java.lang.Object
- org.springframework.jdbc.datasource.DelegatingDataSource
- - org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy

所有已实现的接口:
Wrapper, CommonDataSource, DataSource, InitializingBean
```
public class LazyConnectionDataSourceProxy
extends DelegatingDataSource
```
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.
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 Java 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.
从以下版本开始:
1.1.4
作者:
Juergen Hoeller
另请参阅:
DataSourceTransactionManager

构造器概要

构造器
构造器	说明
`LazyConnectionDataSourceProxy()`	Create a new LazyConnectionDataSourceProxy.
`LazyConnectionDataSourceProxy(DataSource targetDataSource)`	Create a new LazyConnectionDataSourceProxy.

方法概要

所有方法实例方法具体方法
修饰符和类型	方法	说明
`void`	`afterPropertiesSet()`	Invoked by the containing `BeanFactory` after it has set all bean properties and satisfied `BeanFactoryAware`, `ApplicationContextAware` etc.
`protected void`	`checkDefaultConnectionProperties(Connection 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.
`protected Boolean`	`defaultAutoCommit()`	Expose the default auto-commit value.
`protected Integer`	`defaultTransactionIsolation()`	Expose the default transaction isolation value.
`Connection`	`getConnection()`	Return a Connection handle that lazily fetches an actual JDBC Connection when asked for a Statement (or PreparedStatement or CallableStatement).
`Connection`	`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 (-> actual JDBC Connection default not known yet).
`void`	`setDefaultTransactionIsolation(int defaultTransactionIsolation)`	Set the default transaction isolation level to expose when no target Connection has been fetched yet (-> actual JDBC Connection default not known yet).
`void`	`setDefaultTransactionIsolationName(String constantName)`	Set the default transaction isolation level by the name of the corresponding constant in `Connection`, e.g.

从类继承的方法 org.springframework.jdbc.datasource.DelegatingDataSource
getLoginTimeout, getLogWriter, getParentLogger, getTargetDataSource, isWrapperFor, obtainTargetDataSource, setLoginTimeout, setLogWriter, setTargetDataSource, unwrap

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

从接口继承的方法 javax.sql.CommonDataSource
createShardingKeyBuilder

从接口继承的方法 javax.sql.DataSource
createConnectionBuilder

- 构造器详细资料
  - LazyConnectionDataSourceProxy
```
public LazyConnectionDataSourceProxy()
```
    Create a new LazyConnectionDataSourceProxy.
    另请参阅:
    DelegatingDataSource.setTargetDataSource(javax.sql.DataSource)
  - LazyConnectionDataSourceProxy
```
public LazyConnectionDataSourceProxy(DataSource targetDataSource)
```
    Create a new LazyConnectionDataSourceProxy.
    参数:
    targetDataSource - the target DataSource
- 方法详细资料
  - setDefaultAutoCommit
```
public void setDefaultAutoCommit(boolean defaultAutoCommit)
```
    Set the default auto-commit mode to expose when no target Connection has been fetched yet (-> actual JDBC Connection default 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.
    另请参阅:
    Connection.setAutoCommit(boolean)
  - setDefaultTransactionIsolation
```
public void setDefaultTransactionIsolation(int defaultTransactionIsolation)
```
    Set the default transaction isolation level to expose when no target Connection has been fetched yet (-> actual JDBC Connection default 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.
    另请参阅:
    setDefaultTransactionIsolationName(java.lang.String), Connection.setTransactionIsolation(int)
  - setDefaultTransactionIsolationName
```
public void setDefaultTransactionIsolationName(String constantName)
```
    Set the default transaction isolation level by the name of the corresponding constant in Connection, e.g. "TRANSACTION_SERIALIZABLE".
    参数:
    constantName - name of the constant
    另请参阅:
    setDefaultTransactionIsolation(int), Connection.TRANSACTION_READ_UNCOMMITTED, Connection.TRANSACTION_READ_COMMITTED, Connection.TRANSACTION_REPEATABLE_READ, Connection.TRANSACTION_SERIALIZABLE
  - afterPropertiesSet
```
public void afterPropertiesSet()
```
    从接口复制的说明: InitializingBean
    Invoked by the containing BeanFactory after it has set all bean properties and satisfied BeanFactoryAware, 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.
    指定者:
    afterPropertiesSet 在接口中 InitializingBean
    覆盖:
    afterPropertiesSet 在类中 DelegatingDataSource
  - checkDefaultConnectionProperties
```
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.
    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.
    参数:
    con - the Connection to use for checking
    抛出:
    SQLException - if thrown by Connection methods
  - defaultAutoCommit
```
@Nullable
protected Boolean defaultAutoCommit()
```
    Expose the default auto-commit value.
  - defaultTransactionIsolation
```
@Nullable
protected Integer defaultTransactionIsolation()
```
    Expose the default transaction isolation value.
  - getConnection
```
public Connection getConnection()
                         throws SQLException
```
    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.
    指定者:
    getConnection 在接口中 DataSource
    覆盖:
    getConnection 在类中 DelegatingDataSource
    返回:
    a lazy Connection handle
    抛出:
    SQLException
    另请参阅:
    ConnectionProxy.getTargetConnection()
  - getConnection
```
public Connection getConnection(String username,
                                String password)
                         throws SQLException
```
    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.
    指定者:
    getConnection 在接口中 DataSource
    覆盖:
    getConnection 在类中 DelegatingDataSource
    参数:
    username - the per-Connection username
    password - the per-Connection password
    返回:
    a lazy Connection handle
    抛出:
    SQLException
    另请参阅:
    ConnectionProxy.getTargetConnection()

类 LazyConnectionDataSourceProxy

构造器概要

方法概要

从类继承的方法 org.springframework.jdbc.datasource.DelegatingDataSource

从类继承的方法 java.lang.Object

从接口继承的方法 javax.sql.CommonDataSource

从接口继承的方法 javax.sql.DataSource

构造器详细资料

LazyConnectionDataSourceProxy

LazyConnectionDataSourceProxy

方法详细资料

setDefaultAutoCommit

setDefaultTransactionIsolation

setDefaultTransactionIsolationName

afterPropertiesSet

checkDefaultConnectionProperties

defaultAutoCommit

defaultTransactionIsolation

getConnection

getConnection