We had been working on this Grails 2 app for a few weeks and we were finally ready to put it on a test server (instead of running it like run-app locally). More importantly we were ready to point it away from an H2 database and to SQLServer. But then we ran into problems…

SQLServer doesn’t have a boolean type, but instead will use int. And we were using CLOBS and Hibernate was mapping them to text, which is deprecated in SQLServer in favor of nvarchar(max). And a lot of other little things. The CLOB was important to us because we were using that a lot in this app. And there was a bit difference on how H2 handled it as opposed to how SQLServer did.

After googling around the solution came to be to write your own Hibernate Dialiact. That sounded daunting but it actually wasn’t. This is what we came up with:

import java.sql.Types


public class MySqlServerDialect extends org.hibernate.dialect.SQLServerDialect {

    public MySqlServerDialect() {
        registerColumnType(Types.BIGINT, "bigint");
        registerColumnType(Types.BIT, "bit");
        registerColumnType(Types.CHAR, "nchar(1)");
        registerColumnType(Types.VARCHAR, 4000, "nvarchar(\$l)");
        registerColumnType(Types.VARCHAR, "nvarchar(max)");
        registerColumnType(Types.VARBINARY, 4000, "varbinary(\$1)");
        registerColumnType(Types.VARBINARY, "varbinary(max)");
        registerColumnType(Types.BLOB, "varbinary(max)");
        registerColumnType(Types.CLOB, "nvarchar(max)");


    }
}

And then you have to tell Grails about it. In the DataSource.groovy add this to the SQLServer entries:

dialect = com.foo.MySqlServerDialect

And that should be it.