[JDBC 라이브러리 구현하기 - 2단계] 제이미(임정수) 미션 제출합니다.

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

@@ -9,11 +9,11 @@
 
 public class UserDao {
 
-    private static final RowMapper<User> rowMapper = (rs, rowNum) -> new User(
-            rs.getLong(1),
-            rs.getString(2),
-            rs.getString(3),
-            rs.getString(4)
+    private static final RowMapper<User> rowMapper = (rs) -> new User(
+            rs.getLong("id"),
+            rs.getString("account"),
+            rs.getString("password"),
+            rs.getString("email")
     );
 
     private final JdbcTemplate jdbcTemplate;

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

@@ -1,10 +1,9 @@
 package org.springframework.jdbc.core;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import org.springframework.jdbc.core.exception.EmptyResultDataAccessException;
+import org.springframework.jdbc.core.exception.IncorrectResultSizeDataAccessException;
 
 import javax.sql.DataSource;
-import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
@@ -13,83 +12,67 @@
 
 public class JdbcTemplate {
 
-    private static final Logger log = LoggerFactory.getLogger(JdbcTemplate.class);
+    public static final int MAX_RESULT_SIZE = 1;
+    public static final int FIRST_INDEX = 0;
 
-    private final DataSource dataSource;
+    private final PreparedStatementExecutor preparedStatementExecutor;
 
     public JdbcTemplate(final DataSource dataSource) {
-        this.dataSource = dataSource;
+        this.preparedStatementExecutor = new PreparedStatementExecutor(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);
-        }
+        return preparedStatementExecutor.execute(PreparedStatement::executeUpdate, sql, args);
     }
 
-    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) {
+        return preparedStatementExecutor.execute(
+                pstmt -> {
+                    final ResultSet rs = pstmt.executeQuery();
+                    final List<T> results = getResults(rowMapper, rs);
+
+                    return getSingleResult(results);
+                }, sql, args
+        );
     }
 
-    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 <T> List<T> getResults(final RowMapper<T> rowMapper, final ResultSet rs) throws SQLException {
+        final List<T> results = new ArrayList<>();
+
+        while (rs.next()) {
+            final T result = calculateResult(rowMapper, rs);
+            results.add(result);
         }
+
+        return results;
     }
 
-    private static <T> T calculateResult(final RowMapper<T> rowMapper, final ResultSet rs) throws SQLException {
+    private <T> T calculateResult(final RowMapper<T> rowMapper, final ResultSet rs) throws SQLException {
         if (rs.next()) {
-            return rowMapper.mapRow(rs, rs.getRow());
+            return rowMapper.mapRow(rs);
         }
 
         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 <T> T getSingleResult(final List<T> results) {
+        if (results.isEmpty()) {
+            throw new EmptyResultDataAccessException("조회된 결과가 존재하지 않습니다.");
+        }
+        if (results.size() > MAX_RESULT_SIZE) {
+            throw new IncorrectResultSizeDataAccessException("조회된 결과의 개수가 적절하지 않습니다.");
         }
-    }
 
-    private static <T> List<T> getResults(final RowMapper<T> rowMapper, final ResultSet rs) throws SQLException {
-        List<T> results = new ArrayList<>();
+        return results.get(FIRST_INDEX);
+    }
 
-        while (rs.next()) {
-            final T result = calculateResult(rowMapper, rs);
-            results.add(result);
-        }
+    public <T> List<T> query(final String sql, final RowMapper<T> rowMapper) {
+        return preparedStatementExecutor.execute(
+                pstmt -> {
+                    final ResultSet rs = pstmt.executeQuery();
 
-        return results;
+                    return getResults(rowMapper, rs);
+                }, sql
+        );
     }
 }

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

@@ -0,0 +1,10 @@
+package org.springframework.jdbc.core;
+
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+
+@FunctionalInterface
+public interface PreparedStatementExecuteStrategy<T> {
+
+    T strategy(final PreparedStatement pstmt) throws SQLException;
+}

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

@@ -0,0 +1,42 @@
+package org.springframework.jdbc.core;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+
+public class PreparedStatementExecutor {
+
+    private static final Logger log = LoggerFactory.getLogger(JdbcTemplate.class);
+
+    private final DataSource dataSource;
+
+    public PreparedStatementExecutor(final DataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    public <T> T execute(final PreparedStatementExecuteStrategy<T> executeStrategy, 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 executeStrategy.strategy(pstmt);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private 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]);
+        }
+    }
+}

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

@@ -6,5 +6,5 @@
 @FunctionalInterface
 public interface RowMapper<T> {
 
-    T mapRow(final ResultSet rs, final int rowNum) throws SQLException;
+    T mapRow(final ResultSet rs) throws SQLException;
 }

jdbc/src/main/java/org/springframework/jdbc/core/exception/EmptyResultDataAccessException.java

@@ -0,0 +1,10 @@
+package org.springframework.jdbc.core.exception;
+
+import org.springframework.dao.DataAccessException;
+
+public class EmptyResultDataAccessException extends DataAccessException {
+
+    public EmptyResultDataAccessException(final String message) {
+        super(message);
+    }
+}

jdbc/src/main/java/org/springframework/jdbc/core/exception/IncorrectResultSizeDataAccessException.java

@@ -0,0 +1,10 @@
+package org.springframework.jdbc.core.exception;
+
+import org.springframework.dao.DataAccessException;
+
+public class IncorrectResultSizeDataAccessException extends DataAccessException {
+
+    public IncorrectResultSizeDataAccessException(final String message) {
+        super(message);
+    }
+}

jdbc/src/main/java/org/springframework/jdbc/core/exception/ResultSetOverflowException.java

@@ -0,0 +1,8 @@
+package org.springframework.jdbc.core.exception;
+
+public class ResultSetOverflowException extends IllegalArgumentException {
+
+    public ResultSetOverflowException(final String message) {
+        super(message);
+    }
+}