[JDBC 라이브러리 구현하기 - 4단계] 모디(전제희) 미션 제출합니다. (#597)

* refactor: JdbcTemplate이 UncheckedException을 외부로 위임하지 않도록 변경

* feat: TxUserService 구현

* refactor: JdbcTemplate의 close connection 부분 메서드 분리

* refactor: JdbcTemplate의 인스턴스화 로직 변경

* refactor: 사용되는 함수형 인터페이스 직접 정의

* refactor: connection 생성 삭제 책임을 DataSourceUtils로 집중

app/src/main/java/com/techcourse/service/AppUserService.java

@@ -0,0 +1,32 @@
+package com.techcourse.service;
+
+import com.techcourse.dao.UserDao;
+import com.techcourse.dao.UserHistoryDao;
+import com.techcourse.domain.User;
+import com.techcourse.domain.UserHistory;
+
+public class AppUserService implements UserService {
+
+    private final UserDao userDao;
+    private final UserHistoryDao userHistoryDao;
+
+    public AppUserService(final UserDao userDao, final UserHistoryDao userHistoryDao) {
+        this.userDao = userDao;
+        this.userHistoryDao = userHistoryDao;
+    }
+
+    public User findById(final long id) {
+        return userDao.findById(id);
+    }
+
+    public void insert(final User user) {
+        userDao.insert(user);
+    }
+
+    public void changePassword(final long id, final String newPassword, final String createBy) {
+        User user = findById(id);
+        user.changePassword(newPassword);
+        userDao.update(user);
+        userHistoryDao.log(new UserHistory(user, createBy));
+    }
+}

app/src/main/java/com/techcourse/service/TxUserService.java

@@ -0,0 +1,111 @@
+package com.techcourse.service;
+
+import com.techcourse.config.DataSourceConfig;
+import com.techcourse.domain.User;
+import java.sql.Connection;
+import java.sql.SQLException;
+import javax.sql.DataSource;
+import org.springframework.dao.DataAccessException;
+import org.springframework.jdbc.datasource.DataSourceUtils;
+
+public class TxUserService implements UserService {
+
+    private final AppUserService appUserService;
+    private final DataSource datasource = DataSourceConfig.getInstance();
+
+    public TxUserService(AppUserService appUserService) {
+        this.appUserService = appUserService;
+    }
+
+    @Override
+    public User findById(long id) {
+        return execute(() -> appUserService.findById(id));
+    }
+
+    @Override
+    public void insert(User user) {
+        execute(() -> appUserService.insert(user));
+    }
+
+    @Override
+    public void changePassword(long id, String newPassword, String createBy) {
+        execute(() -> appUserService.changePassword(id, newPassword, createBy));
+    }
+
+    private void execute(ExecutableWithoutReturn executable) {
+        try (TransactionExecutor executor = TransactionExecutor.initTransaction(datasource)) {
+            try {
+                executable.execute();
+                executor.commit();
+            } catch (Exception e) {
+                executor.rollback();
+                throw new DataAccessException();
+            }
+        }
+    }
+
+    private <T> T execute(ExecutableWithReturn<T> executable) {
+        try (TransactionExecutor executor = TransactionExecutor.initTransaction(datasource)) {
+            try {
+                T result = executable.execute();
+                executor.commit();
+                return result;
+            } catch (Exception e) {
+                executor.rollback();
+                throw new DataAccessException();
+            }
+        }
+    }
+
+    @FunctionalInterface
+    private interface ExecutableWithoutReturn {
+        void execute();
+    }
+
+    @FunctionalInterface
+    private interface ExecutableWithReturn<T> {
+        T execute();
+    }
+
+    private static class TransactionExecutor implements AutoCloseable {
+
+        private final DataSource dataSource;
+        private final Connection connection;
+
+        private TransactionExecutor(DataSource dataSource, Connection connection) {
+            this.dataSource = dataSource;
+            this.connection = connection;
+        }
+
+        public static TransactionExecutor initTransaction(DataSource dataSource) {
+            try {
+                Connection connection = DataSourceUtils.getConnection(dataSource);
+                connection.setAutoCommit(false);
+                return new TransactionExecutor(dataSource, connection);
+            } catch (SQLException e) {
+                throw new RuntimeException();
+            }
+        }
+
+        public void commit() {
+            try {
+                connection.commit();
+            } catch (SQLException e) {
+                throw new RuntimeException();
+            }
+        }
+
+        public void rollback() {
+            try {
+                connection.rollback();
+            } catch (SQLException e) {
+                throw new RuntimeException();
+            }
+        }
+
+        @Override
+        public void close() {
+            DataSourceUtils.releaseConnection(dataSource);
+        }
+    }
+}

app/src/main/java/com/techcourse/service/UserService.java

@@ -1,61 +1,10 @@
 package com.techcourse.service;
 
