概念:
请求转发,是内部资源跳转的一个过程。
我们在实际的开发过程中,需要写不同的servlet,每个servlet完成不同的功能,当我们访问test01servlet的时候,test01servelt需要跳转到一个新的test02servlet里面,这就是资源跳转的方式,就用到了请求转发。
原理图:
实例如下:
test01:
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;
// 转发
@WebServlet("/test01")
public class Test05 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("转发演示");
// 1、获取request的请求转发器,内部参数为转发的路径
RequestDispatcher dispatcher = request.getRequestDispatcher("/test02");
// 2、调用转发器对象,传入参数request和response
dispatcher.forward(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
test02:
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("/test02")
public class Test06 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("转发之后");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
结果如下:
特点:
- 浏览器地址栏不发生变化
- 只能转发当前服务器的内部资源,不能转发致服务器的外部资源
- 转发只是一次请求,多个资源之间使用同一个请求
数据共享:
一次请求的范围,数据可进行传输的范围,一般用于请求转发多个资源中共享数据
- 存储数据:setAttribute(“money”,“50两”)
- 通过名字获取值:getAttribute(“money”)
- 通过键名移除键值对:removeAttribute(“money”)
实例如下:
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;
// 转发
@WebServlet("/test05")
public class Test05 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("转发演示");
request.setAttribute("money","50两");
// request.removeAttribute("money");
// 1、获取request的请求转发器,内部参数为转发的路径
RequestDispatcher dispatcher = request.getRequestDispatcher("/test06");
// 2、调用转发器对象,传入参数request和response
dispatcher.forward(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
转发后:
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("/test06")
public class Test06 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("转发之后");
Object money = request.getAttribute("money");
System.out.println(money);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
结果如下,成功获取到值:
重定向:
概念:
重定向:一个web资源收到客户端的请求后,通知客户端去访问另外一个web资源,这称之为请求重定向。
原理图:
特点:
- 地址栏发生变化
- 重定向可以访问其他服务器的资源
- 重定向是两次请求,所以不能用request域共享资源
方法一如下:
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("/test08")
public class Test08 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setStatus(302);
response.setHeader("location","/test09");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
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("/test09")
public class Test09 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("重定向过来的");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
结果如下,页面自动跳转到重定向后的页面:
方法二如下:
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("/test08")
public class Test08 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// response.setStatus(302);
// response.setHeader("location","/test09");
System.out.println("重定向之前");
response.sendRedirect("http://www.baidu.com");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
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("/test09")
public class Test09 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("重定向过来的");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
结果如下,页面自动跳转到重定向后的页面: