Which Grails Plugins Will Break Your Migration? Here's How to Find Out

A Practical Technical Guide

In most mature Grails environments, framework upgrades are constrained less by Grails itself and more by the plugin ecosystem surrounding each service. Plugins accumulate gradually, ownership shifts over time, and dependencies that once upgraded cleanly can become long-lived anchors.

Before planning any modernisation work, it is useful to establish a factual inventory of the Grails plugins currently in use and develop a basic sense of their maintenance posture. The objective is not to perform a full dependency audit. Instead, the goal is to surface which plugins are present, how widely they are used, and which ones may warrant closer scrutiny.

This guide describes a lightweight, repeatable method that engineering teams can run across a multi-repository Grails estate.

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Start by Extracting Plugin Declarations

In Grails applications, most plugins are declared in build.gradle under the standard dependency coordinates. Because estates often contain dozens of services, manual inspection does not scale well. A repository-wide search is typically sufficient to surface the majority of plugin usage.

From the root of a workspace containing your cloned repositories, search for Grails plugin coordinates:

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find . \( -name "*.gradle" -o -name "*.gradle.kts" \) \
  -exec grep -Hi "org\.grails\.plugins" {} + | sort -u

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This command surfaces dependency lines that reference the canonical plugin group. In most estates, it will capture the bulk of actively used plugins. The output will still be noisy, but it provides a reliable first pass.

Older environments sometimes include Grails 2.x services, where plugins are declared in BuildConfig.groovy. If your estate has been in operation for many years, it is worth performing an additional sweep:

find . -name "BuildConfig.groovy" -exec grep -H "plugins" {} \;

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Normalise the Results Into a Usable List

Raw grep output is difficult to reason about at scale. The next step is to extract the plugin name and version into a deduplicated list for review or loading into a spreadsheet.

A simple normalisation pipeline is usually sufficient:

git grep -h "org.grails.plugins" \
 | sed -E 's/.*org.grails.plugins:([^:]+):([^"]+).*/\1,\2/' \
 | sort -u

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The resulting output should resemble:

asset-pipeline,3.3.4
cache,4.0.3
spring-security-core,3.2.1

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Develop an Initial Sense of Plugin Health

Once the inventory exists, the next question is whether any of the identified plugins are likely to complicate forward movement. 

The most informative starting point is release recency. Plugins that have been updated within the past year or two and explicitly support newer Grails versions may migrate without significant friction. By contrast, plugins with no visible activity for several years deserve closer attention, particularly if they appear in multiple critical services.

Declared compatibility is the next useful signal. Many plugins document the Grails versions they support in their release notes or READMEs. When that range clearly excludes your intended target version, it is worth validating behaviour early rather than discovering incompatibilities during a broader upgrade effort.

Finally, the depth of framework coupling often predicts the amount of work required. Plugins that primarily provide service-level capabilities, such as mail delivery, HTTP clients, or simple utilities, are more likely to upgrade cleanly. Plugins that extend persistence behaviour, integrate deeply with Spring Security, modify request handling, or rely on AST transforms historically require more careful evaluation. The goal is not to classify every plugin perfectly, but to identify the small subset most likely to create drag.

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Perform a Lightweight Compatibility Check

For any plugin that appears potentially risky, a quick empirical test is usually more informative than speculation.  If the application compiles cleanly, starts without bean wiring failures, and passes integration tests, the plugin is unlikely to be a primary blocker. When migration problems do appear, they usually surface quickly during startup or test execution.

Common failure patterns include Spring bean definition errors, removed or relocated Grails APIs, Hibernate mapping changes, and classpath conflicts. AST transform failures occur less frequently but can require deeper refactoring when present. Capturing these signals early allows teams to scope remediation work while the blast radius is still small.

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Interpreting What You Find

The practical objective of this exercise is to identify the plugins that will pose a challenge during migration. 

Once the inventory is complete and obvious risks are flagged, teams are in a much stronger position to plan deliberately. Some plugins will upgrade cleanly. Some may require minor patching or replacement. A few may warrant deeper engineering workstreams. The important shift is moving from uncertainty to evidence.

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What You Should Have at the End

After completing this process, you should have a deduplicated list of Grails plugins in use across the estate, along with a preliminary sense of which ones are active, ageing, or potentially problematic.