[JDBC 라이브러리 구현하기 - 2, 3단계] 히이로(문제웅) 미션 제출합니다.

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

@@ -22,7 +22,7 @@ public JdbcTemplate(final DataSource dataSource) {
  this.dataSource = dataSource;
  }
 
- public int update(String sql, Object... args) {
+ public int update(final String sql, Object... args) {
  try (
  Connection conn = dataSource.getConnection();
  PreparedStatement pstmt = conn.prepareStatement(sql)
@@ -39,7 +39,7 @@ public int update(String sql, Object... args) {
  }
  }
 
- public int update(Connection conn, String sql, Object... args) {
+ public int update(final Connection conn, final String sql, Object... args) {
  try (
  PreparedStatement pstmt = conn.prepareStatement(sql)
  ) {
@@ -55,48 +55,45 @@ public int update(Connection conn, String sql, Object... args) {
  }
  }
 
- public <T> T queryForObject(String sql, RowMapper<T> rowMapper, Object... args) {
- try (
- Connection conn = dataSource.getConnection();
- PreparedStatement pstmt = conn.prepareStatement(sql)
- ) {
- log.debug("query : {}", sql);
+ public <T> T queryForObject(final String sql, final RowMapper<T> rowMapper, Object... args) {
+ log.debug("query : {}", sql);
 
- ArgumentPreparedStatementSetter pss = new ArgumentPreparedStatementSetter(args);
- pss.setValues(pstmt);
+ PreparedStatementCallback<T> callback = pstmt -> {
  List<T> results = extractResultSet(pstmt.executeQuery(), rowMapper);
-
  if (results.size() == 1) {
  return results.get(0);
  }
  throw new IncorrectResultSizeDataAccessException(results.size());
- } catch (SQLException e) {
- log.error(e.getMessage(), e);
- throw SQLExceptionTranslator.translate(sql, e);
+ };
+ return executeQuery(callback, sql, args);
+ }
+
+ public <T> List<T> query(final String sql, final RowMapper<T> rowMapper, Object... args) {
+ PreparedStatementCallback<List<T>> callBack = pstmt ->
+ extractResultSet(pstmt.executeQuery(), rowMapper);
+ return executeQuery(callBack, sql, args);
+ }
+
+ private <T> List<T> extractResultSet(final ResultSet rs, final RowMapper<T> rowMapper) throws SQLException {
+ List<T> results = new ArrayList<>();
+ int rowNum = 0;
+ while (rs.next()) {
+ results.add(rowMapper.mapRow(rs, rowNum++));
  }
+ return results;
  }
 
- public <T> List<T> query(String sql, RowMapper<T> rowMapper, Object... args) {
+ private <T> T executeQuery(final PreparedStatementCallback<T> action, final String sql, Object... args) {
  try (
  Connection conn = dataSource.getConnection();
  PreparedStatement pstmt = conn.prepareStatement(sql)
  ) {
  ArgumentPreparedStatementSetter pss = new ArgumentPreparedStatementSetter(args);
  pss.setValues(pstmt);
-
- return extractResultSet(pstmt.executeQuery(), rowMapper);
+ return action.doInPreparedStatement(pstmt);
  } catch (SQLException e) {
  log.error(e.getMessage(), e);
  throw SQLExceptionTranslator.translate(sql, e);
  }
  }
-
- private <T> List<T> extractResultSet(ResultSet rs, RowMapper<T> rowMapper) throws SQLException {
- List<T> results = new ArrayList<>();
- int rowNum = 0;
- while (rs.next()) {
- results.add(rowMapper.mapRow(rs, rowNum++));
- }
- return results;
- }
 }

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

@@ -0,0 +1,11 @@
+package org.springframework.jdbc.core;
+
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+import org.springframework.dao.DataAccessException;
+
+@FunctionalInterface
+public interface PreparedStatementCallback<T> {
+
+ T doInPreparedStatement(PreparedStatement ps) throws SQLException, DataAccessException;
+}