Validation check on unique composite key

Question

I have 3 fields of an entity class which I don't want to be unique but instead i want them to be used as composite fields for a key which must itself be unique. My class POJO:

    @Entity
        @Table(name="EMPLOYEE")
        public class Employee {

            @Id
            @GeneratedValue(strategy = GenerationType.IDENTITY)
            private int id;

            @Size(min=3, max=50)
            @Column(name = "NAME", nullable = false)
            private String name;

            @Size(min=3, max=50)
            @Column(name = "A", nullable = false)
            private String a;
            @Size(min=3, max=50)
            @Column(name = "B", nullable = false)
            private String b;
            @Size(min=3, max=50)
            @Column(name = "C", nullable = false)
            private String c;

            @NotNull
            @DateTimeFormat(pattern="dd/MM/yyyy") 
            @Column(name = "JOINING_DATE", nullable = false)
            @Type(type="org.jadira.usertype.dateandtime.joda.PersistentLocalDate")
            private LocalDate joiningDate;

            @NotNull
            @Digits(integer=8, fraction=2)
            @Column(name = "SALARY", nullable = false)
            private BigDecimal salary;

            @NotEmpty
            @Column(name = "SSN", unique=true, nullable = false)
            private String ssn;
    }

Im working with form submission, validating user input via JSR303 annotations.In case of validation failure, default error messages are shown.I configured a ResourceBundleMessageSource:

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = "com.fussa.fyby")
public class AppConfig {

    @Bean
    public ViewResolver viewResolver() {
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setViewClass(JstlView.class);
        viewResolver.setPrefix("/WEB-INF/views/");
        viewResolver.setSuffix(".jsp");
        return viewResolver;
    }

    @Bean
    public MessageSource messageSource() {
        ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
        messageSource.setBasename("messages");
        return messageSource;
    }
}

/src/main/resources/messages.properties

Size.employee.name=between {2} and {1} characters long
NotNull.employee.joiningDate=can not be blank
NotNull.employee.salary=are u working for free !
Digits.employee.salary=Only numeric data with max 8 digits and with max 2 precision is allowed
NotEmpty.employee.ssn=can not be blank
typeMismatch=Invalid format
non.unique.ssn=SSN {0} already exist.

i found this solution for creating an unique key:

@Table( name = "EMPLOYEE",
        uniqueConstraints = { @UniqueConstraint( columnNames = { "A", "B", "C" } ) } )

my question is how can i display a message using messages.properties if that uniqueconstraint has been violated ?

UPDATE 1

@Service("employeeService")
@Transactional
public class EmployeeServiceImpl implements EmployeeService {

    @Autowired
    private EmployeeDao dao;

    //....

    public void saveEmployee(Employee employee) {
        dao.saveEmployee(employee);
    }

}

Thanks for any advice..

Answer 1

I managed to create a unique constraint validation for one field, folowing this steps:

1- Create the constraint annotation. 2-create The constraint validator. 3-The error message. 4-how to use the constraint.

i posted the code with the solution here: Link..