Question

我正在制作一个Java ee Web应用程序。我有User和Permission类，而User类具有List类型的Permission。当休眠获取用户对象表单数据库时，我也想从user_permission表中获取用户的权限。用户和许可具有多对多关系。我正在使用Hibernate 5.4.1。配置SessionFactory时出现此错误：

java.lang.NullPointerException
    org.hibernate.boot.model.source.internal.hbm.ModelBinder$AbstractPluralAttributeSecondPass.bindCollectionElement(ModelBinder.java:3557)
    org.hibernate.boot.model.source.internal.hbm.ModelBinder$AbstractPluralAttributeSecondPass.doSecondPass(ModelBinder.java:3136)
    org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1684)
    org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1652)
    org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:286)
    org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83)
    org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:473)
    org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:84)
    org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:689)
    org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:724)

我的用户类别：

public class User
{
    private int id;
    private String name;
    private String password;
    private List<Permission> permissions;
    public User(){}
    public User(String name,String password)
    {
        this.name=name;
        this.password=password;
    }
    public String getName()
    {
        return name;
    }
    public void setName(String name)
    {
        this.name=name;
    }
    public String getPassword()
    {
        return password;
    }
    public void setPassword(String password)
    {
        this.password=password;
    }
    public int getId()
    {
        return id;
    }
    public void setId(int id)
    {
        this.id=id;
    }
    public void clearPermissions()
    {
        permissions.clear();
    }
    public boolean hasPermission(Permission permission)
    {
        return permissions.contains(permission);
    }
    public void addPermission(Permission permission)
    {
        permissions.add(permission);
    }
    public void deletePermission(Permission permission)
    {
        permissions.remove(permission);
    }
    public List<Permission> getPermissions()
    {
        return permissions;
    }
    public void setPermissions(List<Permission> permissions)
    {
        this.permissions = permissions;
    }
}

用户类映射：

<?xml version="1.0" encoding="UTF-8"?>
<hibernate-mapping>
    <class name="model.User" table="user">
        <id name="id" type="int" column="id">
            <generator class="identity"/>
        </id>
        <property name="name" column="name" type="string"/>
        <property name="password" column="password" type="string"/>
        <list name="permissions" table="user_permission" lazy="false">
            <key column="user_id"/>
            <index column="id"/>
            <many-to-many class="Permission" column="permission_id"/>
        </list>
    </class>
</hibernate-mapping>

我的权限类：

public class Permission
{
    private int id;
    private String name;
    public Permission() {}
    public Permission(int id, String name)
    {
        this.id=id;
        this.name=name;
    }
    public String getName()
    {
        return name;
    }
    public void setName(String name)
    {
        this.name=name;
    }
    public int getId()
    {
        return id;
    }
    public void setId(int id)
    {
        this.id=id;
    }
    public boolean equals(Object obj)
    {
        return ((Permission)obj).id==id;
    }
}

权限类映射：

<?xml version="1.0" encoding="UTF-8"?>
<hibernate-mapping>
    <class name="model.Permission" table="permission">
        <id name="id" type="int" column="id">
            <generator class="identity"/>
        </id>
        <property name="name" column="name" type="string"/>
    </class>
</hibernate-mapping>

Answer 1

多对多映射中缺少packageName。将其从Permission更改为model.Permission。它应该解决问题。下面是代码段

<class name="model.User" table="user">
    <id name="id" type="int" column="id">
        <generator class="identity"/>
    </id>
    <property name="name" column="name" type="string"/>
    <property name="password" column="password" type="string"/>
    <list name="permissions" table="user_permission" lazy="false">
        <key column="user_id"/>
        <index column="id"/>
        <many-to-many class="model.Permission" column="permission_id"/>
    </list>
</class> </hibernate-mapping>

java EE Hibernate List多对多配置错误

1 个答案: