Rails-inspired, annotations-based and functional-style syntactic and semantic validation framework for Java domain models. Supports requiredness, min, max, and length checks by default with the ability to create custom syntactic and semantic validations. Works 'expressly' well with the RestExpress services framework.
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Syntaxe - Domain Model Validation

Syntaxe is an annotations-based, functional-style syntactic (and semantic) domain model validation framework for Java.

Simply annotate fields in your domain model and invoke the ValidationEngine.validate() method to accomplish syntactic validation. Multiple annotations per field can be used to enforce multiple validations, if necessary.

Supported annotations are:

  • @StringValidation - enforces 'required-ness', min/max length.
  • @RegexValidation - enforces the string field to comply with a regular expression.
  • @IntegerValidation - enforces min/max value.
  • @LongValidation - enforced min/max value.
  • @FieldValidation - utilize your own Validator implementation for the annotated field/property.
  • @ObjectValidation - utilize your own Validator implementation for the annotated class.
  • @ChildValidation - utilize ValidationEngine.validate() rules for the annotated field/property.

In addition, to help protect from cross-site scripting (XSS) attacks, annotations are available to leverage the OWASP XSS library on string fields (also, see Maven Usage below):

  • @JavascriptEncoded - performs Javascript encoding.
  • @XmlEncoded - performs XML encoding.
  • @HtmlEncoded - performs HTML encoding.
  • @WebEncoded - A meta-encoder that performs both Javascript and HTML encoding, in that order.
  • @EncodingProvider - a generic field annotation to leverage your own XssEncoder implementation.

Created to be simple, Syntaxe supports the following:

  • Annotation-based validations on fields and objects.
  • AbstractValidatable which is the default implementation of Validatable, which supports the use of @Validate and functional validations.
  • Validations utility class containing foreign methods to perform your own default validations such as requiredness, less-than, greater-than.
  • Validatable interface which calls out the validation contract for in-object validations.
  • Object graph validation to validate an entire payload in one call.

In addition Syntaxe allows annotation of an entire class with the @ObjectValidation annotation to provide object-wide validation in addition to field-level annotation-driven validations.

Maven Usage





Or download the jar directly from: http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22Syntaxe%22

If you want to use the OWASP encoding annotations (available since 0.4.7-SNAPSHOT), also include the OWASP Encoder jar in your pom:


Note that to use the SNAPSHOT version, you must enable snapshots and a repository in your pom file as follows:


Sample Usage:

Option 1, POJO with annotations

--This option enables POJO validations without requiring extension or implementation, using annotations and the ValidationEngine to accomplish validation. In the case of numerics, this works equally well with primitives and object types (e.g. double/Double, float/Float, int/Integer).

public class MyValidatableClass
	@StringValidation(name="ID", required=true)
	private String id;
	@StringValidation(name="Name", required=true, maxLength=25)
	private String name;

	@IntegerValidation(name="Count", min=3, max=21)
	private int count;

	@DoubleValidation(name="Radius", min=0.0, max=3.1459, isNullable=false)
	private Double radius;

	@FloatValidation(name="Float Value", min=0.0, max=6.5)
	private float floatValue;

	@RegexValidation(name="Email Address", pattern="(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6})", message="must be a valid email address")
	private String email;

elsewhere (e.g. before persisting to storage) call the ValidationEngine.validate(object) method passing the MyValidatableClass instance. If the returned List list of error messages is not empty, validation failed. The validation error messages are in the list.

Option 2, extend AbstractValidatable

--This provides the capability to override the validateInto(StringBuffer) method to provide custom validations.

public class MyValidatableClass
extends AbstractValidatable
	@StringValidation(name="ID", required=true)
	private String id;
	@StringValidation(name="Name", required=true, minLength=5, maxLength=25)
	private String name;

	@IntegerValidation(name="Count", min=3, max=21)
	private int count;

elsewhere (e.g. before persisting to storage) call the validate() method on the MyValidatableClass instance.

Option 3, Validatable implementor, no annotations.

--This option allows complete customization of validations by implementing the validate() method and throwing a ValidationException when validation fails.

public class MyValidatableClass
implements Validatable
	private String id;
	private String name;
	private int count;
	public void validate()
		// provide validation throwing new ValidationException(List<String> errors) if validation
		// fails.

Option 4, Object Validation annotation.

--This option enables POJO validations, separating the validation concerns from the object itself. The ValidationEngine will invoke the assigned validator.

--Can be combined with Option 1 (above), POJO with annotations also.

public class SomePojo

elsewhere (e.g. before persisting to storage) call the ValidationEngine.validate(object) method passing the MyValidatableClass instance. If the returned List list of error messages is not empty, validation failed. The validation error messages are in the list.

Creating your own validator:

  1. Create an annotation that captures the fields your validator needs to know about (e.g. Message, etc.).
  2. Create a class that implements com.strategicgains.syntaxe.annotation.ValidationProvider
    • AbstractValidationProvider might be a good start
    • The perform() method returns void, and should populate the List errors parameters with any validation problems
  3. Add a ValidationProvidedBy annotation to your custom validator annotation that points to your class from step 2.
  4. See the com.strategicgains.syntaxe.validators.basic or com.strategicgains.syntaxe.validators.regex for examples.

Validating object graphs:

To validate a graph of objects originating from a root object, annotate the fields with @ChildValidation. Syntaxe will process the fields of the child object, list of objects, or array of objects as described in the options above. Can be combined with @Required to ensure that the property has a value.

public class RootPojo
  @Required("Child POJO")
  private ChildPojo childPojo;

  private List<ChildPojo> childPojoList;

  private ChildPojo[] childPojoArray;


public class ChildPojo

Change History:

1.0 - Released 10 Feb 2016

  • Merge pull request #8 from Noor Dawod, "Added DoubleValidator implementation"
  • Merge pull request #7 from Noor Dawad, "Added FloatValidator implementation"

0.4.10 - Released 28 July 2015

  • Upgraded Java output to 1.7 source and target.

0.4.9 - Released 2 Dec 2014

  • Implemented validation for arrays and collections in all ...Validator sub-classes. Moved validateCollection() and validateArray() to AnnotatedFieldValidator.
  • Added object graph validation (thanks to Jason Reicheneker)

0.4.8 - Released 24 Oct 2014

  • Enabled @IntegerValidation & @LongValidation on non-primitive Integer & Long types, respectively. Adding an isNullable property of the annotation.
  • RegexValidator changed to support validation involving Collections and Arrays.

Release 0.4.7 - Released 3 Apr 2014

  • Added annotations to leverage the OWASP cross-site scripting encoding library: @JavascriptEncoded, @XmlEncoded, @HtmlEncoded, @WebEncoded. To use, include the OWASP library in your pom.xml file (see Maven Usage, above).
  • Enhanced @EncodingProvider to be able to use it directly on a field and leverage your own XssEncoder implementation.
  • Added @LongValidation per issue #2.
  • Fixed stack overflow issue when Validatable.validate() calls ValidationEngine.validate() for the same object (e.g. circular validation). Circular validation will produce more-than the expected number of errors, but no longer cause a stack trace.

Release 0.4.6 - Released 17 Jul 2013

  • Added @Required annotation to require non-null values in non-primitive properties. Also checks array properties for non-null elements.

Release 0.4.5 - Released 8 Mar 2013

  • Renamed getAllDeclaredFields(Class, FieldClosure) to computeDeclaredFields(), exposing it publicly and making it return a generic type.

Release 0.4.4 - Released 16 Jan 2013

  • Removed Ant build-related cruft.
  • Ensured Java 1.6 compatible artifact produced from build.

Release 0.4.3 - Released 08 Jan 2013

  • Released to Maven Central repository.
  • Introduced Maven build.
  • Introduced the @FieldValidation annotation to utilize your own Validator at the field level.
  • Introduced message(), optional parameter to @RegexValidation annotation to facilitate describing the message to end-users instead of giving them the cryptic regex message.
  • Introduced ValidationEngine.validateAndThrow(Object), which throws a ValidationException if there are validation errors in the object.
  • Fixed poor wording in Validations.minLength() error message.

Release 0.3

  • Refactored the ValidationEngine to support the notion of multiple validators per field.
  • This refactoring also now allows for extensible validators be created outside this library.
  • Renamed com.strategicgains.syntaxe.annotation.Validate to com.strategicgains.syntaxe.validators.basic.BasicValidate
  • Removed dependency on the bpel jar, for no other reason than pluggable validators went towards interfaces instead of closures.
  • Validators are now found by being Annotations with the ValidationProvidedBy annotation.
  • Added a Regular Expression validator.

Release 0.2

  • Refactored Validator into ValidationEngine.

Release 0.1

  • Initial extract from RestExpress. Base implementation on which to expand.