ServletContextListener\u662f\u6211\u4eec\u62e5\u6709\u7684\u4f17\u591aServlet\u76d1\u542c\u5668\u4e4b\u4e00\u3002\u8fd9\u662fJava Web\u5e94\u7528\u7a0b\u5e8f\u7cfb\u5217\u4e2d\u7684\u7b2c\u4e94\u7bc7\u6587\u7ae0\uff0c\u60a8\u4e5f\u8bb8\u60f3\u67e5\u770b\u524d\u9762\u7684\u56db\u7bc7\u6587\u7ae0\u3002<\/p>\n
\u5728\u672c\u6559\u7a0b\u4e2d\uff0c\u6211\u4eec\u5c06\u7814\u7a76Servlet\u76d1\u542c\u5668\u3001Servlet\u76d1\u542c\u5668\u7684\u597d\u5904\u3001\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u76d1\u542c\u5668\u5b8c\u6210\u7684\u4e00\u4e9b\u5e38\u89c1\u4efb\u52a1\u3001Servlet API\u76d1\u542c\u5668\u63a5\u53e3\u548c\u4e8b\u4ef6\u5bf9\u8c61\u3002\u6700\u540e\uff0c\u6211\u4eec\u5c06\u521b\u5efa\u4e00\u4e2a\u7b80\u5355\u7684Web\u9879\u76ee\uff0c\u5c55\u793aServletContext\u3001Session\u548cServletRequest\u7684\u5e38\u7528\u76d1\u542c\u5668\u5b9e\u73b0\u7684\u793a\u4f8b\u3002<\/p>\n
\u6211\u4eec\u77e5\u9053\uff0c\u4f7f\u7528ServletContext\uff0c\u6211\u4eec\u53ef\u4ee5\u521b\u5efa\u4e00\u4e2a\u5177\u6709\u5e94\u7528\u7a0b\u5e8f\u8303\u56f4\u7684\u5c5e\u6027\uff0c\u6240\u6709\u5176\u4ed6servlet\u90fd\u53ef\u4ee5\u8bbf\u95ee\uff0c\u4f46\u6211\u4eec\u53ea\u80fd\u5728\u90e8\u7f72\u63cf\u8ff0\u7b26\uff08web.xml\uff09\u4e2d\u5c06ServletContext\u521d\u59cb\u5316\u53c2\u6570\u521d\u59cb\u5316\u4e3a\u5b57\u7b26\u4e32\u3002\u5982\u679c\u6211\u4eec\u7684\u5e94\u7528\u7a0b\u5e8f\u662f\u9762\u5411\u6570\u636e\u5e93\u7684\uff0c\u5e76\u4e14\u6211\u4eec\u60f3\u5728ServletContext\u4e2d\u8bbe\u7f6e\u4e00\u4e2a\u7528\u4e8e\u6570\u636e\u5e93\u8fde\u63a5\u7684\u5c5e\u6027\uff0c\u90a3\u8be5\u600e\u4e48\u529e\u5462\uff1f\u5982\u679c\u60a8\u7684\u5e94\u7528\u7a0b\u5e8f\u53ea\u6709\u4e00\u4e2a\u5165\u53e3\u70b9\uff08\u7528\u6237\u767b\u5f55\uff09\uff0c\u90a3\u4e48\u60a8\u53ef\u4ee5\u5728\u7b2c\u4e00\u4e2aservlet\u8bf7\u6c42\u4e2d\u8fdb\u884c\u8bbe\u7f6e\uff0c\u4f46\u5982\u679c\u6211\u4eec\u6709\u591a\u4e2a\u5165\u53e3\u70b9\uff0c\u90a3\u4e48\u5728\u6bcf\u4e2a\u5730\u65b9\u90fd\u8fdb\u884c\u8bbe\u7f6e\u5c06\u5bfc\u81f4\u5927\u91cf\u7684\u4ee3\u7801\u5197\u4f59\u3002\u6b64\u5916\uff0c\u5982\u679c\u6570\u636e\u5e93\u5173\u95ed\u6216\u914d\u7f6e\u4e0d\u6b63\u786e\uff0c\u6211\u4eec\u5c06\u4e0d\u4f1a\u77e5\u9053\uff0c\u76f4\u5230\u7b2c\u4e00\u4e2a\u5ba2\u6237\u7aef\u8bf7\u6c42\u5230\u8fbe\u670d\u52a1\u5668\u3002\u4e3a\u4e86\u5904\u7406\u8fd9\u4e9b\u60c5\u51b5\uff0cservlet API\u63d0\u4f9b\u4e86\u53ef\u4ee5\u5b9e\u73b0\u548c\u914d\u7f6e\u4ee5\u4fa6\u542c\u4e8b\u4ef6\u5e76\u6267\u884c\u67d0\u4e9b\u64cd\u4f5c\u7684\u4fa6\u542c\u5668\u63a5\u53e3\u3002\u4e8b\u4ef6\u662f\u53d1\u751f\u7684\u67d0\u4e2a\u4e8b\u60c5\uff0c\u5728Web\u5e94\u7528\u7a0b\u5e8f\u4e16\u754c\u4e2d\uff0c\u4e8b\u4ef6\u53ef\u4ee5\u662f\u5e94\u7528\u7a0b\u5e8f\u7684\u521d\u59cb\u5316\u3001\u9500\u6bc1\u5e94\u7528\u7a0b\u5e8f\u3001\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u8bf7\u6c42\u3001\u521b\u5efa\/\u9500\u6bc1\u4f1a\u8bdd\u3001\u4f1a\u8bdd\u4e2d\u7684\u5c5e\u6027\u4fee\u6539\u7b49\u3002Servlet