查询在JDO / Datanucleus / H2中返回重复项

时间：2016-02-08 16:02:39

标签： jdo datanucleus

我将2个对象添加到数据库，Person和Student（Person的子类）。当我在Person上查询时，它会返回每个实例e两次。当我在Student上查询时，它会返回两个实例，即使Person不是Student的子类。该代码基于datanucleus的jdo-test-template。我正在使用Datanucleus 5.0.0m1。

tx.begin();

Person p = new Person(0, "Pete");
Student s = new Student(1, "Sarah");
pm.makePersistent(p);
pm.makePersistent(s);

Query<Person> qP = pm.newQuery(Person.class);
Collection<Person>cP = (Collection<Person>) qP.execute();
for (Person p2: cP) {
    System.out.println("Person: " + p2.getName() + " " + p2.getId() + " " + System.identityHashCode(p2));
}

Query<Student> qS = pm.newQuery(Student.class);
Collection<Student>c = (Collection<Student>) qS.execute();
for (Student s2: c) {
    System.out.println("Student: " + s2.getName() + " " + s2.getId() + " " + System.identityHashCode(s2));
}
tx.commit();

Person类与示例模板保持不变：

@PersistenceCapable(detachable="true")
public class Person {
    @PrimaryKey
    Long id;
    String name;

    public Person(long id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public Long getId() {
        return id;
    }
}

Student类：

@PersistenceCapable(detachable="true")
public class Student extends Person {

    public Student(long id, String name) {
        super(id, name);
    }
}

我还在Student文件中添加了persistence.xml：

<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
    version="1.0">

    <persistence-unit name="MyTest">
        <!-- Add all of your model classes here -->
        <class>mydomain.model.Person</class>
        <class>mydomain.model.Student</class>
        <exclude-unlisted-classes />
        <properties>
            <!-- Update these datastore details if different -->
            <property name="javax.jdo.PersistenceManagerFactoryClass" value="org.datanucleus.api.jdo.JDOPersistenceManagerFactory"/>
            <property name="javax.jdo.option.ConnectionURL" value="jdbc:h2:mem:nucleus"/>
            <property name="javax.jdo.option.ConnectionDriverName" value="org.h2.Driver"/>
            <property name="javax.jdo.option.ConnectionUserName" value="sa"/>
            <property name="javax.jdo.option.ConnectionPassword" value=""/>

            <property name="datanucleus.schema.autoCreateAll" value="true"/>
        </properties>
    </persistence-unit>

</persistence>

运行程序时，我得到以下输出：

Person: Sarah 1 454305524
Person: Sarah 1 1536471117
Person: Pete 0 1961945640
Person: Pete 0 1898155970
Student: Pete 0 1898155970
Student: Sarah 1 1536471117

