Lab 2 A Simple Database

School of Engineering and Computer Science
SWEN221: Software Development
Lab Handout
A Simple Database
The primary purpose of this lab is to get used to working with exceptions. Before the end of the lab,
you should submit your solutions via the online submission system which will automatically mark it.

In this lab, you will be working with a very simple database implementation. The database reads
data from files stored in a particular plain text format, and then allows that data to be accessed from
memory. An example database file is:
ID:int*,Name:str,Age:int
1,John,88
2,Amy,12
3,Sophie,28
4,John,23
The first line of the file describes the database “schema”. That is, the layout which the remaining
lines must follow. This includes the number of items which must be provided on each line, along with
their permitted type (either an Integer or a String). The asterisk indicates which is the “key field”
for the database. This is a special field which uniquely identifies each row such that no two rows may
have the same value for the key field, though they can for other fields (e.g. as for the two johns above).
Getting Started
To get started, download the file database.jar from course website. This contains the following files:
swen221/database/io/DatabaseFileReader.java
swen221/database/lang/ColumnType.java
swen221/database/lang/RowType.java
swen221/database/lang/Database.java
swen221/database/testing/DatabaseTests.java
You should import these files into Eclipse. Note, you will find that they do not compile properly
yet.
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Activity 1 — Adding Exceptions
The first part of the lab is to create the missing classes InvalidRowException, InvalidKeyException
and DuplicateKeyException in the package swen221.database.lang. Having correctly created these
classes, you should find that the code now successfully compiles. However, it will not yet pass any
tests.
Activity 2 — Reading Database Files
The second part of the lab is to complete method DatabaseFileReader.findKeyField(). To do this,
you might find the methods String.split() and String.endsWith() helpful. Having done this, you
may now find the first test is passing (though this depends exactly on how you’ve implemented it).
Activity 3 — Implementing Database
The third part of the lab is to construct a class DatabaseImpl which implements the Database
interface. You should update method DatabaseFileReader.read() to return an appropriate instance
of DatabaseImpl. You will also need to implement all methods from the Database interface correctly.
Having done this, you should find that all tests now pass.
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Submission
Your lab solution should be submitted electronically via the online submission system, linked from
the course homepage. The required files are:
swen221/database/io/DatabaseFileReader.java
swen221/database/lang/ColumnType.java
swen221/database/lang/RowType.java
swen221/database/lang/Database.java
swen221/database/lang/DatabaseImpl.java
You must ensure your submission meets the following requirements (which are needed for the
automatic marking script):
1. Your submission is packaged into a jar file, including the source code. Note, the jar
file does not need to be executable. See the following Eclipse tutorials for more on this:
http://ecs.victoria.ac.nz/Support/TechNoteEclipseTutorials
2. The names of all classes, methods and packages remain unchanged. That is, you
may add new classes and/or new methods and you may modify the body of existing methods.
However, you may not change the name of any existing class, method or package. This is to
ensure the automatic marking script can test your code.
3. All JUnit test files supplied for the assignment remain unchanged. Specifically, you
cannot alter the way in which your code is tested as the marking script relies on this. This does
not prohibit you from adding new tests, as you can still create additional JUnit test files. This
is to ensure the automatic marking script can test your code.
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4. You have removed any debugging code that produces output, or otherwise affects
the computation. This ensures the output seen by the automatic marking script does not
include spurious information.
Note: Failure to meet these requirements could result in your submission being reject by the submission system and/or zero marks being awarded.
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