API\u63d0\u4f9b\u4e86\u4e0d\u540c\u7c7b\u578b\u7684\u4fa6\u542c\u5668\u63a5\u53e3\uff0c\u6211\u4eec\u53ef\u4ee5\u5728web.xml\u4e2d\u5b9e\u73b0\u548c\u914d\u7f6e\uff0c\u4ee5\u5728\u7279\u5b9a\u4e8b\u4ef6\u53d1\u751f\u65f6\u8fdb\u884c\u5904\u7406\u3002\u4f8b\u5982\uff0c\u5728\u4e0a\u8ff0\u60c5\u51b5\u4e2d\uff0c\u6211\u4eec\u53ef\u4ee5\u521b\u5efa\u4e00\u4e2a\u4fa6\u542c\u5668\u7528\u4e8e\u5e94\u7528\u7a0b\u5e8f\u542f\u52a8\u4e8b\u4ef6\uff0c\u4ee5\u8bfb\u53d6\u4e0a\u4e0b\u6587\u521d\u59cb\u5316\u53c2\u6570\u5e76\u521b\u5efa\u6570\u636e\u5e93\u8fde\u63a5\uff0c\u5e76\u5c06\u5176\u8bbe\u7f6e\u4e3a\u4e0a\u4e0b\u6587\u5c5e\u6027\uff0c\u4f9b\u5176\u4ed6\u8d44\u6e90\u4f7f\u7528\u3002<\/p>\n
Servlet API\u4e3a\u4e0d\u540c\u7c7b\u578b\u7684\u4e8b\u4ef6\u63d0\u4f9b\u4e86\u4e0d\u540c\u7c7b\u578b\u7684\u76d1\u542c\u5668\u3002\u76d1\u542c\u5668\u63a5\u53e3\u58f0\u660e\u4e86\u4e0e\u4e00\u7ec4\u7c7b\u4f3c\u4e8b\u4ef6\u4e00\u8d77\u5de5\u4f5c\u7684\u65b9\u6cd5\uff0c\u4f8b\u5982\u6211\u4eec\u6709ServletContext\u76d1\u542c\u5668\u6765\u76d1\u542c\u4e0a\u4e0b\u6587\u7684\u542f\u52a8\u548c\u5173\u95ed\u4e8b\u4ef6\u3002\u76d1\u542c\u5668\u63a5\u53e3\u4e2d\u7684\u6bcf\u4e2a\u65b9\u6cd5\u90fd\u4ee5\u4e8b\u4ef6\u5bf9\u8c61\u4f5c\u4e3a\u8f93\u5165\u3002\u4e8b\u4ef6\u5bf9\u8c61\u4f5c\u4e3a\u4e00\u4e2a\u5305\u88c5\u5668\uff0c\u4e3a\u76d1\u542c\u5668\u63d0\u4f9b\u7279\u5b9a\u7684\u5bf9\u8c61\u3002Servlet API\u63d0\u4f9b\u4e86\u4ee5\u4e0b\u4e8b\u4ef6\u5bf9\u8c61\u3002<\/p>\n
\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528@WebListener\u6ce8\u89e3\u5c06\u4e00\u4e2a\u7c7b\u58f0\u660e\u4e3a\u76d1\u542c\u5668\uff0c\u4f46\u662f\u8fd9\u4e2a\u7c7b\u5e94\u8be5\u5b9e\u73b0\u4e00\u4e2a\u6216\u591a\u4e2a\u76d1\u542c\u5668\u63a5\u53e3\u3002\u6211\u4eec\u53ef\u4ee5\u5728web.xml\u4e2d\u5b9a\u4e49\u76d1\u542c\u5668\uff1a<\/p>\n
<listener>\r\n <listener-class>\r\n com.Olivia.listener.AppContextListener\r\n <\/listener-class>\r\n<\/listener>\r\n<\/code><\/pre>\nServlet\u76d1\u542c\u5668\u793a\u4f8b<\/h3>\n
\u6211\u4eec\u6765\u521b\u5efa\u4e00\u4e2a\u7b80\u5355\u7684Web\u5e94\u7528\u7a0b\u5e8f\u6765\u67e5\u770bServlet\u76d1\u542c\u5668\u7684\u529f\u80fd\u3002\u6211\u4eec\u5c06\u5728Eclipse\u4e2d\u521b\u5efa\u4e00\u4e2a\u52a8\u6001Web\u9879\u76ee\uff0cServletListenerExample\uff0c\u8be5\u9879\u76ee\u7ed3\u6784\u5c06\u5982\u4e0b\u56fe\u6240\u793a\u3002web.xml\uff1a\u5728\u90e8\u7f72\u63cf\u8ff0\u7b26\u4e2d\uff0c\u6211\u5c06\u5b9a\u4e49\u4e00\u4e9b\u4e0a\u4e0b\u6587init\u53c2\u6570\u548c\u76d1\u542c\u5668\u914d\u7f6e\u3002<\/p>\n
