Servlet中的重定向和请求分派.doc

1.重定向在Servlet中的接口HttpServletRequest提供了sendRedirect()方法用于生成302相应码和Location响应头，从而通知客户端去重新访问Location响应头指定的URL，其定义如下：public void sendRedirect(String location ) throws IOException; 对于sendRedirect()方法不仅可以重定向到当前应用程序中的其他资源，也可重定向到一个容器中的其他应用程序中的资源。eg:/Servlet1.javapackage com.lkh.redrect;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 Servlet1 extends HttpServlet Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException / TODO Auto-generated method stub this.doPost(request, response); Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException / TODO Auto-generated method stub response.sendRedirect(Servlet2); /重定向到指定路径的资源 / RequestDispatcher dis=request.getRequestDispatcher(Servlet2); / dis.forward(request, response); /Servlet2.javapackage com.lkh.redrect;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class Servlet2 extends HttpServlet Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException / TODO Auto-generated method stub this.doPost(request, response); Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException / TODO Auto-generated method stub response.setContentType(text/html;charset=utf-8); PrintWriter out = response.getWriter(); out.println(); out.println( servlet2); out.println( ); out.println(从Servlet2中获取请求参数name的值：); out.println(request.getParameter(name); out.println( ); out.println(); 同时要在项目中的web.xml对Servlet进行声明： Servlet1 com.lkh.redrect.Servlet1 Servlet1 /Servlet1 Servlet2 com.lkh.redrect.Servlet2 Servlet2 /Servlet22.请求分派在Servlet中定义一个接口RequestDispatcher其方法如下：public void forward(ServletRequest request,ServletResponse response) throws ServletException,IOException;public void include(ServletRequest request,ServletResponse response) throws ServletException,IOException;对于forward()方法用于将请求转发到RequestDispatcher实例封装的资源，include()方法用于将RequestDispatcher实例封装的资源作为当前响应的一部分包含进来。获取RequestDispatcher实例的方式有两种：(1)调用ServletContext接口提供的getRequestDispatcher(String url) 方法(2)调用ServletRequest接口提供的getRequestDispatcher(String url) 方法ServletContext接口提供的getRequestDispatcher(String url) 方法中的路径参数必须以”/开头ServletRequest接口提供的getRequestDispatcher(String url) 方法中的路径参数可以是相对路径也可为绝对路径。eg:只要将上面中的Servlet1.java 中的doPost()代码改为RequestDispatcher dis=request.getRequestDispatcher(Servlet2);dis.forward(request, response);3.重定向也和请求分派的比较：请求分派只能将请求转发给同一个web应用中的其他组件，而重定向不仅可以定向到当前应用程序中的其他资源，也可重定向到其他站点的资源上重定向的访问过程结束后，浏览器的