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complicated API with mock objects. It's somewhat easier to mock the i BATIS Sql-
MapClient interface. Let's try that now.
Unit-testing a DAO with mock objects
Mock objects are objects that stand in place of true implementations for the pur-
pose of unit testing. Mocks don't generally have very much functionality; they sat-
isfy a single case to allow the unit test to focus on some other area without having
to worry about additional complexity. We'll use mocks in this example to demon-
strate an approach to testing the DAO layer.
In our example, we'll use a simple DAO . We'll leave out the i BATIS DAO frame-
work so that we don't have to worry about transactions and such. The purpose of
this example is to demonstrate testing the DAO layer regardless of which DAO
framework you use, if any at all.
First, let's consider the DAO we want to test. Listing 13.2 shows a SqlMapPerson-
Dao implementation that calls a SQL map similar to the example in section 13.1.1.
Listing 13.2
A simple DAO to test
public class SqlMapPersonDao implements PersonDao {
private SqlMapClient sqlMapClient;
public SqlMapPersonDao(SqlMapClient sqlMapClient) {
this.sqlMapClient = sqlMapClient;
public Person getPerson (int id) {
try {
return (Person)
sqlMapClient.queryForObject("getPerson", id);
} catch (SQLException e) {
throw new DaoRuntimeException(
"Error getting person. Cause: " + e, e);
Notice how we inject the SqlMapClient into the constructor of the DAO in
listing 13.2. This provides an easy way to unit-test this DAO , because we can mock
the SqlMapClient interface. Obviously this is a simple example, and we're not test-
ing very much at all, but every test counts. Listing 13.3 shows the unit test that will
mock the SqlMapClient and test the getPerson() method.
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