查看System.identityHashCode(...)，它为第一个查询返回4个不同的Java实例。 我做错了吗？或者是预期的输出？

修改 我刚刚确认DataNucleus 4.1.8的行为与5.0.0m1相同

修改

来自日志文件：

17:36:21,660 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compiling "SELECT FROM mydomain.model.Person"
17:36:21,668 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compile Time = 8 ms
17:36:21,668 (main) DEBUG [DataNucleus.Query] - QueryCompilation:
  [symbols: this type=mydomain.model.Person]
17:36:21,669 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compiling "SELECT FROM mydomain.model.Person" for datastore
17:36:21,697 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compile Time for datastore = 28 ms
17:36:21,698 (main) DEBUG [DataNucleus.Query] - SELECT FROM mydomain.model.Person Query compiled to datastore query "SELECT 'mydomain.model.Person ' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0 UNION SELECT 'mydomain.model.Student' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0"
17:36:21,698 (main) DEBUG [DataNucleus.Persistence] - ExecutionContext.internalFlush() process started using ordered flush - 2 enlisted objects
17:36:21,698 (main) DEBUG [DataNucleus.Persistence] - ExecutionContext.internalFlush() process finished
17:36:21,698 (main) DEBUG [DataNucleus.Connection] - ManagedConnection found in the pool : "org.datanucleus.store.rdbms.ConnectionFactoryImpl$ManagedConnectionImpl@3c41ed1d [conn=org.datanucleus.store.rdbms.datasource.dbcp.PoolingDataSource$PoolGuardConnectionWrapper@22ff4249, commitOnRelease=false, closeOnRelease=false, closeOnTxnEnd=true]" for key="org.datanucleus.ExecutionContextImpl@40ef3420" in factory="ConnectionFactory:tx[org.datanucleus.store.rdbms.ConnectionFactoryImpl@5b12b668]"
17:36:21,698 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Executing "SELECT FROM mydomain.model.Person" ...
17:36:21,698 (main) DEBUG [DataNucleus.Datastore.Native] - BATCH [INSERT INTO PERSON ("NAME",ID) VALUES (<'Pete'>,<0>); INSERT INTO PERSON ("NAME",ID) VALUES (<'Sarah'>,<1>)]
17:36:21,699 (main) DEBUG [DataNucleus.Datastore] - Execution Time = 1 ms (number of rows = [1, 1]) on PreparedStatement "org.datanucleus.store.rdbms.ParamLoggingPreparedStatement@1573f9fc"
17:36:21,700 (main) DEBUG [DataNucleus.Datastore] - Closing PreparedStatement "org.datanucleus.store.rdbms.datasource.dbcp.DelegatingPreparedStatement@5939a379"
17:36:21,701 (main) DEBUG [DataNucleus.Datastore.Native] - SELECT 'mydomain.model.Person ' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0 UNION SELECT 'mydomain.model.Student' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0
17:36:21,702 (main) DEBUG [DataNucleus.Datastore.Retrieve] - Execution Time = 1 ms
17:36:21,705 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Execution Time = 7 ms
17:36:21,707 (main) DEBUG [DataNucleus.Cache] - Object with id "mydomain.model.Person:1" not found in Level 1 cache [cache size = 2]
17:36:21,707 (main) DEBUG [DataNucleus.Cache] - Object with id "mydomain.model.Person:1" not found in Level 2 cache
17:36:21,708 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Person@1f97cf0d" (id="mydomain.model.Person:1") added to Level 1 cache (loadedFlags="[YN]")
17:36:21,709 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Person@1f97cf0d" (id="1") added to Level 2 cache (fields="[0, 1]", version="")
17:36:21,711 (main) DEBUG [DataNucleus.Lifecycle] - Object "mydomain.model.Person@1f97cf0d" (id="mydomain.model.Person:1") has a lifecycle change : "HOLLOW"->"P_CLEAN"
17:36:21,711 (main) DEBUG [DataNucleus.Transaction] - Object "mydomain.model.Person@1f97cf0d" (id="1") enlisted in transactional cache
17:36:21,712 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Student@477b4cdf" (id="mydomain.model.Student:1") taken from Level 1 cache (loadedFlags="[YY]") [cache size = 3]
