子类映射时的休眠问题 - 实例化默认元组

Question

我有一个用户类和员工类，其中员工类扩展和用户类。另外，我有一个地址类，它与这两个类都有一个 HAS-A 关系。下面是实现类和错误。我收到错误消息。

用户模型

  public class User {
    private int userid;
    private String username;
    private String password;
    private Date dob;
    private String gender;
    private Set<Address> addresses;
//getter and setters
}

员工模型

public class Employee extends User {
    private Date joindate;
    private String role;
    private Branch branch;
//getter and setters
}

地址模型

public class Address {
    private String email;
    private String mobile;
    private String street;
    private String city;
    private String state;
    private String country;
    private String pin;
//getter & setters
}

users.hbm.xml

<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.alok.mypro.model.usermodel.User" table="myuser" schema="mydb">
        <id name="userid">
            <generator class="increment" />
        </id>
        <property name="username" />
        <property name="password" />
        <property name="dob" />
        <property name="gender" />
        <set name="addresses" cascade="all">
            <key column="userid" />
            <one-to-many class="com.alok.mypro.model.usermodel.Address" />
        </set>

        <joined-subclass name="com.alok.mypro.model.usermodel.Employee" table="employee">
            <key column="userid" />
            <property name="joindate" />
            <property name="role" />
            <many-to-one name="branch" class="com.alok.mypro.model.places.Branch"/>
        </joined-subclass>

    </class>
</hibernate-mapping>

address.hbm.xml

<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.alok.mypro.model.usermodel.Address" table="address"
        schema="myuser">

        <id name="email" />
        <property name="mobile" />
        <property name="street" />
        <property name="city" />
        <property name="state" />
        <property name="country" />
        <property name="pin" />
    </class>
</hibernate-mapping>

构建时出现异常

---

线程“主”org.hibernate.HibernateException 中的异常：无法实例化默认 tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer] 在 org.hibernate.tuple.entity.EntityTuplizerFactory.constructTuplizer(EntityTuplizerFactory.java:108) 在 org.hibernate.tuple.entity.EntityTuplizerFactory.constructDefaultTuplizer(EntityTuplizerFactory.java:133) 在 org.hibernate.tuple.entity.EntityEntityModeToTuplizerMapping.(EntityEntityModeToTuplizerMapping.java:80) 在 org.hibernate.tuple.entity.EntityMetamodel.(EntityMetamodel.java:322) 在 org.hibernate.persister.entity.AbstractEntityPersister.(AbstractEntityPersister.java:485) 在 org.hibernate.persister.entity.JoinedSubclassEntityPersister.(JoinedSubclassEntityPersister.java:126) 在 org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:87) 在 org.hibernate.impl.SessionFactoryImpl.(SessionFactoryImpl.java:286) 在 org.hibernate.cfg.Configuration.buildSessionFactory（Configuration.java:1872） 在 Test.main(Test.java:7)

引起：java.lang.reflect.InvocationTargetException 在 sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 在 sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) 在 sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) 在 java.lang.reflect.Constructor.newInstance(Constructor.java:423) 在 org.hibernate.tuple.entity.EntityTuplizerFactory.constructTuplizer(EntityTuplizerFactory.java:105)

原因：org.hibernate.PropertyNotFoundException：在 com.alok.mypro.model.usermodel.Employee 类中找不到地址的 getter 在 org.hibernate.property.BasicPropertyAccessor.createGetter(BasicPropertyAccessor.java:326) 在 org.hibernate.property.BasicPropertyAccessor.getGetter(BasicPropertyAccessor.java:320) 在 org.hibernate.mapping.Property.getGetter(Property.java:304) 在 org.hibernate.tuple.entity.PojoEntityTuplizer.buildPropertyGetter(PojoEntityTuplizer.java:297) 在 org.hibernate.tuple.entity.AbstractEntityTuplizer.(AbstractEntityTuplizer.java:155) 在 org.hibernate.tuple.entity.PojoEntityTuplizer.(PojoEntityTuplizer.java:77) ... 14 更多

Answer 1

错误是由于缺少 getter 属性。

您应该将以下代码添加到地址类

public Set<Address> getAddresses() {
        return addresses;
    }

此外，请检查您是否还有 setter 属性。

private void setAddresses(Set<Address> addresses) {
    this.addresses = addresses;
}

Hibernate 基本上需要 getter 和 setter 属性用于需要持久化的属性，如 https://docs.jboss.org/hibernate/orm/5.0/mappingGuide/en-US/html/ch02.html#domainmodel-pojo-accessors 所述。

您应该将 setter 设为私有，以便在更改期间强制对您的类进行数据封装。