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StatelessClass.md

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Pattern: Stateless class

Issue: -

Description

Checks for non-final fields on a class. The intent of this rule is to check a configured set of classes that should remain "stateless" and reentrant. One example might be Grails service classes which are singletons, by default, and so they should be reentrant.

This rule ignores final fields (either instance or static). Fields that are static and non-final, however, do cause a violation.

This rule also ignores all classes annotated with the @Immutable transformation. It also ignores all fields annotated with the @Inject annotation.

You can configure this rule to ignore certain fields either by name or by type. This can be useful to ignore fields that hold references to (static) dependencies (such as DAOs or Service objects) or static configuration.

Property Description Default Value
ignoreFieldNames Specifies one or more (comma-separated) field names that should be ignored (i.e., that should not cause a rule violation). The names may optionally contain wildcards (*,?). null
addToIgnoreFieldNames Specifies one or more (comma-separated) field names to be added to the ignoreFieldNames property value. This is a special write-only property, and each call to setAddIgnoreFieldNames() adds to (rather than overwrites) the list of field names to be ignored. null
ignoreFieldTypes Specifies one or more (comma-separated) field types that should be ignored (i.e., that should not cause a rule violation). The names may optionally contain wildcards (*,?). null

Notes

  1. The ignoreFieldTypes property matches the field type name as indicated in the field declaration, only including a full package specification IF it is included in the source code. For example, the field declaration BigDecimal value matches an ignoreFieldTypes value of BigDecimal, but not java.lang.BigDecimal.
  2. There is one exception for the ignoreFieldTypes property: if the field is declared with a modifier/type of def, then the type resolves to java.lang.Object.
  3. At least one of the (standard) applyToClassNames, applyToFileNames or applyToFilesMatching properties must be set (i.e., not null or empty) or else this rule does nothing. In other words, you must configure this rule to apply to a specific set of classes or files.
  4. This rule will not catch violations of true statelessness/reentrancy if you define a final field whose value is itself mutable, e.g. a final HashMap.

Further Reading