Web三大知识——关于Application

• 在API中对应的接口：servletcontext 相当于整个webapp在运行过程中的表现
• 类似在设置全局变量
  我们来看一个小例子

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class TestServletContext extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter out = resp.getWriter();
        ServletContext application = this.getServletContext();
        Integer accessCount = (Integer) application.getAttribute("accessCount");
        if (accessCount == null){
            accessCount = new Integer(0);
        }else {
            accessCount = new Integer(accessCount.intValue()+1);
        }
        application.setAttribute("accessCount",accessCount);
        out.println(accessCount);
    }
}

• 补充小知识点：
  当servlet在某个包里的时候，在配置web.xml的时候一定要写全了，即在servlet-class名字处写清楚包名.xxx

请求转发，页面跳转之类，等我们学过jsp在开始