23 Servlet三大组件(Servlet、Filter、Listener)注册

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1 传统注册方式

1.1 web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	id="WebApp_ID" version="2.5">
	<display-name>mall/display-name>

	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:spring/applicationContext*.xml</param-value>
	</context-param>

	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

	<filter>
		<filter-name>encodingFilter</filter-name>
		<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
		<init-param>
			<param-name>encoding</param-name>
			<param-value>UTF8</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>encodingFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

	<!--配置SpringMVC框架入口-->
	<servlet>
		<servlet-name>dispatcherServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>classpath:spring/spring-mvc-cart.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>dispatcherServlet</servlet-name>
		<url-pattern>*.html</url-pattern>
	</servlet-mapping>


</web-app>

1.2 SpringBoot不能使用web.xml注册三大组件的原因

SpringBoot默认是以jar包的方式启动嵌入式的Servlet容器来启动SpringBoot的web应用,没有web.xml文件

2 SpringBoot注册3大组件

2.1 使用ServletRegistrationBean注册Servlet

• MyServlet

package com.gp6.springboot20.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class MyServlet extends HttpServlet {
    //处理get请求
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("Hello MyServlet");
    }
}

• MyConfig

package com.gp6.springboot20.config;

import com.gp6.springboot20.servlet.MyServlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyConfig {
    // 注册Servlet组件
    @Bean
    public ServletRegistrationBean myServlet() {
        // 映射 /myServlet 路径
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(), "/myServlet");
        registrationBean.setLoadOnStartup(1);
        return registrationBean;
    }
}

2.1.1 测试Servlet组件是否注册成功

2.2 使用FilterRegistrationBean注册Filter

• MyFilter

package com.gp6.springboot20.filter;

import javax.servlet.*;
import java.io.IOException;

public class MyFilter implements Filter {

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

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("MyFilter process...");
        // 放行
        chain.doFilter(request,response);
    }

    @Override
    public void destroy() {

    }
}

• MyConfig

package com.gp6.springboot20.config;

import com.gp6.springboot20.filter.MyFilter;
import com.gp6.springboot20.servlet.MyServlet;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Arrays;

@Configuration
public class MyConfig {
    // 注册Servlet组件
    @Bean
    public ServletRegistrationBean myServlet() {
        // 映射 /myServlet 路径
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(), "/myServlet");
        registrationBean.setLoadOnStartup(1);
        return registrationBean;
    }
	
	@Bean
    public FilterRegistrationBean myFilter() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new MyFilter());
        // 拦截的请求
        registrationBean.setUrlPatterns(Arrays.asList("/hello", "/myServlet"));
        return registrationBean;
    }
}

2.2.1 测试Filter组件是否注册成功

访问http://localhost:8080/hello或者http://localhost:8080/myServlet

2.3 使用ServletListenerRegistrationBean注册Listener

• MyListener

package com.gp6.springboot20.listener;

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

public class MyListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("contextInitialized...web应用启动");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        System.out.println("contextDestroyed...当前web项目销毁");
    }
}

• MyConfig

package com.gp6.springboot20.config;

import com.gp6.springboot20.filter.MyFilter;
import com.gp6.springboot20.listener.MyListener;
import com.gp6.springboot20.servlet.MyServlet;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Arrays;

@Configuration
public class MyConfig {
    // 注册Servlet组件
    @Bean
    public ServletRegistrationBean myServlet() {
        // 映射 /myServlet 路径
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(), "/myServlet");
        registrationBean.setLoadOnStartup(1);
        return registrationBean;
    }

	// 注册Filter组件
    @Bean
    public FilterRegistrationBean myFilter() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new MyFilter());
        // 拦截的请求
        registrationBean.setUrlPatterns(Arrays.asList("/hello", "/myServlet"));
        return registrationBean;
    }

    // 注册Listener组件
    @Bean
    public ServletListenerRegistrationBean myListener() {
        return new ServletListenerRegistrationBean<>(new MyListener());
    }
}

• ServletListenerRegistrationBean

// 可以注册的Listener的类型
static {
	Set<Class<?>> types = new HashSet();
	types.add(ServletContextAttributeListener.class);
	types.add(ServletRequestListener.class);
	types.add(ServletRequestAttributeListener.class);
	types.add(HttpSessionAttributeListener.class);
	types.add(HttpSessionListener.class);
	types.add(ServletContextListener.class);
	SUPPORTED_TYPES = Collections.unmodifiableSet(types);
}

2.3.1 测试Listener组件是否注册成功