上下文参数(context-param)
由于init-param是配置在<servlet>标签里的,只能有这个Servlet来读取,因此它不是全局的参数,不能被其他的Servlet读取.
context-param叫做上下文参数,可以被所有的Sevlet读取.上下文标签使用<context-param>配置
<?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"> <context-param> <param-name>upload folder</param-name> <param-value>attachment</param-value> </context-param> <context-param> <param-name>allowed file type</param-name> <param-value>.gif, .jpg, .bmp</param-value> </context-param> <servlet> <servlet-name>ContextParamServlet</servlet-name> <servlet-class>com.helloxr.servlet.ContextParamServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ContextParamServlet</servlet-name> <url-pattern>/servlet/ContextParamServlet</url-pattern> </servlet-mapping>
package com.helloxr.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ContextParamServlet extends HttpServlet { private static final long serialVersionUID = 65464645464L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setCharacterEncoding("UTF-8"); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>读取上下文参数</TITLE></HEAD>"); out.println(" <BODY>"); out.println(" <link rel='stylesheet' type='text/css' href='../css/style.css'>"); out.println("<div align=center><br/>"); out.println("<fieldset style='90%'><legend>所有的上下文参数</legend><br/>"); ServletContext servletContext = getServletConfig().getServletContext(); String uploadFolder = servletContext.getInitParameter("upload folder"); String allowedFileType = servletContext.getInitParameter("allowed file type"); out.println("<div class='line'>"); out.println(" <div align='left' class='leftDiv'>上传文件夹</div>"); out.println(" <div align='left' class='rightDiv'>" + uploadFolder + "</div>"); out.println("</div>"); out.println("<div class='line'>"); out.println(" <div align='left' class='leftDiv'>实际磁盘路径</div>"); out.println(" <div align='left' class='rightDiv'>" + servletContext.getRealPath(uploadFolder) + "</div>"); out.println("</div>"); out.println("<div class='line'>"); out.println(" <div align='left' class='leftDiv'>允许上传的文件类型</div>"); out.println(" <div align='left' class='rightDiv'>" + allowedFileType + "</div>"); out.println("</div>"); out.println("</fieldset></div>"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } }
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