Time to refactor. I took about 10 minutes and ran through about three different refactoring passes, running JUnit each time to ensure I maintained a green bar.
First pass: move responsibilities into a separate class, JdbcAccess. It’s actually a move that will stave off duplication at some future point, once I have another domain class with persistence needs. But right now I’m following the single responsibility principle as my primary refactoring driver.
Second pass: eliminate common code duplication. Example: extraction of the createStatement method.
I made a couple other minor refactorings, including inlining the loadDriver method into createConnection (it wasn’t pulling its own weight, violating simple design rule #4). The bigger move was divorcing the ResultSet from the need to populate the user object.
The code still has lots of problems, of course. There’s still the presumption that there’s a single row of data, and worse now, the JdbcAccess class presumes there are always two string columns.
Also: The User class still has to import java.sql (because of SQLException). And there’s more duplication in the SQL strings that we’ve not touched on yet. And worse, we now have a class (JdbcAccess) with no unit test coverage.
Code from User.java:
public void save() throws SQLException {
new JdbcAccess().execute(
String.format("insert into userdata (name, password) values ('%s', '%s')", name, password));
}
public static User find(String nameKey) throws SQLException {
JdbcAccess access = new JdbcAccess();
List row =
access.executeQuery(String.format("select name, password from userdata where name = '%s'", nameKey));
return new User(row.get(0), row.get(1));
}
JdbcAccess.java:
import java.util.*;
import java.sql.*;
import com.mysql.jdbc.Driver;
public class JdbcAccess {
private Connection connection;
private Statement statement;
public void execute(String sql) throws SQLException {
createStatement();
statement.execute(sql);
closeConnection();
}
public List executeQuery(String sql) throws SQLException {
createStatement();
ResultSet results = statement.executeQuery(sql);
results.next();
List row = getRow(results);
results.close();
connection.close();
return row;
}
private List getRow(ResultSet results) throws SQLException {
List row = new ArrayList();
row.add(results.getString(1));
row.add(results.getString(2));
return row;
}
private void createStatement() throws SQLException {
createConnection();
statement = connection.createStatement();
}
private void createConnection() throws SQLException {
new Driver();
connection = DriverManager.getConnection("jdbc:mysql://localhost/test?user=root&password=xxx");
}
private void closeConnection() throws SQLException {
connection.close();
}
}
