释放双眼,带上耳机,听听看~!
概述
在开发中访问到一个web资源后,需要服务器跳转到另一个资源去处理请求,可以通过sendRedirect重定向方法来实现,也可RequestDispatcher转发对象的forward方法来实现
得到转发对象:RequestDispatcher forwardObj = request.getRequestDisapatcher(“另外一个资源的路径”)
常用的方法:
- 实现请求转发:forwardObj.forward(request,response)
- 实现请求集合:forwardObj》include(request,response)
请求转发
这里要注意重定向与请求转发的区别
重定向是请求到第一台服务器,立马反应给浏览器,告诉浏览器需要访问另外一台服务器,然后服务器再自发访问
请求转发是请求到第一台服务器,由服务器主动进行转发访问,然后由第二台服务器将数据反应回来
package p01;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Forward_2 extends HttpServlet {
private static final long serialVersionUID = 1L;
public Forward_2() {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
//转发是不用写文件路径的,直接写文件名
RequestDispatcher req = request.getRequestDispatcher("/fordward_re");
response.getWriter().print("转发前……");
request.setAttribute("name", "LL");
req.forward(request, response);
//req.include(request, response);
response.getWriter().print("转发后……");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
package p01;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class fordward_re
*/
public class fordward_re extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public fordward_re() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
Object o = request.getAttribute("name");
String name = (String) o;
response.getWriter().print(name);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
结果:只返回转发后页面的内容
## 请求包含
结果将返回原页面+转发后页面的所有输出内容
package p01;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Forward_2 extends HttpServlet {
private static final long serialVersionUID = 1L;
public Forward_2() {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
//转发是不用写文件路径的,直接写文件名
RequestDispatcher req = request.getRequestDispatcher("/fordward_re");
response.getWriter().print("转发前……");
request.setAttribute("name", "LL");
//req.forward(request, response);
req.include(request, response);
response.getWriter().print("转发后……");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
package p01;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class fordward_re
*/
public class fordward_re extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public fordward_re() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
Object o = request.getAttribute("name");
String name = (String) o;
response.getWriter().print(name);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}