<?xml version=\"1.0\" encoding=\"UTF-8\"?>\r\n<web-app xmlns:xsi=\"https:\/\/www.w3.org\/2001\/XMLSchema-instance\" xmlns=\"https:\/\/java.sun.com\/xml\/ns\/javaee\" xsi:schemaLocation=\"https:\/\/java.sun.com\/xml\/ns\/javaee https:\/\/java.sun.com\/xml\/ns\/javaee\/web-app_3_0.xsd\" id=\"WebApp_ID\" version=\"3.0\">\r\n <display-name>ServletListenerExample<\/display-name>\r\n \r\n <context-param>\r\n <param-name>DBUSER<\/param-name>\r\n <param-value>scdev<\/param-value>\r\n <\/context-param>\r\n <context-param>\r\n <param-name>DBPWD<\/param-name>\r\n <param-value>password<\/param-value>\r\n <\/context-param>\r\n <context-param>\r\n <param-name>DBURL<\/param-name>\r\n <param-value>jdbc:mysql:\/\/localhost\/mysql_db<\/param-value>\r\n <\/context-param>\r\n \r\n <listener>\r\n <listener-class>com.Olivia.listener.AppContextListener<\/listener-class>\r\n <\/listener>\r\n <listener>\r\n <listener-class>com.Olivia.listener.AppContextAttributeListener<\/listener-class>\r\n <\/listener>\r\n <listener>\r\n <listener-class>com.Olivia.listener.MySessionListener<\/listener-class>\r\n <\/listener>\r\n <listener>\r\n <listener-class>com.Olivia.listener.MyServletRequestListener<\/listener-class>\r\n <\/listener>\r\n<\/web-app>\r\n<\/code><\/pre>\nDBConnectionManager<\/h4>\n
\u8fd9\u662f\u7528\u4e8e\u6570\u636e\u5e93\u8fde\u63a5\u7684\u7c7b\uff0c\u4e3a\u4e86\u7b80\u5355\u8d77\u89c1\uff0c\u6211\u6ca1\u6709\u63d0\u4f9b\u5b9e\u9645\u6570\u636e\u5e93\u8fde\u63a5\u7684\u4ee3\u7801\u3002\u6211\u4eec\u5c06\u628a\u6b64\u5bf9\u8c61\u8bbe\u7f6e\u4e3aServlet\u4e0a\u4e0b\u6587\u7684\u5c5e\u6027\u3002<\/p>\n
package com.Olivia.db;\r\n\r\nimport java.sql.Connection;\r\n\r\npublic class DBConnectionManager {\r\n\r\n\tprivate String dbURL;\r\n\tprivate String user;\r\n\tprivate String password;\r\n\tprivate Connection con;\r\n\t\r\n\tpublic DBConnectionManager(String url, String u, String p){\r\n\t\tthis.dbURL=url;\r\n\t\tthis.user=u;\r\n\t\tthis.password=p;\r\n\t\t\/\/create db connection now\r\n\t}\r\n\t\r\n\tpublic Connection getConnection(){\r\n\t\treturn this.con;\r\n\t}\r\n\t\r\n\tpublic void closeConnection(){\r\n\t\t\/\/close DB connection here\r\n\t}\r\n}\r\n<\/code><\/pre>\nMyServlet<\/h4>\n
\u4e00\u4e2a\u7b80\u5355\u7684Servlet\u7c7b\uff0c\u6211\u5c06\u5728\u5176\u4e2d\u5904\u7406\u4f1a\u8bdd\u3001\u5c5e\u6027\u7b49\u3002<\/p>\n
package com.Olivia.servlet;\r\n\r\nimport java.io.IOException;\r\nimport java.io.PrintWriter;\r\n\r\nimport javax.servlet.ServletContext;\r\nimport javax.servlet.ServletException;\r\nimport javax.servlet.annotation.WebServlet;\r\nimport javax.servlet.http.HttpServlet;\r\nimport javax.servlet.http.HttpServletRequest;\r\nimport javax.servlet.http.HttpServletResponse;\r\nimport javax.servlet.http.HttpSession;\r\n\r\n@WebServlet(\"\/MyServlet\")\r\npublic class MyServlet extends HttpServlet {\r\n\tprivate static final long serialVersionUID = 1L;\r\n \r\n\tprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {\r\n\t\t\tServletContext ctx = request.getServletContext();\r\n\t\t\tctx.setAttribute(\"User\", \"Pankaj\");\r\n\t\t\tString user = (String) ctx.getAttribute(\"User\");\r\n\t\t\tctx.removeAttribute(\"User\");\r\n\t\t\t\r\n\t\t\tHttpSession session = request.getSession();\r\n\t\t\tsession.invalidate();\r\n\t\t\t\r\n\t\t\tPrintWriter out = response.getWriter();\r\n\t\t\tout.write(\"Hi \"+user);\r\n\t}\r\n}\r\n<\/code><\/pre>\n\u73b0\u5728\u6211\u4eec\u5c06\u5b9e\u73b0\u76d1\u542c\u5668\u7c7b\uff0c\u4e3a\u5e38\u7528\u7684\u76d1\u542c\u5668\u63d0\u4f9b\u793a\u4f8b\u76d1\u542c\u5668\u7c7b-ServletContextListener\u3001ServletContextAttributeListener\u3001ServletRequestListener\u548cHttpSessionListener\u3002<\/p>\n
ServletContextListener<\/h4>\n
\u6211\u4eec\u5c06\u8bfb\u53d6servlet\u4e0a\u4e0b\u6587\u521d\u59cb\u5316\u53c2\u6570\u6765\u521b\u5efaDBConnectionManager\u5bf9\u8c61\uff0c\u5e76\u5c06\u5176\u8bbe\u7f6e\u4e3aServletContext\u5bf9\u8c61\u7684\u5c5e\u6027\u3002<\/p>\n
package com.Olivia.listener;\r\n\r\nimport javax.servlet.ServletContext;\r\nimport javax.servlet.ServletContextEvent;\r\nimport javax.servlet.ServletContextListener;\r\nimport javax.servlet.annotation.WebListener;\r\n\r\nimport com.Olivia.db.DBConnectionManager;\r\n\r\n@WebListener\r\npublic class AppContextListener implements ServletContextListener {\r\n\r\n public void contextInitialized(ServletContextEvent servletContextEvent) {\r\n \tServletContext ctx = servletContextEvent.getServletContext();\r\n \t\r\n \tString url = ctx.getInitParameter(\"DBURL\");\r\n \tString u = ctx.getInitParameter(\"DBUSER\");\r\n \tString p = ctx.getInitParameter(\"DBPWD\");\r\n \t\r\n \t\/\/create database connection from init parameters and set it to context\r\n \tDBConnectionManager dbManager = new DBConnectionManager(url, u, p);\r\n \tctx.setAttribute(\"DBManager\", dbManager);\r\n \tSystem.out.println(\"Database connection initialized for Application.\");\r\n }\r\n\r\n public void contextDestroyed(ServletContextEvent servletContextEvent) {\r\n \tServletContext ctx = servletContextEvent.getServletContext();\r\n \tDBConnectionManager dbManager = (DBConnectionManager) ctx.getAttribute(\"DBManager\");\r\n \tdbManager.closeConnection();\r\n \tSystem.out.println(\"Database connection closed for Application.\");\r\n }\r\n}\r\n<\/code><\/pre>\nServletContextAttributeListener<\/h4>\n
\u5728servlet\u4e0a\u4e0b\u6587\u4e2d\uff0c\u5f53\u5c5e\u6027\u6dfb\u52a0\u3001\u5220\u9664\u6216\u66ff\u6362\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528\u7b80\u5355\u7684\u5b9e\u73b0\u6765\u8bb0\u5f55\u4e8b\u4ef6\u3002<\/p>\n
