是否有可能在類中持有OrmLite的枚舉字段？

Question

我試圖用OrmLite堅持以下類：

public class Field { 
    @DatabaseField(id = true) 
    public String name; 

    @DatabaseField(canBeNull = false) 
    public FieldType type; 
    ... 
} 

的FieldType是public enum。該字段對應於type是SQLite中的字符串（不支持枚舉）。當我嘗試使用它，我得到以下異常：

INFO [main] (SingleConnectionDataSource.java:244) - Established shared JDBC Connection: org.sqlite.Conn@5224ee 
Exception in thread "main" org.springframework.beans.factory.BeanInitializationException: Initialization of DAO failed; nested exception is java.lang.IllegalArgumentException: Unknown field class class enums.FieldType for field FieldType:name=type,class=class orm.Field 
at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:51) 
at orm.FieldDAO.getInstance(FieldDAO.java:17) 
at orm.Field.fromString(Field.java:23) 
at orm.Field.main(Field.java:38) 
Caused by: java.lang.IllegalArgumentException: Unknown field class class enums.FieldType for field FieldType:name=type,class=class orm.Field 
at com.j256.ormlite.field.FieldType.<init>(FieldType.java:54) 
at com.j256.ormlite.field.FieldType.createFieldType(FieldType.java:381) 
at com.j256.ormlite.table.DatabaseTableConfig.fromClass(DatabaseTableConfig.java:82) 
at com.j256.ormlite.dao.BaseJdbcDao.initDao(BaseJdbcDao.java:116) 
at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:48) 
... 3 more 

那我怎麼告訴OrmLite，值在Java端是從enum？

Answer 1

ORMLite能堅持枚舉無論是作爲VARCHAR enum name (default)：

// this saves it as a string in the database 
@DatabaseField 
OurEnum ourEnum; 
... 
private enum OurEnum { 
    FIRST, 
    SECOND, ; 
} 

作爲替代方案，可以節省ordinal INTEGER。

// this saves it as an integer in the database 
@DatabaseField(dataType = DataType.ENUM_INTEGER) 
OurEnum ourEnum; 

雖然你可以店序，推薦VARCHAR名稱的版本（這是默認的），因爲如果從枚舉添加或刪除條目序號值可以改變。

對於這兩種枚舉類型，您可以指定一個unknownEnumName = "..." field，這有助於向前和向後兼容。如果數據庫包含枚舉的未知值，則由DAO返回的對象將具有此枚舉值。

@DatabaseField(unknownEnumName = "FIRST") 
OurEnum ourEnum;