HP Integrity NonStop J-Series - Manual (Page 97)

When the SQL/MX table contains the identity column and the mapping does not specify the
generator class as “identity or "org.hibernate.dialect.SqlMxIdentityGenerator “, then the dialect
returns the following errors which are captured in the log:
Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not insert:
Caused by: com.tandem.t4jdbc.SQLMXException: *** ERROR[3428] IDENTITY column ID defined
as GENERATED ALWAYS cannot accept values specified by the user.
Error Mapping
Sometimes when errors occur in Hibernate, the exceptions (such as database connection errors,
SQL errors, etc.) are displayed with error codes which are not very user-friendly in nature. The
HibernateException, which wraps most of the errors that can occur in a Hibernate persistence
layer, is an unchecked exception. Hibernate wraps these SQLExceptions thrown while interacting
with the database in a JDBCException. It attempts to convert the exception into a more meaningful
subclass of JDBCException. For this purpose, custom error mapping is required as it helps in building
recovery mechanisms for custom SQL/MX errors in a standard way.
To achieve error mapping, a new class, SqlMxSQLStateConverter, has been added to the dialect
package to implement error mapping. This class is available by default when the dialect is installed.
SqlMxSQLStateConverter class uses the SqlErrorCodesMapping.properties property file.
This file can be made available to the class in the following methods:
•
By placing the SqlErrorCodesMapping.properties file in the application class path.
•
By defining a java property sqlmxhibernate.er-map with a value. This value is the path
to the SqlErrorCodesMapping.properties file. You can make this property available
to the application by passing it as a Java application argument line
-Dsqlmxhibernate.er-map=/SqlErrorCodesMapping.properties
NOTE: If the SqlErrorCodesMapping.properties file is not loaded, the following message
is logged into the hibernate log:
“SqlErrorCodesMapping.properties (The system cannot find the file specified)”
The error messages are categorized based on the type of error and each group is assigned to an
exception. Hibernate uses the SQLExceptionConverter to convert an SQLException into an
appropriate JDBCException subclass, provided SQLMXDialect provides a SQLExceptionConverter
implementation so that based on SQL/MX error codes appropriate JDBCException subtype can
be created.
The following exception types are handled:
•
JDBCConnectionException : indicates an error with the JDBC communication.
•
SQLGrammarException : indicates a grammatical error or a syntax problem with the issued
SQL statement.
•
ConstraintViolationException : indicates integrity constraint violation.
•
LockAcquisitionException : indicates an error acquiring a lock level necessary to
perform the requested operation.
For example, all SQL grammatical or syntax related error messages are categorized under a
subclass and are mapped to the SQLGrammarException.
The following is a simple hibernate code that queries address table and gets the data in a List. The
method list() on the query object queries the underlying database and returns the result as a List
object.
Currently, without SQLExceptionConverter you must catch HibernateException (which is an
unchecked exception) as follows.
Configuration cfg = new Configuration().configure();
SessionFactory sf = cfg.buildSessionFactory();
Installing the Hibernate Framework 97