Chapter 6. The DbException Class

#include <db_cxx.h>
class DbException {
    int get_errno() const;
    virtual const char *what() const;
    DbEnv *get_env() const;

This information describes the DbException class and how it is used by the various Berkeley DB classes.

Most methods in the Berkeley DB classes return an int, but also throw an exception. This allows for two different error behaviors. By default, the Berkeley DB C++ API is configured to throw an exception whenever a serious error occurs. This generally allows for cleaner logic for transaction processing because a try block can surround a single transaction. Alternatively, Berkeley DB can be configured to not throw exceptions, and instead have the individual function return an error code, by setting the DB_CXX_NO_EXCEPTIONS for the Db and DbEnv constructors.

A DbException object contains an informational string, an errno, and a reference to the environment from which the exception was thrown. The errno can be obtained by using the DbException::get_errno() method, and can be used, in standard cases, to determine the type of the exception. The informational string can be obtained by using the DbException::what(). And, the environment can be obtained using the DbException::get_env() method.

We expect in the future that this class will inherit from the standard class exception, but certain language implementation bugs currently prevent this on some platforms.

Some methods may return non-zero values without issuing an exception. This occurs in situations that are not normally considered an error, but when some informational status is returned. For example, the Db::get() method returns DB_NOTFOUND when a requested key does not appear in the database.

DB C++ Exceptions