Jetty：将对象从main方法传递给servlet

问题描述

我有两个类服务器（使用main方法，启动服务器）和 StartPageServlet 使用Servlet。

I have two classes Server (with the main method, starting the server) and StartPageServlet with a Servlet.

代码最重要的部分是：

public class Server {
    public static void main(String[] args) throws Exception {
        // some code

        // I want to pass "anObject" to every Servlet.
        Object anObject = new Object();

        Server server = new Server(4000);
        ServletContextHandler context =
            new ServletContextHandler(ServletContextHandler.SESSIONS);
        context.addServlet(StartPageServlet.class, "/");
        // more code
}

和StartPageServlet：

And the StartPageServlet:

public class StartPageServlet extends HttpServlet {

    @Override
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
            throws ServletException, IOException
    {
        // Here I want to access "anObject"
    }

我该怎么做？

推荐答案

嵌入式Jetty是这样的很棒。

Embedded Jetty is so wonderful here.

您有几个常见的选择：

1. 直接实例化servlet，使用构造函数或setter，然后通过 ServletHolder 将其交给Jetty（可以是任何值或对象类型）


2. 将它添加到main中的 ServletContext ，然后通过应用程序中的 ServletContext 访问它（可以是任何值或对象类型）。

1. Direct instantiation of the servlet, use constructors or setters, then hand it off to Jetty via the ServletHolder (can be any value or object type)
2. Add it to the ServletContext in your main, and then access it via the ServletContext in your application (can be any value or object type).

示例：

package jetty;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;

public class ObjectPassingExample
{
    public static void main(String args[]) throws Exception
    {
        Server server = new Server(8080);

        ServletContextHandler context = new ServletContextHandler();
        context.setContextPath("/");

        // Option 1: Direct servlet instantiation and ServletHolder
        HelloServlet hello = new HelloServlet("everyone");
        ServletHolder helloHolder = new ServletHolder(hello);
        context.addServlet(helloHolder, "/hello/*");

        // Option 2: Using ServletContext attribute
        context.setAttribute("my.greeting", "you");
        context.addServlet(GreetingServlet.class, "/greetings/*");

        server.setHandler(context);
        server.start();
        server.join();
    }

    public static class HelloServlet extends HttpServlet
    {
        private final String hello;

        public HelloServlet(String greeting)
        {
            this.hello = greeting;
        }

        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
        {
            resp.setContentType("text/plain");
            resp.getWriter().println("Hello " + this.hello);
        }
    }

    public static class GreetingServlet extends HttpServlet
    {
        private String greeting;

        @Override
        public void init() throws ServletException
        {
            this.greeting = (String) getServletContext().getAttribute("my.greeting");
        }

        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
        {
            resp.setContentType("text/plain");
            resp.getWriter().println("Greetings to " + this.greeting);
        }
    }
}

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