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What is the Inter-Servlet Communication?

What is the Inter-Servlet Communication?

Inter-servlet communication refers to the exchange of data or messages between different servlets running within the same web application. This communication allows servlets to collaborate, share information, or delegate tasks based on the needs of the application.

Inter-Servlet Communication

Purpose of Inter-Servlet Communication

  • Data Sharing: Servlets can pass data (such as parameters or attributes) to each other to coordinate their activities.
  • Task Delegation: One servlet can invoke another servlet to perform specific tasks or actions, allowing for modular and organized application design.
  • Workflow Management: Servlets can work together to manage complex workflows or handle different stages of request processing.

Let’s illustrate how servlets can communicate with each other using request forwarding and attribute sharing in a Java web application.

Example: Inter-Servlet Communication
1. Servlet A:

java
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/ServletA")
public class ServletA extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // Set data in request attribute
        request.setAttribute("message", "Hello from Servlet A!");

        // Forward the request to Servlet B
        request.getRequestDispatcher("/ServletB").forward(request, response);
    }
}

Servlet B:

java
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/ServletB")
public class ServletB extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // Retrieve data from request attribute set by Servlet A
        String messageFromA = (String) request.getAttribute("message");

        // Output the message to the response
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().println("<html><body>");
        response.getWriter().println("<h2>Message from Servlet A:</h2>");
        response.getWriter().println("<p>" + messageFromA + "</p>");
        response.getWriter().println("</body></html>");
    }
}

Explanation of the Inter-Servlet Communication

  • Servlet A (/ServletA):
    • Sets a message (“Hello from Servlet A!”) in the request attribute.
    • Forwards the request to Servlet B using request.getRequestDispatcher(“/ServletB”).forward(request, response).
    • This passes control and data to Servlet B.

  • Servlet B (/ServletB):
    • Retrieves the message from the request attribute (“message”).
    • Displays the message retrieved from Servlet A in the HTTP response to the client.

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