Servlet JSP之 ServletConfig对象

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
<servlet>
        <servlet-name>TestServletConfig</servlet-name>
        <servlet-class>com.djun.serveleMapping.TestServletConfig</servlet-class>
 
        <!--配置Servlet的初始化参数-->
        <!-- 如何获取初始化的参数？
            1、getInitParameter(String name)
            Returns a String containing the value of the named initialization parameter,
            or null if the parameter does not exist.
            2、 getInitParameterNames()
            Returns the names of the servlet&#39;s initialization parameters as an Enumeration of String objects,
            or an empty Enumeration if the servlet has no initialization parameters.
        -->
        <init-param>
            <param-name>username</param-name>
            <param-value>admin</param-value>
        </init-param>
 
        <init-param>
            <param-name>passworld</param-name>
            <param-value>admin</param-value>
        </init-param>
        <!--
         指定Servlet JSP被创建的时机
         若数值 a<0,则仅在第一次的时候被创建。
         若 a>=0 , 则在当前应用被Servlet容器加载时创建实例
         数值越小越早被创建
      -->
        <load-on-startup>1</load-on-startup>
    </servlet>
 
    <servlet-mapping>
        <servlet-name>TestServletConfig</servlet-name>
        <!--只要后缀为html的文件都由该类处理-->
        <url-pattern>/servletConfig</url-pattern>
    </servlet-mapping>
</web-app>

import javax.servlet.*;
import java.io.IOException;
import java.util.Enumeration;
 
public class TestServletConfig implements Servlet {
    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        System.out.println("Init TestServletConfig...");
        System.out.println("-----------执行getInitParameter--------");
        String username = servletConfig.getInitParameter("username");
        String passworld = servletConfig.getInitParameter("passworld");
        System.out.println("username: " + username+"\n"+"password : "+passworld);
 
        System.out.println("----------执行getInitParameterNames------");
        Enumeration<String> names = servletConfig.getInitParameterNames();
 
        while(names.hasMoreElements()){
            String name = names.nextElement();
            String value = servletConfig.getInitParameter(name);
            System.out.println("username: " + name+"\n"+"password : "+value);
        }
        String servletName = servletConfig.getServletName();
        System.out.println(servletName);
    }
 
    @Override
    public ServletConfig getServletConfig() {
        return null;
    }
 
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("TestServletConfig....");
    }
 
    @Override
    public String getServletInfo() {
        return null;
    }
 
    @Override
    public void destroy() {
 
    }
}

System.out.println("getContextPath() -----------");
        String contextPath = servletContext.getContextPath();
        System.out.println(contextPath);
        String fileName = "application.properties";
        try {
            File file = new File(realPath+ "/" + fileName);
            ClassLoader classLoader = getClass().getClassLoader();
 
            InputStream is = classLoader.getResourceAsStream(realPath + "/" + fileName);
            System.out.println(realPath+ "/" + fileName);
 
            System.out.println("1. "+ is);
 
        } catch (Exception e) {
            e.printStackTrace();
        }