Obtaining a Collaboration Kit Instance in a Servlet

When a VaadinService instance isn’t available, it’s impossible to get a CollaborationEngine instance with the getInstance() method. In a servlet, you can get the instance with the getAttribute() method, as long as it’s been configured.

Source code

MyServlet.javapackage com.vaadin.demo.collaboration;

import java.io.IOException;

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

import com.vaadin.collaborationengine.CollaborationEngine;
import com.vaadin.collaborationengine.MessageManager;
import com.vaadin.collaborationengine.SystemConnectionContext;
import com.vaadin.collaborationengine.UserInfo;

public class MyServlet extends HttpServlet {
    private final UserInfo systemUser = new UserInfo("system");
    private final String topicId = "topic";

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        CollaborationEngine ce = (CollaborationEngine) getServletContext()
                .getAttribute(CollaborationEngine.class.getName());
        if (ce == null) {
            resp.sendError(500,
                    "Collaboration Kit has not yet been initialized");
            return;
        }
        // Retrieve message that was sent in this POST request
        String userMessage = req.getParameter("message");
        String message = "An anonymous user posted the following message: "
                + userMessage;
        sendMessageToTopic(ce, message);
        resp.setStatus(202);
    }

    public void sendMessageToTopic(CollaborationEngine ce, String message) {
        // Get SystemConnectionContext from Collaboration Kit
        SystemConnectionContext systemConnectionContext = ce.getSystemContext();

        MessageManager messageManager = new MessageManager(
                systemConnectionContext, systemUser, topicId, () -> ce);

        messageManager.submit(message) // Send message to topic
                .whenComplete((a, t) -> {
                    // Close the message manager when done
                    messageManager.close();
                });
    }
}

In the following example, a message posted through a form is added to a topic as a system message:

Source code

MyServlet.javapackage com.vaadin.demo.collaboration;

import java.io.IOException;

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

import com.vaadin.collaborationengine.CollaborationEngine;
import com.vaadin.collaborationengine.MessageManager;
import com.vaadin.collaborationengine.SystemConnectionContext;
import com.vaadin.collaborationengine.UserInfo;

public class MyServlet extends HttpServlet {
    private final UserInfo systemUser = new UserInfo("system");
    private final String topicId = "topic";

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        CollaborationEngine ce = (CollaborationEngine) getServletContext()
                .getAttribute(CollaborationEngine.class.getName());
        if (ce == null) {
            resp.sendError(500,
                    "Collaboration Kit has not yet been initialized");
            return;
        }
        // Retrieve message that was sent in this POST request
        String userMessage = req.getParameter("message");
        String message = "An anonymous user posted the following message: "
                + userMessage;
        sendMessageToTopic(ce, message);
        resp.setStatus(202);
    }

    public void sendMessageToTopic(CollaborationEngine ce, String message) {
        // Get SystemConnectionContext from Collaboration Kit
        SystemConnectionContext systemConnectionContext = ce.getSystemContext();

        MessageManager messageManager = new MessageManager(
                systemConnectionContext, systemUser, topicId, () -> ce);

        messageManager.submit(message) // Send message to topic
                .whenComplete((a, t) -> {
                    // Close the message manager when done
                    messageManager.close();
                });
    }
}

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Docs

Docs

Obtaining a Collaboration Kit Instance in a Servlet