Lambda와 익명 내부 클래스 사용

JdbcCallback 인터페이스를 필요에 따라 바로 오버라이딩하여 람다로 콜백

jdbc-template/src/main/java/com/example/jdbctemplate/pattern/JdbcTemplate.java

@@ -10,7 +10,7 @@ private Connection getConnection(String url, String username, String password) t
     }
 
     // SQL 쿼리 생성 및 실행
-    public void executeQuery(UserCallback callback, String url, String username, String password){
+    public void executeQuery(JdbcCallback callback, String url, String username, String password){
         Connection conn = null;
         PreparedStatement ps = null;
         try {

jdbc-template/src/main/java/com/example/jdbctemplate/pattern/PatternMain.java

@@ -1,6 +1,10 @@
 package com.example.jdbctemplate.pattern;
 
 
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+
 public class PatternMain {
 
     public static void main(String[] args) {
@@ -10,8 +14,12 @@ public static void main(String[] args) {
 
         JdbcTemplate jdbcTemplate = new JdbcTemplate();
 
-        String sql = "SELECT * FROM USER";
-        jdbcTemplate.executeQuery(new UserCallback(), url, username, password);
+        jdbcTemplate.executeQuery(new JdbcCallback(){
+            @Override
+            public PreparedStatement setPreparedStatement(Connection conn) throws SQLException {
+                return conn.prepareStatement("SELECT * FROM USER");
+            }
+        }, url, username, password);
     }