Servlet共享数据

共享数据：

　　1.域对象：有一个作用范围的对象，可以在范围内共享数据

　　2.request域：代表一次请求范围，一般用于请求转发的多个资源中共享数据

　　方法：

　　　　1.存储数据：setAttrbute(String name,Object obj)

　　　　2.通过键获取值：Object getAttitude(String name)

　　　　3.通过键移除值：void RemoveAttribute(String name)

代码实现：

跳转前代码：

 import javax.servlet.RequestDispatcher;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;

 /**
  * @Author: 艾康
  * @Date: 2019/10/15 14:35
  */
 @WebServlet("/servlettest3")
 public class ServletTest3 extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     //点击登录后跳转到另一个html
         //步骤：
         //1.存储对象
         request.setAttribute("username","ads");
         //2.通过request对象获取请求转发器对象
         RequestDispatcher requestDispatcher = request.getRequestDispatcher("/servlettest4");
         //2.使用RequestDispatcher对象进行转发
         requestDispatcher.forward(request,response);
     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         this.doPost(request,response);
     }
 }

跳转后代码：

 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;

 /**
  * @Author: 艾康
  * @Date: 2019/10/15 14:49
  */
 @WebServlet("/servlettest4")
 public class ServletTest4 extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         System.out.println(request.getAttribute("username"));
     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     this.doPost(request,response);
     }
 }

　　　　4.获取ServletContext对象：

         ServletContext servletContext = request.getServletContext();
         System.out.println(servletContext);