Question

我有一些类，我们正在尝试扩展以允许重用代码，但是hibernate却没有。以下是新类及其扩展名：

超级语句类

@MappedSuperclass
public abstract class CoreStatement<S extends Approval>
    implements java.io.Serializable
{

    public abstract Long getId();

    public abstract void setId(Long id);

    public abstract Set<S> getApprovals();

    public abstract void setApprovals(Set<S> approvals);

}

基本语句类 - 稍后会扩展，但是通过单个表继承

@Entity
@Table(name="EXPNS_STTMNT")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(
        name="CLASS_ID",
        discriminatorType = DiscriminatorType.INTEGER
)
public abstract class ExpenseStatement extends CoreStatement<ExpenseApproval>
{
    private Set<ExpenseApproval> approvals;

    @Override
    @Id
    @Column(name="ID", unique=true, nullable=false, precision=10, scale=0)
    public Long getId() {
        return this.id;
    }

    @Override
    public void setId(Long id) {
        this.id = id;
    }

    @Override
    @OneToMany(cascade=CascadeType.ALL, fetch=FetchType.LAZY, mappedBy="statement",
        targetEntity = ExpenseApproval.class)
    public Set<ExpenseApproval> getApprovals() {
        return approvals;
    }

    public void setApprovals(Set<ExpenseApproval> approvals) {
        this.approvals = approvals;
    }
}

批准超类

@MappedSuperclass
public abstract class Approval<T extends CoreStatement> implements java.io.Serializable  {
    public abstract Long getId();

    public abstract void setId(Long id);
    public abstract T getStatement();

    public abstract void setStatement(T statement);
}

审批基类

@Entity
@Table(name="APPRVL")
public class ExpenseApproval extends Approval<ExpenseStatement>{
    private Long id;
    private ExpenseStatement statement;
    @Id
    @Column(name="ID", unique=true, nullable=false, precision=10, scale=0)
    public Long getId() {
        return this.id;
    }

    @Override
    public void setId(Long id) {
        this.id = id;
    }
    @Override
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="EXPENSE_STATEMENT_ID", nullable=true)
    public ExpenseStatement getStatement() {
        return statement;
    }

    @Override
    public void setStatement(ExpenseStatement statement) {
        this.statement= statement;
    }
}

当通过UnitTests运行时，我们收到错误：

java.lang.ExceptionInInitializerError由以下原因引起： org.hibernate.MappingException：无法确定以下类型： java.util.Set，在表：EXPNS_STTMNT，用于列： [org.hibernate.mapping.Column（approvals）] at org.hibernate.mapping.SimpleValue.getType（SimpleValue.java:314）at org.hibernate.mapping.SimpleValue.isValid（SimpleValue.java:292） ....

它似乎是某种映射错误，但我无法缩小范围。许多之前发布过这个问题的人都有这样的问题，即他们的注释位于私有财产之上，也有吸气剂，即他们混合并匹配他们的注释位置，但这似乎不是这里的情况。是否有其他人对可能导致此问题的原因有任何建议？

Answer 1

Hibernate和它的错误消息通常很糟糕，但我设法解决了这个问题。它与集合无关，但更多的是注释的位置。注释通常应该在超类而不是基类上。

所以例子是：

@MappedSuperclass
public abstract class Approval<T extends CoreStatement> implements java.io.Serializable  {

    private Long id;
    private T statement


    @Id
    @Column(name="ID", unique=true, nullable=false)
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="STATEMENT_ID", nullable=true)
    public T getStatement() {
        return statement;
    }

    public void setStatement(T statement) {
        this.statement = statement;
    }
}

然后要设置适当的列或覆盖注释的属性，可以在类命名约定之上使用@AssociationOverrides。

@Entity
@Table(name="APPRVL")
@AssociationOverrides({
    @AssociationOverride(name="statement", joinColumns = @JoinColumn(name = "EXPENSE_STATEMENT_ID"))
})    
public class ExpenseApproval extends Approval<ExpenseStatement>{
    private ExpenseStatement statement;

}

Hibernate和Java泛型 - 无法使用MappedSuperClass

1 个答案: