JavaWeb基础 通过配置web.xml 让servlet类和服务器共同启动

Posted 2020-10-11

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       javaEE：7           
       javaSE：1.8
          JSTL：1.2.2  
      server：tomcat 8.5
    explorer：Firefox        
             os：windows7 x64
            ide：MyEclipse 2017

工程目录结构

 

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">

	<servlet>
		<servlet-name>SpecialServletOne</servlet-name>
		<servlet-class>jizuiku.web.servlet.SpecialServletOne</servlet-class>
		<load-on-startup>0</load-on-startup><!-- 按照非负数字，从大到小 一次启动相应服务 -->
	</servlet>
	<servlet-mapping>
		<servlet-name>SpecialServletOne</servlet-name>
		<url-pattern>/SpecialServletOne</url-pattern>
	</servlet-mapping>

	<servlet>
		<servlet-name>SpecialServletTwo</servlet-name>
		<servlet-class>jizuiku.web.servlet.SpecialServletTwo</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>SpecialServletTwo</servlet-name>
		<url-pattern>/SpecialServletTwo</url-pattern>
	</servlet-mapping>

	<servlet>
		<servlet-name>CommonServlet</servlet-name>
		<servlet-class>jizuiku.web.servlet.CommonServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>CommonServlet</servlet-name>
		<url-pattern>/CommonServlet</url-pattern>
	</servlet-mapping>

</web-app>

 　　分析xml文件，可知有三个servlet类。其中SpecialServletTwo、SpecialServletOne随着服务器启动而启动，而CommonServlet是普通的，有访问时才会启动。

　　
CommonServlet

package jizuiku.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 
 * 
 * @author 给最苦
 * @version V17.10.20
 */
public class CommonServlet extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Override
	public void init() throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("CommonServlet已启动");
	}
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}
}

 

SpecialServletOne

package jizuiku.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 
 * 
 * @author 给最苦
 * @version V17.10.20
 */
public class SpecialServletOne extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Override
	public void init() throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("SpecialServletOne已启动");
	}
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}
}

 

SpecialServletTwo

package jizuiku.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 
 * 
 * @author 给最苦
 * @version V17.10.20
 */
public class SpecialServletTwo extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Override
	public void init() throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("SpecialServletTwo已启动");
	}
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}
}

 

服务器启动时，控制台输出的部分内容

信息: Starting Servlet Engine: Apache Tomcat/8.5.23
十月 20, 2017 9:10:41 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\Day09]
十月 20, 2017 9:10:41 下午 org.apache.jasper.servlet.TldScanner scanJars
信息: At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
SpecialServletOne已启动
SpecialServletTwo已启动
十月 20, 2017 9:10:41 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deployment of web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\Day09] has finished in [729] ms
十月 20, 2017 9:10:41 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\docs]
十月 20, 2017 9:10:41 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deployment of web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\docs] has finished in [26] ms
十月 20, 2017 9:10:41 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\examples]
十月 20, 2017 9:10:42 下午 org.apache.catalina.core.ApplicationContext log
信息: ContextListener: contextInitialized()
十月 20, 2017 9:10:42 下午 org.apache.catalina.core.ApplicationContext log
信息: SessionListener: contextInitialized()
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deployment of web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\examples] has finished in [429] ms
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\host-manager]
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deployment of web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\host-manager] has finished in [41] ms
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\manager]
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deployment of web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\manager] has finished in [39] ms
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\ROOT]
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deployment of web application directory [E:\\develop\\apache-tomcat-8.5.23\\webapps\\ROOT] has finished in [33] ms
十月 20, 2017 9:10:42 下午 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["http-nio-8081"]
十月 20, 2017 9:10:42 下午 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["ajp-nio-8009"]
十月 20, 2017 9:10:42 下午 org.apache.catalina.startup.Catalina start
信息: Server startup in 1383 ms

 

浏览器访问 CommonServlet 所对应的网页时

 

 

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