@Pattern From validation.api want to configure all the pattern in one property file

Question

Can anybody help me of configuring the @Pattern annotation from validation-api.1.1.jar

@Pattern(regex = "PATTERN")this configuration is simple but my requirement is to have a central file consisting of all the pattern with key and value as pattern .i.e properties file.

Please your help would be appreciated.

Answer 1

Unfortunately, it isn't really feasible to have a properties file, per se, that contains your pattern regexes for use with the @Pattern annotation because Java requires that annotations use compile-time constants. These compile-time regexes cannot be retrieved from a properties file, because a properties file can't be parsed at compile time; properties files are parsed at runtime.

That being said, you can keep all of your compile-time constant regex patterns in a central class or interface. For example, consider the following code:

public class FooClass {
  @Pattern(regex = Patterns.FOO_PATTERN)
  public void foo() {}
}

public class BarClass {
  @Pattern(regex = Patterns.BAR_PATTERN)
  public void bar() {}
}

public class Patterns {
  public static final String BAR_PATTERN = "bar?";
  public static final String FOO_PATTERN = "foo*";
}

As you can see, you can have a common class where you keep all of your regex pattern strings. I hope that helps.

Answer 2

As mentioned in the other answer, its not possible to make the pattern configurable in application.properties for @Pattern. The best approach to make the pattern configurable via application.properties is by writing a custom annotation like below:

@Documented
@Target({ElementType.PARAMETER})
@Constraint(validatedBy = DynamicPatternValidator.class)
@Retention(RetentionPolicy.RUNTIME)
public @interface DynamicPattern {

    String message() default "";

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

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

You then have to write the custom validator to do the validation:

import javax.validation.ConstraintValidatorContext;

import static org.apache.commons.lang3.StringUtils.isEmpty;

    public class DynamicPatternValidator implements ConstraintValidator<DynamicPattern, String> {

    @Value("${validation.email.pattern}")
    private String pattern;
    
        public boolean isValid(String chars, ConstraintValidatorContext context) {
            java.util.regex.Pattern pattern = java.util.regex.Pattern.compile(pattern);
            context.buildConstraintViolationWithTemplate("Must match pattern " + getPattern())
                    .addConstraintViolation().disableDefaultConstraintViolation();
            return pattern.matcher(chars).matches();
        }
    }