Question

在servlet中我们可以使用requestdispatcher，它将从一个servlet转发到另一个servlet，在同一个项目中具有相同的会话。但是如果我使用不同的项目，则getRequestDispatcher不起作用。给出404错误。因为它附加的servlet名称在网址。如何在同一台服务器的不同项目中实现getRequestDispatcher？

RequestDispatcher rd = request.getRequestDispatcher("/v1/status1/toreply1"); 
rd.forward(request, response);

在同一项目中getRequestDispatcher正常工作。但是在不同的项目中它不起作用？任何人都可以解释它为什么会发生......？

Answer 1

您可以在同一台服务器上的不同项目中实现getRequestDispatcher。

查看https://stackoverflow.com/a/19273223/1428052

通过使用它可以在不同项目的同一台服务器上运行 getServletContext（）。getContext（）方法。

您可以按照以下步骤进行详细实施。

首先，您需要在下面的文件中进行更改

（Windows）C：\ Program Files \ Apache Software Foundation \ Tomcat 7.0 \ conf \ context.xml 将crossContext的值设置为true。

<强> context.xml中

<Context crossContext="true">

    <!-- Default set of monitored resources -->
    <WatchedResource>WEB-INF/web.xml</WatchedResource>

    <!-- Uncomment this to disable session persistence across Tomcat restarts -->
    <!--
    <Manager pathname="" />
    -->

    <!-- Uncomment this to enable Comet connection tacking (provides events
         on session expiration as well as webapp lifecycle) -->
    <!--
    <Valve className="org.apache.catalina.valves.CometConnectionManagerValve" />
    -->

</Context>

请注意 crossContext =“true”。

假设您有两个名为 InterServletComm1 和 InterServletComm2 的Web应用程序在每个Web应用程序中分别具有servlet Servlet1 和 Servlet1 。然后每个servlet中的代码如下：

<强> Servlet1.java

package interServletComm1;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Servlet1
 */
@WebServlet("/Servlet1")
public class Servlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Servlet1() {
        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");
        PrintWriter pw = response.getWriter();

        request.setAttribute("name", "WebApp1");
        ServletContext context = getServletContext().getContext("/InterServletComm2");
        RequestDispatcher rd = context.getRequestDispatcher("/Servlet2");
        rd.forward(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

<强> Servlet2.java

package interServletComm2;

import java.io.IOException;
import java.io.PrintWriter;

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;

/**
 * Servlet implementation class Servlet2
 */
@WebServlet("/Servlet2")
public class Servlet2 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Servlet2() {
        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");
        PrintWriter pw = response.getWriter();
        String name = (String) request.getAttribute("name");
        pw.println("This is web application 2.");
        pw.println("<br>The value received from web application one is: " + name);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

以上代码从 InterServletComm1 发送属性 name ，并在 InterServletComm2 中接收。如果答案不明确，请告诉我。

Answer 2

您必须使用其他网络应用程序的ServletContext来获取RequestDispatcher。可以通过ServletContext#getContext(String uri)：

查找其他上下文

ServletContext otherContext = request.getServletContext().getContext("/other");
RequestDispatcher rd = otherContext.getRequestDispatcher("/v1/status1/toreply1");

getRequestDispatcher如何在同一服务器的不同项目中为servlet工作？

2 个答案: