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This example shows how to persist objects that use Boost smart pointers,
containers, and value types with the help of the Boost profile library
(libodb-boost).
The example consists of the following files:
employee.hxx
Header file defining the 'employee' and 'employer' persistent classes.
We use shared_ptr/weak_ptr smart pointers provided by Boost (as well
as their lazy versions provided by the Boost profile library) to
establish a bidirectional employee-employer relationship. We also use
the boost::gregorian::date type to store the employee's date of birth
and the boost::unordered_set container to keep track of the employee's
email addresses. The employee's object id is boost::uuids::uuid. Finally,
we use boost::optional for the optional middle name. If the middle name
is not present, it will be represented in the database as a NULL value.
employee-odb.hxx
employee-odb.ixx
employee-odb.cxx
employee.sql
The first three files contain the database support code and the last file
contains the database schema for the employee.hxx header.
These files are generated by the ODB compiler from employee.hxx using the
following command line:
odb -d <database> -p boost --generate-schema --generate-query \
--generate-session employee.hxx
Where <database> stands for the database system we are using, for example,
'mysql'.
The -p option is used to instruct the ODB compiler to load the Boost
profile. The --generate-session option is used to enable session support
for all the persistent classes in employee.hxx.
database.hxx
Contains the create_database() function which instantiates the concrete
database class corresponding to the database system we are using.
driver.cxx
Driver for the example. It includes the employee.hxx and employee-odb.hxx
headers to gain access to the persistent classes and their database support
code. It also includes database.hxx for the create_database() function
declaration.
In main() the driver first calls create_database() to obtain the database
instance. It then creates a number of 'employee' and 'employer' objects and
persists them in the database. The next transaction loads all the employees
of a particular employer using the employee-employer relationship. Finally,
the driver performs a few database queries which use data members of the
various Boost value types in their criterion.
To run the example we may first need to create the database schema (for some
database systems, such as SQLite, the schema is embedded into the generated
code which makes this step unnecessary). Using MySQL as an example, this
can be achieved with the following command:
mysql --user=odb_test --database=odb_test < employee.sql
Here we use 'odb_test' as the database login and also 'odb_test' as the
database name.
Once the database schema is ready, we can run the example (using MySQL as
the database):
./driver --user odb_test --database odb_test
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