ServletContext简易模拟实现服务器访问量统计
ServletContext可以读取,设置全局变量,让每个Servlet都可以使用
而对应的ServletConfig和Servlet是一对一的关系
package contextdemo;
import java.io.IOException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletContextDemo extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//Tomcat启动时会创建唯一的context,并且会调用它的方法
//读取web.xml中公用的参数。context是全局的,任何servle都可以使用
ServletContext context = getServletContext();
String size = context.getInitParameter("size");
System.out.println("分页查询部门信息");
System.out.println(size);
Integer count = (Integer)context.getAttribute("count");
context.setAttribute("count", ++count);
System.out.println("服务器共访问了"+count+"次");
}
}
package contextdemo;
import java.io.IOException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletContextDemo2 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//Tomcat启动时会创建唯一的context,并且会调用它的方法
//读取web.xml中公用的参数。context是全局的,任何servle都可以使用
ServletContext context = getServletContext();
String size = context.getInitParameter("size");
System.out.println("分页查询员工信息");
System.out.println(size);
Integer count = (Integer)context.getAttribute("count");
context.setAttribute("count", ++count);
System.out.println("服务器共访问了"+count+"次");
}
}
package contextdemo;
import java.io.IOException;
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;
/**
* 该servlet不处理具体的业务逻辑,
*只在Tomcat启动时负责初始化数据
*一般每个项目中都有一到两个这种servlet
* @author Fly
*
*/
public class InitServlet extends HttpServlet {
@Override
public void init(ServletConfig config) throws ServletException {
super.init(config);
//Tomcat启动时会有先创建context,后在创建Servlet
ServletContext ctx = getServletContext();
ctx.setAttribute("count", 0);
}
}
<servlet>
<servlet-name>finddept</servlet-name>
<servlet-class>contextdemo.ServletContextDemo</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>finddept</servlet-name>
<url-pattern>/finddept</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>findemp</servlet-name>
<servlet-class>contextdemo.ServletContextDemo2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>findemp</servlet-name>
<url-pattern>/findemp</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>init</servlet-name>
<servlet-class>contextdemo.InitServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>