feat: UserDao 구현

README.md

@@ -1 +1,10 @@
 # JDBC 라이브러리 구현하기
+
+개발자는 SQL 쿼리 작성, 쿼리에 전달할 인자, SELECT 구문일 경우
+조회 결과를 추출하는 것만 집중할 수 있도록 라이브러리를 만들자.
+
+## 힌트
+
+- 리팩터링은 UserDaoTest를 활용해 진행한다.
+- 중복을 제거하기 위한 라이브러리는 JdbcTemplate 클래스에 구현한다.
+- DataSource는 DataSourceConfig 클래스의 getInstance() 메서드를 호출하면 된다.

app/src/main/java/com/techcourse/dao/UserDao.java

@@ -1,6 +1,7 @@
 package com.techcourse.dao;
 
 import com.techcourse.domain.User;
+import java.util.ArrayList;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -11,6 +12,7 @@
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.List;
+import org.springframework.jdbc.core.RowMapper;
 
 public class UserDao {
 
@@ -28,7 +30,10 @@ public UserDao(final JdbcTemplate jdbcTemplate) {
 
     public void insert(final User user) {
         final var sql = "insert into users (account, password, email) values (?, ?, ?)";
+        execute(sql, user.getAccount(), user.getPassword(), user.getEmail());
+    }
 
+    private void execute(String sql, Object... parameters) {
         Connection conn = null;
         PreparedStatement pstmt = null;
         try {
@@ -37,9 +42,10 @@ public void insert(final User user) {
 
             log.debug("query : {}", sql);
 
-            pstmt.setString(1, user.getAccount());
-            pstmt.setString(2, user.getPassword());
-            pstmt.setString(3, user.getEmail());
+            for (int i = 0; i < parameters.length; i++) {
+                pstmt.setObject(i + 1, parameters[i]);
+            }
+
             pstmt.executeUpdate();
         } catch (SQLException e) {
             log.error(e.getMessage(), e);
@@ -60,36 +66,56 @@ public void insert(final User user) {
     }
 
     public void update(final User user) {
-        // todo
+        final var sql = "update users set password = ?, email = ?, account = ? where id = ?";
+        execute(sql, user.getPassword(), user.getEmail(), user.getAccount(), user.getId());
     }
 
     public List<User> findAll() {
-        // todo
-        return null;
+        final var sql = "select id, account, password, email from users";
+        return query(sql, (rs, rowNum) -> new User(rs.getLong("id"),
+                rs.getString("account"),
+                rs.getString("password"),
+                rs.getString("email")));
     }
 
     public User findById(final Long id) {
         final var sql = "select id, account, password, email from users where id = ?";
+        return queryForObject(sql, (rs, rowNum) -> new User(rs.getLong("id"),
+                rs.getString("account"),
+                rs.getString("password"),
+                rs.getString("email")), id);
+    }
 
+    private <T> T queryForObject(String sql, RowMapper<T> rowMapper, Object... params) {
+        List<T> query = query(sql, rowMapper, params);
+        if (query.size() > 1) {
+            throw new RuntimeException("too many result");
+        }
+        if (query.isEmpty()) {
+            return null;
+        }
+        return query.get(0);
+    }
+
+    private <T> List<T> query(String sql, RowMapper<T> rowMapper, Object... parameters) {
         Connection conn = null;
         PreparedStatement pstmt = null;
         ResultSet rs = null;
         try {
             conn = dataSource.getConnection();
             pstmt = conn.prepareStatement(sql);
-            pstmt.setLong(1, id);
+            for (int i = 0; i < parameters.length; i++) {
+                pstmt.setObject(i + 1, parameters[i]);
+            }
             rs = pstmt.executeQuery();
 
             log.debug("query : {}", sql);
 
+            final List<T> results = new ArrayList<>();
             if (rs.next()) {
-                return new User(
-                        rs.getLong(1),
-                        rs.getString(2),
-                        rs.getString(3),
-                        rs.getString(4));
+                results.add(rowMapper.mapRow(rs, 0));
             }
-            return null;
+            return results;
         } catch (SQLException e) {
             log.error(e.getMessage(), e);
             throw new RuntimeException(e);
@@ -115,7 +141,10 @@ public User findById(final Long id) {
     }
 
     public User findByAccount(final String account) {
-        // todo
-        return null;
+        final var sql = "select id, account, password, email from users where account = ?";
+        return queryForObject(sql, (rs, rowNum) -> new User(rs.getLong("id"),
+                rs.getString("account"),
+                rs.getString("password"),
+                rs.getString("email")), account);
     }
 }