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[JDBC 라이브러리 구현하기 - 1단계] 포이(김보준) 미션 제출합니다. #269

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merged 3 commits into from
Sep 29, 2023
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[JDBC 라이브러리 구현하기 - 1단계] 포이(김보준) 미션 제출합니다. #269

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06379e5
패키지 위치 변경 및 코드 정리
kang-hyungu Sep 21, 2023
0aa75ae
feat: JDBC Template 추가
poi1649 Sep 26, 2023
87d9aa5
fix : 몇몇 메서드들이 예외를 명시적으로 던지도록 변경
poi1649 Sep 26, 2023
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111 changes: 21 additions & 90 deletions app/src/main/java/com/techcourse/dao/UserDao.java
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@@ -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> rowMapper = rs -> 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.execute(sql, user.getAccount(), user.getPassword(), user.getEmail());
}

public void update(final User user) {
// todo
public int update(final User user) {
final var sql = "update users set password = ?, email = ? where id = ?";
return jdbcTemplate.update(sql, 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);
}
}
49 changes: 5 additions & 44 deletions app/src/main/java/com/techcourse/dao/UserHistoryDao.java
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@@ -1,62 +1,23 @@
package com.techcourse.dao;

import com.techcourse.domain.UserHistory;
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.SQLException;
import org.springframework.jdbc.core.JdbcTemplate;

public class UserHistoryDao {

private static final Logger log = LoggerFactory.getLogger(UserHistoryDao.class);

private final DataSource dataSource;
private final JdbcTemplate jdbcTemplate;

public UserHistoryDao(final DataSource dataSource) {
this.dataSource = dataSource;
this.jdbcTemplate = new JdbcTemplate(dataSource);
}

public UserHistoryDao(final JdbcTemplate jdbcTemplate) {
this.dataSource = null;
this.jdbcTemplate = jdbcTemplate;
}

public void log(final UserHistory userHistory) {
final var sql = "insert into user_history (user_id, account, password, email, created_at, created_by) values (?, ?, ?, ?, ?, ?)";

Connection conn = null;
PreparedStatement pstmt = null;
try {
conn = dataSource.getConnection();
pstmt = conn.prepareStatement(sql);

log.debug("query : {}", sql);

pstmt.setLong(1, userHistory.getUserId());
pstmt.setString(2, userHistory.getAccount());
pstmt.setString(3, userHistory.getPassword());
pstmt.setString(4, userHistory.getEmail());
pstmt.setObject(5, userHistory.getCreatedAt());
pstmt.setString(6, userHistory.getCreateBy());
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.execute(sql, userHistory.getUserId(), userHistory.getAccount(), userHistory.getPassword(), userHistory.getEmail(), userHistory.getCreatedAt(), userHistory.getCreateBy());
}
}
98 changes: 96 additions & 2 deletions jdbc/src/main/java/org/springframework/jdbc/core/JdbcTemplate.java
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@@ -1,9 +1,15 @@
package org.springframework.jdbc.core;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;
import javax.annotation.Nullable;
import javax.sql.DataSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.sql.DataSource;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.CannotGetJdbcConnectionException;

public class JdbcTemplate {

Expand All @@ -14,4 +20,92 @@ public class JdbcTemplate {
public JdbcTemplate(final DataSource dataSource) {
this.dataSource = dataSource;
}

public void execute(final String sql, final Object... params) throws DataAccessException {
log.debug("query : {}", sql);
execute(sql, new PreparedStatementCreator(), ps -> {
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PreparedStatementCreator를 사용해주셨네요! 생성의 책임을 다른 객체로 넘긴 것 좋은 것 같아요 👍👍
다만 궁금한 점이 있는데, 해당 객체는 매번 생성되어야 하는 이유가 있을까요? 현재 preparedstatement를 생성하는 역할만 수행하는데, 필드로 두지 않으신 이유가 궁금해요 :)

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처음에는 preparedStatement 또한 여러 종류가 있고, creator도 이에 따라 다양해 질 수 있을 것 같아 Functional Interface 로 구현하였는데 과한 확장인 것 같아 이를 폐기했습니다.

인터페이스이다 보니까 구현체를 만들어줘야했고, 중복되는 곳에서 사용되는 SimplePreparedStatementCreator를 만들어줬었는데 폐기하면서 이를 꼼꼼하게 수정하지 않았네요! 😅

doSetValue(params, ps);
ps.execute();
return null;
});
}

public int update(final String sql, final Object... params) throws DataAccessException {
log.debug("query : {}", sql);
return updateCount(execute(
sql,
new PreparedStatementCreator(),
ps -> {
doSetValue(params, ps);
return ps.executeUpdate();
}
));
}

private int updateCount(@Nullable final Integer result) throws DataAccessException {
if (result == null) {
throw new DataAccessException("no update count");
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result == null 인 경우는 언제일까요?

