SpringBoot2.0初识

核心特性
- 组件自动装配: Web MVC , Web Flux , JDBC 等
  
  激活: @EnableAutoConfiguration
  
  配置: /META_INF/spring.factories
  
  实现: XXXAutoConfiguration
- 嵌入式的Web容器: Tomcat , Jetty以及Undertow
  
  Web Servlet: Tomcat , Jetty 和 Undertow
  
  Web Reactive: Netty Web Server(基于web flux)
- 生产准备特性:指标 , 健康检查 , 外部化配置等
  
  指标: /actuator/metrics
  
  健康配置: /actuator/health
  
  外部化配置: /actuator/configprops

Web应用

传统的Servlet应用

引入依赖

<dependency>    
<groupId>org.springframework.boot</groupId>    
<artifactId>spring-boot-starter-web</artifactId>
</dependency>

使用Servlet组件

package cn.lisongyu.demo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;@SpringBootApplication
@ServletComponentScan(basePackages = "cn.lisongyu.demo")//使用java原生操作需添加@ServletComponentScan注解来实现对应的@WebServlet,@WebFilter,@WebListener
public class DemoApplication {    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

Servlet

实现

在类上添加@WebServlet注解

继承HttpServlet,重写doGet,doPost方法

注册到mapping中
URL映射

给@WebServlet(urlPatterns = "/my/servlet")添加属性urlPatterns,指明映射的路径

注册到应用中

在应用的启动主类上添加@ServletComponentScan(basePackages = "cn.lisongyu.demo")

使用java原生添加Servlet

package cn.lisongyu.demo;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/**
 * @author lisongyu
 * @ClassName cn.lisongyu.demo.MyServlet
 * @description
 * @create 2018年11月26日 14:57
 */
@WebServlet(urlPatterns = "/my/servlet")
public class MyServlet extends HttpServlet {    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("这里是servlet");
        resp.getWriter().append("hello,world!");
    }
}

使用spring注解添加Servlet

package cn.lisongyu.demo;import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/**
 * @author lisongyu
 * @ClassName cn.lisongyu.demo.MyServlet2
 * @description
 * @create 2018年11月26日 17:05
 */
@Configuration
public class MyServlet2 {    @Bean
    public ServletRegistrationBean getMyServlet(){
        ServletRegistrationBean servlet = new ServletRegistrationBean();
        servlet.setServlet(new HttpServlet() {
            @Override
            protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
                System.out.println("这里是servlet");
                resp.getWriter().append("hello,world!");
            }
        });        return servlet;
    }}

Filter

通过实现Filter(javax.servlet.*),重写其init(),doFilter(),destroy()方法,主要重写其doFilter()方法,在类上添加@Component注解,将组件添加到spring容器中

package cn.lisongyu.demo;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/**
 * @author lisongyu
 * @ClassName cn.lisongyu.demo.MyFilter
 * @description
 * @create 2018年11月26日 15:14
 */
@WebFilter(urlPatterns = "/my/*",filterName = "myfilter")   //是java原生提供,所以在项目容器启动主类上要添加@ServletComponentScan()
public class MyFilter implements Filter {    @Override
    public void init(FilterConfig filterConfig) throws ServletException {    }    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("这是我的拦截器------");
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        HttpServletResponse response = (HttpServletResponse)servletResponse;
        String servlet = request.getServletPath();
        if (!servlet.endsWith("servlet")){
            response.sendRedirect("/error");
            return;
        }
        // 有值，就继续执行下一个过滤链
        filterChain.doFilter(request, response);
    }    @Override
    public void destroy() {    }
}

通过注解@Configuration和@Bean实现启动服务时候加载Bean

package cn.lisongyu.demo;/**
 * @author lisongyu
 * @ClassName cn.lisongyu.demo.MyFilter2
 * @description
 * @create 2018年11月26日 15:56
 */
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;@Configuration//装配配置到spring容器中
public class MyFilter2 {    @Bean
    public FilterRegistrationBean getMyFilter(){
        FilterRegistrationBean<Filter> filter = new FilterRegistrationBean<>();
        filter.setFilter(new Filter() {
            @Override
            public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
                System.out.println("这是我的拦截器------");
                HttpServletRequest request = (HttpServletRequest)servletRequest;
                HttpServletResponse response = (HttpServletResponse)servletResponse;
                String servlet = request.getServletPath();
                if (!servlet.endsWith("servlet")){
                    response.sendRedirect("/error");
                    return;
                }
                // 有值，就继续执行下一个过滤链
                filterChain.doFilter(request, response);
            }
        });
        //过滤规则
        filter.addUrlPatterns("/my/*");
        //过滤器名称
        filter.setName("myfilter2");
        //过滤器顺序
        filter.setOrder(1);        return filter;
    }}

Listener

监听器类型很多,本篇只做一个举例(HttpSessionListener)

java原生@WebListener

package cn.lisongyu.demo;import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;/**
 * @author lisongyu
 * @ClassName cn.lisongyu.demo.MyListener
 * @description
 * @create 2018年11月26日 16:17
 */
@WebListener
public class MyListener implements HttpSessionListener {    public int count = 0;    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("这里是listener.创建");
        count ++;
        se.getSession().getServletContext().setAttribute("count",count);
    }    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("这里是listener.关闭");
        count --;
        se.getSession().getServletContext().setAttribute("count",count);
    }
}

springboot2.0集成,通过@Configuration和@Bean注解实现

package cn.lisongyu.demo;import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;/**
 * @author lisongyu
 * @ClassName cn.lisongyu.demo.MyListener2
 * @description
 * @create 2018年11月26日 16:50
 */
@Configuration
public class MyListener2 {    @Bean
    public ServletListenerRegistrationBean getMyListener(){
        ServletListenerRegistrationBean listener = new ServletListenerRegistrationBean();
        listener.setListener(new HttpSessionListener() {
            int count;
            @Override
            public void sessionCreated(HttpSessionEvent se) {
                System.out.println("这里是listener.创建");
                count ++;
                se.getSession().getServletContext().setAttribute("count",count);
            }            @Override
            public void sessionDestroyed(HttpSessionEvent se) {
                System.out.println("这里是listener.关闭");
                count --;
                se.getSession().getServletContext().setAttribute("count",count);
            }
        });
        return listener;
    }}

在Servlet组件当中,当前端发送请求时,后端的执行顺序是Filter->Servlet->Listener

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