Struts 2 - Annotations Types

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Struts 2 applications can use Java 5 annotations as an alternative to XML and Java properties configuration. Here is the list of most important annotations related to different categories −

Namespace Annotation (Action Annotation)

The @Namespace annotation allows the definition of an Action's namespace in the Action class rather than based on Zero Configuration's conventions.

@Namespace("/content")
public class Employee extends ActionSupport{
  ...
}

Result Annotation - (Action Annotation)

The @Result annotation allows the definition of Action results in the Action class rather than an XML file.

@Result(name = "success", value = "/success.jsp")
public class Employee extends ActionSupport{
 ...
}

Results Annotation - (Action Annotation)

The @Results annotation defines a set of results for an Action.

@Results({
   @Result(name = "success", value = "/success.jsp"),
   @Result(name = "error", value = "/error.jsp")
})
public class Employee extends ActionSupport{
 ...
}

After Annotation - (Interceptor Annotation)

The @After annotation marks a action method that needs to be called after the main action method and the result was executed. Return value is ignored.

public class Employee extends ActionSupport{
   @After
   public void isValid() throws ValidationException {
      // validate model object, throw exception if failed
   }
   public String execute() {
      // perform secure action
      return SUCCESS;
   }
}

Before Annotation - (Interceptor Annotation)

The @Before annotation marks a action method that needs to be called before the main action method and the result was executed. Return value is ignored.

public class Employee extends ActionSupport{
   @Before
   public void isAuthorized() throws AuthenticationException {
      // authorize request, throw exception if failed
   }
   public String execute() {
      // perform secure action
      return SUCCESS;
   }
}

BeforeResult Annotation - (Interceptor Annotation)

The @BeforeResult annotation marks a action method that needs to be executed before the result. Return value is ignored.

public class Employee extends ActionSupport{
   @BeforeResult
   public void isValid() throws ValidationException {
    // validate model object, throw exception if failed
   }

   public String execute() {
      // perform action
      return SUCCESS;
   }
}

ConversionErrorFieldValidator Annotation - (Validation Annotation)

This validation annotation checks if there are any conversion errors for a field and applies them if they exist.

public class Employee extends ActionSupport{
   @ConversionErrorFieldValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true)
   public String getName() {
      return name;
   }
}

DateRangeFieldValidator Annotation - (Validation Annotation)

This validation annotation checks that a date field has a value within a specified range.

public class Employee extends ActionSupport{
   @DateRangeFieldValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true, 
      min = "2005/01/01", max = "2005/12/31")
   public String getDOB() {
      return dob;
   }
}

DoubleRangeFieldValidator Annotation - (Validation Annotation)

This validation annotation checks that a double field has a value within a specified range. If neither min nor max is set, nothing will be done.

public class Employee extends ActionSupport{

   @DoubleRangeFieldValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true, 
      minInclusive = "0.123", maxInclusive = "99.987")
   public String getIncome() {
      return income;
   }
}

EmailValidator Annotation - (Validation Annotation)

This validation annotation checks that a field is a valid e-mail address if it contains a non-empty String.

public class Employee extends ActionSupport{

   @EmailValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true)
   public String getEmail() {
      return email;
   }
}

ExpressionValidator Annotation - (Validation Annotation)

This non-field level validator validates a supplied regular expression.

@ExpressionValidator(message = "Default message", key = "i18n.key", 
shortCircuit = true, expression = "an OGNL expression" )

IntRangeFieldValidator Annotation - (Validation Annotation)

This validation annotation checks that a numeric field has a value within a specified range. If neither min nor max is set, nothing will be done.

public class Employee extends ActionSupport{

   @IntRangeFieldValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true, 
      min = "0", max = "42")
   public String getAge() {
      return age;
   }
}

RegexFieldValidator Annotation - (Validation Annotation)

This annotation validates a string field using a regular expression.

@RegexFieldValidator( key = "regex.field", expression = "yourregexp")

RequiredFieldValidator Annotation - (Validation Annotation)

This validation annotation checks that a field is non-null. The annotation must be applied at method level.

public class Employee extends ActionSupport{

   @RequiredFieldValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true)
   public String getAge() {
      return age;
   }
}

RequiredStringValidator Annotation - (Validation Annotation)

This validation annotation checks that a String field is not empty (i.e. non-null with a length > 0).

public class Employee extends ActionSupport{

   @RequiredStringValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true, trim = true)
   public String getName() {
      return name;
   }
}

StringLengthFieldValidator Annotation - (Validation Annotation)

This validator checks that a String field is of the right length. It assumes that the field is a String. If neither minLength nor maxLength is set, nothing will be done.

public class Employee extends ActionSupport{

   @StringLengthFieldValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true, 
      trim = true, minLength = "5",  maxLength = "12")
   public String getName() {
      return name;
   }
}

UrlValidator Annotation - (Validation Annotation)

This validator checks that a field is a valid URL.

public class Employee extends ActionSupport{

   @UrlValidator(message = "Default message", 
      key = "i18n.key", shortCircuit = true)
   public String getURL() {
      return url;
   }
}

Validations Annotation - (Validation Annotation)

If you want to use several annotations of the same type, these annotation must be nested within the @Validations() annotation.

public class Employee extends ActionSupport{

  @Validations(
      requiredFields =
         {@RequiredFieldValidator(type = ValidatorType.SIMPLE, 
            fieldName = "customfield", 
            message = "You must enter a value for field.")},
      requiredStrings =
         {@RequiredStringValidator(type = ValidatorType.SIMPLE, 
         fieldName = "stringisrequired", 
         message = "You must enter a value for string.")}
   )
   public String getName() {
      return name;
   }
}

CustomValidator Annotation - (Validation Annotation)

This annotation can be used for custom validators. Use the ValidationParameter annotation to supply additional params.

@CustomValidator(type ="customValidatorName", fieldName = "myField")

Conversion Annotation - (Type Conversion Annotation)

This is a marker annotation for type conversions at Type level. The Conversion annotation must be applied at Type level.

@Conversion()
   public class ConversionAction implements Action {
}

CreateIfNull Annotation - (Type Conversion Annotation)

This annotation sets the CreateIfNull for type conversion. The CreateIfNull annotation must be applied at field or method level.

@CreateIfNull( value = true )
private List<User> users;

Element Annotation - (Type Conversion Annotation)

This annotation sets the Element for type conversion. The Element annotation must be applied at field or method level.

@Element( value = com.acme.User )
private List<User> userList;

Key Annotation - (Type Conversion Annotation)

This annotation sets the Key for type conversion. The Key annotation must be applied at field or method level.

@Key( value = java.lang.Long.class )
private Map<Long, User> userMap;

KeyProperty Annotation - (Type Conversion Annotation)

This annotation sets the KeyProperty for type conversion. The KeyProperty annotation must be applied at field or method level.

@KeyProperty( value = "userName" )
protected List<User> users = null;

TypeConversion Annotation - (Type Conversion Annotation)

This annotation annotation is used for class and application wide conversion rules. The TypeConversion annotation can be applied at property and method level.

@TypeConversion(rule = ConversionRule.COLLECTION, 
converter = "java.util.String")
public void setUsers( List users ) {
   this.users = users;
}