会话Bean中的EntityManager异常处理

Question

I have a managed stateless session bean with injected EntityManager em.

What I am trying to do is to have a database table with unique column. Then I run some algorithm which is trying to insert an entity. If entity exists however it will update it or skip it.

I would like to have something like this:

try {   
em.persist(cd);     
em.flush();     
} catch (PersistenceException e) {  
// Check if the exception is DatabaseException and ConstraintViolation
    // Update instead or skip it
}

Problem is that I am able to catch only PersistenceException . DatabaseException is not catched. It is sad because only DatabaseException has method called getDatabaseErrorCode() I would like to use to check duplicate entry. I dont understand it because PersistenceException.getCause() returns DatabaseException .

So my question is: How do I catch DatabaseException and check the MySQL error code?

Thank you for any ideas and experiences with this.

Answer 1

I have a suggestion which is I use in my application. We can retrieve the SQLException from PersistenceException . After that, try to get sql error code for SQLException . If your requirement is to get the sql error code , your can follow my example;

public void insert(Group group) throws DAOException {
    try {
        //your operation
        em.flush();
        logger.debug("insert() method has been successfully finisehd.");
    } catch (PersistenceException pe) {
        String sqlErroCode = getErrorCode(pe);
        // do your operation based on sql errocode
    }
}

protected String getErrorCode(RuntimeException e) {
    Throwable throwable = e;
    while (throwable != null && !(throwable instanceof SQLException)) {
        throwable = throwable.getCause();
    }
    if (throwable instanceof SQLException) {
        Properties properties = --> load sql error code form configuration file.
        SQLException sqlex = (SQLException) throwable;
        String errorCode = properties.getProperty(sqlex.getErrorCode() + "");
        return errorCode;
    }
    return "NONE";
}

Example error code configuration of mysql

mysql_error_code.properties

#MySQL Database
1062=DUPLICATE_KEY_FOUND
1216=CHILD_RECORD_FOUND
1217=PARENT_RECORD_NOT_FOUND
1048=NULL_VALUE_FOUND
1205=RECORD_HAS_BEEN_LOCKED