Question

我有一个包的结构如下：

<bag name="foo" fetch="select" table="table_of_foos">
    <key column="foo_ids"/>
    <many-to-many class="Bar" column="bar_ids"/>
</bag>

我的“table_of_foos”表有两列：“foo_ids”和“bar_ids”，两者都不是唯一的。我想在这个表中添加另一个列，其中包含有关foos与bars之间关系的一些信息，以便我的表将包含三列。然后，我希望能够在我的webapp中访问此信息。

不幸的是，似乎我不能在包中添加属性或元素。我想做的是这样的事情：

<bag name="foo" fetch="select" table="table_of_foos">
    <key column="foo_ids"/>
    <many-to-many class="Bar" column="bar_ids"/>
    <element column="still_valid" type="integer"/>
</bag>

实现这一目标的最佳方法是什么？

Answer 1

如果您的已加入的表需要除其（复合）主键之外的其他列，则必须实现其他已加入的类。

public class Foo {

    Collection<FooBar> bar = new ArrayList<FooBar>();

}

public class Bar {

    Collection<FooBar> foo = new ArrayList<FooBar>();

}

连接类（需要复合主键 - 实现为静态内部类）描述如下

public class FooBar {

    private FooBarId fooBarId;

    private String additionalProperty;

    public static class FooBarId implements Serializable {

        private Integer fooId;
        private Integer barId;

        private Foo foo;
        private Bar bar;

        // getter's and setter's

        public FooBarId() {}
        public FooBarId(Integer fooId, Integer barId) {
            this.fooId = fooId;
            this.barId = barId;
        }

        public boolean equals(Object o) {
            if(!(o instanceof FooBarId))
                return false;

            FooBarId other = (FooBarId) o;
            return new EqualsBuilder()
                       .append(getFooId(), other.getFooId())
                       .append(getBarId(), other.getBarId())
                       .isEquals();
        }

        public int hashCode() {
            return new HashCodeBuilder()
                       .append(getFooId())
                       .append(getBarId())
                       .hashCode();
        }

    }

}

将您的映射重写为

/* Foo.class */ 

<bag name="bar" table="table_of_foos">
    <key column="BAR_ID" insert="false" update="false"/>
    <one-to-many class="FooBar" table="table_of_foos"/>
</bag>

/* Bar.class */ 

<bag name="foo" table="table_of_foos">
    <key column="FOO_ID" insert="false" update="false"/>
    <one-to-many class="FooBar" table="table_of_foos"/>
</bag>

和FooBar映射

<class name="FooBar">
    <composite-id name="fooBarId" class="FooBar$FooBarId">
        <key-property name="fooId" column="FOO_ID"/>
        <key-property name="barId" column="BAR_ID"/>
    </composite-id>
    <property name="additionalProperty" type="string"/>
    <many-to-one name="foo" column="FOO_ID" class="Foo" insert="false" update="false"/>
    <many-to-one name="bar" column="BAR_ID" class="Bar" insert="false" update="false"/>
</class>

如果需要，还可以映射复合元素而不是连接类（组件元素不需要（复合）主键，的生命周期与其拥有的实体实例的生命周期绑定< / strong>。记住这一点）

创建复合元素（现在没有标识符）

public class FooBar { private String additionalProperty; private Foo foo; private Bar bar; }

并定义以下映射

/* Foo.class */ <bag name="bar" table="table_of_foos"> <key column="BAR_ID"/> <composite-element class="FooBar"> <property name="additionalProperty" type="string"/> <many-to-one name="foo" column="FOO_ID" class="Foo" insert="false" update="false"/> <many-to-one name="bar" column="BAR_ID" class="Bar"/> </composite-element> </bag> /* Bar.class */ <bag name="foo" table="table_of_foos"> <key column="FOO_ID"/> <composite-element class="FooBar"> <property name="additionalProperty" type="string"/> <many-to-one name="foo" column="FOO_ID" class="Foo" insert="false" update="false"/> <many-to-one name="bar" column="BAR_ID" class="Bar"/> </composite-element> </bag>

Answer 2

我无法按照Arthur Ronald F D Garcia的说法使这些映射工作。此代码不起作用并导致MappingException。

无效尝试

<set name="StoreDepartments" table="`ou_store_org_unit`">
    <key column="`ou_id`" />
    <composite-element class="NHibernate.Map.OrganizationUnit+StoreDepartment+Relation, CentralDataLayer">
        <property name="Id" column="`ou_store_id`" type="Int32" />
        <many-to-one name="OrganizationUnit" column="`ou_id`" class="NHibernate.Map.OrganizationUnit, CentralDataLayer" />
        <many-to-one name="StoreDepartment" column="`store_ou_id`" class="NHibernate.Map.OrganizationUnit+StoreDepartment, CentralDataLayer" />
    </composite-element>
</set>

Resulting Error: Repeated column in mapping for collection:
NHibernate.Map.OrganizationUnit.StoreDepartments column: ou_id

我能够使用以下内容。

有效尝试

<set name="StoreDepartments" table="`ou_store_org_unit`">
    <key column="`ou_id`" />
    <composite-element class="NHibernate.Map.OrganizationUnit+StoreDepartment+Relation">
        <parent name="OrganizationUnit" />
        <property name="Id" column="`ou_store_id`" type="Int32" />
        <many-to-one name="StoreDepartment" column="`store_ou_id`" class="NHibernate.Map.OrganizationUnit+StoreDepartment" />
    </composite-element>
</set>

<强> 此外：

如果nHibernate尝试更新您的设置，即使您没有修改它，请尝试覆盖GetHasCode和Equals方法。更多information here。

Hibernate包有多个元素

2 个答案: