servlet,filter,sessionListener,cookie,session操作

最新推荐文章于 2024-08-31 16:31:35 发布

丿Nireus

最新推荐文章于 2024-08-31 16:31:35 发布

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本文详细介绍了Servlet、Filter和Session的基本配置方法及其实现原理。包括如何通过web.xml配置Servlet映射、初始化参数，Filter的配置及其工作流程，以及Session监听器的使用方法。

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感谢作者分享，文章转自“：http://blog.youkuaiyun.com/tengdazhang770960436/article/details/7075034

servlet配置:

过程:程序根据客户端发送过来的请求,获取客户端要访问的url里面代表访问文件的那一部分,之后去web.xml里面去查找,根据所匹配的<servlet-mapping>来获取对应的servlet-name,根据servlet-name去查找对应的servlet-class所在的位置,根据servlet-class的位置去调用它里面的方法,调用的时候是由apache来实现的.

web.xml中的配置:

<servlet>

<servlet-name>test</servlet-name>

<servlet-class>dada.test.FirstServlet</servlet-class>
<init-param>

<param-name>name</param-name>

<param-value>dada</param-value>
</init-param>
</servlet>

<servlet-mapping>

<servlet-name>test</servlet-name>

<url-pattern>/test</url-pattern>
</servlet-mapping>

servlet文件中处理:

private String name;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {}

@Override
public void init(ServletConfig config) throws ServletException {
name = config.getInitParameter("name");
System.out.println(name);
}

filter配置:

web.xml中的配置:

<filter>
<description>filter</description>
<filter-name>encoding</filter-name>
<filter-class>dada.test.EncodingFilter</filter-class>
<init-param>
<description>param</description>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

filter文件中处理:

//定义初始化的字符编码
private String encoding="ISO-8859-1";
@Override
public void destroy() {
this.encoding = null;
}

@Override
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
request.setCharacterEncoding(encoding);
System.out.println("当前的编码:"+request.getCharacterEncoding());
chain.doFilter(req, resp);
}

@Override
public void init(FilterConfig config) throws ServletException {
//获取初始化的参数
String encoding1 = config.getInitParameter("encoding");
System.out.println(encoding1);
this.encoding = encoding1==null||encoding1.equals("")?encoding:encoding1;
}

session配置:
web.xml

<listener>
<listener-class>
dada.CounterListener
</listener-class>
</listener>

CounterListener类:

public class CounterListener implements HttpSessionListener {
private static long onlineNumber = 0;

//开放获取在线人数的方法
public static long getOnlineNumber() {
return onlineNumber;
}
//当session创建时执行的方法
public void sessionCreated(HttpSessionEvent arg0) {
System.out.println("created");
onlineNumber++;
}
//当session销毁是执行的方法
public void sessionDestroyed(HttpSessionEvent arg0) {
System.out.println("created");
onlineNumber--;
}
}

调用监听器输出:

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@page import="dada.CounterListener"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
本网站目前访问人数:<%=CounterListener.getOnlineNumber()%>
</body>
</html>

Cookie操作:

setCookie:

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
Cookie cookie1 = new Cookie("username", username);
//cookie的有效期为1个月
cookie1.setMaxAge(24 * 60 * 60 * 30);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Cookie cookie2 = new Cookie("lastTime", sdf.format(new Date()));
cookie2.setMaxAge(24 * 60 * 60 * 30);
response.addCookie(cookie1);
response.addCookie(cookie2);
}

getCookie:

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Cookie[] cookies = request.getCookies();
Cookie cookie = null;
for (int i = 0; i < cookies.length; i++) {
cookie = cookies[i];
if (cookie.getName().equals("username")) {
out.println("用户名：" + cookie.getValue());
out.println(" ");
}
if (cookie.getName().equals("lastTime")) {
out.println("上次登录时间：" + cookie.getValue());
out.println(" ");
}
}
}

session操作:

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
Integer counter = (Integer) session.getAttribute("counter");
if (counter == null) {
counter = new Integer(1);
} else {
counter = new Integer(counter.intValue() + 1);
}
session.setAttribute("counter", counter);
session.setMaxInactiveInterval(3600);

response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
if (session.isNew()) {
out.println("这是一个新建的Session. ");
} else {
out.println("这不是一个新建的Session. ");
}
out.println("jsessionid: " + session.getId() + " ");
out.println("LastAccessedTime: " + session.getLastAccessedTime() + " ");
out.println("格式转换以后的LastAccessedTime: " + new Date(session.getLastAccessedTime()) + " ");
out.println("CreationTime: " + session.getCreationTime() + " ");
out.println("格式转换以后的CreationTime: " + new Date(session.getCreationTime()) + " ");
out.println("MaxInactiveInterval: " + session.getMaxInactiveInterval() + "秒 ");
out.println(" 使用Session对象的getAttributeNames ");
Enumeration enumer = session.getAttributeNames();
String name = null;
while (enumer.hasMoreElements()) {
name = (String) enumer.nextElement();
out.println("Session name:" + name + " ");
out.println("Session value:" + session.getAttribute(name) + " ");
}
// session.removeAttribute("counter");
// session.invalidate();
out.println("</body>");
out.println("</html>");
out.flush();
out.close();
}