[Java知识库] Tomcat初始化怎么做，初始化顺序

开发: C++知识库 Java知识库 JavaScript Python PHP知识库人工智能区块链大数据移动开发嵌入式开发工具数据结构与算法开发测试游戏开发网络协议系统运维
教程: HTML教程 CSS教程 JavaScript教程 Go语言教程 JQuery教程 VUE教程 VUE3教程 Bootstrap教程 SQL数据库教程 C语言教程 C++教程 Java教程 Python教程 Python3教程 C#教程
数码: 电脑笔记本显卡显示器固态硬盘硬盘耳机手机 iphone vivo oppo 小米华为单反装机图拉丁

-> Java知识库 -> Tomcat初始化怎么做，初始化顺序 -> 正文阅读

[Java知识库]Tomcat初始化怎么做，初始化顺序

1.实现ServletContainerInitializer
2.实现ServletContextListener
3.实现Filter
4.servlet启动init

ServletContainerInitializer

package com.xy.core;

import com.xy.util.ReflectionUtils;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.GenericWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.util.WebUtils;

import javax.servlet.Filter;
import javax.servlet.MultipartConfigElement;
import javax.servlet.Servlet;
import javax.servlet.ServletContainerInitializer;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration;
import javax.servlet.annotation.HandlesTypes;
import javax.servlet.http.HttpServlet;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

/**
 * @ClassName ContainerInitializer
 * @Description
 * @Author xy
 * @Date 2022/5/20
 * @Version 1.0
 **/

//@HandlesTypes({ HttpServlet.class, Filter.class , Initializer.class})
@HandlesTypes({ Initializer.class})
public class ContainerInitializer implements ServletContainerInitializer, ApplicationContextInitializer<GenericApplicationContext> {
    @Override
    public void onStartup(Set<Class<?>> classes, ServletContext servletContext) throws ServletException {
        List<Class<Initializer>> initializerClasses = new ArrayList();
        for(Class clazz : classes) {
            if (Initializer.class.isAssignableFrom(clazz)) {
                initializerClasses.add(clazz);
            }
        }
        for (Class<Initializer> initializerClass : initializerClasses) {
            try {
                ((Initializer)initializerClass.newInstance()).init();
            } catch (IllegalAccessException | InstantiationException var26) {
                //throw ....
            }
        }
    }

    @Override
    public void initialize(GenericApplicationContext genericApplicationContext) {

    }


}

ServletContextListener

package com.xy.core;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

/**
 * @ClassName MyServletContextListener
 * @Description
 * @Author xy
 * @Date 2022/5/20
 * @Version 1.0
 **/
@WebListener
public class MyServletContextListener implements ServletContextListener {
   public void contextInitialized(ServletContextEvent sce) {
       System.out.println("------MyServletContextListener----------");
    }
}

Filter

package com.xy.core;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

/**
 * @ClassName MyFilter
 * @Description
 * @Author xy
 * @Date 2022/5/20
 * @Version 1.0
 **/
@WebFilter
public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("-------MyFilter-----");
//        Filter.super.init(filterConfig);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

    }

    @Override
    public void destroy() {
        Filter.super.destroy();
    }
}

HttpServlet

package com.xy.servlet;

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;

/**
 * @ClassName MyServlet
 * @Description
 * @Author xy
 * @Date 2022/5/19
 * @Version 1.0
 **/
@WebServlet(
        urlPatterns = {"/my/servlet"},
        loadOnStartup = 1
)
public class MyServlet extends HttpServlet {

    public void init() throws ServletException {
        System.out.println("-------------servlet init--------------------");
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("-------------doGet--------------------");
        resp.getWriter().println("this is doGet");
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)   throws  ServletException, IOException {
        System.out.println("-------------doPost--------------------");
        resp.getWriter().println("this is doPost");

    }

    protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws  ServletException, IOException {
        System.out.println("-------------doPut--------------------");
        resp.getWriter().println("this is doPut");
    }
}

控制台打印初始化顺序：

----------ServletContainerInitializer ?init-------
------ServletContextListener init ----------
-------Filter init -----
-------------servlet init--------------------