How do I externalize named queries in a Hibernate

问题:

Is there a way to externalize HQL named queries to an external file. I have too many named queries and using @NamedQueries and @NamedQuery at the head of my entities classes is hurting.

Is there a way to externalize to several files?

回答1:

You can put the queries into package-info.java class, in, say, root package of your domain objects. However, you must use Hibernate's own @NamedQueries and @NamedQuery annotations, rather than those from javax.persistence.

Example package-info.java file:

@org.hibernate.annotations.NamedQueries({
    @org.hibernate.annotations.NamedQuery(
        name = "foo.findAllUsers", 
        query="from Users") 
}) 

package com.foo.domain;

Then, you have to add the package to your AnnotationConfiguration. I use Spring, so there it's a matter of setting annonatedPackages property:

<bean id="sessionFactory" 
class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="annotatedClasses">
      <list>
      ...
      </list>
</property>
<property name="annotatedPackages">
  <list>
      <value>com.foo.domain</value>
  </list>
</property>

You can also put type and filter definitions in the same file as well.

回答2:

I don't think that this is possible as Annotation attribute/property values must be available at compile time. Therefore, Strings cannot be externalized to a file that needs to be read in by some sort of process.

I tried to find if there was something that package-info.java might be able to provide, but could not find anything.

An alternative strategy for organization could be storing the queries as constants in a Class.

In your entity class:

@NamedQuery(name="plane.getAll", query=NamedQueries.PLANE_GET_ALL)

Then define a class for your query constants:

public class NamedQueries {
    ...
    public static final String PLANE_GET_ALL = "select p from Plane p";
    ...
}

回答3:

Maybe this is not exactly what author asked for (to externalize to non-java file), but this is how I solved it:

1.) in my application context xml file I added mappingResources to sessionFactory

<bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="mappingResources">
      <list>
        <value>META-INF/Country.hbm.xml</value>
      </list>
    </property>
    <property name="annotatedClasses">
        <util:list>
            <value>com.example.Country</value>
        </util:list>
    </property>
    <property name="hibernateProperties" ref="hibernateProperties" />
</bean>

and in that Country.hbm.xml I have

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings 
    xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_2_0.xsd"
    version="2.0">

    <entity class="com.example.Country">

        <named-query name="countryFindByCode">
            <query><![CDATA[
                select c
                  from Country c
                 where c.code = :code
            ]]></query>
        </named-query>

        <named-query name="countryFindByName">
            <query><![CDATA[
                select c
                  from Country c
                 where c.name = :name
            ]]></query>
        </named-query>

    </entity>

</entity-mappings>

I used that just to define named queries, the rest of entity configuration is in annotations.

Maybe that helps someone.

回答4:

<bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="mappingResources">
      <list>
        <value>META-INF/Country.hbm.xml</value>
      </list>
    </property>
    <property name="annotatedCla 
                  from Country c
                 where c.name = :name
            ]]></query>
        </named-query>

    </entity>

</entity-mappings>