详解MySQL与Spring的自动提交(autocommit)

mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit  | ON  |
+---------------+-------+

mysql> show global variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit  | ON  |
+---------------+-------+

关闭当前会话的自动提交模式
mysql> set autocommit=0;

 
mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit  | OFF  |
+---------------+-------+

 全局的autocommit还是开启状态
mysql> show global variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit  | ON  |
+---------------+-------+

 
 关闭全局的autocommit
mysql> set global autocommit=0;

 
mysql> show global variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit  | OFF  |
+---------------+-------+

[mysqld]
...
autocommit=0

//com.mysql.cj.protocol.a.NativeServerSession.java
  private boolean autoCommit = true;

com.alibaba.druid.pool.DruidAbstractDataSource.java
  protected volatile boolean             defaultAutoCommit             = true;
  ...
  public void initPhysicalConnection(Connection conn, Map<String, Object> variables, Map<String, Object> globalVariables) throws SQLException {
    if (conn.getAutoCommit() != defaultAutoCommit) {
      //将connection的autocommit设置为true
      conn.setAutoCommit(defaultAutoCommit);
    }
    ...
 
  }

com.zaxxer.hikari.HikariConfig.java
  public HikariConfig()
  {
   ...
   isAutoCommit = true;
  }

	@Override
	protected void doBegin(Object transaction, TransactionDefinition definition) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		Connection con = null;

		try {
      		........

			// Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
			// so we don't want to do it unnecessarily (for example if we've explicitly
			// configured the connection pool to set it already).
			if (con.getAutoCommit()) {
				txObject.setMustRestoreAutoCommit(true);
				if (logger.isDebugEnabled()) {
					logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
				}
                //关闭自动提交模
                con.setAutoCommit(false);
			}

      		.......
		}

		catch (Throwable ex) {
     		.......
		}
	}