2、SpringBoot整合Web层技术

整合Servlet方式一（通过注解扫描完成Servlet组件的注册）

1.创建Serverlet
2.修改启动类，添加 @ServletComponentScan

添加web依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>2.3.1.RELEASE</version>
</dependency>

1.创建Serverlet

@WebServlet(name="FirstServlet", urlPatterns = "/first")
public class FirstServlet extends HttpServlet{
    public void doGet(HttpServletRequest request, HttpServletResponse response){
        System.out.println("First Servlet...");
    }
}

2.修改启动类，添加 @ServletComponentScan

@SpringBootApplication
@ServletComponentScan//在SpringBoot启动时会扫描@WebServlet，对该类进行实例化
public class SpringbootwebApplication {

   public static void main(String[] args) {
      SpringApplication.run(SpringbootwebApplication.class, args);
   }
}

通过：localhost:8080/first 访问

整合Servlet方式二（通过方法完成Servlet组件的注册）

1.创建Serverlet继承HttpServlet
2.创建Servlet配置类

1.创建Serverlet

public class SecondServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response){
        System.out.println("Second Servlet...");
    }
}

2.创建Servlet配置类

@Configuration
public class ServletConfig {
//    完成Servlet组件的注册
    @Bean
    public ServletRegistrationBean getServletRegistrationBean(){
        ServletRegistrationBean bean = new ServletRegistrationBean(new SecondServlet());
//添加该Servlet的访问路径
        bean.addUrlMappings("/second");
        return bean;
    }
}

启动类

@SpringBootApplication
public class SpringbootwebApplication {

   public static void main(String[] args) {
      SpringApplication.run(SpringbootwebApplication.class, args);
   }
}

添加@Configuration相当于这个类是一个spring配置文件上下文，添加@Bean的这个方法会在spring容器启动的时候进行实例化

通过url：localhost:8080/second 访问

整合Filter方式一（通过注解扫描完成Filter组件注册）

1.创建Filter
2.修改启动类，添加@ServletComponentScan注解

1.创建Filter

//@WebFilter(filterName = "FirstFilter",urlPatterns = {"*.do","*.jsp"})
@WebFilter(filterName = "FirstFilter", urlPatterns = "/first")
public class FirstFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("进入First Filter");
        filterChain.doFilter(servletRequest, servletResponse);
        System.out.println("离开First Filter");
    }
}

2.修改启动类，添加@ServletComponentScan注解

@SpringBootApplication
@ServletComponentScan
public class SpringbootwebApplication {


   public static void main(String[] args) {
      SpringApplication.run(SpringbootwebApplication.class, args);
   }
}

因为Filter本身属于Servlet的一个子技术，所以通过@ServletComponentScan也可以扫描到@WebFilter的类

通过url:localhost:8080/first 访问

整合Filter方式二（通过方法完成Filter组件注册）

1.创建Filter实现Filter
2.创建Filter配置类

1.创建Filter

public class SecondFilter implements Filter{
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("进入Second Filter");
        filterChain.doFilter(servletRequest, servletResponse);
        System.out.println("离开Second Filter");
    }
}

创建Filter配置类

@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean getFilterRegistrationBean(){
        FilterRegistrationBean bean = new FilterRegistrationBean(new SecondFilter());
//        bean.addUrlPatterns(new String[]{"*.do","*.jsp"});
        bean.addUrlPatterns("/second");
        return bean;
    }
}

通过 url：localhost:8080/second

整合Listener方式一(通过注解扫描完成Listener组件注册)

1.编写Listener实现ServletContextListener
2.修改启动类添加@ServletComponentScan

1.编写Listener

@WebListener
public class FirstListener implements ServletContextListener{
    //监听销毁的方法
    public void contextDestroyed(ServletContextEvent event){

    }

    // 监听初始化的方法
    public void contextInitialized(ServletContextEvent event){
        System.out.println("Listener....Init.....");
    }
}

2.修改启动类添加@ServletComponentScan

@SpringBootApplication
@ServletComponentScan
public class SpringbootwebApplication {
   public static void main(String[] args) {
      SpringApplication.run(SpringbootwebApplication.class, args);
   }
}

整合Listener方式二（通过方法完成Listener组件注册）

1.编写Listener
2.创建Listenter启动类

1.编写Listener

public class SecondListener implements ServletContextListener {
    //监听销毁的方法
    public void contextDestroyed(ServletContextEvent event){
    }


    // 监听初始化的方法
    public void contextInitialized(ServletContextEvent event){
        System.out.println("SecondListener....Init.....");
    }
}

2.创建Listenter启动类

@Configuration
public class ListenerConfig {
    @Bean
    public ServletListenerRegistrationBean getServletListenerRegistrationBean(){
        ServletListenerRegistrationBean bean = new ServletListenerRegistrationBean(new SecondListener());
        return bean;
    }
}