IsolationLevelDataSourceRouter

Class Overview

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>

Summary

[Expand] Inherited Fields
From class org.springframework.jdbc.datasource.AbstractDataSource protected final Log logger Logger available to subclasses

Public Constructors
	IsolationLevelDataSourceRouter()

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

[Expand] Inherited Methods
From class org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource void afterPropertiesSet() Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware). abstract Object determineCurrentLookupKey() Determine the current lookup key. DataSource determineTargetDataSource() Retrieve the current target DataSource. Connection getConnection() Connection getConnection(String username, String password) DataSource resolveSpecifiedDataSource(Object dataSource) Resolve the specified data source object into a DataSource instance. Object resolveSpecifiedLookupKey(Object lookupKey) Resolve the given lookup key object, as specified in the targetDataSources map, into the actual lookup key to be used for matching with the current lookup key. void setDataSourceLookup(DataSourceLookup dataSourceLookup) Set the DataSourceLookup implementation to use for resolving data source name Strings in the targetDataSources map. void setDefaultTargetDataSource(Object defaultTargetDataSource) Specify the default target DataSource, if any. void setLenientFallback(boolean lenientFallback) Specify whether to apply a lenient fallback to the default DataSource if no specific DataSource could be found for the current lookup key. void setTargetDataSources(Map<Object, Object> targetDataSources) Specify the map of target DataSources, with the lookup key as key.
From class org.springframework.jdbc.datasource.AbstractDataSource PrintWriter getLogWriter() LogWriter methods are not supported. int getLoginTimeout() Returns 0, indicating the default system timeout is to be used. boolean isWrapperFor(Class<?> iface) void setLogWriter(PrintWriter pw) LogWriter methods are not supported. void setLoginTimeout(int timeout) Setting a login timeout is not supported. <T> T unwrap(Class<T> iface)
From class java.lang.Object Object clone() boolean equals(Object arg0) void finalize() final Class<?> getClass() int hashCode() final void notify() final void notifyAll() String toString() final void wait() final void wait(long arg0, int arg1) final void wait(long arg0)
From interface java.sql.Wrapper abstract boolean isWrapperFor(Class<?> arg0) abstract <T> T unwrap(Class<T> arg0)
From interface javax.sql.CommonDataSource abstract PrintWriter getLogWriter() abstract int getLoginTimeout() abstract void setLogWriter(PrintWriter arg0) abstract void setLoginTimeout(int arg0)
From interface javax.sql.DataSource abstract Connection getConnection() abstract Connection getConnection(String arg0, String arg1)
From interface org.springframework.beans.factory.InitializingBean abstract void afterPropertiesSet() Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).