android - 创建包含多级外键的表时，ORM Lite引发错误

创建表ActivityLog时，在ORM Lite上出现此错误：

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。从下面的POJO类中可以看到，ActivityLog具有Activity，而Activity具有Category。

活动和类别工作正常。

关于如何进行正确映射的任何想法？

@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;
}

最佳答案

不，ORMLite可以处理多级外键，没有任何问题。问题是您不能混合使用@DatabaseField和@DatabaseFieldForeign批注。您想要的是：

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

或者，如果您想使用在Android下运行更快的较小注释：

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

您仅使用@DatabaseField或@DatabaseFieldSimple以及其他@DatabaseField...批注。以下是@DatabaseFieldSimple的文档：


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

关于android - 创建包含多级外键的表时，ORM Lite引发错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/7872880/