Using EclipseLink JPA to bind Strings larger than 255 characters
I inherited a project which uses EclipseLink JPA to persist objects into any SQL database. Currently it comes with a local Derby DB distribution. During some tests I found out that the program will throw the following exception:
012-08-03 10:21:11.357--UnitOfWork(32349505)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException Internal Exception: java.sql.SQLDataException: A truncation error was encountered trying to shrink VARCHAR 'some necessarily really long text' to length 255. Error Code: 20000
Obviously VARCHAR isn't (usually) suitable for storing Strings larger than 255 characters yet I didn't find the code fragment where the objects variable is explicitely assigned to a VARCHAR field. I understand that JPA or EclipseLink automatically assigns this for you, so my question, where I couldn't find a simple answer yet, is:
How can I make sure that EclipseLink / JPA stores Strings larger than 255 characters?
You need to annotate the property so it gets persisted as Clob. Use @Lob; for Strings this will default to Clob. See here for the documentation. Of course you need to make sure that the database column type is correct (i.e. not VARCHAR) if you create the database manually.
I show you data type that to bind String larger than 255 characters. See this;
Java Type - byte, java.lang.Byte, java.sql.Clob
Java DB, Derby, CloudScape - CLOB(64000)
Oracle - LONG
DB2 - CLOB(64000)
Sybase - TEXT
MSSQL - TEXT
MySQL - TEXT(64000)
In many enviroments @Column of type String has limit larger than 255, for example to 4kB. You need use 'length' to change default 255