开门见山

关于事务的基本概念和介绍请参阅另一篇博客事务处理机制与协议，这里着重讲解如何在Spring中基于JTA(Java Transaction API)实现分布式事务并实践。

Spring Boot除了对非XA的事务进行了封装处理，并提供了注解@Transactional的方式实现事务管理，也对多XA资源的分布式JTA事务提供了很好的支持，通常可选的内嵌事务管理器有Atomikos和Bitronix，任意选择一个作为实现XA事务管理的管理器即可。

接下来就分别介绍利用Spring Boot实现非XA和XA的事务处理。

Spring对非XA事务的实现

使用Spring Boot实现非XA事务非常简单，只需要简单的两步即可：

  1. 在构建脚本文件中加入依赖org.springframework.boot:spring-boot-starter-jdbc。
  2. 无论采用基本的JdbcTemplate或封装的JPA与数据库进行交互，只需要在具体方法上加注解@Transactional(org.springframework.transaction.annotation.Transactional)。

这样就将该块的操作序列当作一个事务单元进行管理，任何失败或异常都将导致所有操作序列回滚，一个具体的简单Demo可参见Transaction Demo，另外，如果注解加在类名上，则代表该类中每个方法都将作为一个事务单元被管理。

采用Atomikos事务管理器

Atomikos是一款JTA事务管理器的开源库，能够Embedded到Spring Boot中，可以通过添加依赖spring-boot-starter-jta-atomikos，然后Spring Boot会自动配置Atomikos并下载其依赖库，默认的事务日志文件会被写在项目下的transaction-logs文件目录下的日志文件中，可以通过配置spring.jta.log-dir来指定日志目录。可以设置spring.jta.atomikos.properties读取相应的配置文件。可以参阅完成的详细信息AtomikosProperties Javadoc。

为了保证多个事务管理器能够正常安全地协调相同的资源管理器，每一个Atomikos实例必须配置一个唯一的ID，默认值为当前所在机器IP，通常在产品环境中，可以为每个应用程序实例配置spring.jta.transaction-manager-id为不同的值。

