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Explain the internal working of a GORM dynamic finder at runtime?

Because a dynamic finder like findByTitleAndAuthor() never appears as real source code, GORM has to intercept the call at the moment it happens and figure out, from the method name string alone, what query the caller actually intended.

flowchart TD A[Code calls Book.findByTitleAndAuthor(t, a)] --> B[Method not found on the real class] B --> C[Groovy's methodMissing/GroovyObject hook invoked] C --> D[GORM's dynamic method dispatcher inspects the method name string] D --> E[Strip prefix: find/findAll/countBy] E --> F[Parse remaining segment: split on And/Or, extract property names] F --> G{Each parsed property exists on the domain class?} G -- No --> H[Throw MissingMethodException at runtime] G -- Yes --> I[Detect suffix operators: Like, GreaterThan, Between, etc.] I --> J[Build the underlying query object programmatically] J --> K[Execute the query against the datastore] K --> L[Return result matching the finder's prefix: single instance, list, or count]

Since the method genuinely doesn't exist on the class, Groovy's dynamic dispatch machinery (methodMissing, part of the language's metaprogramming support) hands the call to GORM's own dynamic method handler, which strips the recognized prefix (findBy, findAllBy, countBy), splits the remaining text on conjunction keywords like And/Or, and checks each resulting segment against the domain class's actual properties — a property that doesn't exist throws a runtime exception right there, which is exactly the compile-time-blind-spot GORM Data Services were built to avoid.

Once every segment resolves to a real property (optionally with a recognized comparison suffix like GreaterThan or Like), GORM assembles the equivalent query programmatically and executes it, returning either a single instance, a list, or a count depending on which prefix the original method name started with.

What Groovy language feature does GORM rely on to intercept a call to a dynamic finder method that doesn't really exist?
What happens if a dynamic finder's method name references a property that doesn't actually exist on the domain class?

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