContext
ApplicationContext context = (ApplicationContext) servletContext.getAttribute("context");
UserServiceImpl userService = context.getBean(UserServiceImpl.class);
userService.save();
}
}
Tomcat restart to complete the test.
4. Optimize II:
- 1_ configured to load the file in the web.xml file applicationContext.xml
web.xml
<!--改进二: 之前的基础上添加配置-->
<!--全局初始化参数-->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
- 2. rewrite ContextLoaderListener listener class, get global initialization parameters
public class ContextLoaderListener implements ServletContextListener {
/**
* 优化二: 获取全局初始化参数
*
* @param servletContextEvent
*/
@Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
//获取域对象
ServletContext servletContext = servletContextEvent.getServletContext();
//从配置文件中获取applicationContext
/*
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
*/
String contextConfigLocation = servletContext.getInitParameter("contextConfigLocation");
//获取应用上下文
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(contextConfigLocation);
//将Spring的应用上下文 存储到ServletContext域对象中
servletContext.setAttribute("context",context);
System.out.println("spring容器创建完毕...");
}
}
- 3. Optimization strong turn ApplicationContext, using tools from the object directly obtain applicationContext servletContext domain object.
//创建工具类
package cn.ppvir.listener;
import org.springframework.context.ApplicationContext;
import javax.servlet.ServletContext;
/**
* 工具类,强转context上下文为ApplicationContext
*/
public class WebApplicationContextUtils {
/**
* @param servletContext 参数是域对象
* @return 返回值是强转后的对象ApplicationContext
*/
public static ApplicationContext getWebapplicationContext(ServletContext servletContext){
return (ApplicationContext)servletContext.getAttribute("context");
}
}
- 4. Modify UserServlet class context transfer using strong optimization WebApplicationContextUtils
public class ContextLoaderListener implements ServletContextListener {
/**
* 优化二: 使用WebApplicationContextUtils工具类,简化强转上下文对象的操作
* @param req
* @param resp
* @throws ServletException
* @throws IOException
*/
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取域对象
ServletContext servletContext = this.getServletContext();
ApplicationContext context = WebApplicationContextUtils.getWebapplicationContext(servletContext);
UserServiceImpl userService = context.getBean(UserServiceImpl.class);
userService.save();
}
}
Tomcat restart to complete the test
1.2 spring to provide listeners will spring integrated into the web environment
UserDao UserService layer as above, and
- Import dependence
pom.xml
<!--spring-web坐标-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.0.5.RELEASE</version>
</dependency>
- Configure listeners ContextLoaderListener Spring offer
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<!--全局参数-->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<!--监听器-->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!--配置servlet-->
<servlet>
<servlet-name>service</servlet-name>
<servlet-class>web.UserServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>service</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
- applicationContext.xml management configuration for spring injection
applicationContext.xml
<bean class="dao.impl.UserDaoImpl" id="userDao"></bean>
<bean class="service.impl.UserServiceImpl" id="userService">
<property name="userDao" ref="userDao"></property>
</bean>
- servlet application context object obtained by the tool
public class UserServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取servletContext域对象
ServletContext servletContext = this.getServletContext();
//使用spring框架自带的WebApplicationContextUtils工具,获取上下文对象
WebApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(servletContext);
UserServiceImpl userService = context.getBean(UserServiceImpl.class);
userService.save();
}
}
1.3 Summary:
1.web environment integrated spring only need to configure the listener can
manage at 2.Spring = In addition to the controller of all objects bean