Mapping ESB Integration Points from Visual UI Events: The Architect’s Documentation Guide

The most expensive part of a legacy rewrite isn't the new code; it's the forensic investigation required to understand the old logic. In many enterprise environments, the Enterprise Service Bus (ESB) is a "black box" of undocumented SOAP calls, complex XML transformations, and brittle orchestration layers. When you lose the original developers, you lose the map.

According to Replay's analysis, 67% of legacy systems lack any form of up-to-date documentation, leaving architects to guess how a button click in a 15-year-old PowerBuilder or Java Swing app triggers a cascading series of middleware events. This documentation gap is a primary driver of the $3.6 trillion global technical debt crisis. If you cannot identify the exact data requirements of your legacy UI, you cannot safely migrate to a modern microservices architecture.

TL;DR: Mapping integration points from legacy UIs to ESBs is traditionally a manual, 40-hour-per-screen process prone to error. By using Replay, architects can leverage visual reverse engineering to record user workflows and automatically generate documented React components and integration schemas, reducing modernization timelines by up to 70%.

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The Complexity of Mapping Integration Points From Legacy UIs#

When we talk about mapping integration points from a visual interface, we are essentially performing a post-mortem on a living system. Legacy applications often hide complex business logic within UI event handlers. A single "Submit" button might trigger three different ESB endpoints, a legacy mainframe transaction, and a local database update—none of which are documented.

Industry experts recommend a "top-down" discovery approach, but without the right tools, this becomes an exercise in frustration. Developers are forced to use network sniffers or debuggers on ancient runtimes just to see what the XML payload looks like.

Visual Reverse Engineering is the process of capturing the visual state changes and user interactions of an application to reconstruct its underlying business logic, data models, and integration requirements.

Why Manual Mapping Fails#

The traditional approach involves an architect sitting with a subject matter expert (SME), recording a screen share, and manually transcribing every field, validation rule, and API call. This process is:

1. •Slow: Averaging 40 hours per screen.
2. •Inaccurate: Missing hidden fields or conditional logic.
3. •Expensive: Diverting senior talent toward "detective work" instead of innovation.

Table 1: Manual Documentation vs. Replay Visual Reverse Engineering

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The Architect’s Workflow for Mapping Integration Points From Visual Events#

To successfully modernize, you need a repeatable framework for mapping integration points from the UI to the backend. This involves three distinct phases: Observation, Extraction, and Translation.

1. The Observation Phase (Recording the Flow)#

Instead of digging through millions of lines of COBOL or legacy Java code, start with the user's reality. By recording real-world workflows, you capture the "happy path" and the edge cases. Replay allows teams to record these sessions, turning the visual output into a structured data stream.

2. The Extraction Phase (Identifying the Schema)#

Once the workflow is recorded, the next step is identifying which visual elements correspond to which ESB data points. For instance, a "Customer ID" field in a legacy UI might map to a

in a SOAP header.

According to Replay's analysis, automated extraction of these schemas reduces the "discovery" phase of a project from months to weeks. This is critical for Legacy Modernization Strategies that prioritize speed without sacrificing stability.

3. The Translation Phase (Generating Modern Code)#

The final step is translating these legacy points into modern TypeScript interfaces and React components. Below is an example of how a legacy ESB integration point is mapped into a modern React hook using a structured approach.

typescript
// Example: Mapping a legacy SOAP-based ESB call to a modern React Hook
// Legacy Endpoint: /ESB/V1/CustomerUpdate (SOAP/XML)
// Modern Target: /api/v2/customers (REST/JSON)

import { useState, useEffect } from 'react';

interface LegacyCustomerPayload {
  CUST_ID: string;
  FIRST_NAME: string;
  LAST_NAME: string;
  ADDR_LINE_1: string;
  ZIP_CODE: string;
}

export const useCustomerIntegration = (customerId: string) => {
  const [data, setData] = useState<LegacyCustomerPayload | null>(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    // Replay identifies this mapping during the visual trace
    async function fetchLegacyData() {
      try {
        const response = await fetch(`/api/bridge/customer/${customerId}`);
        const result = await response.json();
        
        // Mapping integration points from the bridge layer
        setData({
          CUST_ID: result.id,
          FIRST_NAME: result.firstName,
          LAST_NAME: result.lastName,
          ADDR_LINE_1: result.address,
          ZIP_CODE: result.postalCode
        });
      } finally {
        setLoading(false);
      }
    }
    fetchLegacyData();
  }, [customerId]);

  return { data, loading };
};

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Best Practices for Mapping Integration Points From Visual UI Events#

When mapping integration points from visual cues, architects must look beyond the input fields. You must account for the "invisible" state.

Capture the "Side Effects"#

Legacy UIs often perform multiple operations on a single event. A "Save" button might:

1. •POST to an ESB.
2. •Trigger a local print spooler.
3. •Update a session cookie.
4. •Navigate to a "Success" screen.

Replay's "Flows" feature allows you to visualize these side effects as a sequence diagram, ensuring that your modern React application doesn't miss critical business logic that was never written down in the first place.

