Proxy for a target DataSource, fetching actual JDBC Connections lazily, i.e. not until first creation of a Statement. Connection initialization properties like auto-commit mode, transaction isolation and read-only mode will be kept and applied to the actual JDBC Connection as soon as an actual Connection is fetched (if ever). Consequently, commit and rollback calls will be ignored if no Statements have been created. As of 6.1.2, there is also special support for a read-only DataSource to use during a read-only transaction, in addition to the regular target DataSource.

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. As a bonus, this allows for taking the transaction-synchronized read-only flag and/or isolation level into account in a routing DataSource (e.g. org.springframework.jdbc.datasource.lookup.IsolationLevelDataSourceRouter).

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. As of 6.1.2, LazyConnectionDataSourceProxy will initialize its default connection characteristics on first Connection access; to enforce this on startup, call checkDefaultConnectionProperties().

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 Connection#unwrap to retrieve the native JDBC Connection.

Nested and Inner Type Summary

Modifier and Type	Class and Description
private class	LazyConnectionDataSourceProxy.LazyConnectionInvocationHandler Invocation handler that defers fetching an actual JDBC Connection until first creation of a Statement.

Field Summary

Modifier and Type	Field and Description
pack-priv static final Map<String, Integer>	constants Map of constant names to constant values for the isolation constants defined in `java.sql.Connection`.
private volatile Boolean	defaultAutoCommit
private volatile Integer	defaultTransactionIsolation
private static final Log	logger
private DataSource	readOnlyDataSource

Access	Constructor and Description
public	LazyConnectionDataSourceProxy() Create a new LazyConnectionDataSourceProxy.
public	LazyConnectionDataSourceProxy(DataSource the target DataSource targetDataSource) Create a new LazyConnectionDataSourceProxy.

Method Summary

Modifier and Type	Method and Description
public void	checkDefaultConnectionProperties() Determine default auto-commit and transaction isolation via a Connection from the target DataSource, if possible.
protected void	checkDefaultConnectionProperties(Connection the Connection to use for checking con) 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 later on.
protected Boolean	defaultAutoCommit() Expose the default auto-commit value.
protected Integer	defaultTransactionIsolation() Expose the default transaction isolation value.
public Connection	Returns: a lazy Connection handle getConnection() Overrides org.springframework.jdbc.datasource.DelegatingDataSource.getConnection. Implements javax.sql.DataSource.getConnection. Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).
public Connection	Returns: a lazy Connection handle getConnection(String the per-Connection username username, String the per-Connection password password) Overrides org.springframework.jdbc.datasource.DelegatingDataSource.getConnection. Implements javax.sql.DataSource.getConnection. Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).
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).
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).
public void	setDefaultTransactionIsolationName(String name of the constant constantName) Set the default transaction isolation level by the name of the corresponding constant in `java.sql.Connection` — for example, `"TRANSACTION_SERIALIZABLE"`.
public void	setReadOnlyDataSource(DataSource readOnlyDataSource) Specify a variant of the target DataSource to use for read-only transactions.

Inherited from org.springframework.jdbc.datasource.DelegatingDataSource:: afterPropertiesSet createConnectionBuilder createShardingKeyBuilder getLoginTimeout getLogWriter getParentLogger getTargetDataSource isWrapperFor obtainTargetDataSource setLoginTimeout setLogWriter setTargetDataSource unwrap

Field Detail

constants	back to summary
pack-priv static final Map<String, Integer> constants Map of constant names to constant values for the isolation constants defined in `java.sql.Connection`.

defaultAutoCommit	back to summary
private volatile Boolean defaultAutoCommit Annotations @Nullable

defaultTransactionIsolation	back to summary
private volatile Integer defaultTransactionIsolation Annotations @Nullable

logger	back to summary
private static final Log logger

readOnlyDataSource	back to summary
private DataSource readOnlyDataSource Annotations @Nullable

LazyConnectionDataSourceProxy	back to summary
public LazyConnectionDataSourceProxy() Create a new LazyConnectionDataSourceProxy. See Also `setTargetDataSource`, `setReadOnlyDataSource`

LazyConnectionDataSourceProxy	back to summary
public LazyConnectionDataSourceProxy(DataSource targetDataSource) Create a new LazyConnectionDataSourceProxy. Parameters targetDataSource:DataSource the target DataSource See Also `setTargetDataSource`

Method Detail

checkDefaultConnectionProperties back to summary

checkDefaultConnectionProperties	back to summary
public void checkDefaultConnectionProperties() Determine default auto-commit and transaction isolation via a Connection from the target DataSource, if possible. Since 6.1.2 See Also `checkDefaultConnectionProperties(Connection)`

public void checkDefaultConnectionProperties()

Determine default auto-commit and transaction isolation via a Connection from the target DataSource, if possible.

