Question

创建表ActivityLog时，我在ORM Lite上收到此错误：

10-23 04:06:32.255: E/com.timelord.dao.DatabaseHelper(1487): 
Caused by: java.sql.SQLException: ORMLite can't store unknown class class 
com.timelord.pojo.Category for field 'category'. Serializable fields must 
specify dataType=DataType.SERIALIZABLE

我怀疑这是由多级外键引起的。正如您在下面的POJO类中看到的，ActivityLog具有Activity，而Activity具有Category。

活动和类别工作正常。

有关如何进行正确映射的想法吗？

@DatabaseTable(tableName = "activityLogs")
public class AcitvityLog implements Serializable {

    private static final long serialVersionUID = 1L;

    @DatabaseField(generatedId = true)
    private int id;

    @DatabaseField(canBeNull = false)
    @DatabaseFieldForeign(foreign = true)
    private Activity activity;

    @DatabaseField(dataType = DataType.DATE, canBeNull = false)
    private Timestamp start;

    @DatabaseField(dataType = DataType.DATE, canBeNull = true)
    private Timestamp end;
}

@DatabaseTable(tableName = "activities")
public class Activity extends BaseEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @DatabaseField(canBeNull = false)
    @DatabaseFieldForeign(foreign = true)
    private Category category;
}

@DatabaseTable(tableName = "categories")
public class Category extends BaseEntity implements Serializable {

    private static final long serialVersionUID = 1L;
}

public class BaseEntity {
    @DatabaseField(generatedId = true)
    private Integer id;

    @DatabaseField(canBeNull = false)
    private String name;
}

Answer 1

不，ORMLite可以处理多级外键而不会出现任何问题。问题是您无法混合@DatabaseField和@DatabaseFieldForeign注释。你想要的是：

@DatabaseField(canBeNull = false, foreign = true)
private Activity activity;

或者，如果您想使用在Android下运行速度更快的较小注释：

@DatabaseFieldSimple(canBeNull = false)
@DatabaseFieldForeign(foreign = true)

您使用 @DatabaseField或@DatabaseFieldSimple以及其他@DatabaseField...注释。以下是@DatabaseFieldSimple的文档：

http://ormlite.com/javadoc/ormlite-core/com/j256/ormlite/field/DatabaseFieldSimple.html

创建包含多级外键的表时，ORM Lite会引发错误

1 个答案: