监听包括三种情况,分别是HttpRequest、Session、ServletContext监听。
常用的是implements servletContextListener(全局变量)两个方法
public void contextInitialized(ServletContextEvent arg0)
arg0.getServletContext()
Session监听事件所示:
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import com.kettas.upp02.util.Constant;
public class SessionListener implements HttpSessionListener {
public void sessionCreated(HttpSessionEvent ent) {
HttpSession session = ent.getSession();
synchronized (this) {
ServletContext ctx = session.getServletContext();
Integer counter = (Integer) ctx.getAttribute("sessionCount");
ctx.setAttribute("sessionCount", counter.intValue() + 1);
System.out.println(Constant.LOGO + "SessionCount:"
+ (counter.intValue() + 1));
}}
public void sessionDestroyed(HttpSessionEvent ent) {
HttpSession session = ent.getSession();
synchronized (this) {
ServletContext ctx = session.getServletContext();
Integer counter = (Integer) ctx.getAttribute("sessionCount");
ctx.setAttribute("sessionCount", counter.intValue() - 1);
System.out.println(Constant.LOGO + "SessionCount:"
+ (counter.intValue() - 1));
}
}
}
在web.xml文件中配置如下:
<listener>
<listener-class>shop. SessionListener </listener-class>
</listener>
其他两个监听事件的实现同上并无二致。
过滤器 // 实现Filter接口
import java.io.IOException;
import javax.servlet.*;
public class EncodingFilter implements Filter{
//销毁时执行,没必要覆盖
public void destroy() {}
//发送请求时执行
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//设置发送请求和接收请求时的编码方式,统一才能达到过滤作用
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
try {
chain.doFilter(request, response); 请求转发
} catch (RuntimeException e) {
e.printStackTrace();
}}
//加载时执行,也没必要执行
public void init(FilterConfig arg0) throws ServletException {}
}
web.xml文件中:
//配置当发生什么要的请求时,让那个过滤流执行操作
<filter>
<filter-name>encodingFilter</filter-name>
<filter-class>filter.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
原文地址:https://www.cnblogs.com/yuyu666/p/9743904.html
时间: 2024-10-18 04:28:41