Since: 6.1.2
See Also: checkDefaultConnectionProperties(Connection)

checkDefaultConnectionProperties	back to summary
protected void checkDefaultConnectionProperties(Connection con) throws SQLException 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 later on. Parameters con:Connection the Connection to use for checking Exceptions SQLException: if thrown by Connection methods

checkDefaultConnectionProperties

back to summary

protected void checkDefaultConnectionProperties(Connection con) throws SQLException

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 later on.

Parameters

con:Connection: the Connection to use for checking

Exceptions

SQLException:: if thrown by Connection methods

defaultAutoCommit	back to summary
protected Boolean defaultAutoCommit() Expose the default auto-commit value. Annotations @Nullable

defaultAutoCommit

back to summary

protected Boolean defaultAutoCommit()

Expose the default auto-commit value.

Annotations

@Nullable

defaultTransactionIsolation	back to summary
protected Integer defaultTransactionIsolation() Expose the default transaction isolation value. Annotations @Nullable

defaultTransactionIsolation

back to summary

protected Integer defaultTransactionIsolation()

Expose the default transaction isolation value.

Annotations

@Nullable

getConnection back to summary

getConnection	back to summary
public Connection getConnection() throws SQLException Overrides org.springframework.jdbc.datasource.DelegatingDataSource.getConnection. Implements javax.sql.DataSource.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. Returns:Connection a lazy Connection handle Annotations @Override Exceptions SQLException: Doc from javax.sql.DataSource.getConnection. if a database access error occurs See Also `ConnectionProxy#getTargetConnection()`

public Connection getConnection() throws SQLException

Overrides org.springframework.jdbc.datasource.DelegatingDataSource.getConnection.

Implements javax.sql.DataSource.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.

Returns:Connection

a lazy Connection handle

Annotations

@Override

Exceptions

SQLException:

Doc from javax.sql.DataSource.getConnection.

if a database access error occurs

See Also

ConnectionProxy#getTargetConnection()

getConnection back to summary

getConnection	back to summary
public Connection getConnection(String username, String password) throws SQLException Overrides org.springframework.jdbc.datasource.DelegatingDataSource.getConnection. Implements javax.sql.DataSource.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. Parameters username:String the per-Connection username password:String the per-Connection password Returns:Connection a lazy Connection handle Annotations @Override Exceptions SQLException: Doc from javax.sql.DataSource.getConnection. if a database access error occurs See Also `ConnectionProxy#getTargetConnection()`

public Connection getConnection(String username, String password) throws SQLException

Overrides org.springframework.jdbc.datasource.DelegatingDataSource.getConnection.

Implements javax.sql.DataSource.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.

Parameters

username:String: the per-Connection username
password:String: the per-Connection password

Returns:Connection

a lazy Connection handle

Annotations

@Override

Exceptions

SQLException:

Doc from javax.sql.DataSource.getConnection.

if a database access error occurs

See Also

ConnectionProxy#getTargetConnection()

setDefaultAutoCommit back to summary

setDefaultAutoCommit	back to summary
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 lazily on first access of a Connection. See Also `java.sql.Connection#setAutoCommit`

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 lazily on first access of a Connection.

See Also: java.sql.Connection#setAutoCommit

setDefaultTransactionIsolation back to summary

setDefaultTransactionIsolation	back to summary
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 `java.sql.Connection` interface; it is mainly intended for programmatic use. Consider using the "defaultTransactionIsolationName" property for setting the value by name (for example, `"TRANSACTION_SERIALIZABLE"`). If not specified, the default gets determined by checking lazily on first access of a Connection. See Also `setDefaultTransactionIsolationName`, `java.sql.Connection#setTransactionIsolation`

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 java.sql.Connection interface; it is mainly intended for programmatic use. Consider using the "defaultTransactionIsolationName" property for setting the value by name (for example, "TRANSACTION_SERIALIZABLE").

If not specified, the default gets determined by checking lazily on first access of a Connection.

