1.ServletConfig
ServletConfig:代表当前Servlet在web.xml中的配置信息
- String getServletName() -- 获取当前Servlet在web.xml中配置的名字
- String getInitParameter(String name) -- 获取当前Servlet指定名称的初始化参数的值
- Enumeration getInitParameterNames() -- 获取当前Servlet所有初始化参数的名字组成的枚举
- ServletContext getServletContext() -- 获取代表当前web应用的ServletContext对象
在Servlet的配置文件中，可以使用一个或多个
当servlet配置了初始化参数后，web容器在创建servlet实例对象时，会自动将这些初始化参数封装到ServletConfig对象中
配置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">
<display-name>Servlet_ServletConfigdisplay-name>
<welcome-file-list>
<welcome-file>index.jspwelcome-file>
welcome-file-list>
<servlet>
<servlet-name>AchieveParamservlet-name>
<servlet-class>com.servlets.AchieveParamServletservlet-class>
<init-param>
<param-name>userNameparam-name>
<param-value>jtxparam-value>
init-param>
<init-param>
<param-name>userPwdparam-name>
<param-value>123456param-value>
init-param>
<load-on-startup>1load-on-startup>
servlet>
<servlet-mapping>
<servlet-name>AchieveParamservlet-name>
<url-pattern>*.dourl-pattern>
servlet-mapping>
web-app>
Servlet处理类
package com.servlets; import java.io.IOException; import java.util.Enumeration; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * 可以实现Servlet接口 * * @author yyx 2019年3月13日 */ public class AchieveParamServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 设置输出内容的编码方式 response.setCharacterEncoding("UTF-8"); // 获得Session HttpSession httpSession = request.getSession(); // 获得ServletConfig对象 ServletConfig servletConfig = this.getServletConfig(); String userName = servletConfig.getInitParameter("userName"); String userPwd = servletConfig.getInitParameter("userPwd"); httpSession.setAttribute("userName", userName); httpSession.setAttribute("userPwd", userPwd); /* * getServletName()获取当前Servlet在web.xml中配置的名字 * getServletContext()获取代表当前web应用的ServletContext对象 * getInitParameterNames()获取当前Servlet所有初始化参数的名字组成的枚举 */ System.out.println(servletConfig.getServletName()); ServletContext sContext = servletConfig.getServletContext(); Enumerationenumeration = servletConfig.getInitParameterNames(); while (enumeration.hasMoreElements()) { String name= enumeration.nextElement();
String value = servletConfig.getInitParameter(name); System.out.println(value); } // 转发 request.getRequestDispatcher("/success.jsp").forward(request, response); } @Override public void destroy() { super.destroy(); System.out.println("Servlet销毁"); } @Override public void init(ServletConfig config) throws ServletException { super.init(config); System.out.println("Servlet初始化"); } }
JSP页面
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title heretitle> head> <body> <a href="${pageContext.request.contextPath}/achieveparamservlet.do">获取参数a> body> html>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title heretitle> head> <body> <h2>${ userName}h2> <h2>${ userPwd}h2> body> html>
2.ServletContext
ServletContext官方叫servlet上下文
WEB容器在启动时，它会为每个WEB应用程序都创建一个对应的ServletContext对象，它代表当前web应用
- 是一个域对象
- 可以读取全局配置参数
- 可以搜索当前工程目录下面的资源文件
- 可以获取当前工程名字
配置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">
<display-name>Servlet_ServletConfigdisplay-name>
<welcome-file-list>
<welcome-file>index.jspwelcome-file>
welcome-file-list>
<context-param>
<param-name>companyparam-name>
<param-value>Alibabaparam-value>
context-param>
<servlet>
<servlet-name>AchieveParamservlet-name>
<servlet-class>com.servlets.AchieveParamServletservlet-class>
<load-on-startup>1load-on-startup>
servlet>
<servlet-mapping>
<servlet-name>AchieveParamservlet-name>
<url-pattern>*.dourl-pattern>
servlet-mapping>
web-app>
Servlet处理类
package com.servlets; import java.io.IOException; import java.io.InputStream; import java.util.Enumeration; import java.util.Properties; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * 可以实现Servlet接口 * * @author yyx 2019年3月13日 */ public class AchieveParamServlet extends HttpServlet { private static final long serialVersionUID = 1L; private int count; @Override protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 设置输出内容的编码方式 response.setCharacterEncoding("UTF-8"); // 获得Session HttpSession httpSession = request.getSession(); // 获得ServletContext对象，读取全局参数 ServletContext servletContext = this.getServletContext(); String company = servletContext.getInitParameter("company"); httpSession.setAttribute("company", company); Enumerationnames = servletContext.getInitParameterNames(); while (names.hasMoreElements()) { String name = names.nextElement(); String value = servletContext.getInitParameter(name); System.out.println(value); } // web应用范围内共享数据,每调用一次方法都会加1 servletContext.setAttribute("count", count++); // 读取配置文件 InputStream is = servletContext.getResourceAsStream("/WEB-INF/classes/jdbc.properties"); Properties properties = new Properties(); properties.load(is); System.out.println(properties.getProperty("driverClass")); System.out.println(properties.getProperty("url")); is.close(); // 获取工程名称 System.out.println(servletContext.getContextPath()); // 转发 request.getRequestDispatcher("/success.jsp").forward(request, response); } @Override public void destroy() { super.destroy(); System.out.println("Servlet销毁"); } @Override public void init(ServletConfig config) throws ServletException { super.init(config); System.out.println("Servlet初始化"); } }
JSP页面
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title heretitle> head> <body> <a href="${pageContext.request.contextPath}/achieveparamservlet.do">获取参数a> body> html>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title heretitle> head> <body> <h2>${ company}h2> <h2>${ count}h2> body> html>