spring注解驱动开发(三):servlet3.0

servlet3.0查看官网: 属于jsr规范

查看tomcat支持servlet的版本 : 发现只有tomcat7以上才能支持servlet3.0

servlet示例:

 支持WebServlet,Webfilter,WebListener注解,示例如下:

package com.atguigu.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //super.doGet(req, resp);
        System.out.println(Thread.currentThread()+" start...");
        try {
            sayHello();
        } catch (Exception e) {
            e.printStackTrace();
        }
        resp.getWriter().write("hello...");
        System.out.println(Thread.currentThread()+" end...");
    }
    
    public void sayHello() throws Exception{
        System.out.println(Thread.currentThread()+" processing...");
        Thread.sleep(3000);
    }

}

Shared libraries（共享库） / runtimes pluggability（运行时插件能力）

1、Servlet容器启动会扫描，当前应用里面每一个jar包的ServletContainerInitializer接口的实现类.
2、提供ServletContainerInitializer的实现类方法:
必须绑定在，META-INF/services/javax.servlet.ServletContainerInitializer文件的内容就是ServletContainerInitializer实现类的全类名；

总结：容器在启动应用的时候，会扫描当前应用每一个jar包里面META-INF/services/javax.servlet.ServletContainerInitializer指定的实现类，启动并运行这个实现类的方法；传入感兴趣的类型；

ServletContainerInitializer；
@HandlesTypes；

 示例:

1): 在目录(没有则创建此文件)META-INF/services/javax.servlet.ServletContainerInitializer文件添加启动类:

2):创建并实现这个类MyServletContainerInitializer,如下:

备注: @HandlesTypes(value={HelloService.class})这个注解会将接口HelloService的所有子接口包括抽象类及实现类加载进来

package com.atguigu.servlet;

import java.util.EnumSet;
import java.util.Set;

import javax.servlet.DispatcherType;
import javax.servlet.FilterRegistration;
import javax.servlet.ServletContainerInitializer;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration;
import javax.servlet.annotation.HandlesTypes;

import com.atguigu.service.HelloService;

//容器启动的时候会将@HandlesTypes指定的这个类型下面的子类（实现类，子接口等）传递过来；
//传入感兴趣的类型；
@HandlesTypes(value={HelloService.class})
public class MyServletContainerInitializer implements ServletContainerInitializer {

    /**
     * 应用启动的时候，会运行onStartup方法；
     * 
     * Set<Class<?>> arg0：感兴趣的类型的所有子类型；
     * ServletContext arg1:代表当前Web应用的ServletContext；一个Web应用一个ServletContext；
     * 
     * 1）、使用ServletContext注册Web组件（Servlet、Filter、Listener）
     * 2）、使用编码的方式，在项目启动的时候给ServletContext里面添加组件；
     *         必须在项目启动的时候来添加；
     *         1）、ServletContainerInitializer得到的ServletContext；
     *         2）、ServletContextListener得到的ServletContext；
     */
    @Override
    public void onStartup(Set<Class<?>> arg0, ServletContext sc) throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("感兴趣的类型：");
        for (Class<?> claz : arg0) {
            System.out.println(claz);
        }
        
        //注册组件  ServletRegistration  
        ServletRegistration.Dynamic servlet = sc.addServlet("userServlet", new UserServlet());
        //配置servlet的映射信息
        servlet.addMapping("/user");
        
        
        //注册Listener
        sc.addListener(UserListener.class);
        
        //注册Filter  FilterRegistration
        FilterRegistration.Dynamic filter = sc.addFilter("userFilter", UserFilter.class);
        //配置Filter的映射信息
        filter.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), true, "/*");
        
    }

}

以上代码注册的servlet,filter,listener三个组件的实现类如下:

servlet:

package com.atguigu.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class UserServlet extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        resp.getWriter().write("tomcat...");
    }

}

filter:

package com.atguigu.servlet;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class UserFilter implements Filter {

    @Override
    public void destroy() {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
            throws IOException, ServletException {
        // 过滤请求
        System.out.println("UserFilter...doFilter...");
        //放行
        arg2.doFilter(arg0, arg1);
        
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        
    }

}

listener:

package com.atguigu.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * 监听项目的启动和停止
 * @author lfy
 *
 */
public class UserListener implements ServletContextListener {

    
    //监听ServletContext销毁
    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
        System.out.println("UserListener...contextDestroyed...");
    }

    //监听ServletContext启动初始化
    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
        ServletContext servletContext = arg0.getServletContext();
        System.out.println("UserListener...contextInitialized...");
    }

}

启动tomcat的结果如下: