[forge-issues] [JBoss JIRA] (FORGE-1667) Improve the constraint-new-annotation command

[Antonio Goncalves (JIRA)]

Antonio Goncalves created FORGE-1667:
----------------------------------------

             Summary: Improve the constraint-new-annotation command 
                 Key: FORGE-1667
                 URL: https://issues.jboss.org/browse/FORGE-1667
             Project: Forge
          Issue Type: Sub-task
          Components: Java EE
    Affects Versions: 2.1.1.Final
            Reporter: Antonio Goncalves
             Fix For: 2.x Future


This allows the developer to create a constraint (with or without implementation) with a default error message (as a resource bundle). 

h2. Constraint with no implementation

The following command will create a *constraint annotation* with no  implementation, and a default *error message* :

{code}
constraint-new-annotation --named URL
{code}

This command first creates the constraint annotation (notice validatedBy = {})

{code}
@Documented
@Constraint(validatedBy = {})
@Target( { METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@ReportAsSingleViolation
public @interface URL {
	String message() default "{org.mycompany.myproject.constraints.URL.message}";

	Class<?>[] groups() default { };

	Class<? extends Payload>[] payload() default { };

	@Target( { METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
	@Retention(RUNTIME)
	@Documented
	public @interface List {
		URL[] value();
	}
}
{code}

Then, it creates a message entry in the {{ValidationMessages.properties}} file (the file is created under {{resources}} directory if it doesn't already exist)

{code}
org.mycompany.myproject.constraints.URL.message=invalid URL
{code}

We could have attributes to the command to change the target

{code}
constraint-new-annotation --named URL --targets METHOD FIELD
{code}

This will generate the following code only with @Target METHOD, FIELD

{code}
@Documented
@Constraint(validatedBy = {})
@Target( { METHOD, FIELD })
@Retention(RUNTIME)
@ReportAsSingleViolation
public @interface URL {
	String message() default "{org.mycompany.myproject.constraints.URL.message}";

	Class<?>[] groups() default { };

	Class<? extends Payload>[] payload() default { };

	@Target( { METHOD, FIELD })
	@Retention(RUNTIME)
	@Documented
	public @interface List {
		URL[] value();
	}
}
{code}
 
h2. Constraint with an implementation

The {{constraint-new-annotation}} can have a {{validatedBy}} and a {{type}} attribute, it will then create a *constraint annotation*, an *error message*, and a default *implementation* :

{code}
constraint-new-annotation --named URL --validatedBy URLValidator --type String
{code}

The constraint will now refer to the implementation class {{URLValidator.class}} :

{code}
@Documented
@Constraint(validatedBy = URLValidator.class)
@Target( { METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@ReportAsSingleViolation
public @interface URL {
	String message() default "{org.mycompany.myproject.constraints.URL.message}";

	Class<?>[] groups() default { };

	Class<? extends Payload>[] payload() default { };

	@Target( { METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
	@Retention(RUNTIME)
	@Documented
	public @interface List {
		URL[] value();
	}
}
{code}

And the default implementation will look like : 

{code}
public class URLValidator implements ConstraintValidator<URL, String> {

  @Override
  public void initialize(URL url) {
  }

  @Override
  public boolean isValid(String value, ConstraintValidatorContext context) {
    return false;
  }
}
{code}

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