SSM-MyBatis-09：Mybatis中SqlSession的close为什么能造成事务的回滚

public void close() {
        try {
            this.executor.close(this.isCommitOrRollbackRequired(false));
            this.closeCursors();
            this.dirty = false;
        } finally {
            ErrorContext.instance().reset();
        }

    }

private boolean isCommitOrRollbackRequired(boolean force) {
        return !this.autoCommit && this.dirty || force;
    }

public void close(boolean forceRollback) {
        try {
            try {
                this.rollback(forceRollback);
            } finally {
                if(this.transaction != null) {
                    this.transaction.close();
                }

            }
        } catch (SQLException var11) {
            log.warn("Unexpected exception on closing transaction.  Cause: " + var11);
        } finally {
            this.transaction = null;
            this.deferredLoads = null;
            this.localCache = null;
            this.localOutputParameterCache = null;
            this.closed = true;
        }

    }

public void rollback(boolean required) throws SQLException {
        if(!this.closed) {
            try {
                this.clearLocalCache();
                this.flushStatements(true);
            } finally {
                if(required) {
                    this.transaction.rollback();
                }

            }
        }

    }