Class LazyConnectionDataSourceProxy
- All Implemented Interfaces:
Wrapper
,CommonDataSource
,DataSource
,InitializingBean
This DataSource proxy allows to avoid fetching JDBC Connections from a pool unless actually necessary. JDBC transaction control can happen without fetching a Connection from the pool or communicating with the database; this will be done lazily on first creation of a JDBC Statement.
If you configure both a LazyConnectionDataSourceProxy and a TransactionAwareDataSourceProxy, make sure that the latter is the outermost DataSource. In such a scenario, data access code will talk to the transaction-aware DataSource, which will in turn work with the LazyConnectionDataSourceProxy.
Lazy fetching of physical JDBC Connections is particularly beneficial in a generic transaction demarcation environment. It allows you to demarcate transactions on all methods that could potentially perform data access, without paying a performance penalty if no actual data access happens.
This DataSource proxy gives you behavior analogous to JTA and a transactional JNDI DataSource (as provided by the Jakarta EE server), even with a local transaction strategy like DataSourceTransactionManager or HibernateTransactionManager. It does not add value with Spring's JtaTransactionManager as transaction strategy.
Lazy fetching of JDBC Connections is also recommended for read-only operations with Hibernate, in particular if the chances of resolving the result in the second-level cache are high. This avoids the need to communicate with the database at all for such read-only operations. You will get the same effect with non-transactional reads, but lazy fetching of JDBC Connections allows you to still perform reads in transactions.
NOTE: This DataSource proxy needs to return wrapped Connections
(which implement the ConnectionProxy
interface) in order to handle
lazy fetching of an actual JDBC Connection. Use Wrapper.unwrap(java.lang.Class<T>)
to retrieve the native JDBC Connection.
- Since:
- 1.1.4
- Author:
- Juergen Hoeller
- See Also:
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Constructor Summary
ConstructorDescriptionCreate a new LazyConnectionDataSourceProxy.LazyConnectionDataSourceProxy
(DataSource targetDataSource) Create a new LazyConnectionDataSourceProxy. -
Method Summary
Modifier and TypeMethodDescriptionvoid
Invoked by the containingBeanFactory
after it has set all bean properties and satisfiedBeanFactoryAware
,ApplicationContextAware
etc.protected void
Check the default connection properties (auto-commit, transaction isolation), keeping them to be able to expose them correctly without fetching an actual JDBC Connection from the target DataSource.protected Boolean
Expose the default auto-commit value.protected Integer
Expose the default transaction isolation value.Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).getConnection
(String username, String password) Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).void
setDefaultAutoCommit
(boolean defaultAutoCommit) Set the default auto-commit mode to expose when no target Connection has been fetched yet (when the actual JDBC Connection default is not known yet).void
setDefaultTransactionIsolation
(int defaultTransactionIsolation) Set the default transaction isolation level to expose when no target Connection has been fetched yet (when the actual JDBC Connection default is not known yet).void
setDefaultTransactionIsolationName
(String constantName) Set the default transaction isolation level by the name of the corresponding constant inConnection
, e.g.Methods inherited from class org.springframework.jdbc.datasource.DelegatingDataSource
getLoginTimeout, getLogWriter, getParentLogger, getTargetDataSource, isWrapperFor, obtainTargetDataSource, setLoginTimeout, setLogWriter, setTargetDataSource, unwrap
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface javax.sql.CommonDataSource
createShardingKeyBuilder
Methods inherited from interface javax.sql.DataSource
createConnectionBuilder
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Constructor Details
-
LazyConnectionDataSourceProxy
public LazyConnectionDataSourceProxy()Create a new LazyConnectionDataSourceProxy. -
LazyConnectionDataSourceProxy
Create a new LazyConnectionDataSourceProxy.- Parameters:
targetDataSource
- the target DataSource
-
-
Method Details
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setDefaultAutoCommit
public void setDefaultAutoCommit(boolean defaultAutoCommit) Set the default auto-commit mode to expose when no target Connection has been fetched yet (when the actual JDBC Connection default is not known yet).If not specified, the default gets determined by checking a target Connection on startup. If that check fails, the default will be determined lazily on first access of a Connection.
- See Also:
-
setDefaultTransactionIsolation
public void setDefaultTransactionIsolation(int defaultTransactionIsolation) Set the default transaction isolation level to expose when no target Connection has been fetched yet (when the actual JDBC Connection default is not known yet).This property accepts the int constant value (e.g. 8) as defined in the
Connection
interface; it is mainly intended for programmatic use. Consider using the "defaultTransactionIsolationName" property for setting the value by name (e.g. "TRANSACTION_SERIALIZABLE").If not specified, the default gets determined by checking a target Connection on startup. If that check fails, the default will be determined lazily on first access of a Connection.
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setDefaultTransactionIsolationName
Set the default transaction isolation level by the name of the corresponding constant inConnection
, e.g. "TRANSACTION_SERIALIZABLE".- Parameters:
constantName
- name of the constant- See Also:
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afterPropertiesSet
public void afterPropertiesSet()Description copied from interface:InitializingBean
Invoked by the containingBeanFactory
after it has set all bean properties and satisfiedBeanFactoryAware
,ApplicationContextAware
etc.This method allows the bean instance to perform validation of its overall configuration and final initialization when all bean properties have been set.
- Specified by:
afterPropertiesSet
in interfaceInitializingBean
- Overrides:
afterPropertiesSet
in classDelegatingDataSource
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checkDefaultConnectionProperties
Check the default connection properties (auto-commit, transaction isolation), keeping them to be able to expose them correctly without fetching an actual JDBC Connection from the target DataSource.This will be invoked once on startup, but also for each retrieval of a target Connection. If the check failed on startup (because the database was down), we'll lazily retrieve those settings.
- Parameters:
con
- the Connection to use for checking- Throws:
SQLException
- if thrown by Connection methods
-
defaultAutoCommit
Expose the default auto-commit value. -
defaultTransactionIsolation
Expose the default transaction isolation value. -
getConnection
Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).The returned Connection handle implements the ConnectionProxy interface, allowing to retrieve the underlying target Connection.
- Specified by:
getConnection
in interfaceDataSource
- Overrides:
getConnection
in classDelegatingDataSource
- Returns:
- a lazy Connection handle
- Throws:
SQLException
- See Also:
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getConnection
Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).The returned Connection handle implements the ConnectionProxy interface, allowing to retrieve the underlying target Connection.
- Specified by:
getConnection
in interfaceDataSource
- Overrides:
getConnection
in classDelegatingDataSource
- Parameters:
username
- the per-Connection usernamepassword
- the per-Connection password- Returns:
- a lazy Connection handle
- Throws:
SQLException
- See Also:
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