What are the best workarounds for known problems with Hibernate's schema validation of floating point columns when using Oracle 10g?

Question

I have several Java classes with double fields that I am persisting via Hibernate. For example, I have

@Entity
public class Node ...

  private double value         


        

Answer 1

There was a similar problem HHH-1598 with HSQL mappings of boolean fields, and a discussion of it here.

The solution I chose to use was in the discussion referenced above, with an extension of HSQLDialect.

I saw no problems with this, though I only use HSQL in tests.

It certainly doesn't interfere with any other DB.

Answer 2

just adding (columnDefinition = "NUMBER(9,2)") works!

@Column(name = "CREDIT_AMOUNT", columnDefinition = "NUMBER(9,2)")
@Basic
private double creditAmount;

Answer 3

This is a known limitation of the schema validator, check HHH-2315. So you have three options here (actually four but I guess that deactivating validation is not wanted). Either:

• Use a float instead of a double at the Java level - this might not be an option though.

• Patch org.hibernate.mapping.Table.validateColumns(Dialect dialect, Mapping mapping, TableMetadata tableInfo) to add a special condition for this particular case - this isn't really a light option.

• Extends the org.hibernate.dialect.Oracle10gDialect to make it use float for the SQL type DOUBLE

  public class MyOracle10gDialect extends Oracle10gDialect {
      public MyOracle10gDialect() {
          super();
      }
      protected void registerNumericTypeMappings() {
          super.registerNumericTypeMappings();
          registerColumnType( Types.DOUBLE, "float" );
      }
  }
  

The later option seems safe but will require some testing to see if it doesn't introduce any regression. I didn't look at Oracle's JDBC driver code, so I can't say how float and double precision differ at the driver level.

Answer 4

Use 'scale' attribute on your member.