[JDBC 라이브러리 구현하기 - 1단계] 허브(방대의) 미션 제출합니다.

README.md

@@ -1 +1,6 @@
 # JDBC 라이브러리 구현하기
+
+### 1단계 - JDBC 라이브러리 구현하기
+
+- [x] RowMapper 인터페이스를 추가한다.
+- [x] JdbcTemplate으로 코드 이동시킨다.

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

@@ -1,121 +1,52 @@
 package com.techcourse.dao;
 
 import com.techcourse.domain.User;
-import org.springframework.jdbc.core.JdbcTemplate;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import javax.sql.DataSource;
-import java.sql.Connection;
-import java.sql.PreparedStatement;
-import java.sql.ResultSet;
-import java.sql.SQLException;
 import java.util.List;
+import javax.sql.DataSource;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.jdbc.core.RowMapper;
 
 public class UserDao {
 
-    private static final Logger log = LoggerFactory.getLogger(UserDao.class);
+    private static final RowMapper<User> USER_ROW_MAPPER = (resultSet) -> new User(
+            resultSet.getLong(1),
+            resultSet.getString(2),
+            resultSet.getString(3),
+            resultSet.getString(4)
+    );
 
-    private final DataSource dataSource;
+    private final JdbcTemplate jdbcTemplate;
 
     public UserDao(final DataSource dataSource) {
-        this.dataSource = dataSource;
+        this.jdbcTemplate = new JdbcTemplate(dataSource);
     }
 
     public UserDao(final JdbcTemplate jdbcTemplate) {
-        this.dataSource = null;
+        this.jdbcTemplate = jdbcTemplate;
     }
 
     public void insert(final User user) {
-        final var sql = "insert into users (account, password, email) values (?, ?, ?)";
-
-        Connection conn = null;
-        PreparedStatement pstmt = null;
-        try {
-            conn = dataSource.getConnection();
-            pstmt = conn.prepareStatement(sql);
-
-            log.debug("query : {}", sql);
-
-            pstmt.setString(1, user.getAccount());
-            pstmt.setString(2, user.getPassword());
-            pstmt.setString(3, user.getEmail());
-            pstmt.executeUpdate();
-        } catch (SQLException e) {
-            log.error(e.getMessage(), e);
-            throw new RuntimeException(e);
-        } finally {
-            try {
-                if (pstmt != null) {
-                    pstmt.close();
-                }
-            } catch (SQLException ignored) {}
-
-            try {
-                if (conn != null) {
-                    conn.close();
-                }
-            } catch (SQLException ignored) {}
-        }
+        final String sql = "insert into users (account, password, email) values (?, ?, ?)";
+        jdbcTemplate.update(sql, user.getAccount(), user.getPassword(), user.getEmail());
     }
 
     public void update(final User user) {
-        // todo
+        final String sql = "update users set (account, password, email) = (?, ?, ?) where id = ?";
+        jdbcTemplate.update(sql, user.getAccount(), user.getPassword(), user.getEmail(), user.getId());
     }
 
     public List<User> findAll() {
-        // todo
-        return null;
+        final String sql = "select id, account, password, email from users";
+        return jdbcTemplate.queryForList(sql, USER_ROW_MAPPER);
     }
 
