Time for action – adding custom validation support

In this section, you will learn how to create custom validation annotations and use them. Add a custom product ID validation to your add product page to validate duplicate product IDs by performing the following steps:

1. Create an annotation interface called ProductId (ProductId.java) under the package com.packt.webstore.validator in the source folder src/main/java. Then, add the following code snippet in it:

   package com.packt.webstore.validator;
   
   import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
   import static java.lang.annotation.ElementType.FIELD;
   import static java.lang.annotation.ElementType.METHOD;
   import static java.lang.annotation.RetentionPolicy.RUNTIME;
   import java.lang.annotation.Documented;
   import java.lang.annotation.Retention;
   import java.lang.annotation.Target;
   import javax.validation.Constraint;
   import javax.validation.Payload;
   
   @Target( { METHOD, FIELD, ANNOTATION_TYPE })
   @Retention(RUNTIME)
   @Constraint(validatedBy...