refactor: TransactionManager에서 전달받을 함수형 인터페이스를 명시적으로 정의

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

@@ -1,14 +1,14 @@
 package com.techcourse.service;
 
 import com.techcourse.domain.User;
-import org.springframework.transaction.support.TransactionExecutor;
+import org.springframework.transaction.support.JdbcTransactionManager;
 import org.springframework.transaction.support.TransactionManager;
 
 import javax.sql.DataSource;
 
 public class TxUserService implements UserService {
 
-    private final TransactionManager transactionManager = new TransactionExecutor();
+    private final TransactionManager transactionManager = new JdbcTransactionManager();
     private final DataSource dataSource;
     private final UserService userService;
 
@@ -19,22 +19,17 @@ public TxUserService(DataSource dataSource, UserService userService) {
 
     @Override
     public User findById(long id) {
-        return transactionManager.execute(dataSource, () -> userService.findById(id));
+        return transactionManager.executeAndReturn(dataSource, () -> userService.findById(id));
     }
 
     @Override
     public void insert(User user) {
-        transactionManager.execute(dataSource, () -> {
-            userService.insert(user);
-            return null;
-        });
+        transactionManager.execute(dataSource, () -> userService.insert(user));
     }
 
     @Override
     public void changePassword(long id, String newPassword, String createBy) {
-        transactionManager.execute(dataSource, () -> {
-            userService.changePassword(id, newPassword, createBy);
-            return null;
-        });
+        transactionManager.execute(dataSource, () -> userService.changePassword(id, newPassword, createBy)
+        );
     }
 }

jdbc/src/main/java/org/springframework/transaction/support/JdbcTransactionManager.java

@@ -0,0 +1,55 @@
+package org.springframework.transaction.support;
+
+import org.springframework.dao.DataAccessException;
+import org.springframework.jdbc.datasource.DataSourceUtils;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+
+public class JdbcTransactionManager implements TransactionManager {
+
+    @Override
+    public void execute(DataSource dataSource, TransactionExecutor method) {
+        final var connection = TransactionManager.getConnection(dataSource);
+        try {
+            connection.setAutoCommit(false);
+            method.execute();
+            connection.commit();
+        } catch (RuntimeException | SQLException e) {
+            handleTransactionException(connection, e);
+        } finally {
+            cleanUpTransaction(dataSource, connection);
+        }
+    }
+
+    @Override
+    public <T> T executeAndReturn(DataSource dataSource, TransactionSupplier<T> method) {
+        final var connection = TransactionManager.getConnection(dataSource);
+        try {
+            connection.setAutoCommit(false);
+            T result = method.get();
+            connection.commit();
+            return result;
+        } catch (RuntimeException | SQLException e) {
+            handleTransactionException(connection, e);
+            return null;
+        } finally {
+            cleanUpTransaction(dataSource, connection);
+        }
+    }
+
+    private static void handleTransactionException(Connection connection, Exception e) {
+        try {
+            connection.rollback();
+            throw new DataAccessException(e);
+        } catch (SQLException rollbackException) {
+            throw new RuntimeException(rollbackException);
+        }
+    }
+
+    private void cleanUpTransaction(DataSource dataSource, Connection connection) {
+        DataSourceUtils.releaseConnection(connection, dataSource);
+        TransactionSynchronizationManager.unbindResource(dataSource);
+    }
+}

jdbc/src/main/java/org/springframework/transaction/support/TransactionExecutor.java

@@ -1,32 +1,6 @@
 package org.springframework.transaction.support;
 
-import org.springframework.dao.DataAccessException;
-import org.springframework.jdbc.datasource.DataSourceUtils;
-
-import javax.sql.DataSource;
-import java.sql.SQLException;
-import java.util.function.Supplier;
-
-public class TransactionExecutor implements TransactionManager {
-
-    @Override
-    public <T> T execute(DataSource dataSource, Supplier<T> method) {
-        final var connection = TransactionManager.getConnection(dataSource);
-        try {
-            connection.setAutoCommit(false);
-            T result = method.get();
-            connection.commit();
-            return result;
-        } catch (RuntimeException | SQLException e) {
-            try {
-                connection.rollback();
-                throw new DataAccessException(e);
-            } catch (SQLException rollbackException) {
-                throw new RuntimeException(rollbackException);
-            }
-        } finally {
-            DataSourceUtils.releaseConnection(connection, dataSource);
-            TransactionSynchronizationManager.unbindResource(dataSource);
-        }
-    }
+@FunctionalInterface
+public interface TransactionExecutor {
+    void execute();
 }

jdbc/src/main/java/org/springframework/transaction/support/TransactionManager.java

@@ -4,13 +4,14 @@
 
 import javax.sql.DataSource;
 import java.sql.Connection;
-import java.util.function.Supplier;
 
 public interface TransactionManager {
 
     static Connection getConnection(DataSource dataSource) {
         return DataSourceUtils.getConnection(dataSource);
     }
 
-    <T> T execute(DataSource dataSource, Supplier<T> method);
+    void execute(DataSource dataSource, TransactionExecutor method);
+
+    <T> T executeAndReturn(DataSource dataSource, TransactionSupplier<T> method);
 }

jdbc/src/main/java/org/springframework/transaction/support/TransactionSupplier.java

@@ -0,0 +1,6 @@
+package org.springframework.transaction.support;
+
+@FunctionalInterface
+public interface TransactionSupplier<T> {
+    T get();
+}