-import com.techcourse.config.DataSourceConfig;
-import com.techcourse.dao.UserDao;
-import com.techcourse.dao.UserHistoryDao;
 import com.techcourse.domain.User;
-import com.techcourse.domain.UserHistory;
-import java.sql.Connection;
-import java.sql.SQLException;
-import javax.sql.DataSource;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.springframework.dao.DataAccessException;
-import org.springframework.transaction.support.TransactionSynchronizationManager;
 
-public class UserService {
+public interface UserService {
 
-    private static final Logger log = LoggerFactory.getLogger(UserService.class);
-    private final UserDao userDao;
-    private final UserHistoryDao userHistoryDao;
-
-    public UserService(final UserDao userDao, final UserHistoryDao userHistoryDao) {
-        this.userDao = userDao;
-        this.userHistoryDao = userHistoryDao;
-    }
-
-    public User findById(final long id) {
-        return userDao.findById(id);
-    }
-
-    public void insert(final User user) {
-        userDao.insert(user);
-    }
-
-    public void changePassword(final long id, final String newPassword, final String createBy) {
-        DataSource dataSource = DataSourceConfig.getInstance();
-        Connection conn = null;
-        try {
-            conn = dataSource.getConnection();
-            conn.setAutoCommit(false);
-            TransactionSynchronizationManager.bindResource(dataSource, conn);
-            User user = findById(id);
-            user.changePassword(newPassword);
-            userDao.update(user);
-            userHistoryDao.log(new UserHistory(user, createBy));
-            conn.commit();
-        } catch (Exception e) {
-            log.error(e.getMessage(), e);
-            if (conn != null) {
-                try {
-                    TransactionSynchronizationManager.unbindResource(dataSource);
-                    conn.rollback();
-                    conn.close();
-                } catch (SQLException ex) {
-                    log.error(ex.getMessage(), ex);
-                }
-            }
-            throw new DataAccessException();
-        }
-    }
+    User findById(final long id);
+    void insert(final User user);
+    void changePassword(final long id, final String newPassword, final String createBy);
 }

app/src/test/java/com/techcourse/service/UserServiceTest.java

@@ -31,7 +31,7 @@ void setUp() {
     @Test
     void testChangePassword() {
         final var userHistoryDao = new UserHistoryDao(jdbcTemplate);
-        final var userService = new UserService(userDao, userHistoryDao);
+        final var userService = new AppUserService(userDao, userHistoryDao);
 
         final var newPassword = "qqqqq";
         final var createBy = "gugu";
@@ -46,7 +46,10 @@ void testChangePassword() {
     void testTransactionRollback() {
         // 트랜잭션 롤백 테스트를 위해 mock으로 교체
         final var userHistoryDao = new MockUserHistoryDao(jdbcTemplate);
-        final var userService = new UserService(userDao, userHistoryDao);
+        // 애플리케이션 서비스
+        final var appUserService = new AppUserService(userDao, userHistoryDao);
+        // 트랜잭션 서비스 추상화
+        final var userService = new TxUserService(appUserService);
 
         final var newPassword = "newPassword";
         final var createBy = "gugu";

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

@@ -1,8 +1,10 @@
 package org.springframework.jdbc.core;
 
+import java.lang.reflect.Constructor;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.List;
@@ -11,7 +13,7 @@
 import org.slf4j.LoggerFactory;
 import org.springframework.dao.DataAccessException;
 import org.springframework.jdbc.IncorrectResultSizeDataAccessException;
-import org.springframework.transaction.support.TransactionSynchronizationManager;
+import org.springframework.jdbc.datasource.DataSourceUtils;
 
 public class JdbcTemplate {
 
@@ -23,32 +25,49 @@ public JdbcTemplate(final DataSource dataSource) {
         this.dataSource = dataSource;
     }
 
-    public int update(String sql, Object... args) throws DataAccessException {
+    public int update(String sql, Object... args) {
         return execute(sql, (pstmt) -> {
             prepareStatement(pstmt, args);
             return pstmt.executeUpdate();
         });
     }
 
-    public <T> T queryForObject(String sql, Class<T> requiredType, Object... args)
-            throws DataAccessException {
+    public <T> T queryForObject(String sql, Class<T> requiredType, Object... args) {
         return execute(sql, (pstmt) -> {
             prepareStatement(pstmt, args);
             try (ResultSet rs = pstmt.executeQuery()) {
-                int columnCount = rs.getMetaData().getColumnCount();
-                if (rs.first() && rs.isLast()) {
-                    Object[] initArgs = new Object[columnCount];
-                    for (int i = 1; i <= columnCount; i++) {
-                        initArgs[i - 1] = rs.getObject(i);
-                    }
-                    return InstantiateUtil.instantiate(rs, requiredType, initArgs);
-                }
-                throw new IncorrectResultSizeDataAccessException();
+                return instantiate(rs, requiredType);
             }
         });
     }
 
-    public <T> List<T> query(String sql, RowMapper<T> rowMapper) throws DataAccessException {
+    private <T> T instantiate(ResultSet rs, Class<T> requiredType) throws Exception {
+        int columnCount = rs.getMetaData().getColumnCount();
+        if (rs.first() && rs.isLast()) {
+            Object[] initArgs = new Object[columnCount];
+            for (int i = 1; i <= columnCount; i++) {
+                initArgs[i - 1] = rs.getObject(i);
+            }
+            return instantiate(rs, requiredType, initArgs);
+        }
+        throw new IncorrectResultSizeDataAccessException();
+    }
+
+    private <T> T instantiate(ResultSet rs, Class<T> requiredType, Object[] initArgs)
+            throws Exception {
+        ResultSetMetaData metaData = rs.getMetaData();
+        int columnCount = metaData.getColumnCount();
+
+        Class<?>[] columnTypes = new Class[columnCount];
+        for (int i = 1; i <= columnCount; i++) {
+            int columnType = metaData.getColumnType(i);
+            columnTypes[i - 1] = ColumnTypes.convertToClass(columnType);
+        }
+        Constructor<?> constructor = requiredType.getDeclaredConstructor(columnTypes);
+        return requiredType.cast(constructor.newInstance(initArgs));
+    }
+
+    public <T> List<T> query(String sql, RowMapper<T> rowMapper) {
         return execute(sql, (pstmt) -> {
             try (ResultSet resultSet = pstmt.executeQuery()) {
                 List<T> results = new ArrayList<>();
@@ -67,34 +86,14 @@ private void prepareStatement(PreparedStatement pstmt, Object[] args) throws SQL
     }
 
     private <T> T execute(String sql, StatementExecution<PreparedStatement, T> function) {
-        Connection conn = null;
+        Connection conn;
         try {
-            conn = getConnection();
+            conn = DataSourceUtils.getConnection(dataSource);
             PreparedStatement pstmt = conn.prepareStatement(sql);
             return function.apply(pstmt);
         } catch (Exception e) {
             log.error(e.getMessage(), e);
             throw new DataAccessException(e);
-        } finally {
-            try {
-                if (isConnectionManuallyInstantiated(conn)) {
-                    conn.close();
-                }
-            } catch (SQLException e) {
-                log.error(e.getMessage(), e);
-                throw new DataAccessException(e);
-            }
-        }
-    }
-
-    private Connection getConnection() throws SQLException {
-        if (TransactionSynchronizationManager.getResource(dataSource) != null) {
-            return TransactionSynchronizationManager.getResource(dataSource);
         }
-        return dataSource.getConnection();
-    }
-
-    private boolean isConnectionManuallyInstantiated(Connection conn) {
-        return conn != null && TransactionSynchronizationManager.getResource(dataSource) == null;
     }
 }

jdbc/src/main/java/org/springframework/jdbc/datasource/DataSourceUtils.java

@@ -27,8 +27,9 @@ public static Connection getConnection(DataSource dataSource) throws CannotGetJd
         }
     }
 
-    public static void releaseConnection(Connection connection, DataSource dataSource) {
+    public static void releaseConnection(DataSource dataSource) {
         try {
+            Connection connection = TransactionSynchronizationManager.unbindResource(dataSource);
             connection.close();
         } catch (SQLException ex) {
             throw new CannotGetJdbcConnectionException("Failed to close JDBC Connection");