在Spring Boot中，可以自定义在应用程序配置文件中配置AtomikosProperties参数：

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spring.jta.atomikos.connectionfactory.borrow-connection-timeout=30 # Timeout, in seconds, for borrowing connections from the pool.
spring.jta.atomikos.connectionfactory.ignore-session-transacted-flag=true # Whether or not to ignore the transacted flag when creating session.
spring.jta.atomikos.connectionfactory.local-transaction-mode=false # Whether or not local transactions are desired.
spring.jta.atomikos.connectionfactory.maintenance-interval=60 # The time, in seconds, between runs of the pool's maintenance thread.
spring.jta.atomikos.connectionfactory.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.atomikos.connectionfactory.max-lifetime=0 # The time, in seconds, that a connection can be pooled for before being destroyed. 0 denotes no limit.
spring.jta.atomikos.connectionfactory.max-pool-size=1 # The maximum size of the pool.
spring.jta.atomikos.connectionfactory.min-pool-size=1 # The minimum size of the pool.
spring.jta.atomikos.connectionfactory.reap-timeout=0 # The reap timeout, in seconds, for borrowed connections. 0 denotes no limit.
spring.jta.atomikos.connectionfactory.unique-resource-name=jmsConnectionFactory # The unique name used to identify the resource during recovery.
spring.jta.atomikos.datasource.borrow-connection-timeout=30 # Timeout, in seconds, for borrowing connections from the pool.
spring.jta.atomikos.datasource.default-isolation-level= # Default isolation level of connections provided by the pool.
spring.jta.atomikos.datasource.login-timeout= # Timeout, in seconds, for establishing a database connection.
spring.jta.atomikos.datasource.maintenance-interval=60 # The time, in seconds, between runs of the pool's maintenance thread.
spring.jta.atomikos.datasource.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.atomikos.datasource.max-lifetime=0 # The time, in seconds, that a connection can be pooled for before being destroyed. 0 denotes no limit.
spring.jta.atomikos.datasource.max-pool-size=1 # The maximum size of the pool.
spring.jta.atomikos.datasource.min-pool-size=1 # The minimum size of the pool.
spring.jta.atomikos.datasource.reap-timeout=0 # The reap timeout, in seconds, for borrowed connections. 0 denotes no limit.
spring.jta.atomikos.datasource.test-query= # SQL query or statement used to validate a connection before returning it.
spring.jta.atomikos.datasource.unique-resource-name=dataSource # The unique name used to identify the resource during recovery.
spring.jta.atomikos.properties.checkpoint-interval=500 # Interval between checkpoints.
spring.jta.atomikos.properties.console-file-count=1 # Number of debug logs files that can be created.
spring.jta.atomikos.properties.console-file-limit=-1 # How many bytes can be stored at most in debug logs files.
spring.jta.atomikos.properties.console-file-name=tm.out # Debug logs file name.
spring.jta.atomikos.properties.console-log-level= # Console log level.
spring.jta.atomikos.properties.default-jta-timeout=10000 # Default timeout for JTA transactions.
spring.jta.atomikos.properties.enable-logging=true # Enable disk logging.
spring.jta.atomikos.properties.force-shutdown-on-vm-exit=false # Specify if a VM shutdown should trigger forced shutdown of the transaction core.
spring.jta.atomikos.properties.log-base-dir= # Directory in which the log files should be stored.
spring.jta.atomikos.properties.log-base-name=tmlog # Transactions log file base name.
spring.jta.atomikos.properties.max-actives=50 # Maximum number of active transactions.
spring.jta.atomikos.properties.max-timeout=300000 # Maximum timeout (in milliseconds) that can be allowed for transactions.
spring.jta.atomikos.properties.output-dir= # Directory in which to store the debug log files.
spring.jta.atomikos.properties.serial-jta-transactions=true # Specify if sub-transactions should be joined when possible.
spring.jta.atomikos.properties.service= # Transaction manager implementation that should be started.
spring.jta.atomikos.properties.threaded-two-phase-commit=true # Use different (and concurrent) threads for two-phase commit on the participating resources.
spring.jta.atomikos.properties.transaction-manager-unique-name= # Transaction manager's unique name.

一个具体的Atomikos分布式事务管理示例可参见Atomikos Demo。

采用Bitronix事务管理器

Bitronix是一款JTA事务管理器的开源库，可以通过添加依赖spring-boot-starter-jta-bitronix，然后Spring Boot会自动配置Bitronix，默认的事务日志文件会被写在项目下的transaction-logs文件目录下的part1.btm和part2.btm中，可以通过配置spring.jta.log-dir来指定日志目录。可以设置spring.jta.bitronix.properties读取相应的配置文件，相当于自定义配置bitronix.tm.configuration实例。

为了保证多个事务管理器能够正常安全地协调相同的资源管理器，每一个Bitronix实例必须配置一个唯一的ID，默认值为当前所在机器IP，通常在产品环境中，可以为每个应用程序实例配置spring.jta.transaction-manager-id为不同的值。

