Servlet配置初始值，并获取初始值

<!--配置Servlet的初始化参数  -->
    <init-param>
      <!-- 初始化参数的名 -->
      <param-name>username</param-name>
       <!-- 初始化参数的名的值 --> 
      <param-value>root</param-value>
    </init-param>
    <init-param>
      <param-name>password</param-name>
      <param-value>123456</param-value>
    </init-param>

@Override
  public void init(ServletConfig config) throws ServletException {
    System.out.println("init");
      String userName = config.getInitParameter("username");//对单个初始值进行获取
    String passWord = config.getInitParameter("password");
    System.out.println("账号："+userName);
    System.out.println("密码："+passWord);
    Enumeration<String> names = config.getInitParameterNames();  //获取所有的name属性的名字，并且返回一个集合
    while (names.hasMoreElements()) {  //遍历这个集合的所有的name名字
      String name = (String) names.nextElement();
      String value = config.getInitParameter(name); //通过遍历对单个初始值进行获取
      System.out.println("name:"+name+",value:"+value);
    }
  }

<?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">
  <display-name>JavaWeb_HelloWord</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list> 
  <!--配置servlet  -->
  <servlet>
    <!--Servlet 注册的名字  -->
    <servlet-name>helloServlet</servlet-name>
    <!--Servlet 的全类名  -->
    <servlet-class>com.zhenghui.HelloServlet</servlet-class>
    <!--配置Servlet的初始化参数  -->
    <init-param>
      <!-- 初始化参数的名 -->
      <param-name>username</param-name>
       <!-- 初始化参数的名的值 --> 
      <param-value>root</param-value>
    </init-param>
    <init-param>
      <param-name>password</param-name>
      <param-value>123456</param-value>
    </init-param>
  </servlet>
 <!--映射servlet  -->
  <servlet-mapping> 
    <!--需要和某一个Servlet的servlet-name子节点的文本节点一致  -->
    <servlet-name>helloServlet</servlet-name>
    <!--映射具体的访问路径：/代表当前WEB应用的根目录-->
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>  
</web-app>

package com.zhenghui;
import java.io.IOException;
import java.util.Enumeration;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class HelloServlet implements Servlet{
  @Override
  public void destroy() {
    System.out.println("destroy");
  }
  @Override
  public ServletConfig getServletConfig() {
    System.out.println("getServletConfig");
    return null;
  }
  @Override
  public String getServletInfo() {
    System.out.println("getServletInfo");
    return null;
  }
  @Override
  public void init(ServletConfig config) throws ServletException {
    System.out.println("init");
    String userName = config.getInitParameter("username");
    String passWord = config.getInitParameter("password");
    System.out.println("账号："+userName);
    System.out.println("密码："+passWord);
    Enumeration<String> names = config.getInitParameterNames();
    while (names.hasMoreElements()) {
      String name = (String) names.nextElement();
      String value = config.getInitParameter(name);
      System.out.println("name:"+name+",value:"+value);
    }
  }
  @Override
  public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
    System.out.println("service");
  }
  public HelloServlet() {
    System.out.println("This is a HelloServlet");
  }
}