See Also: setDefaultTransactionIsolationName, java.sql.Connection#setTransactionIsolation

setDefaultTransactionIsolationName back to summary

setDefaultTransactionIsolationName	back to summary
public void setDefaultTransactionIsolationName(String constantName) Set the default transaction isolation level by the name of the corresponding constant in `java.sql.Connection` — for example, `"TRANSACTION_SERIALIZABLE"`. Parameters constantName:String name of the constant See Also `setDefaultTransactionIsolation`, `java.sql.Connection#TRANSACTION_READ_UNCOMMITTED`, `java.sql.Connection#TRANSACTION_READ_COMMITTED`, `java.sql.Connection#TRANSACTION_REPEATABLE_READ`, `java.sql.Connection#TRANSACTION_SERIALIZABLE`

public void setDefaultTransactionIsolationName(String constantName)

Set the default transaction isolation level by the name of the corresponding constant in java.sql.Connection — for example, "TRANSACTION_SERIALIZABLE".

Parameters

constantName:String: name of the constant

setReadOnlyDataSource back to summary

setReadOnlyDataSource	back to summary
public void setReadOnlyDataSource(DataSource readOnlyDataSource) Specify a variant of the target DataSource to use for read-only transactions. If available, a Connection from such a read-only DataSource will be lazily obtained within a Spring-managed transaction that has been marked as read-only. The `Connection#setReadOnly` flag will be left untouched, expecting it to be pre-configured as a default on the read-only DataSource, avoiding the overhead of switching it at the beginning and end of every transaction. Also, the default auto-commit and isolation level settings are expected to match the default connection properties of the primary target DataSource. Since 6.1.2 See Also `setTargetDataSource`, `setDefaultAutoCommit`, `setDefaultTransactionIsolation`, `org.springframework.transaction.TransactionDefinition#isReadOnly()`

public void setReadOnlyDataSource(DataSource readOnlyDataSource)

Specify a variant of the target DataSource to use for read-only transactions.

If available, a Connection from such a read-only DataSource will be lazily obtained within a Spring-managed transaction that has been marked as read-only. The Connection#setReadOnly flag will be left untouched, expecting it to be pre-configured as a default on the read-only DataSource, avoiding the overhead of switching it at the beginning and end of every transaction. Also, the default auto-commit and isolation level settings are expected to match the default connection properties of the primary target DataSource.

Since: 6.1.2
See Also: setTargetDataSource, setDefaultAutoCommit, setDefaultTransactionIsolation, org.springframework.transaction.TransactionDefinition#isReadOnly()

org.springframework.jdbc.datasource back to summary

private Class LazyConnectionDataSourceProxy.LazyConnectionInvocationHandler

Class Inheritance

extends Object
implements InvocationHandler

java.lang.Object
org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy.LazyConnectionInvocationHandler

All Implemented Interfaces

java.lang.reflect.InvocationHandler

Invocation handler that defers fetching an actual JDBC Connection until first creation of a Statement.

Field Summary

Modifier and Type	Field and Description
private Boolean	autoCommit
private boolean	closed
private int	holdability
private String	password
private boolean	readOnly
private Connection	target
private Integer	transactionIsolation
private String	username

Constructor Summary

Access	Constructor and Description
public	LazyConnectionInvocationHandler()
public	LazyConnectionInvocationHandler(String username, String password)

Method Summary

Modifier and Type	Method and Description
private DataSource	getDataSourceToUse()
private Connection	getTargetConnection(Method operation) Return the target Connection, fetching it and initializing it if necessary.
private boolean	hasTargetConnection() Return whether the proxy currently holds a target Connection.
public Object	invoke(Object the proxy instance that the method was invoked on proxy, Method the `Method` instance corresponding to the interface method invoked on the proxy instance. The declaring class of the `Method` object will be the interface that the method was declared in, which may be a superinterface of the proxy interface that the proxy class inherits the method through. method, Object[] an array of objects containing the values of the arguments passed in the method invocation on the proxy instance, or `null` if interface method takes no arguments. Arguments of primitive types are wrapped in instances of the appropriate primitive wrapper class, such as `java.lang.Integer` or `java.lang.Boolean`. args) Implements java.lang.reflect.InvocationHandler.invoke. Processes a method invocation on a proxy instance and returns the result.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

autoCommit	back to summary
private Boolean autoCommit Annotations @Nullable

closed	back to summary
private boolean closed

holdability	back to summary
private int holdability

password	back to summary
private String password Annotations @Nullable

readOnly	back to summary
private boolean readOnly

target	back to summary
private Connection target Annotations @Nullable

transactionIsolation	back to summary
private Integer transactionIsolation Annotations @Nullable

username	back to summary
private String username Annotations @Nullable

Constructor Detail

LazyConnectionInvocationHandler	back to summary
public LazyConnectionInvocationHandler()

