IsolationLevelDataSourceRouter (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

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org.springframework.jdbc.datasource.lookup
Class IsolationLevelDataSourceRouter

java.lang.Object
  org.springframework.jdbc.datasource.AbstractDataSource
      org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource
          org.springframework.jdbc.datasource.lookup.IsolationLevelDataSourceRouter

All Implemented Interfaces:: Wrapper, CommonDataSource, DataSource, InitializingBean

public class IsolationLevelDataSourceRouter
extends AbstractRoutingDataSource
extends AbstractRoutingDataSource

DataSource that routes to one of various target DataSources based on the current transaction isolation level. The target DataSources need to be configured with the isolation level name as key, as defined on the TransactionDefinition interface.

This is particularly useful in combination with JTA transaction management (typically through Spring's JtaTransactionManager). Standard JTA does not support transaction-specific isolation levels. Some JTA providers support isolation levels as a vendor-specific extension (e.g. WebLogic), which is the preferred way of addressing this. As alternative (e.g. on WebSphere), the target database can be represented through multiple JNDI DataSources, each configured with a different isolation level (for the entire DataSource). The present DataSource router allows to transparently switch to the appropriate DataSource based on the current transaction's isolation level.

The configuration can for example look like this, assuming that the target DataSources are defined as individual Spring beans with names "myRepeatableReadDataSource", "mySerializableDataSource" and "myDefaultDataSource":

 <bean id="dataSourceRouter" class="org.springframework.jdbc.datasource.lookup.IsolationLevelDataSourceRouter">
   <property name="targetDataSources">
     <map>
       <entry key="ISOLATION_REPEATABLE_READ" value-ref="myRepeatableReadDataSource"/>
       <entry key="ISOLATION_SERIALIZABLE" value-ref="mySerializableDataSource"/>
     </map>
   </property>
   <property name="defaultTargetDataSource" ref="myDefaultDataSource"/>
 </bean>

Alternatively, the keyed values can also be data source names, to be resolved through a DataSourceLookup: by default, JNDI names for a standard JNDI lookup. This allows for a single concise definition without the need for separate DataSource bean definitions.

 <bean id="dataSourceRouter" class="org.springframework.jdbc.datasource.lookup.IsolationLevelDataSourceRouter">
   <property name="targetDataSources">
     <map>
       <entry key="ISOLATION_REPEATABLE_READ" value="java:comp/env/jdbc/myrrds"/>
       <entry key="ISOLATION_SERIALIZABLE" value="java:comp/env/jdbc/myserds"/>
     </map>
   </property>
   <property name="defaultTargetDataSource" value="java:comp/env/jdbc/mydefds"/>
 </bean>

Note: If you are using this router in combination with Spring's JtaTransactionManager, don't forget to switch the "allowCustomIsolationLevels" flag to "true". (By default, JtaTransactionManager will only accept a default isolation level because of the lack of isolation level support in standard JTA itself.)

 <bean id="transactionManager" class="org.springframework.transaction.jta.JtaTransactionManager">
   <property name="allowCustomIsolationLevels" value="true"/>
 </bean>

Since:: 2.0.1
Author:: Juergen Hoeller
See Also:: AbstractRoutingDataSource.setTargetDataSources(java.util.Map), AbstractRoutingDataSource.setDefaultTargetDataSource(java.lang.Object), TransactionDefinition.ISOLATION_READ_UNCOMMITTED, TransactionDefinition.ISOLATION_READ_COMMITTED, TransactionDefinition.ISOLATION_REPEATABLE_READ, TransactionDefinition.ISOLATION_SERIALIZABLE, JtaTransactionManager

Field Summary

Fields inherited from class org.springframework.jdbc.datasource.AbstractDataSource

logger

Constructor Summary

IsolationLevelDataSourceRouter()


Method Summary

protected Object determineCurrentLookupKey()
          Determine the current lookup key.

protected Object resolveSpecifiedLookupKey(Object lookupKey)
          Supports Integer values for the isolation level constants as well as isolation level names as defined on the TransactionDefinition interface.

Methods inherited from class org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource

afterPropertiesSet, determineTargetDataSource, getConnection, getConnection, resolveSpecifiedDataSource, setDataSourceLookup, setDefaultTargetDataSource, setTargetDataSources

Methods inherited from class org.springframework.jdbc.datasource.AbstractDataSource

getLoginTimeout, getLogWriter, isWrapperFor, setLoginTimeout, setLogWriter, unwrap

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Fields inherited from class org.springframework.jdbc.datasource.AbstractDataSource
`logger`

Constructor Summary
`IsolationLevelDataSourceRouter()`

Method Summary
`protected Object`	`determineCurrentLookupKey()` Determine the current lookup key.
`protected Object`	`resolveSpecifiedLookupKey(Object lookupKey)` Supports Integer values for the isolation level constants as well as isolation level names as defined on the `TransactionDefinition interface`.

Methods inherited from class org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource
`afterPropertiesSet, determineTargetDataSource, getConnection, getConnection, resolveSpecifiedDataSource, setDataSourceLookup, setDefaultTargetDataSource, setTargetDataSources`

Methods inherited from class org.springframework.jdbc.datasource.AbstractDataSource
`getLoginTimeout, getLogWriter, isWrapperFor, setLoginTimeout, setLogWriter, unwrap`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

IsolationLevelDataSourceRouter

public IsolationLevelDataSourceRouter()

Method Detail

resolveSpecifiedLookupKey

protected Object resolveSpecifiedLookupKey(Object lookupKey)

Supports Integer values for the isolation level constants as well as isolation level names as defined on the TransactionDefinition interface.

Overrides:: resolveSpecifiedLookupKey in class AbstractRoutingDataSource

Parameters:: lookupKey - the lookup key object as specified by the user
Returns:: the lookup key as needed for matching

determineCurrentLookupKey

protected Object determineCurrentLookupKey()

Description copied from class: AbstractRoutingDataSource

Determine the current lookup key. This will typically be implemented to check a thread-bound transaction context.

Allows for arbitrary keys. The returned key needs to match the stored lookup key type, as resolved by the AbstractRoutingDataSource.resolveSpecifiedLookupKey(java.lang.Object) method.