Value Type

When you choose a value class for a particular attribute, you sometimes do not provide Enterprise Objects with all the information the JDBC adaptor needs to negotiate with the data source.

For example, when you specify Number as the value class for a particular attribute, you are telling Enterprise Objects to use java.lang.Number, which is an abstract class. This is where the value type characteristic steps in. It specifies the exact class an attribute should map to.

The possible value types for numeric attributes are as follows(note case):

• b—java.lang.Byte
• s—java.lang.Short
• i—java.lang.Integer
• l—java.lang.Long
• f—java.lang.Float
• d—java.lang.Double
• B—java.math.BigDecimal
• c—java.lang.Boolean

The value type also specifies which JDBC methods are used to send and retrieve the data to and from the database. These value types affect which method the java.sql.PreparedStatement object uses to transfer text data between the database and the JDBC adaptor. For attributes with a value class of String, the following value types are defined:

• <none>—uses setString if the text is less than the database’s advertised maximum varchar length and setCharacterStream if it is too large. If the database fails to advertise a maximum length, the default is 256 characters.
• S—uses setString regardless of the text’s length.
• C—uses setCharacterString regardless of the text’s length.
• E—converts the text into raw UTF-8 bytes and then uses setBinaryStream to save them in a binary-typed column in the database.
• c—tells the adaptor to generate SQL using RTRIM to strip off all trailing spaces.

Database columns of type char hold string values that are right-padded with spaces to the width of the column. String values in Enterprise Objects, however, normally do not have trailing spaces for performance and other efficiency reasons. An attribute that maps to an external type of char should have a value type of c to tell the JDBC adaptor to trim trailing spaces when fetching values that correspond to that attribute. If the value type is left blank for attributes that map to an external type of char, then no trimming occurs. Attributes that map to varchar columns are never trimmed, regardless of value type.

S is the appropriate value type for most text columns. C is good for columns that usually contain large amounts of data. c should be used when trailing spaces are not significant in a char column. It is not recommended to use E, except when absolutely necessary. It is the database’s responsibility to handle text encoding issues and using E usually indicates that the database is not properly configured.

For attributes with a value class of NSTimestamp, the following value types are defined:

• <none>—uses getObject on the java.sql.ResultSet object and setObject on the java.sql.PreparedStatement object. It assumes the database can provide a value compatible with a java.sql.Timestamp object.
• D—java.util.Date uses setDate and getDate.
• t—java.sql.Time uses getTime and setTime.
• T—java.sql.Timestamp uses getTimestamp and setTimestamp.
• M—use in place of D if using Microsoft SQL Server. Supports only java.sql.Date.