Assignment 4 - Choice C - Automatic Generation of DAO implementations

This is one of the choices for Assignment 4 The goal of this assignment choice is to understand the DAO pattern and methods for automatic generation of DAO implementations.

Deadlines: This assignment puts together 2 lab sessions (corresponding weeks 11 and 12) and contains up to two Bonus point. Results should be presented no later than week 14.

General grading policy: Grades reflect your individual knowledge and contribution. Each student must complete and present their own solutions. The solutions developed "in group" or copied will be assigned 0(zero) points. Not presenting the assignment is assigned 4 points.

Problem description

The goal of the DAOpattern is to abstract and encapsulate all access to the data source by introducing a DAO interface. The implementation of such a DAO interface will always contain some boilerplate code, thus it could be automatically generated by tools.

References

lecture notes of week 11 dacss11-DAO.ppt
an example of DAO generator (your competitor): Spring Data

Design and implement a (part of) a very simplified DAO generator. The user of the DAO generator tool must provide as input:

a Java class (the entity that is persisted / the data transfer object). Consider the simplified case when the class has only attributes of types string and numeric.
a connection URL to the database containing a table with a structure corresponding to the class. Consider that by default there is a correspondence between class name and table name, and class attribute names and table column names.
a Java interface which is the DAO interface. The methods in the DAO interface must follow a strict naming convention. The DAO methods can be of types find, save or delete. The method names for find and delete type of methods must also specify the selection clause, as in findAll, deleteAll, findBy[attribute], findBy[attribute1]And[attribute2], etc. These methods will take as arguments the attribute values. For example: findByNameAndAge("John", 31). The method save takes as argument the entity/data transfer object.

Implement a DAO generator as described above. The implementation of any method with a name following the pattern findBy[attribute], having one argument attributevalue, will use a JDBC connection to the database and execute a query such as SELECT * WHERE ATTRIBUTE=ATTRIBUTEVALUE. The DAO Generator parses the method names and constructs the corresponding queries and execures them. All the query methods return lists of datatransfer objects (no ResultSets are returned !) To generate the DAOImplementation class you can use any one of the following 2 strategies (similar with generating clientside proxies for broker):

a generator tool that generates the source code of the DAOImplementation class
dynamic generation at runtime, using DynamicProxy

Demonstrate the use of your DAO generator in 2 different applications:

an application dealing with Employees (name, surname, SSN, salary, age). The DAO interface should define methods such as find Employees by SSN; find by name AND surname; find by salary and age; delete by name and surname, etc.
an application dealing with Books (title,author, year, price). DAO interface should define some appropriate methods.

This assignment contains one exam bonus point in the initial requirements stated above.

Further extension (a second bonus point): eliminate some of the restrictions relative to the allowed forms of Java classes accepted. Accept classes that may have associations with other classes. Assume a default pattern of mapping classes to tables (for associations). Methods in the DAO interface can include find methods that refer to attributes of associated classes using the dot notation. For example, class Order has an attribute of type Customer. You can define in the DAO interface handling Orders a method such as findByCustomerName(aName). The same query method can use values for its own attributes and attributes of associated classes, such as findByCustomerNameAndDate(aName, aDate): Date is an attribute of Order, Order is associated with Customer and Customer has an attribute Name.