关于Java中的mysql时区问题详解

CREATE TABLE `user` (
 `name` varchar(50) NOT NULL,
 `birth_date` timestamp NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1

mysql> insert into `user`
  -> values ('Tom', time('2020-05-15 08:00:00'));
Query OK, 1 row affected (0.01 sec)

mysql> select * from user;
+------+---------------------+
| name | birth_date     |
+------+---------------------+
| Tom | 2020-05-14 08:00:00 |
+------+---------------------+
1 row in set (0.00 sec)

Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useSSL=false", "root", "root");
Statement stmt = conn.createStatement();
stmt.execute("select * from user where name = 'Tom'");
ResultSet rs = stmt.getResultSet();
while (rs.next()) {
  Timestamp timestamp = rs.getTimestamp("birth_date");
  System.out.println(timestamp.toLocalDateTime().toString());
}

/* mysql-connector-java-8.0.20 (Revision: afc0a13cd3c5a0bf57eaa809ee0ee6df1fd5ac9b) */
SELECT @@session.auto_increment_increment AS auto_increment_increment,
    @@character_set_client       AS character_set_client,
    @@character_set_connection     AS character_set_connection,
    @@character_set_results      AS character_set_results,
    @@character_set_server       AS character_set_server,
    @@collation_server         AS collation_server,
    @@collation_connection       AS collation_connection,
    @@init_connect           AS init_connect,
    @@interactive_timeout       AS interactive_timeout,
    @@license             AS license,
    @@lower_case_table_names      AS lower_case_table_names,
    @@max_allowed_packet        AS max_allowed_packet,
    @@net_write_timeout        AS net_write_timeout,
    @@performance_schema        AS performance_schema,
    @@query_cache_size         AS query_cache_size,
    @@query_cache_type         AS query_cache_type,
    @@sql_mode             AS sql_mode,
    @@system_time_zone         AS system_time_zone,
    @@time_zone            AS time_zone,
    @@transaction_isolation      AS transaction_isolation,
    @@wait_timeout           AS wait_timeout;

this.defaultTimestampValueFactory = new SqlTimestampValueFactory(pset, null, this.session.getServerSession().getServerTimeZone());@Overridepublic Timestamp getTimestamp(int columnIndex) throws SQLException {
  checkRowPos();
  checkColumnBounds(columnIndex);  return this.thisRow.getValue(columnIndex - 1, this.defaultTimestampValueFactory);
}

public void configureTimezone() {
  #从mysql的响应获取 time_zone 和 system_time_zone 的设置
  String configuredTimeZoneOnServer = this.serverSession.getServerVariable("time_zone");

  if ("SYSTEM".equalsIgnoreCase(configuredTimeZoneOnServer)) {
    configuredTimeZoneOnServer = this.serverSession.getServerVariable("system_time_zone");
  }

  #从 jdbc url 参数 serverTimezone 获取时区
  String canonicalTimezone = getPropertySet().getStringProperty(PropertyKey.serverTimezone).getValue();

  if (configuredTimeZoneOnServer != null) {
    //如果 jdbc url 中未通过 serverTimezone 指定时区。则从TimeZoneMapping.properties中获取mysql 回传的时区缩写对应的标准时区，比如此处的 BST => Europe/London
    //会出现无法映射的情况，不如 CEST 无法映射到 => Europe/Berlin，可以指定自定义的 Properties 文件进行映射
    // user can override this with driver properties, so don't detect if that's the case
    if (canonicalTimezone == null || StringUtils.isEmptyOrWhitespaceOnly(canonicalTimezone)) {
      try {
        canonicalTimezone = TimeUtil.getCanonicalTimezone(configuredTimeZoneOnServer, getExceptionInterceptor());
      } catch (IllegalArgumentException iae) {
        throw ExceptionFactory.createException(WrongArgumentException.class, iae.getMessage(), getExceptionInterceptor());
      }
    }
  }
  
  //如果 jdbc url 中通过 serverTimezone 指定了时区，则优先使用该时区
  if (canonicalTimezone != null && canonicalTimezone.length() > 0) {
    this.serverSession.setServerTimeZone(TimeZone.getTimeZone(canonicalTimezone));

    //
    // The Calendar class has the behavior of mapping unknown timezones to 'GMT' instead of throwing an exception, so we must check for this...
    //
    if (!canonicalTimezone.equalsIgnoreCase("GMT") && this.serverSession.getServerTimeZone().getID().equals("GMT")) {
      throw ExceptionFactory.createException(WrongArgumentException.class, Messages.getString("Connection.9", new Object[] { canonicalTimezone }),
          getExceptionInterceptor());
    }
  }

}