Request和Response学习笔记5

服务器内部请求的转发

这里请求传递所使用的方法：

// 通过request对象获取请求转发器对象
RequestDispatcher getRequestDispatcher(String path)

// 使用RequestDispatcher对象来进行转发
forward(ServletRequest request, ServletResponse response) 

实例引入

1. 创建一个Web项目：RequestDelivery

2. 创建两个类，在这两个类之间进行请求的传递：

   1. RequestDemo01.java

      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;
      
      @WebServlet("/demo01")
      public class RequestDemo01 extends HttpServlet {
          @Override
          protected void doGet(HttpServletRequest request, HttpServletResponse response)
                  throws ServletException, IOException {
              System.out.println("demo01被访问了！");
              // 获取请求发送对象
              RequestDispatcher requestDispatcher = request.getRequestDispatcher("/demo02");
              // 发送请求
              requestDispatcher.forward(request, response);
          }
          @Override
          protected void doPost(HttpServletRequest request, HttpServletResponse response)
                  throws ServletException, IOException {
              this.doGet(request, response);
          }
      }
      
      

   2. RequestDemo02.java

      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;
      
      @WebServlet("/demo02")
      public class RequestDemo02 extends HttpServlet {
          @Override
          protected void doGet(HttpServletRequest request, HttpServletResponse response)
                  throws ServletException, IOException {
              System.out.println("我是demo02，demo01的请求对象已经传递过来了！");
          }
          @Override
          protected void doPost(HttpServletRequest request, HttpServletResponse response)
                  throws ServletException, IOException {
              this.doGet(request, response);
          }
      }
      

3. 启动服务器，访问：http://localhost:8080/RequestDelivery_war_exploded/demo01

   控制台输出：

   demo01被访问了！
   我是demo02，demo01的请求对象已经传递过来了！
   

   页面不会跳转，还在在demo1页面。

特点

1. 浏览器地址栏路径不发生变化
2. 只能转发到当前服务器内部资源中。不能转发到其他服务器。
3. 用户的发送请求是一次，被转发的请求也是用户发送的请求对象。

Request共享数据

1. 备注：

   • 域对象：一个有作用范围的对象，可以在一定范围内共享数据。
   • request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据。

2. 方法：

   // 存储数据
   void setAttribute(String name,Object obj)
   
   // 通过键获取值
   Object getAttitude(String name)
   
   // 通过键移除键值对
   void removeAttribute(String name)
   

实例引入

创建两类：

1. RequestDemo03.java

   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;
   
   @WebServlet("/demo03")
   public class RequestDemo03 extends HttpServlet {
       @Override
       protected void doGet(HttpServletRequest request, HttpServletResponse response)
               throws ServletException, IOException {
           System.out.println("demo03被访问了！");
           // 获取请求发送对象
           RequestDispatcher requestDispatcher = request.getRequestDispatcher("/demo04");
           // 发送请求
           requestDispatcher.forward(request, response);
       }
       @Override
       protected void doPost(HttpServletRequest request, HttpServletResponse response)
               throws ServletException, IOException {
           this.doGet(request, response);
       }
   }
   

2. RequestDemo04.java

   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;
   
   @WebServlet("/demo04")
   public class RequestDemo04 extends HttpServlet {
       @Override
       protected void doGet(HttpServletRequest request, HttpServletResponse response)
               throws ServletException, IOException {
           System.out.println("我是demo04，demo03的请求对象已经传递过来了！");
       }
       @Override
       protected void doPost(HttpServletRequest request, HttpServletResponse response)
               throws ServletException, IOException {
           this.doGet(request, response);
       }
   }
   

存储数据

1. 修改RequestDemo03.java中的doGet()方法：

   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       System.out.println("demo03被访问了！");
       // 存储数据到request域中
       request.setAttribute("Set's Message", "Hello, setAttribute!");
   
       // 获取请求发送对象
       RequestDispatcher requestDispatcher = request.getRequestDispatcher("/demo04");
       // 发送请求
       requestDispatcher.forward(request, response);
   }
   

2. 修改RequestDemo04.java中的doGet()方法：

   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       System.out.println("我是demo04，demo03的请求对象已经传递过来了！");
       // 获取request域数据
       System.out.println(request.getAttribute("Set's Message"));
   }
   

3. 启动服务器，访问：http://localhost:8080/RequestDelivery_war_exploded/demo03

   控制台输出：

   demo03被访问了！
   我是demo04，demo03的请求对象已经传递过来了！
   Hello, setAttribute!
   

参考文献

无