Convert tuples from different databases into a particular Java object

Question

Well folks, I don’t know if the title of my question is quite correct, if not, someone please edit. I’ll explain my problem.

I developed a tool that checks conflicts between access control policies in Software as a course completion work. For example, it checks whether the software has two policies that cannot be executed by the user at the same time, such as the two policies:

-> You are allowed to open a form.

-> It is forbidden for the user to open a form.

With this my tool compares the Java objects called Politica, which has the second structure:

Policy(type, organization, user, action, object, dateInicio, dataFim).

But I look for these policies in databases, such as my university, which is DB2. What I need to do and I have no idea how to do is:

-> How to connect to the database and get its structure.

-> After getting your structure, define which columns in the database, refer to the attributes of my Policy object?

If a table has the following structure:

ID - Type - Application - Action - Expiration date - Insertion date - Unit

How to make a match and say that: Type = Type, Application = Object, Action = Action, Validity Date = End Date and so on...

And get a query of this? And how to do this even if the tables are different, there are Joins?

Summarizing and trying to explain again: How to make any database that has policies return a Query with objects equal to my Policy object.

I need a north to know where it goes and if it is possible to do. Thank you very much.

Answer 1

How to connect to the database and get its structure.

Each database has at least one client software for you to access. If you have DB at your college, ask for access and tools for the service maintainer.

On the Java side, all access to traditional banks is done using JDBC. The API is the same, you just need to find the driver specific to your bank.

For IBM DB2, see the page DB2 JDBC Driver Versions and Downloads. Give preference to JDBC version 4.0 because it is more efficient.

After getting your structure, define which columns in the database, refer to the attributes of my Policy object?

When you’re retrieving data from the database after executing the query, you enter the field name and do whatever you want with the value. Example:

    ResultSet rs = stmt.executeQuery(query);
    while (rs.next()) {
        String valor = rs.getString("NOME_CAMPO");
        ...
    }

And get a query of this? And how to do this even if the tables are different, there are Joins?

Basically you:

1. Makes a different query for each type of bank you want.
2. For each query you recover the values in variables, as in the above example.
3. With these variables, you then create an instance of your class Politica passing the values as deemed appropriate and placing in the class attributes.

Once you have all the data in a uniform list of objects of type Politica, then you can create a method to go through this list and detect conflicts by making simple comparisons on the attributes of these objects.

Note that there are several other ways to solve the problem, but I tried to synthesize a simple and straightforward way without technical sophistications.