Package io.mats3.util.wrappers

Class DeferredConnectionProxyDataSourceWrapper

java.lang.Object

io.mats3.util.wrappers.DataSourceWrapper

io.mats3.util.wrappers.DeferredConnectionProxyDataSourceWrapper

All Implemented Interfaces:

MatsFactory.MatsWrapper<DataSource>, Wrapper, CommonDataSource, DataSource

Direct Known Subclasses:

JmsMatsTransactionManager_JmsAndSpringManagedSqlTx.DeferredConnectionProxyDataSourceWrapper_InfrastructureProxy

public class DeferredConnectionProxyDataSourceWrapper
extends DataSourceWrapper

DataSource wrapper which returns thin Connection proxies (currently employing Java's "dynamic proxy" functionality) which do not actually fetch a Connection until it is needed. It defers as long as possible, "holding back" calls to setAutoCommit(..), setTransactionIsolation(..), setReadOnly(..), and ignores any commit() and rollback(), as well as handling some surrounding methods like toString(), equals(), hashCode() etc, until the user code e.g. creates a Statement or PreparedStatement - i.e. not until the user code actually needs to talk to the database. This deferring results in a situation where if the user code opens a transaction, but does not need to talk to the database after all, and then commits the transaction, the entire operation is elided - saving several round-trips over the wire.

The use of Java Dynamic Proxies is a simple way to ensure that the implementation is future proof, in that any method that appears on the Connection in any Java version will be handled by triggering actual Connection fetching and subsequent call-through to the actual method. Only the methods that are used in standard transaction management are specially handled to defer the getting of the actual Connection.

Note that it is assumed that the AutoCommit, TransactionIsolation and ReadOnly values are identical for all fetched Connections (that is, the pool resets them to some default when connection.close() is invoked). The default values for these properties are retrieved from the very first Connection that is actually fetched. The deferring works as such: If you set one of these value on the returned proxied Connection, this will be recorded, and will subsequently be set on the actual Connection once it is fetched because it is needed (e.g. when a PreparedStatement is created). However, as a further performance optimization, when about to set the value, it is compared against those default values gotten from the first Connection, and if they are equal, the actual setting-invocation is elided.

Inspired by Spring's LazyConnectionDataSourceProxy, but with the additional feature that you can query the Connection proxy for whether the underlying Connection was actually gotten, since it is a DeferredConnectionProxy (extends Connection). It also has the method actualConnectionWasRetrieved(proxy, actualConnection) which can be interesting for extensions. It also has the method methodInvoked(..), which is invoked after every method invoked on the returned DeferredConnectionProxys, which primarily is interesting for testing, but might have other uses.

If in a Spring environment, the returned Connection instances furthermore implements org.springframework.jdbc.datasource.ConnectionProxy.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy	Provides a method to query whether the Connection actually was gotten.
protected class	DeferredConnectionProxyDataSourceWrapper.DeferredFetchInvocationHandler	Implementation of Java's "dynamic proxy" InvocationHandler for deferring fetching of actual Connection until necessary.

Field Summary

Fields

Modifier and Type	Field	Description
protected Boolean	_autoCommitFromWrappedDataSource
protected Boolean	_readOnlyFromWrappedDataSource
protected Integer	_transactionIsolationFromWrappedDataSource

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	DeferredConnectionProxyDataSourceWrapper()
protected	DeferredConnectionProxyDataSourceWrapper(DataSource targetDataSource)

Method Summary

Modifier and Type	Method	Description
protected void	actualConnectionWasRetrieved(DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy connectionProxy, Connection actualConnection)	Override if you want to know when the actual Connection was retrieved.
Boolean	getAutoCommitFromWrappedDataSource()
DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy	getConnection()
DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy	getConnection(String username, String password)
Boolean	getReadOnlyFromWrappedDataSource()
Integer	getTransactionIsolationFromWrappedDataSource()
protected void	methodInvoked(boolean answeredByProxy, DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy connectionProxy, Connection actualConnection, Method method, Object[] args, Object result)	Override if you want to know about every method invoked on the DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy, its arguments and its return value, and whether it was the proxy or the actual Connection that answered.
protected void	retrieveDefaultAutoCommitAndTransactionIsolationAndReadOnlyValues(Connection con)
static DeferredConnectionProxyDataSourceWrapper	wrap(DataSource dataSource)