package com.Olivia.listener;\r\n\r\nimport javax.servlet.ServletContextAttributeEvent;\r\nimport javax.servlet.ServletContextAttributeListener;\r\nimport javax.servlet.annotation.WebListener;\r\n\r\n@WebListener\r\npublic class AppContextAttributeListener implements ServletContextAttributeListener {\r\n\r\n public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {\r\n \tSystem.out.println(\"ServletContext attribute added::{\"+servletContextAttributeEvent.getName()+\",\"+servletContextAttributeEvent.getValue()+\"}\");\r\n }\r\n\r\n public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {\r\n \tSystem.out.println(\"ServletContext attribute replaced::{\"+servletContextAttributeEvent.getName()+\",\"+servletContextAttributeEvent.getValue()+\"}\");\r\n }\r\n\r\n public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {\r\n \tSystem.out.println(\"ServletContext attribute removed::{\"+servletContextAttributeEvent.getName()+\",\"+servletContextAttributeEvent.getValue()+\"}\");\r\n }\r\n}\r\n<\/code><\/pre>\nHttpSessionListener<\/h4>\n
\u5f53\u4f1a\u8bdd\u521b\u5efa\u6216\u9500\u6bc1\u65f6\uff0c\u8bb0\u5f55\u8be5\u4e8b\u4ef6\u7684\u7b80\u5355\u5b9e\u73b0\u3002<\/p>\n
package com.Olivia.listener;\r\n\r\nimport javax.servlet.annotation.WebListener;\r\nimport javax.servlet.http.HttpSessionEvent;\r\nimport javax.servlet.http.HttpSessionListener;\r\n\r\n@WebListener\r\npublic class MySessionListener implements HttpSessionListener {\r\n\r\n public void sessionCreated(HttpSessionEvent sessionEvent) {\r\n \tSystem.out.println(\"Session Created:: ID=\"+sessionEvent.getSession().getId());\r\n }\r\n\r\n public void sessionDestroyed(HttpSessionEvent sessionEvent) {\r\n \tSystem.out.println(\"Session Destroyed:: ID=\"+sessionEvent.getSession().getId());\r\n }\r\n}\r\n<\/code><\/pre>\nServletRequestListener<\/h4>\n
\u5f53\u8bf7\u6c42\u521d\u59cb\u5316\u548c\u9500\u6bc1\u65f6\uff0c\u4f7f\u7528ServletRequestListener\u63a5\u53e3\u7684\u7b80\u5355\u5b9e\u73b0\u8bb0\u5f55ServletRequest\u7684IP\u5730\u5740\u3002<\/p>\n
package com.Olivia.listener;\r\n\r\nimport javax.servlet.ServletRequest;\r\nimport javax.servlet.ServletRequestEvent;\r\nimport javax.servlet.ServletRequestListener;\r\nimport javax.servlet.annotation.WebListener;\r\n\r\n@WebListener\r\npublic class MyServletRequestListener implements ServletRequestListener {\r\n\r\n public void requestDestroyed(ServletRequestEvent servletRequestEvent) {\r\n \tServletRequest servletRequest = servletRequestEvent.getServletRequest();\r\n \tSystem.out.println(\"ServletRequest destroyed. Remote IP=\"+servletRequest.getRemoteAddr());\r\n }\r\n\r\n public void requestInitialized(ServletRequestEvent servletRequestEvent) {\r\n \tServletRequest servletRequest = servletRequestEvent.getServletRequest();\r\n \tSystem.out.println(\"ServletRequest initialized. Remote IP=\"+servletRequest.getRemoteAddr());\r\n }\r\n}\r\n<\/code><\/pre>\n\u8fd0\u884c\u7ed3\u679c<\/h4>\n