java – hibernate复合键

如果您将复合ID映射为实体的属性,则实体本身就是标识符.

第二种方法称为映射复合标识符,其中在< composite-id>内部命名的标识符属性.元素在持久化类和单独的标识符类上都是重复的

最后,composite-id可以是组件类.在这种情况下,组件类是标识符类.

请注意,强烈建议将ID作为单独的类.否则,您将只使用session.get()或session.load()查找对象的方法非常笨拙.

参考文档的相关部分：

> composite-id
> Components as composite identifiers

在此示例中,composite-id被映射为实体的属性. (以下假设您正在定义Employee类).

<composite-id>
    <key-property name="EmployeeNumber"/>
    <key-property name="Dependent"/>
</composite-id>

class EmployeeAssignment implements Serializable
{
    string getEmployeeNumber()
    void setEmployeeNumber( string value )
    string getDepartment()
    void setDepartment( string value )
    boolean equals( Object obj )
    int hashCode()
}

映射的composite-id：

<composite-id class="EmployeeAssignmentId" mapped="true">
    <key-property name="EmployeeNumber"/>
    <key-property name="Dependent"/>
</composite-id>

class EmployeeAssignment
{
    string getEmployeeNumber()
    void setEmployeeNumber( string value )
    string getDepartment()
    void setDepartment( string value )
}

class EmployeeAssignmentId implements Serializable
{
    string getEmployeeNumber()
    void setEmployeeNumber( string value )
    string getDepartment()
    void setDepartment( string value )
    boolean equals( Object obj )
    int hashCode()
}

作为composite-id的组件：

<composite-id name="Id" class="EmployeeAssignmentId">
    <key-property name="EmployeeNumber"/>
    <key-property name="Dependent"/>
</composite-id>

class EmployeeAssignment
{
    EmployeeAssignmentId getId()
    void setId( EmployeeAssignmentId value )
}

class EmployeeAssignmentId implements Serializable
{
    string getEmployeeNumber()
    void setEmployeeNumber( string value )
    string getDepartment()
    void setDepartment( string value )
    boolean equals( Object obj )
    int hashCode()
}