在Spring Boot集成应用中，可以根据自定义需求在应用程序配置文件中配置以下参数：

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spring.jta.bitronix.connectionfactory.acquire-increment=1 # Number of connections to create when growing the pool.
spring.jta.bitronix.connectionfactory.acquisition-interval=1 # Time, in seconds, to wait before trying to acquire a connection again after an invalid connection was acquired.
spring.jta.bitronix.connectionfactory.acquisition-timeout=30 # Timeout, in seconds, for acquiring connections from the pool.
spring.jta.bitronix.connectionfactory.allow-local-transactions=true # Whether or not the transaction manager should allow mixing XA and non-XA transactions.
spring.jta.bitronix.connectionfactory.apply-transaction-timeout=false # Whether or not the transaction timeout should be set on the XAResource when it is enlisted.
spring.jta.bitronix.connectionfactory.automatic-enlisting-enabled=true # Whether or not resources should be enlisted and delisted automatically.
spring.jta.bitronix.connectionfactory.cache-producers-consumers=true # Whether or not produces and consumers should be cached.
spring.jta.bitronix.connectionfactory.defer-connection-release=true # Whether or not the provider can run many transactions on the same connection and supports transaction interleaving.
spring.jta.bitronix.connectionfactory.ignore-recovery-failures=false # Whether or not recovery failures should be ignored.
spring.jta.bitronix.connectionfactory.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.bitronix.connectionfactory.max-pool-size=10 # The maximum size of the pool. 0 denotes no limit.
spring.jta.bitronix.connectionfactory.min-pool-size=0 # The minimum size of the pool.
spring.jta.bitronix.connectionfactory.password= # The password to use to connect to the JMS provider.
spring.jta.bitronix.connectionfactory.share-transaction-connections=false #  Whether or not connections in the ACCESSIBLE state can be shared within the context of a transaction.
spring.jta.bitronix.connectionfactory.test-connections=true # Whether or not connections should be tested when acquired from the pool.
spring.jta.bitronix.connectionfactory.two-pc-ordering-position=1 # The position that this resource should take during two-phase commit (always first is Integer.MIN_VALUE, always last is Integer.MAX_VALUE).
spring.jta.bitronix.connectionfactory.unique-name=jmsConnectionFactory # The unique name used to identify the resource during recovery.
spring.jta.bitronix.connectionfactory.use-tm-join=true Whether or not TMJOIN should be used when starting XAResources.
spring.jta.bitronix.connectionfactory.user= # The user to use to connect to the JMS provider.
spring.jta.bitronix.datasource.acquire-increment=1 # Number of connections to create when growing the pool.
spring.jta.bitronix.datasource.acquisition-interval=1 # Time, in seconds, to wait before trying to acquire a connection again after an invalid connection was acquired.
spring.jta.bitronix.datasource.acquisition-timeout=30 # Timeout, in seconds, for acquiring connections from the pool.
spring.jta.bitronix.datasource.allow-local-transactions=true # Whether or not the transaction manager should allow mixing XA and non-XA transactions.
spring.jta.bitronix.datasource.apply-transaction-timeout=false # Whether or not the transaction timeout should be set on the XAResource when it is enlisted.
spring.jta.bitronix.datasource.automatic-enlisting-enabled=true # Whether or not resources should be enlisted and delisted automatically.
spring.jta.bitronix.datasource.cursor-holdability= # The default cursor holdability for connections.
spring.jta.bitronix.datasource.defer-connection-release=true # Whether or not the database can run many transactions on the same connection and supports transaction interleaving.
spring.jta.bitronix.datasource.enable-jdbc4-connection-test= # Whether or not Connection.isValid() is called when acquiring a connection from the pool.
spring.jta.bitronix.datasource.ignore-recovery-failures=false # Whether or not recovery failures should be ignored.
spring.jta.bitronix.datasource.isolation-level= # The default isolation level for connections.
spring.jta.bitronix.datasource.local-auto-commit= # The default auto-commit mode for local transactions.
spring.jta.bitronix.datasource.login-timeout= # Timeout, in seconds, for establishing a database connection.
spring.jta.bitronix.datasource.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.bitronix.datasource.max-pool-size=10 # The maximum size of the pool. 0 denotes no limit.
spring.jta.bitronix.datasource.min-pool-size=0 # The minimum size of the pool.
spring.jta.bitronix.datasource.prepared-statement-cache-size=0 # The target size of the prepared statement cache. 0 disables the cache.
spring.jta.bitronix.datasource.share-transaction-connections=false #  Whether or not connections in the ACCESSIBLE state can be shared within the context of a transaction.
spring.jta.bitronix.datasource.test-query= # SQL query or statement used to validate a connection before returning it.
spring.jta.bitronix.datasource.two-pc-ordering-position=1 # The position that this resource should take during two-phase commit (always first is Integer.MIN_VALUE, always last is Integer.MAX_VALUE).
spring.jta.bitronix.datasource.unique-name=dataSource # The unique name used to identify the resource during recovery.
spring.jta.bitronix.datasource.use-tm-join=true Whether or not TMJOIN should be used when starting XAResources.
spring.jta.bitronix.properties.allow-multiple-lrc=false # Allow multiple LRC resources to be enlisted into the same transaction.
spring.jta.bitronix.properties.asynchronous2-pc=false # Enable asynchronously execution of two phase commit.
spring.jta.bitronix.properties.background-recovery-interval-seconds=60 # Interval in seconds at which to run the recovery process in the background.
spring.jta.bitronix.properties.current-node-only-recovery=true # Recover only the current node.
spring.jta.bitronix.properties.debug-zero-resource-transaction=false # Log the creation and commit call stacks of transactions executed without a single enlisted resource.
spring.jta.bitronix.properties.default-transaction-timeout=60 # Default transaction timeout in seconds.
spring.jta.bitronix.properties.disable-jmx=false # Enable JMX support.
spring.jta.bitronix.properties.exception-analyzer= # Set the fully qualified name of the exception analyzer implementation to use.
spring.jta.bitronix.properties.filter-log-status=false # Enable filtering of logs so that only mandatory logs are written.
spring.jta.bitronix.properties.force-batching-enabled=true #  Set if disk forces are batched.
spring.jta.bitronix.properties.forced-write-enabled=true # Set if logs are forced to disk.
spring.jta.bitronix.properties.graceful-shutdown-interval=60 # Maximum amount of seconds the TM will wait for transactions to get done before aborting them at shutdown time.
spring.jta.bitronix.properties.jndi-transaction-synchronization-registry-name= # JNDI name of the TransactionSynchronizationRegistry.
spring.jta.bitronix.properties.jndi-user-transaction-name= # JNDI name of the UserTransaction.
spring.jta.bitronix.properties.journal=disk # Name of the journal. Can be 'disk', 'null' or a class name.
spring.jta.bitronix.properties.log-part1-filename=btm1.tlog # Name of the first fragment of the journal.
spring.jta.bitronix.properties.log-part2-filename=btm2.tlog # Name of the second fragment of the journal.
spring.jta.bitronix.properties.max-log-size-in-mb=2 # Maximum size in megabytes of the journal fragments.
spring.jta.bitronix.properties.resource-configuration-filename= # ResourceLoader configuration file name.
spring.jta.bitronix.properties.server-id= # ASCII ID that must uniquely identify this TM instance. Default to the machine's IP address.
spring.jta.bitronix.properties.skip-corrupted-logs=false # Skip corrupted transactions log entries.
spring.jta.bitronix.properties.warn-about-zero-resource-transaction=true # Log a warning for transactions executed without a single

