// https://mvnrepository.com/artifact/javax.el/javax.el-api
    compile group: ‘javax.el‘, name: ‘javax.el-api‘, version: ‘3.0.0‘
    // https://mvnrepository.com/artifact/org.glassfish.web/javax.el
    compile group: ‘org.glassfish.web‘, name: ‘javax.el‘, version: ‘2.2.6‘
    // https://mvnrepository.com/artifact/org.hibernate/hibernate-validator
    compile group: ‘org.hibernate‘, name: ‘hibernate-validator‘, version: ‘5.4.1.Final‘

public static ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    
    public String validObject(Object msg) {
        String result = ConstantUtil.VALID_PASS;
        Validator validator = factory.getValidator();
        Set<ConstraintViolation<Object>> constraintViolations = validator.validate(msg);
        if(constraintViolations.isEmpty()){
            return result; 
        }
        StringBuffer buff = new StringBuffer();
        for (ConstraintViolation<Object> constraintViolation : constraintViolations) {
            buff.append(constraintViolation.getInvalidValue());
            buff.append(":");
            buff.append(constraintViolation.getMessage());
            buff.append("!\n");
        }
        return buff.toString().substring(0,buff.toString().length()-1);
    }

public MsgBaseResponse processEmService(Emp em) {
        MsgBaseResponse response = new MsgBaseResponse();
        String validResult = validUtil.validObject(em);
        if (validResult.equals(ConstantUtil.VALID_PASS)) {
            //TODO: the Operate and data.
            System.out.println("valid success, can write to store.");
            response.setData("");
        } else {
            response.setResult(-1);
            response.setData(validResult);
        }
        return response;