Servlet获取初始化参数

最新推荐文章于 2023-06-03 00:50:10 发布

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本文介绍如何在Servlet中通过ServletConfig接口获取web.xml中配置的初始化参数，并展示了一个具体的示例，包括配置文件web.xml的内容、GetInitParameterServlet的实现及index.jsp页面链接。

1>在web.xml中配置Servlet时，可以配置一些初始化参数。而在Servlet中可以通过ServletConfig接口提供的方法来取得这些参数。
2>在index.jsp中改<a href="servlet/GetInitParameterServlet">获取初始化参数Servlet</a>
3>建一个Servlet，在web.xml中设置初始化参数
4>private String username;
private String password;封装一下
5>在public void init() throws ServletException{
this.setUsername( this.getInitParameter（"username"）)；
this.setPassword( this.getInitParameter（"username"）)；
6>在body中输出设置的名字和密码
this.getUername();
this.getPassword();

GetInitParameterServlet

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

public class GetInitParameterServlet extends HttpServlet {

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	
	private String username;
	private String password;
	
	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doPost(request, response);
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
		out.println("<HTML>");
		out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
		out.println("  <BODY>");
		out.println("<h2>"+"用户名： "+this.getUsername()+"</h2>");
		out.println("<h2> "+"密码："+this.getPassword()+"</h2>");
		out.println("  </BODY>");
		out.println("</HTML>");
		out.flush();
		out.close();
	}
	public void  init() throws ServletException {
		this.setUsername(this.getInitParameter("username"));
		this.setPassword(this.getInitParameter("password"));
		
	}

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>GetInitParameterServlet</servlet-name>
    <servlet-class>servlet.GetInitParameterServlet</servlet-class>
    <init-param>
    <param-name>username</param-name>
	<param-value>admin</param-value>
    </init-param>
    <init-param>
    <param-name>password</param-name>
	<param-value>123456</param-value>
    </init-param>
  </servlet>

  <servlet-mapping>
    <servlet-name>GetInitParameterServlet</servlet-name>
    <url-pattern>/servlet/GetInitParameterServlet</url-pattern>
  </servlet-mapping>

</web-app>

index.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>
  
  <body>
    <h1>获取初始化参数演示案例</h1>
    <hr>
    <a href="servlet/GetInitParameterServlet">获取初始化参数Servlet</a>
  </body>
</html>