17:36:21,712 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Person@8dbdac1" (id="mydomain.model.Person:0") taken from Level 1 cache (loadedFlags="[YY]") [cache size = 3]
17:36:21,712 (main) DEBUG [DataNucleus.Cache] - Object with id "mydomain.model.Student:0" not found in Level 1 cache [cache size = 3]
17:36:21,713 (main) DEBUG [DataNucleus.Cache] - Object with id "mydomain.model.Student:0" not found in Level 2 cache
17:36:21,713 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Student@49dc7102" (id="mydomain.model.Student:0") added to Level 1 cache (loadedFlags="[YN]")
17:36:21,713 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Student@49dc7102" (id="0") added to Level 2 cache (fields="[0, 1]", version="")
17:36:21,713 (main) DEBUG [DataNucleus.Lifecycle] - Object "mydomain.model.Student@49dc7102" (id="mydomain.model.Student:0") has a lifecycle change : "HOLLOW"->"P_CLEAN"
17:36:21,713 (main) DEBUG [DataNucleus.Transaction] - Object "mydomain.model.Student@49dc7102" (id="0") enlisted in transactional cache
17:36:21,713 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compiling "SELECT FROM mydomain.model.Student"
17:36:21,713 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compile Time = 0 ms
17:36:21,713 (main) DEBUG [DataNucleus.Query] - QueryCompilation:
  [symbols: this type=mydomain.model.Student]
17:36:21,713 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compiling "SELECT FROM mydomain.model.Student" for datastore
17:36:21,714 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Compile Time for datastore = 1 ms
17:36:21,714 (main) DEBUG [DataNucleus.Query] - SELECT FROM mydomain.model.Student Query compiled to datastore query "SELECT 'mydomain.model.Student' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0"
17:36:21,714 (main) DEBUG [DataNucleus.Connection] - ManagedConnection found in the pool : "org.datanucleus.store.rdbms.ConnectionFactoryImpl$ManagedConnectionImpl@3c41ed1d [conn=org.datanucleus.store.rdbms.datasource.dbcp.PoolingDataSource$PoolGuardConnectionWrapper@22ff4249, commitOnRelease=false, closeOnRelease=false, closeOnTxnEnd=true]" for key="org.datanucleus.ExecutionContextImpl@40ef3420" in factory="ConnectionFactory:tx[org.datanucleus.store.rdbms.ConnectionFactoryImpl@5b12b668]"
17:36:21,714 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Executing "SELECT FROM mydomain.model.Student" ...
17:36:21,714 (main) DEBUG [DataNucleus.Datastore] - Closing PreparedStatement "org.datanucleus.store.rdbms.datasource.dbcp.DelegatingPreparedStatement@6b8ca3c8"
17:36:21,715 (main) DEBUG [DataNucleus.Datastore.Native] - SELECT 'mydomain.model.Student' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0
17:36:21,715 (main) DEBUG [DataNucleus.Datastore.Retrieve] - Execution Time = 1 ms
17:36:21,715 (main) DEBUG [DataNucleus.Query] - JDOQL Query : Execution Time = 1 ms
17:36:21,715 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Student@49dc7102" (id="mydomain.model.Student:0") taken from Level 1 cache (loadedFlags="[YY]") [cache size = 4]
17:36:21,715 (main) DEBUG [DataNucleus.Cache] - Object "mydomain.model.Student@477b4cdf" (id="mydomain.model.Student:1") taken from Level 1 cache (loadedFlags="[YY]") [cache size = 4]

我认为有趣的是Student查询在PERSON表上执行而没有其他参数。不确定它们如何映射数据库中的继承，但是如果所有类都映射到单个表中，那么我至少会期望一个列具有类型标识符：

    17:36:21,715 (main) DEBUG [DataNucleus.Datastore.Native] - SELECT 'mydomain.model.Student' AS NUCLEUS_TYPE,A0.ID,A0."NAME" FROM PERSON A0

1 个答案:

答案 0 :(得分：1)

您尚未指定继承策略以及您希望持久性机制如何区分共享表的类。 根据{{​​3}}使用function getComparisonByKeyFn($key) { return function($a, $b) use ($key) { return $a[$key] < $b[$key] ? -1 : ($a[$key] > $b[$key] ? 1 : 0); }; } usort($arr, getComparisonByKeyFn('weight')); usort($arr, getComparisonByKeyFn('key')); usort($arr, getComparisonByKeyFn('value')); 和@Inheritance。虽然它将默认继承策略为基类的NEW_TABLE和子类的SUPERCLASS_TABLE，但它不会默认任何鉴别器，因为可能你不想拥有一个并且从不需要分离存储在该表中的内容

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