How to write Junit to test catch block - junit

Question

I have to write Junit for below method. How i can cover catch block with Junit
using #Test(expected = SQLException.class).
public int getId(final String col1, final int col2,
String col3) throws DatabaseDownException {
final String IdQuery = "Select id from Manager where col1= ? and col2 = ? and col3 = ?";
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
int Id = 0;
try {
con = getDataSource().getConnection();
stmt = con.prepareStatement(IdQuery);
stmt.setString(1, col1);
stmt.setInt(2, col2);
stmt.setString(3, col3);
rs = stmt.executeQuery();
if (null != rs && rs.next()) {
Id = rs.getInt(1);
}
} catch (SQLException e) {
logger.error("ERROR-WARNING:<<<getId():: ID "+col1+" SQLException occurred while selecting data table.");
} finally {
cleanUp(rs, stmt, con);
}
return Id;
}

Answer 1

You should create an inner method from the code inside try block (refactor extract method) that both JUnit test and your method will use:
protected int getId(final String col1, final int col2, String col3, final String IdQuery, int Id) throws SQLException {
Connection con;
PreparedStatement stmt;
ResultSet rs;
con = getDataSource().getConnection();
stmt = con.prepareStatement(IdQuery);
stmt.setString(1, col1);
stmt.setInt(2, col2);
stmt.setString(3, col3);
rs = stmt.executeQuery();
if (null != rs && rs.next()) {
Id = rs.getInt(1);
}
return Id;
}
Unit test:
#Test(expected = SQLException.class)
public void testGetId() {
getId(...)
}