LazyConnectionInvocationHandler	back to summary
public LazyConnectionInvocationHandler(String username, String password)

Method Detail

getDataSourceToUse	back to summary
private DataSource getDataSourceToUse()

getTargetConnection	back to summary
private Connection getTargetConnection(Method operation) throws SQLException Return the target Connection, fetching it and initializing it if necessary.

hasTargetConnection	back to summary
private boolean hasTargetConnection() Return whether the proxy currently holds a target Connection.

invoke back to summary

invoke	back to summary
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable Implements java.lang.reflect.InvocationHandler.invoke. Doc from java.lang.reflect.InvocationHandler.invoke. Processes a method invocation on a proxy instance and returns the result. This method will be invoked on an invocation handler when a method is invoked on a proxy instance that it is associated with. Parameters proxy:Object the proxy instance that the method was invoked on method:Method the `Method` instance corresponding to the interface method invoked on the proxy instance. The declaring class of the `Method` object will be the interface that the method was declared in, which may be a superinterface of the proxy interface that the proxy class inherits the method through. args:Object[] an array of objects containing the values of the arguments passed in the method invocation on the proxy instance, or `null` if interface method takes no arguments. Arguments of primitive types are wrapped in instances of the appropriate primitive wrapper class, such as `java.lang.Integer` or `java.lang.Boolean`. Returns:Object the value to return from the method invocation on the proxy instance. If the declared return type of the interface method is a primitive type, then the value returned by this method must be an instance of the corresponding primitive wrapper class; otherwise, it must be a type assignable to the declared return type. If the value returned by this method is `null` and the interface method's return type is primitive, then a `NullPointerException` will be thrown by the method invocation on the proxy instance. If the value returned by this method is otherwise not compatible with the interface method's declared return type as described above, a `ClassCastException` will be thrown by the method invocation on the proxy instance. Annotations @Override @Nullable Exceptions Throwable: the exception to throw from the method invocation on the proxy instance. The exception's type must be assignable either to any of the exception types declared in the `throws` clause of the interface method or to the unchecked exception types `java.lang.RuntimeException` or `java.lang.Error`. If a checked exception is thrown by this method that is not assignable to any of the exception types declared in the `throws` clause of the interface method, then an `UndeclaredThrowableException` containing the exception that was thrown by this method will be thrown by the method invocation on the proxy instance.

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable

Implements java.lang.reflect.InvocationHandler.invoke.

Doc from java.lang.reflect.InvocationHandler.invoke.

Processes a method invocation on a proxy instance and returns the result. This method will be invoked on an invocation handler when a method is invoked on a proxy instance that it is associated with.

Parameters

proxy:Object: the proxy instance that the method was invoked on
method:Method: the Method instance corresponding to the interface method invoked on the proxy instance. The declaring class of the Method object will be the interface that the method was declared in, which may be a superinterface of the proxy interface that the proxy class inherits the method through.
args:Object[]: an array of objects containing the values of the arguments passed in the method invocation on the proxy instance, or null if interface method takes no arguments. Arguments of primitive types are wrapped in instances of the appropriate primitive wrapper class, such as java.lang.Integer or java.lang.Boolean.

Returns:Object

the value to return from the method invocation on the proxy instance. If the declared return type of the interface method is a primitive type, then the value returned by this method must be an instance of the corresponding primitive wrapper class; otherwise, it must be a type assignable to the declared return type. If the value returned by this method is null and the interface method's return type is primitive, then a NullPointerException will be thrown by the method invocation on the proxy instance. If the value returned by this method is otherwise not compatible with the interface method's declared return type as described above, a ClassCastException will be thrown by the method invocation on the proxy instance.

Annotations

@Override
@Nullable

Exceptions

Throwable:: the exception to throw from the method invocation on the proxy instance. The exception's type must be assignable either to any of the exception types declared in the throws clause of the interface method or to the unchecked exception types java.lang.RuntimeException or java.lang.Error. If a checked exception is thrown by this method that is not assignable to any of the exception types declared in the throws clause of the interface method, then an UndeclaredThrowableException containing the exception that was thrown by this method will be thrown by the method invocation on the proxy instance.

public Class LazyConnectionDataSourceProxy

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private Class LazyConnectionDataSourceProxy.LazyConnectionInvocationHandler

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail