Hibernate L2 缓存用于多对一关联

Question

I am somewhat new to hibernate and am attempting to implement second level caching using ehCache. I am running into a problem when attempting to use the L2 cache to retrieve a many-to-one association. The association mapping in my foo.hbm.xml file looks like:

<hibernate-mapping>
    <class name="com.test.Foo" table="FOO" >
        <id name="id" type="long">
            <column name="FOO_ID" precision="11" scale="0" />
            <generator class="assigned" />
        </id>

        <many-to-one name="bar" class="com.test.Bar" >
            <cache usage="read-only" />
            <column name="BAR_TY" not-null="true" />
            <column name="BAR_VAL" length="4" not-null="true" />
        </many-to-one>

    </class>
</hibernate-mapping>

(This is a very shortened/modified version of my actual hbm.xml file, hopefully no errors in it)

Note that I am only caching "bar", not "foo". However when I run a unit test with this mapping I get the following error:

SEVERE: Error parsing XML: XML InputStream(40) The content of element type "many-to-one" must match "(meta*,(column|formula)*)".

When I take out it works fine, just no L2 caching. Is it simply that the many-to-one relationship doesn't support caching? And if so, any suggestions on how to get around this?

FYI I have another unit test that reads "bar" directly (ie not through an association) and it works correctly - the 2nd time I get a "bar" it gets it from the L2 cache, so I'm fairly confident I have the rest of the configuration done correctly. And so sorry, still in the stone ages at work so no annotations etc.

Answer 1

Your XML is malformed. It is illegal node <cache> inside <many-to-one> .
See hibernate-mapping-3.0.dtd . Declaration on many-to-one element:

<!ELEMENT many-to-one (meta*,(column|formula)*)>
    <!ATTLIST many-to-one name CDATA #REQUIRED>
    <!ATTLIST many-to-one access CDATA #IMPLIED>
    <!ATTLIST many-to-one class CDATA #IMPLIED>
    <!ATTLIST many-to-one entity-name CDATA #IMPLIED>
    <!ATTLIST many-to-one column CDATA #IMPLIED>
    <!ATTLIST many-to-one not-null (true|false) #IMPLIED>
    <!ATTLIST many-to-one unique (true|false) "false">
    <!ATTLIST many-to-one unique-key CDATA #IMPLIED>
    <!ATTLIST many-to-one index CDATA #IMPLIED>
    <!ATTLIST many-to-one cascade CDATA #IMPLIED>
    <!ATTLIST many-to-one outer-join (true|false|auto) #IMPLIED>
    <!ATTLIST many-to-one fetch (join|select) #IMPLIED>
    <!ATTLIST many-to-one update (true|false) "true">
    <!ATTLIST many-to-one insert (true|false) "true">
    <!ATTLIST many-to-one optimistic-lock (true|false) "true">  
    <!ATTLIST many-to-one foreign-key CDATA #IMPLIED>
    <!ATTLIST many-to-one property-ref CDATA #IMPLIED>
    <!ATTLIST many-to-one formula CDATA #IMPLIED>
    <!ATTLIST many-to-one lazy (false|proxy|no-proxy) #IMPLIED>
    <!ATTLIST many-to-one not-found (exception|ignore) "exception">
    <!ATTLIST many-to-one node CDATA #IMPLIED>
    <!ATTLIST many-to-one embed-xml (true|false) "true">  

Cache element can be placed on class level:

<hibernate-mapping>
    <class name="com.test.Foo" table="FOO" >
        <cache usage="read-only" />
        <id name="id" type="long">

or for collections like set , map , bag etc.

Answer 2

Have you tried moving definition of bar into another, separate .hbm.xml and only referencing it from foo ?