Methods inherited from class io.mats3.util.wrappers.DataSourceWrapper

getLoginTimeout, getLogWriter, getParentLogger, isWrapperFor, setLoginTimeout, setLogWriter, setWrappee, toString, unwrap, unwrap

Methods inherited from class java.lang.Object

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

Methods inherited from interface javax.sql.CommonDataSource

createShardingKeyBuilder

Methods inherited from interface javax.sql.DataSource

createConnectionBuilder

Methods inherited from interface io.mats3.MatsFactory.MatsWrapper

unwrapFully, unwrapTo

Field Details

_autoCommitFromWrappedDataSource

protected volatile Boolean _autoCommitFromWrappedDataSource

_transactionIsolationFromWrappedDataSource

protected volatile Integer _transactionIsolationFromWrappedDataSource

_readOnlyFromWrappedDataSource

protected volatile Boolean _readOnlyFromWrappedDataSource

Constructor Details

DeferredConnectionProxyDataSourceWrapper

protected DeferredConnectionProxyDataSourceWrapper()

DeferredConnectionProxyDataSourceWrapper

protected DeferredConnectionProxyDataSourceWrapper(DataSource targetDataSource)

Method Details

wrap

public static DeferredConnectionProxyDataSourceWrapper wrap(DataSource dataSource)

Parameters:

dataSource - the DataSource to wrap.

Returns:

an instance of this class wrapping the supplied DataSource.

getConnection

public DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy getConnection()
                                                                               throws SQLException

Specified by:

getConnection in interface DataSource

Overrides:

getConnection in class DataSourceWrapper

Returns:

a "thin Proxy", implemented as Java's "dynamic proxy", NOT YET proxying an actual Connection.

Throws:

SQLException - can actually never throw SQLException, since it just gives you a proxy.

getConnection

public DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy getConnection(String username,
 String password)
                                                                               throws SQLException

Specified by:

getConnection in interface DataSource

Overrides:

getConnection in class DataSourceWrapper

Parameters:

username - username to to forward to underlying DataSource.getConnection(username, password) when Connection needs to be gotten.

password - password to to forward to underlying DataSource.getConnection(username, password) when Connection needs to be gotten.

Returns:

a "thin Proxy", implemented as Java's "dynamic proxy", NOT YET proxying an actual Connection.

Throws:

SQLException - can actually never throw SQLException, since it just gives you a proxy.

actualConnectionWasRetrieved

protected void actualConnectionWasRetrieved(DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy connectionProxy,
 Connection actualConnection)

Override if you want to know when the actual Connection was retrieved. Default implementation logs to debug.

methodInvoked

protected void methodInvoked(boolean answeredByProxy,
 DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy connectionProxy,
 Connection actualConnection,
 Method method,
 Object[] args,
 Object result)

Override if you want to know about every method invoked on the DeferredConnectionProxyDataSourceWrapper.DeferredConnectionProxy, its arguments and its return value, and whether it was the proxy or the actual Connection that answered. Default implementation does nothing.

getAutoCommitFromWrappedDataSource

public Boolean getAutoCommitFromWrappedDataSource()

Returns:

null until the first underlying Connection has actually been gotten, after that what this first underlying Connection replied to invocation of Connection.getAutoCommit().

getTransactionIsolationFromWrappedDataSource

public Integer getTransactionIsolationFromWrappedDataSource()

Returns:

null until the first underlying Connection has actually been gotten, after that what this first underlying Connection replied to invocation of Connection.getTransactionIsolation().

getReadOnlyFromWrappedDataSource

public Boolean getReadOnlyFromWrappedDataSource()

Returns:

null until the first underlying Connection has actually been gotten, after that what this first underlying Connection replied to invocation of Connection.isReadOnly().

retrieveDefaultAutoCommitAndTransactionIsolationAndReadOnlyValues

protected void retrieveDefaultAutoCommitAndTransactionIsolationAndReadOnlyValues(Connection con)
                                                                          throws SQLException

Throws:

SQLException