Spring. Creating a Custom Java Annotaiton

 package com.luv2code.springmvcdemo.validation;

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Constraint(validatedBy = CourseCodeConstraintValidator.class)
@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface CourseCode {

    // define default course code
    public String value() default "LUV";

    // define default error message
    public String message() default "must start with LUV";

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

    // define default payloads
    public Class<? extends Payload>[] payload() default {};
}

package com.luv2code.springmvcdemo.validation;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class CourseCodeConstraintValidator implements ConstraintValidator<CourseCode, String> {

    private String coursePrefix;

    @Override
    public void initialize(CourseCode constraintAnnotation) {
        coursePrefix = constraintAnnotation.value();
    }

    @Override
    public boolean isValid(String theCode, ConstraintValidatorContext constraintValidatorContext) {
        boolean result;
        if (theCode != null) {
            result = theCode.startsWith(coursePrefix);
        } else {
            result = true;
        }
        return result;
    }
}
package com.luv2code.springmvcdemo;


import com.luv2code.springmvcdemo.validation.CourseCode;

import javax.validation.constraints.*;

public class Customer {

    private String firstName;

    @NotNull(message = "is required")
    @Size(min = 1, message = "is required")
    private String lastName;

    @NotNull(message = "is required")
    @Min(value = 0, message = "must be grater or equal to zero")
    @Max(value = 10, message = "must be less than or equal to ten")
    private Integer freePasses;

    @Pattern(regexp = "^[a-zA-Z0-9]{5}", message = "only 5 characters of digits is allowed")
    private String postalCode;

//    @CourseCode(value = "TOPS", message = "must start with TOPS")
    @CourseCode
    private String courseCode;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public Integer getFreePasses() {
        return freePasses;
    }

    public void setFreePasses(Integer freePasses) {
        this.freePasses = freePasses;
    }

    public String getPostalCode() {
        return postalCode;
    }

    public void setPostalCode(String postalCode) {
        this.postalCode = postalCode;
    }

    public String getCourseCode() {
        return courseCode;
    }

    public void setCourseCode(String courseCode) {
        this.courseCode = courseCode;
    }
}