1장: DAO의 확장 - 인터페이스의 도입

앞서 SimpleConnectionMaker에 종속적이 었으므로 확장이 어려웠다.
중간에 추상적인 느슨한 연결고리인 인터페이스를 만들어줌으로써, 긴밀하게 연결되지 않도록 변경할 수 있다.

하지만, UserDao에서 ConnectionMaker를 생성하는 코드는 여전히 남아있다.

src/main/java/com/toby/tobyspring/user/dao/ConnectionMaker.java

@@ -0,0 +1,8 @@
+package com.toby.tobyspring.user.dao;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+
+public interface ConnectionMaker {
+    public Connection makeNewConnection() throws ClassNotFoundException, SQLException;
+}

src/main/java/com/toby/tobyspring/user/dao/SimpleConnectionMaker.java → src/main/java/com/toby/tobyspring/user/dao/DUserConnectionMaker.java

@@ -4,7 +4,8 @@
 import java.sql.DriverManager;
 import java.sql.SQLException;
 
-public class SimpleConnectionMaker {
+public class DUserConnectionMaker implements ConnectionMaker {
+    @Override
     public Connection makeNewConnection() throws ClassNotFoundException, SQLException {
         Class.forName("oracle.jdbc.driver.OracleDriver");
         Connection connection = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl", "dahye", "dahye");

src/main/java/com/toby/tobyspring/user/dao/NUserConnectionMaker.java

@@ -0,0 +1,14 @@
+package com.toby.tobyspring.user.dao;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+
+public class NUserConnectionMaker implements ConnectionMaker {
+    @Override
+    public Connection makeNewConnection() throws ClassNotFoundException, SQLException {
+        Class.forName("oracle.jdbc.driver.OracleDriver");
+        Connection connection = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl", "dahye", "dahye");
+        return connection;
+    }
+}

src/main/java/com/toby/tobyspring/user/dao/UserDao.java

@@ -5,13 +5,13 @@
 import java.sql.*;
 
 public abstract class UserDao {
-    private SimpleConnectionMaker simpleConnectionMaker;
+    private ConnectionMaker connectionMaker;
 
     public UserDao() {
-        this.simpleConnectionMaker = new SimpleConnectionMaker();
+        this.connectionMaker = new DUserConnectionMaker();
     }
     public void add(User user) throws ClassNotFoundException, SQLException {
-        Connection connection = simpleConnectionMaker.makeNewConnection();
+        Connection connection = connectionMaker.makeNewConnection();
         // sql 실행
         PreparedStatement preparedStatement = connection.prepareStatement("insert into users(id, name, password) values(?, ?, ?)");
         preparedStatement.setString(1, user.getId());
@@ -26,7 +26,7 @@ public void add(User user) throws ClassNotFoundException, SQLException {
     }
 
     public User get(String id) throws ClassNotFoundException, SQLException {
-        Connection connection = simpleConnectionMaker.makeNewConnection();
+        Connection connection = connectionMaker.makeNewConnection();
 
         // sql 실행
         PreparedStatement preparedStatement = connection.prepareStatement("select * from users where id = ?");