[Java知识库]Servlet学习（八）：请求转发（两个servlet程序的交互）

?请求转发的流程图：

具体代码：

Servlet1.java

package demo01;

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

/**
 * 用于实现请求转发
 */
public class Servlet1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String username = request.getParameter("username");
        System.out.println("在servlet1中查看参数："+username);

//        给材料盖个章，并传递到servlet2中查看
        request.setAttribute("key1","柜台1的章");
        //  请求转发必须以/打头
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/servlet2");
        requestDispatcher.forward(request,response);
    }
}

Servlet2.java：

package demo01;

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

/**
 * 用于实现请求转发
 */


public class Servlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String username = request.getParameter("username");
        System.out.println("在servlet2中查看材料:"+username);

        Object key1 = request.getAttribute("key1");
        System.out.println("柜台1是否有章:"+key1);

        //然后可以处理自己的业务

    }
}

最主要的是setAttribute()和getAttribute()方法

setAttribute()相当于将值作为参数绑定给request，然后再在Servlet2中获取。?

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