[JDBC 라이브러리 구현하기 - 1단계] 제이미(임정수) 미션 제출합니다!

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

@@ -2,120 +2,55 @@
 
 import com.techcourse.domain.User;
 import org.springframework.jdbc.core.JdbcTemplate;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import org.springframework.jdbc.core.RowMapper;
 
 import javax.sql.DataSource;
-import java.sql.Connection;
-import java.sql.PreparedStatement;
-import java.sql.ResultSet;
-import java.sql.SQLException;
 import java.util.List;
 
 public class UserDao {
 
-    private static final Logger log = LoggerFactory.getLogger(UserDao.class);
+    private static final RowMapper<User> rowMapper = (rs, rowNum) -> new User(
+            rs.getLong(1),
+            rs.getString(2),
+            rs.getString(3),
+            rs.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) {}
-        }
+        jdbcTemplate.update(sql, user.getAccount(), user.getPassword(), user.getEmail());
     }
 
     public void update(final User user) {
-        // todo
+        final var 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 var sql = "select id, account, password, email from users";
+
+        return jdbcTemplate.query(sql, rowMapper);
     }
 
     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) {}
-        }
+        return jdbcTemplate.queryForObject(sql, rowMapper, id);
     }
 
     public User findByAccount(final String account) {
-        // todo
-        return null;
+        final var sql = "select id, account, password, email from users where account = ?";
+
+        return jdbcTemplate.queryForObject(sql, rowMapper, account);
     }
 }

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

@@ -4,6 +4,12 @@
 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.ArrayList;
+import java.util.List;
 
 public class JdbcTemplate {
 
@@ -14,4 +20,76 @@ public class JdbcTemplate {
     public JdbcTemplate(final DataSource dataSource) {
         this.dataSource = dataSource;
     }
+
+    public int update(final String sql, final Object... args) {
+        try (
+                final Connection conn = dataSource.getConnection();
+                final PreparedStatement pstmt = conn.prepareStatement(sql)
+        ) {
+            setArguments(pstmt, args);
+
+            log.debug("query : {}", sql);
+
+            return pstmt.executeUpdate();
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static void setArguments(final PreparedStatement pstmt, final Object[] args) throws SQLException {
+        for (int i = 0; i < args.length; i++) {
+            final int parameterIndex = i + 1;
+            pstmt.setObject(parameterIndex, args[i]);
+        }
+    }
+
+    public <T> T queryForObject(final String sql, final RowMapper<T> rowMapper, final Object... args) {
+        try (
+                final Connection conn = dataSource.getConnection();
+                final PreparedStatement pstmt = conn.prepareStatement(sql)
+        ) {
+            setArguments(pstmt, args);
+            ResultSet rs = pstmt.executeQuery();
+
+            log.debug("query : {}", sql);
+
+            return calculateResult(rowMapper, rs);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static <T> T calculateResult(final RowMapper<T> rowMapper, final ResultSet rs) throws SQLException {
+        if (rs.next()) {
+            return rowMapper.mapRow(rs, rs.getRow());
+        }
+
+        return null;
+    }
+
+    public <T> List<T> query(final String sql, final RowMapper<T> rowMapper) {
+        try (
+                final Connection conn = dataSource.getConnection();
+                final PreparedStatement pstmt = conn.prepareStatement(sql)
+        ) {
+            ResultSet rs = pstmt.executeQuery();
+
+            log.debug("query : {}", sql);
+
+            return getResults(rowMapper, rs);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static <T> List<T> getResults(final RowMapper<T> rowMapper, final ResultSet rs) throws SQLException {
+        List<T> results = new ArrayList<>();
+
+        while (rs.next()) {
+            final T result = calculateResult(rowMapper, rs);
+            results.add(result);
+        }
+
+        return results;
+    }
 }

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(final ResultSet rs, final int rowNum) throws SQLException;
+}