[JDBC 라이브러리 구현하기 - 1단계] 헙크(정현승) 미션 제출합니다.

app/src/test/java/com/techcourse/dao/UserDaoTest.java

@@ -5,16 +5,22 @@
 import com.techcourse.support.jdbc.init.DatabasePopulatorUtils;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.jdbc.core.RowMapper;
+
+import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 class UserDaoTest {
 
     private UserDao userDao;
+    private JdbcTemplate template;
 
     @BeforeEach
     void setup() {
         DatabasePopulatorUtils.execute(DataSourceConfig.getInstance());
+        template = new JdbcTemplate(DataSourceConfig.getInstance());
 
         userDao = new UserDao(DataSourceConfig.getInstance());
         final var user = new User("gugu", "password", "[email protected]");
@@ -23,22 +29,25 @@ void setup() {
 
     @Test
     void findAll() {
-        final var users = userDao.findAll();
+        final String sql = "SELECT id, account, password, email FROM users";
+        final List<User> users = template.query(sql, userRowMapper());
 
         assertThat(users).isNotEmpty();
     }
 
     @Test
     void findById() {
-        final var user = userDao.findById(1L);
+        final String sql = "SELECT id, account, password, email FROM users WHERE id = ?";
+        final User user = template.queryForObject(sql, userRowMapper(), 1L).orElseThrow();
 
         assertThat(user.getAccount()).isEqualTo("gugu");
     }
 
     @Test
     void findByAccount() {
         final var account = "gugu";
-        final var user = userDao.findByAccount(account);
+        final String sql = "SELECT id, account, password, email FROM users WHERE account = ?";
+        final User user = template.queryForObject(sql, userRowMapper(), account).orElseThrow();
 
         assertThat(user.getAccount()).isEqualTo(account);
     }
@@ -47,7 +56,8 @@ void findByAccount() {
     void insert() {
         final var account = "insert-gugu";
         final var user = new User(account, "password", "[email protected]");
-        userDao.insert(user);
+        final String sql1 = "INSERT INTO users(account, password, email) VALUES(?, ?, ?)";
+        final int updatedRow = template.update(sql1, user.getAccount(), user.getPassword(), user.getEmail());
 
         final var actual = userDao.findById(2L);
 
@@ -60,10 +70,18 @@ void update() {
         final var user = userDao.findById(1L);
         user.changePassword(newPassword);
 
-        userDao.update(user);
-
+        final String sql2 = "UPDATE users SET password = ? WHERE id = ?";
+        template.update(sql2, user.getPassword(), user.getId());
         final var actual = userDao.findById(1L);
 
         assertThat(actual.getPassword()).isEqualTo(newPassword);
     }
+
+    private RowMapper<User> userRowMapper() {
+        return rs -> new User(
+                rs.getString("account"),
+                rs.getString("password"),
+                rs.getString("email")
+        );
+    }
 }

jdbc/src/main/java/org/springframework/jdbc/core/JdbcTemplate.java

@@ -1,17 +1,65 @@
 package org.springframework.jdbc.core;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import org.springframework.dao.DataAccessException;
 
 import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
 
 public class JdbcTemplate {
-
-    private static final Logger log = LoggerFactory.getLogger(JdbcTemplate.class);
-
     private final DataSource dataSource;
 
     public JdbcTemplate(final DataSource dataSource) {
         this.dataSource = dataSource;
     }
+
+    public <T> Optional<T> queryForObject(final String sql, final RowMapper<T> rowMapper, Object... args) {
+        try (final Connection conn = dataSource.getConnection();
+             final PreparedStatement pstmt = conn.prepareStatement(sql)) {
+            for (int i = 0; i < args.length; i++) {
+                pstmt.setObject(i + 1, args[i]);
+            }
+            try (final ResultSet rs = pstmt.executeQuery()) {
+                if (rs.next()) {
+                    return Optional.ofNullable(rowMapper.mapRow(rs));
+                }
+                return Optional.empty();
+            }
+        } catch (final SQLException e) {
+            throw new DataAccessException(e);
+        }
+    }
+
+    public <T> List<T> query(String sql, RowMapper<T> rowMapper) throws DataAccessException {
+        try (final Connection conn = dataSource.getConnection();
+             final PreparedStatement pstmt = conn.prepareStatement(sql)) {
+            final List<T> result = new ArrayList<>();
+            try (final ResultSet rs = pstmt.executeQuery()) {
+                if (rs.next()) {
+                    result.add(rowMapper.mapRow(rs));
+                }
+                return result;
+            }
+
+        } catch (final SQLException e) {
+            throw new DataAccessException(e);
+        }
+    }
+
+    public int update(final String sql, final Object... args) {
+        try (final Connection conn = dataSource.getConnection();
+             final PreparedStatement pstmt = conn.prepareStatement(sql)) {
+            for (int i = 0; i < args.length; i++) {
+                pstmt.setObject(i + 1, args[i]);
+            }
+            return pstmt.executeUpdate();
+        } catch (final SQLException e) {
+            throw new DataAccessException(e);
+        }
+    }
 }

jdbc/src/main/java/org/springframework/jdbc/core/RowMapper.java

@@ -0,0 +1,13 @@
+package org.springframework.jdbc.core;
+
+import javax.annotation.Nullable;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+@FunctionalInterface
+public interface RowMapper<T> {
+
+    @Nullable
+    T mapRow(ResultSet rs) throws SQLException;
+
+}