Patterns of Legacy Displacement: Event Interception

When we gradually replace a legacy system, we have plenty of cases where the legacy system and its replacement need to interact. Since these legacy systems are often difficult, and costly, to change, we need a mechanism that can integrate elements of the replacement while minimizing the impact to the legacy system. Ian Cartwright, Rob Horn, and James Lewis explain how we can use Event Interception on state-changing events, allowing us to forward them to the replacement.

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from Martin Fowler https://ift.tt/01AuRBI