这是由于默认情况下不可能的安全原因。您首先需要配置Tomcat，以便将当前webapp的ServletContext公开给其他webapp。这可以通过将the crossContext attribute of context.xml设置为true来完成。

<Context ... crossContext="true">

完成后，您可以使用ServletContext#getContext()通过其上下文路径获得另一个servlet上下文，最后使用ServletContext#getRequestDispatcher()获得的RequestDispatcher，就像您对HttpServletRequest#getRequestDispatcher()获得的RequestDispatcher所做的那样。
例如：

ServletContext otherContext = getServletContext().getContext("/otherContext");
otherContext.getRequestDispatcher("/WEB-INF/some.jsp").forward(request, response);

是的
您需要做的第一件事是为另一个Web应用程序获取ServletContext。您可以在自己的ServletContext上使用ServletContext::getContext，传递其他webapp的上下文路径。
然后，您只需在外部上下文上正常执行ServletContext::getRequestDispatcher。
我还没有真正尝试过，但我100%保证它会工作。

我不确定不同的servlet容器。但它对同一个容器使用**getServletContext（）.getContext（）**方法。
首先你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。

context.xml

<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，每个Web应用程序中分别有servlet Servlet1 和 Servlet1。然后每个servlet中的代码如下所示：

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
    }

}

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
    }

}

上面的代码从 InterServletComm1 发送属性 name，并在 InterServletComm2 中接收。请让我知道如果这个答案不清楚。