     public User findById(final Long id) {
-        final var sql = "select id, account, password, email from users where id = ?";
-
-        Connection conn = null;
-        PreparedStatement pstmt = null;
-        ResultSet rs = null;
-        try {
-            conn = dataSource.getConnection();
-            pstmt = conn.prepareStatement(sql);
-            pstmt.setLong(1, id);
-            rs = pstmt.executeQuery();
-
-            log.debug("query : {}", sql);
-
-            if (rs.next()) {
-                return new User(
-                        rs.getLong(1),
-                        rs.getString(2),
-                        rs.getString(3),
-                        rs.getString(4));
-            }
-            return null;
-        } catch (SQLException e) {
-            log.error(e.getMessage(), e);
-            throw new RuntimeException(e);
-        } finally {
-            try {
-                if (rs != null) {
-                    rs.close();
-                }
-            } catch (SQLException ignored) {}
-
-            try {
-                if (pstmt != null) {
-                    pstmt.close();
-                }
-            } catch (SQLException ignored) {}
-
-            try {
-                if (conn != null) {
-                    conn.close();
-                }
-            } catch (SQLException ignored) {}
-        }
+        final String sql = "select id, account, password, email from users where id = ?";
+        return jdbcTemplate.queryForObject(sql, USER_ROW_MAPPER, id);
     }
 
     public User findByAccount(final String account) {
-        // todo
-        return null;
+        final String sql = "select id, account, password, email from users where account = ?";
+        return jdbcTemplate.queryForObject(sql, USER_ROW_MAPPER, account);
     }
 }

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

@@ -1,10 +1,15 @@
 package org.springframework.jdbc.core;
 
+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 javax.sql.DataSource;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import javax.sql.DataSource;
-
 public class JdbcTemplate {
 
     private static final Logger log = LoggerFactory.getLogger(JdbcTemplate.class);
@@ -14,4 +19,61 @@ public class JdbcTemplate {
     public JdbcTemplate(final DataSource dataSource) {
         this.dataSource = dataSource;
     }
+
+    public void update(final String sql, final Object... parameters) {
+        try (final Connection connection = dataSource.getConnection();
+             final PreparedStatement preparedStatement = getPreparedStatement(sql, connection, parameters)) {
+            log.debug("query : {}", sql);
+            for (int i = 0; i < parameters.length; i++) {
+                preparedStatement.setObject(i + 1, parameters[i]);
+            }
+            preparedStatement.executeUpdate();
+        } catch (SQLException e) {
+            log.error(e.getMessage(), e);
+            throw new RuntimeException(e);
+        }
+    }
+
+    public <T> T queryForObject(final String sql, final RowMapper<T> rowMapper, final Object... parameters) {
+        try (final Connection connection = dataSource.getConnection();
+             final PreparedStatement preparedStatement = getPreparedStatement(sql, connection, parameters);
+             final ResultSet resultSet = preparedStatement.executeQuery()) {
+            log.debug("query : {}", sql);
+            if (resultSet.next()) {
+                return rowMapper.mapRow(resultSet);
+            }
+            return null;
+        } catch (SQLException e) {
+            log.error(e.getMessage(), e);
+            throw new RuntimeException(e);
+        }
+    }
+
+    private PreparedStatement getPreparedStatement(
+            final String sql,
+            final Connection connection,
+            final Object[] parameters
+    ) throws SQLException {
+        final PreparedStatement preparedStatement = connection.prepareStatement(sql);
+        for (int i = 0; i < parameters.length; i++) {
+            preparedStatement.setObject(i + 1, parameters[i]);
+        }
+        return preparedStatement;
+    }
+
+    public <T> List<T> queryForList(final String sql, final RowMapper<T> rowMapper, final Object... parameters) {
+        try (final Connection connection = dataSource.getConnection();
+             final PreparedStatement preparedStatement = getPreparedStatement(sql, connection, parameters);
+             final ResultSet resultSet = preparedStatement.executeQuery()) {
+            log.debug("query : {}", sql);
+            final List<T> result = new ArrayList<>();
+            while (resultSet.next()) {
+                result.add(rowMapper.mapRow(resultSet));
+            }
+            return result;
+        } catch (SQLException e) {
+            log.error(e.getMessage(), e);
+            throw new RuntimeException(e);
+        }
+    }
 }

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

@@ -0,0 +1,10 @@
+package org.springframework.jdbc.core;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+@FunctionalInterface
+public interface RowMapper<T> {
+
+    T mapRow(ResultSet resultSet) throws SQLException;
+}