Specification Pattern

AbstractSpecification.java

public abstract class AbstractSpecification<T> implements Specification<T> {
    protected String messageKey;

    public AbstractSpecification(String messageKey) {
        this.messageKey = messageKey;
    }

    public AbstractSpecification() {
        this.messageKey = "specification_" + getClass() + "_broken";
    }

    public abstract boolean isSatisfiedBy(T t);

    public Specification<T> and(final Specification<T> other) {
        return new AndSpecification<T>(this, other);
    }

    public Specification<T> or(final Specification<T> other) {
        return new OrSpecification<T>(this, other);
    }

    public Specification<T> not(final Specification<T> other) {
        return new NotSpecification<T>(other);
    }

    @Override
    public boolean equals(Object o) {
        return EqualsBuilder.reflectionEquals(this, o);
    }

    @Override
    public int hashCode() {
        return HashCodeBuilder.reflectionHashCode(this);
    }
}

AndSpecification.java

public class AndSpecification<T> extends AbstractSpecification<T> {

    private Specification<T> spec1;
    private Specification<T> spec2;

    public AndSpecification(final Specification<T> spec1, final Specification<T> spec2) {
        this.spec1 = spec1;
        this.spec2 = spec2;
    }

    public boolean isSatisfiedBy(final T t) {
        return spec1.isSatisfiedBy(t) && spec2.isSatisfiedBy(t);
    }

}

NotSpecification.java

public class NotSpecification<T> extends AbstractSpecification<T> {

    private Specification<T> spec1;

    public NotSpecification(final Specification<T> spec1) {
        this.spec1 = spec1;
    }

    public boolean isSatisfiedBy(final T t) {
        return !spec1.isSatisfiedBy(t);
    }
}

OrSpecification.java

public class OrSpecification<T> extends AbstractSpecification<T> {

    private Specification<T> spec1;
    private Specification<T> spec2;

    public OrSpecification(final Specification<T> spec1, final Specification<T> spec2) {
        this.spec1 = spec1;
        this.spec2 = spec2;
    }

    public boolean isSatisfiedBy(final T t) {
        return spec1.isSatisfiedBy(t) || spec2.isSatisfiedBy(t);
    }

}

Specification.java

public interface Specification<T> {

    boolean isSatisfiedBy(T t);

    Specification<T> and(Specification<T> specification);

    Specification<T> or(Specification<T> specification);

    Specification<T> not(Specification<T> specification);

}