固定长度字符字段的Hibernate架构验证失败

使用Hibernate根据数据库架构验证一组JPA实体时，我遇到以下错误：

Caused by: org.hibernate.HibernateException: Wrong column type in public.postal_code for column country. Found: bpchar, expected: bytea
    at org.hibernate.mapping.Table.validateColumns(Table.java:282)
    at org.hibernate.cfg.Configuration.validateSchema(Configuration.java:1268)
    at org.hibernate.tool.hbm2ddl.SchemaValidator.validate(SchemaValidator.java:155)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:460)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1737)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:84)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:904)
    ... 9 more

实体定义如下：

@Entity
public class Country implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="code_alpha2", columnDefinition="bpchar")
    private String codeAlpha2;

    @Column(name="code_alpha3", columnDefinition="bpchar")
    private String codeAlpha3;

    public Country() {
    }

    public String getCodeAlpha2() {
        return this.codeAlpha2;
    }

    public void setCodeAlpha2(String codeAlpha2) {
        this.codeAlpha2 = codeAlpha2;
    }

    public String getCodeAlpha3() {
        return this.codeAlpha3;
    }

    public void setCodeAlpha3(String codeAlpha3) {
        this.codeAlpha3 = codeAlpha3;
    }
}

@Entity
@IdClass(PostalCodePK.class)
@Table(name="postal_code")
public class PostalCode implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @ManyToOne(fetch=FetchType.EAGER)
    @JoinColumn(name="country")
    private Country country;

    @Id
    private String code;

    public PostalCode() {
    }

    public Country getCountry() {
        return country;
    }

    public void setCountry(Country country) {
        this.country = country;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }
}

最后，定义邮政编码主键的类：

@Embeddable
public class PostalCodePK implements Serializable {
    //default serial version id, required for serializable classes.
    private static final long serialVersionUID = 1L;

    @Column(columnDefinition="bpchar")
    private Country country;

    private String code;

    public PostalCodePK() {
    }
    public Country getCountry() 
        return this.country;
    }
    public void setCountry(Country country) {
        this.country = country;
    }
    public String getCode() {
        return this.code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof PostalCodePK)) {
            return false;
        }
        PostalCodePK castOther = (PostalCodePK)other;
        return 
            this.country.equals(castOther.country)
            && this.code.equals(castOther.code);
    }

    public int hashCode() {
        final int prime = 31;
        int hash = 17;
        hash = hash * prime + this.country.hashCode();
        hash = hash * prime + this.code.hashCode();

        return hash;
    }
}

---

为什么Hibernate希望在这个国家有一个副作用？我怎样才能说服验证器接受原样的模式呢？

回答我自己的问题：Hibernate并没有将依赖项视为一个实体，而是将其视为一个要序列化并存储在数据库中的对象。解决方案是将PostalCode中字段“country”的数据类型更改为String，并在PostalCode中将注释@MapsId添加到字段“country”时切换为使用嵌入ID：

    @EmbeddedId
    PostalCodePK id;

    @MapsId("country")
    @ManyToOne
    @JoinColumn(name="country")
    private Country country;

    @EmbeddedId
    PostalCodePK id;

    @MapsId("country")
    @ManyToOne
    @JoinColumn(name="country")
    private Country country;