Standardize via a Component Library#

Once you have mapped the integration points, don't just write one-off code. Use the data to build a Design System for Enterprise applications. By creating a standardized library of components that already "know" how to talk to your ESB, you ensure consistency across the entire modernization portfolio.

ESB (Enterprise Service Bus) is a middleware architecture used to distribute work among connected components of an application, often acting as a translator between different protocols (e.g., SOAP to REST).

Handling Data Transformations#

The hardest part of mapping integration points from legacy systems is the data transformation. Legacy systems often use non-standard date formats (e.g., YYYYMMDD as a string) or cryptic status codes (e.g., Status "A" for Active, "4" for Pending).

typescript
/**
 * Transformation Utility generated after Replay analysis 
 * of legacy UI behavior and ESB response patterns.
 */
export const transformLegacyStatus = (code: string): 'active' | 'pending' | 'closed' => {
  const mapping: Record<string, 'active' | 'pending' | 'closed'> = {
    'A': 'active',
    '4': 'pending',
    'X': 'closed',
    'DELETED': 'closed'
  };

  return mapping[code] || 'pending';
};

// Component usage
const CustomerStatusBadge = ({ statusCode }: { statusCode: string }) => {
  const status = transformLegacyStatus(statusCode);
  return <div className={`badge badge-${status}`}>{status.toUpperCase()}</div>;
};

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How Replay Accelerates the Documentation of Integration Points#

For architects in regulated industries like Financial Services or Healthcare, "guessing" is not an option. You need a SOC2 and HIPAA-ready environment to perform your reverse engineering. Replay is built specifically for these high-stakes environments, offering on-premise deployments to ensure that sensitive legacy data never leaves your perimeter.

When you use Replay, the platform doesn't just show you what the UI looks like; it builds a "Blueprint." This blueprint includes:

• •The Visual Hierarchy: A complete React component tree.
• •The Data Flow: Every integration point mapped from the UI event to the network request.
• •The Logic Map: Conditional rendering rules extracted from the legacy runtime.

Industry experts recommend that for any project exceeding 50 screens, manual documentation is the single biggest point of failure. By automating the process of mapping integration points from visual recordings, Replay cuts the average enterprise rewrite timeline from 18–24 months down to just a few months or even weeks.

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Bridging the Gap: From ESB to Microservices#

The ultimate goal of mapping integration points from your legacy system is usually to move toward a microservices architecture. However, you cannot jump straight to microservices if you don't understand the current data dependencies.

The "Sidecar" Modernization Pattern#

A common strategy is to use the documented integration points to build a "Sidecar" or "Adapter" layer. This layer sits between your new React frontend and the old ESB.

1. •Record: Use Replay to capture the legacy workflow.
2. •Document: Automatically generate the integration map.
3. •Build the Adapter: Create a Node.js or Go-based BFF (Backend for Frontend) that mimics the legacy ESB's expectations but serves clean JSON to the React app.
4. •Swap: Gradually replace the ESB services with modern microservices without changing the frontend code.

This "Strangler Fig" pattern is only possible if your initial mapping is 100% accurate. If you miss one field in a SOAP header, the entire transaction fails. This is why the precision of visual reverse engineering is superior to manual analysis.

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Frequently Asked Questions#

How does Replay handle encrypted or secure legacy traffic?#

Replay operates at the UI and DOM level, capturing the state and interactions within the browser or application runtime. For network-level mapping, it correlates visual events with the resulting API calls. In highly secure environments, Replay can be deployed on-premise, ensuring that all data remains within your secure network while still providing the full suite of AI-driven documentation tools.

Can I map integration points from desktop applications, or only web?#

Replay is designed to handle a wide range of legacy environments. While it excels at web-based legacy systems (like old ASP.NET or Java WebForms apps), its visual reverse engineering engine can be applied to any interface that can be recorded. The platform converts these visual flows into modern, web-standard React code and documented integration schemas.

What happens if the legacy system has no API at all?#

In some cases, the "integration" is directly to a database or a local file system. When mapping integration points from these systems, Replay identifies the data entry patterns and the resulting state changes. This allows architects to define what the new API should look like to support the existing business process, effectively "spec-ing" the new backend based on the legacy UI's requirements.

How much time can I really save on a large-scale enterprise project?#

According to Replay's analysis of enterprise-grade migrations, teams save an average of 70% on their total modernization timeline. For a standard 100-screen application, a manual rewrite typically takes 18 months. With Replay, the discovery and documentation phase is compressed from 6 months to 2 weeks, allowing the actual development to begin almost immediately.

Does Replay generate production-ready code?#

Replay generates high-quality React components and TypeScript interfaces that serve as a robust foundation for your new application. While your team will still apply specific styling and business logic refinements, the "heavy lifting" of structural components and integration mapping is done automatically. This allows developers to focus on feature enhancement rather than basic reconstruction.

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Ready to modernize without rewriting? Book a pilot with Replay and see how visual reverse engineering can transform your legacy documentation process.