Spring Boot 學習系列（08）—自定義servlet、filter及listener

時間 2019-12-05

標籤 spring boot 學習系列自定義 servlet filter listener 欄目 Spring 简体版

原文原文鏈接

此文已由做者易國強受權網易雲社區發佈。
html

歡迎訪問網易雲社區，瞭解更多網易技術產品運營經驗。java

傳統的filter及listener配置

在傳統的Java web項目中，servlet、filter和listener的配置很簡單，直接在web.xml中按順序配置好便可，程序啓動時，就會按照你配置的順序依次加載（固然，web.xml中各配置信息總的加載順序是context-param -> listener -> filter -> servlet），項目搭建完成後，估計通常新來的開發同窗沒啥事都不會去關注裏面都作了些啥~ = =web
廢話少說，上代碼，下面是一個傳統的web.xml配置示例。spring

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class></listener><!-- define charset --><filter>
    <filter-name>Set UTF-8</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
    <init-param>
        <param-name>forceEncoding</param-name>
        <param-value>true</param-value>
    </init-param></filter><servlet>
    <servlet-name>silver</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:xxx-servlet.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup></servlet><servlet-mapping>
    <servlet-name>silver</servlet-name>
    <url-pattern>/</url-pattern></servlet-mapping>複製代碼

Spring Boot中該如何配置？

須要說明的是，Spring Boot項目裏面是沒有web.xml的，那麼listener和filter咱們該如何配置呢？安全
在Spring Boot項目中有兩種方式進行配置，一種是經過Servlet3.0+提供的註解進行配置，分別爲@WebServlet、@WebListener、@WebFilter。示例以下：bash

import javax.servlet.*;import javax.servlet.annotation.WebFilter;import java.io.IOException;/**
 * @author bjyiguoqiang
 * @date 2017/11/9 17:28.
 */@WebFilter(urlPatterns = "/*", filterName = "helloFilter")public class HelloFilter implements Filter {    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("init helloFilter");
    }    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("doFilter helloFilter");
        filterChain.doFilter(servletRequest,servletResponse);

    }    @Override
    public void destroy() {

    }
}複製代碼

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 bjyiguoqiang
 * @date 2017/11/9 17:27.
 */@WebServlet(name = "hello",urlPatterns = "/hello")public class HelloServlet extends HttpServlet {    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().print("hello word");
        resp.getWriter().flush();
        resp.getWriter().close();
    }    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        this.doGet(req, resp);
    }
}複製代碼

import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener;/**
 * @author bjyiguoqiang
 * @date 2017/11/9 17:28.
 */@WebListenerpublic class HelloListener implements ServletContextListener {    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("HelloListener contextInitialized");
    }    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}複製代碼

最後在程序入口類加入掃描註解@ServletComponentScan便可生效。session

@SpringBootApplication@ServletComponentScanpublic class DemoaApplication {    public static void main(String[] args) {
        SpringApplication.run(DemoaApplication.class, args);
    }
}複製代碼

須要注意的是，使用@WebFilter 是沒法實現filter的過濾順序的，使用org.springframework.core.annotation包中的@Order註解在spring boot環境中也是不支持的。全部若是須要對自定義的filter排序，那麼能夠採用下面所述的方式。app
另外一種配置則是經過Spring Boot提供的三種相似Bean實現的，分別爲ServletRegistrationBean、ServletListenerRegistrationBean以及FilterRegistrationBean。使用示例分別以下：ide

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;/**
 * @author bjyiguoqiang
 * @date 2017/11/9 17:44.
 */@Configurationpublic class MyConfigs {    /**
     * 配置hello過濾器
     */
    @Bean
    public FilterRegistrationBean sessionFilterRegistration() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new HelloFilter());
        registrationBean.addUrlPatterns("/*");
        registrationBean.addInitParameter("session_filter_key", "session_filter_value");
        registrationBean.setName("helloFilter");        //設置加載順序，數字越小，順序越靠前,建議最小從0開始配置，最大爲Integer.MAX_VALUE
        registrationBean.setOrder(10);        return registrationBean;
    }    /**
     * 配置hello Servlet
     */
    @Bean
    public ServletRegistrationBean helloServletRegistration() {
        ServletRegistrationBean registration = new ServletRegistrationBean(new HelloServlet());
        registration.addUrlMappings("/hello");        //設置加載順序，數字越小，順序越靠前,建議最小從0開始配置，最大爲Integer.MAX_VALUE
        registration.setOrder(3);        return registration;
    }    /**
     * 配置hello Listner
     */
    @Bean
    public ServletListenerRegistrationBean helloListenerRegistrationBean(){
        ServletListenerRegistrationBean servletListenerRegistrationBean = new ServletListenerRegistrationBean();
        servletListenerRegistrationBean.setListener(new HelloListener());        //設置加載順序，數字越小，順序越靠前,建議最小從0開始配置，最大爲Integer.MAX_VALUE
        servletListenerRegistrationBean.setOrder(3);        return servletListenerRegistrationBean;
    }
}複製代碼