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@poi1649 poi1649 Sep 30, 2023 •
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템플릿 콜백패턴을 위해 사용한 execute 메서드에서 Null 을 반환하는 경우가 있어 @Nullable 어노테이션을 붙였는데, 이 때문에 그냥 사용할 경우 경고가 표시되어 이런 검사로직을 넣게 됐네요~ 그렇지만 updateCount는 executeUpdate시에만 사용되고 이 메서드는 null을 반환하지 않으니 supressedWarning을 붙여주는게 더 적절한 사용방식일 수 있겠군요

}
return result;
}

@Nullable
public <T> T queryForObject(final String sql, final RowMapper<T> rowMapper, final Object... params) throws DataAccessException {
final var results = query(sql, rowMapper, params);
if (results.isEmpty()) {
return null;
}
return results.get(0);
}

public <T> List<T> query(final String sql, final RowMapper<T> rowMapper, final Object... params) throws DataAccessException {
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현재 상황에서는 query 메서드의 기본 리턴 값을 List로 두는 것과, queryForList 라는 메서드를 추가하는 것 중 어떤게 나은 것 같으신가요? 이 부분은 정답이 없는 것 같아서 포이의 의견이 궁금하네요 😆

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음 이 부분에서는 사실 기존의 JDBCTemplate를 의식하지 않는다면 어떤 이름도 상관 없을 것이라는 생각이 들어요! 오히려 List가 더 바람직한 이름이라고 생각하실 분들도 계실 것 같습니다!

그렇지만 기존의 JDBCTemplate를 고려한다면, 두 메서드는 약간의 차이를 갖는데요,

JDBCTemplate의 queryForList 메서드를 살펴보면

	@Override
	public <T> List<T> queryForList(String sql, Class<T> elementType) throws DataAccessException {
		return query(sql, getSingleColumnRowMapper(elementType));
	}

	@Override
	public List<Map<String, Object>> queryForList(String sql) throws DataAccessException {
		return query(sql, getColumnMapRowMapper());
	}

위처럼 SingleColumnRowMapper 나 ColumnMapRowMapper를 사용하고 있는 것을 볼 수 있어요.
즉, RowMapper를 사용자 정의를 통해 지정해주지 못하고, 특정 컬럼에 대한 반환타입만 지정하거나, 전부 컬럼이름(key, String) : 컬럼 값(value, Obejct) 방식으로 전달해줄 수 밖에 없습니다.

제가 이번 미션에서 만들고자 하는 메서드는 RowMapper를 통해 사용자가 지정한 타입의 객체로 각각의 Row를 매핑하여 반환하는 것이기 때문에 queryForList보다는 query가 적합하다는 생각이 드네요! ♞

log.debug("query : {}", sql);
return results(execute(
sql,
new PreparedStatementCreator(),
ps -> {
doSetValue(params, ps);
final var rs = ps.executeQuery();
final var extractor = new ResultSetExtractor<>(rs, rowMapper);
return extractor.extractData();
}
));
}

private <T> List<T> results(@Nullable final List<T> results) throws DataAccessException {
if (results == null) {
throw new DataAccessException("no result");
}
return results;
}

private void doSetValue(final Object[] params, final PreparedStatement ps) throws SQLException {
for (int i = 1; i <= params.length; i++) {
ps.setObject(i, params[i - 1]);
}
}

@Nullable
private <T> T execute(
final String sql,
final PreparedStatementCreator psc,
final PreparedStatementCallback<T> action
) throws DataAccessException {
try (
final var conn = getConnection();
final var ps = psc.createPreparedStatement(conn, sql)
) {
return action.doInPreparedStatement(ps);
} catch (SQLException e) {
throw new DataAccessException(e);
}
}

private Connection getConnection() {
try {
return dataSource.getConnection();
} catch (SQLException e) {
throw new CannotGetJdbcConnectionException(e.getMessage());
}
}
}
13 changes: 13 additions & 0 deletions jdbc/src/main/java/org/springframework/jdbc/core/PreparedStatementCallback.java
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package org.springframework.jdbc.core;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import javax.annotation.Nullable;
import org.springframework.dao.DataAccessException;

@FunctionalInterface
public interface PreparedStatementCallback<T> {

@Nullable
T doInPreparedStatement(PreparedStatement ps) throws SQLException, DataAccessException;
}
12 changes: 12 additions & 0 deletions jdbc/src/main/java/org/springframework/jdbc/core/PreparedStatementCreator.java
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package org.springframework.jdbc.core;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class PreparedStatementCreator {

public PreparedStatement createPreparedStatement(final Connection conn, final String sql) throws SQLException {
return conn.prepareStatement(sql);
}
}
25 changes: 25 additions & 0 deletions jdbc/src/main/java/org/springframework/jdbc/core/ResultSetExtractor.java
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package org.springframework.jdbc.core;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class ResultSetExtractor<T> {

private final ResultSet rs;
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개인 취향이긴 하지만 resultSet은 어떨까요 ㅎㅎ 반영 안 하셔도 됩니다!

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아직은 rs만으로 명확하다고 생각하여 혼동할만한 다른 변수명이 있을 때 바꿔보겠습니다~

private final RowMapper<T> rowMapper;

public ResultSetExtractor(final ResultSet rs, final RowMapper<T> rowMapper) {
this.rs = rs;
this.rowMapper = rowMapper;
}

public List<T> extractData() throws SQLException {
final var results = new ArrayList<T>();
while (rs.next()) {
results.add(rowMapper.mapRow(rs));
}
return results;
}
}
12 changes: 12 additions & 0 deletions jdbc/src/main/java/org/springframework/jdbc/core/RowMapper.java
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package org.springframework.jdbc.core;

import java.sql.ResultSet;
import java.sql.SQLException;
import javax.annotation.Nullable;

@FunctionalInterface
public interface RowMapper<T> {

@Nullable
T mapRow(ResultSet rs) throws SQLException;
}
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