definindo uma chave composta no hibernate usando @embeddable

ChaveComposta.java

//Definindo
@Embeddable
public class ExemploPK implements Serializable {

    private static final long serialVersionUID = -4978349929535369754L;

    public ExemploPK() {

    }

    @Column(name = "COLUNA_1", nullable = false)
    private Long coluna1;

    @Column(name = "COLUNA_2")
    private String coluna2;

    public Long getcoluna1() {
	return coluna1;
    }

    public void setcoluna1(Long coluna1) {
	this.coluna1 = coluna1;
    }

    public String getcoluna2() {
	return coluna2;
    }

    public void setcoluna2(String coluna2) {
	this.coluna2 = coluna2;
    }

    @Override
    public boolean equals(Object obj) {
	if (obj == null || !(obj instanceof ExemploPK))
	    return false;

	if (this == obj)
	    return true;

	ExemploPK castObj = (ExemploPK) obj;

	return castObj.getcoluna1().equals(this.getcoluna1())
		&& castObj.getcoluna2().equals(this.getcoluna2());
    }

    @Override
    public int hashCode() {
	return 7 * coluna1.hashCode() ^ coluna2.hashCode();
    }

}

//usando

@EmbeddedId
private ExemploPK tituloPK = new ExemploPK();