sql-server - Microsoft JDBC 驱动程序和 jTDS JDBC 驱动程序中的 XA 数据源

Question

我对 SQL Server 有点陌生，并且在连接到它的 Java 应用程序中工作。我找到了这两个著名的 JDBC 驱动程序，一个是 Microsoft 一个，另一个是 jTDS。我正在尝试使用 XA 数据源。

根据 Microsoft 文档，here它说我必须在使用 XA 数据源之前配置服务器。根据这个文档，它要求做的是在服务器中启用 XA。

但我没有看到 jTDS 需要任何此类服务器端修改。 (我找不到任何文档这么说，here)

所以，我的问题是 jTDS 本身如何设法在服务器中启用 XA，而 Microsoft 需要我来完成启用任务？

还是我在这里遗漏了什么？

Answer 1

在深入了解 jTDS 驱动程序分发后找到了答案。它有 README.XA 文件说明了一切。复制以下内容。

XA support in jTDS
==================

This version of jTDS includes a XADataSource class which allows the driver to
be used with J2EE servers that only support XA JDBC connections. The class name
is net.sourceforge.jtds.jdbcx.JtdsDataSource.

By default the driver will emulate distributed transactions fooling the J2EE
environment into believing that two phase commit is supported. This emulation
has the serious drawback that when used in a true distributed environment, the
driver may not be able to commit or rollback when requested by the transaction
manager. In this situation data loss or corruption can occur.

In general this emulation is safe to use when jTDS is the only transactional
resource manager or where the database is read only and never updated.
Emulation is much faster than support for true distributed transactions and
this may be another reason to consider using the driver in this mode if the
risks are understood.

Many J2EE servers provide their own XA emulations that allow the normal
net.sourceforge.jtds.jdbc.Driver to be used. The recommendation is to use the
vendor's emulation, if available, rather than the XADataSource as this
configuration is likely to be more stable.

The driver will support true distributed transactions with MS SQL2000 provided
that the extended stored procedure in JtdsXA.dll is installed in the target
server. To disable the XA emulation and use the stored procedure, set the
connection property "xaemulation" to "false". This implementation is very
immature and cannot be recommended for production use at this stage. It may
however be useful for development when true two phase commit support is
required.

Another connection property, "LogFile" has been added to JtdsDataSource which
allows the jTDS logging to be enabled in a J2EE environment. The parameter
value specifies the output file path for the logging information.

Two example configurations for the popular JBoss server are included in the
conf directory. One configuration uses the Driver interface and the server's XA
emulation the other shows how to use the driver's XA support in either emulated
or real mode.


Installing JtdsXA.dll
=====================

For true distributed transaction support JtdsXA.dll has to be installed on the
server. The installation procedure consists of two simple steps:

 1. Copy JtdsXA.dll from the XA directory to the <SQL_Server_Root>/binn
    directory of the SQL Server installation.

 2. From the command prompt run the following command in the directory where
    you extracted jTDS:

    isql -Usa -P<sa_password> -S<server_name_or_ip> -iXA\instjtds.sql

    Alternatively, use any DB tool (such as Query Analyzer or any JDBC tool) to
    execute the script within the 'master' database. Don't forget to log in as
    'sa'.

This will install the xp_jtdsxa extended stored procedure, used by jTDS to
provide true distributed transacition support.