一个具体的Bitronix分布式事务管理示例可参见Bitronix Demo。

混合XA/非XA事务的JMS连接

当使用JTA时，默认情况下，主要的JMSConnectionFactory实例会被自动加入到XA资源中，并参与XA事务。如果在某些情况下，如JMS处理时间较长，超过了XA的Timeout时间，则需要在处理JMS时不使用XA的ConnectionFactory，只需在注入时使用nonXaJmsConnectionFactory即可，以下是代码示例：

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// Inject the primary (XA aware) ConnectionFactory
@Autowired
private ConnectionFactory defaultConnectionFactory;
// Inject the XA aware ConnectionFactory (uses the alias and injects the same as above)
@Autowired
@Qualifier("xaJmsConnectionFactory")
private ConnectionFactory xaConnectionFactory;
// Inject the non-XA aware ConnectionFactory
@Autowired
@Qualifier("nonXaJmsConnectionFactory")
private ConnectionFactory nonXaConnectionFactory;

General Databases

针对不同的数据库可能需要设置一些不同的参数开启XA功能，比如Postgresql，需要设置参数max_prepared_transactions，整型值，它决定能够同时处于prepared状态的事务的最大数目，0表示关闭prepared事务的特性，该值通常应该和max_connections的值一样大。

postgresql.conf
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max_prepared_transactions=30

如果使用AWS的Postgresql RDS数据库，则需要在Parameter Group中设置该值，否则默认会为0，表示关闭XA功能。

References