Class StatementDecoratorInterceptor

java.lang.Object

org.apache.tomcat.jdbc.pool.JdbcInterceptor

org.apache.tomcat.jdbc.pool.interceptor.AbstractCreateStatementInterceptor

org.apache.tomcat.jdbc.pool.interceptor.StatementDecoratorInterceptor

All Implemented Interfaces:

InvocationHandler

Direct Known Subclasses:

StatementCache

public class StatementDecoratorInterceptor
extends AbstractCreateStatementInterceptor

Implementation of JdbcInterceptor that proxies statements and result sets so that neither the physical session nor the driver's own handles reach the application through them: Statement.getConnection() is answered with the pool's connection handle rather than the driver's connection, and ResultSet.getStatement() with the statement handle rather than the driver's statement - the hiding of the physical connection this interceptor exists for (Bug 48392, described in this interceptor's section of the jdbc-pool documentation page).

Beyond the hiding, the statement proxy keeps its own handle contract: calls reach the driver statement only while the proxy is open, a repeat close answers as a no-op, every other call on a retired handle is refused with an SQLException, and the driver's answer to a close that failed is passed to the caller - the handle is retired whichever way the driver answered. The connection the proxy reports is a snapshot of the borrow that created it, so a component that reuses a statement across borrows - StatementCache - must re-bind the handle first, as StatementDecoratorInterceptor.StatementProxy.setConnection(Object) documents. The result set proxy answers ResultSet.getStatement() and the Object identity methods (toString, equals, hashCode) itself; every other call, the Wrapper methods included, reaches the driver object unchanged.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	StatementDecoratorInterceptor.ResultSetProxy	Invocation handler that proxies ResultSet instances.
protected class	StatementDecoratorInterceptor.StatementProxy<T extends Statement>	Invocation handler behind a statement proxy: it keeps the handle contract the class javadoc describes - lifecycle answered from its own state, close failures passed on, the borrow's connection handle reported instead of the driver's - and wraps the result sets of the calls named in RESULTSET_TYPES.

Field Summary

Fields

Modifier and Type	Field	Description
protected static final String[]	RESULTSET_TYPES	Method names that return a ResultSet, spelled with the base class's constants.
protected static Constructor<?>	resultSetConstructor	the constructor to create the resultSet proxies

Fields inherited from class AbstractCreateStatementInterceptor

CREATE_STATEMENT, CREATE_STATEMENT_IDX, EXECUTE, EXECUTE_BATCH, EXECUTE_LARGE_BATCH, EXECUTE_LARGE_UPDATE, EXECUTE_QUERY, EXECUTE_TYPES, EXECUTE_UPDATE, GET_GENERATED_KEYS, GET_RESULTSET, GET_STATEMENT, PREPARE_CALL, PREPARE_CALL_IDX, PREPARE_STATEMENT, PREPARE_STATEMENT_IDX, RESULTSET_IDX, STATEMENT_TYPE_COUNT, STATEMENT_TYPES

Fields inherited from class JdbcInterceptor

ABORT_VAL, CLOSE_VAL, EQUALS_VAL, GETCONNECTION_VAL, HASHCODE_VAL, ISCLOSED_VAL, ISVALID_VAL, ISWRAPPERFOR_VAL, properties, TOSTRING_VAL, UNWRAP_VAL

Constructor Summary

Constructors

Constructor	Description
StatementDecoratorInterceptor()	Default constructor.

Method Summary

Modifier and Type	Method	Description
void	closeInvoked()	Method invoked when the operation Connection.close() is invoked.
protected Object	createDecorator(Object proxy, Method method, Object[] args, Object statement, Constructor<?> constructor, String sql)	Creates a proxy for a Statement.
Object	createStatement(Object proxy, Method method, Object[] args, Object statement, long time)	Wraps the statement the connection call has just created in this interceptor's proxy.
protected Constructor<?>	getResultSetConstructor()	Gets the constructor for creating ResultSet proxies.
protected boolean	isResultSet(Method method, boolean process)	Checks if the given method returns a ResultSet.

Methods inherited from class AbstractCreateStatementInterceptor

elapsedMillis, getConstructor, invoke, isExecute, isStatement, process, reset

Methods inherited from class JdbcInterceptor

compare, compare, disconnected, getNext, getProperties, isUseEquals, poolClosed, poolStarted, setNext, setProperties, setUseEquals, unregisterMBean

Methods inherited from class Object

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

Field Details

RESULTSET_TYPES

protected static final String[] RESULTSET_TYPES

Method names that return a ResultSet, spelled with the base class's constants.

resultSetConstructor

protected static volatile Constructor<?> resultSetConstructor

the constructor to create the resultSet proxies

Constructor Details

StatementDecoratorInterceptor

public StatementDecoratorInterceptor()

Default constructor.

Method Details

closeInvoked

public void closeInvoked()

Description copied from class: AbstractCreateStatementInterceptor

Method invoked when the operation Connection.close() is invoked. It runs before the close is passed down the chain, so that a hook can still reach the connection while it is alive - statements must be closed before the session is handed to the next borrower. Implementation of this method should be thought through with care, as no actions should trigger an exception. An interceptor that nevertheless throws is isolated: the exception is logged and ignored, the remaining interceptors in the chain still receive the close, and the connection is returned to the pool as it would have been. The fatal virtual machine errors the pool never swallows are the exception: those propagate.

Specified by:

closeInvoked in class AbstractCreateStatementInterceptor

getResultSetConstructor

protected Constructor<?> getResultSetConstructor()
                                          throws NoSuchMethodException

Gets the constructor for creating ResultSet proxies.

Returns:

the ResultSet proxy constructor

Throws:

NoSuchMethodException - if the constructor is not found

createStatement

public Object createStatement(Object proxy,
 Method method,
 Object[] args,
 Object statement,
 long time)

Wraps the statement the connection call has just created in this interceptor's proxy. This method will be invoked after a successful statement creation. This method can choose to return a wrapper around the statement or return the statement itself. If this method returns a wrapper then it should return a wrapper object that implements one of the following interfaces. Statement, PreparedStatement or CallableStatement

An implementation must not make the statement reachable from any other code before it returns, because if this method throws then the statement is closed on a best-effort basis by the interceptor base class before the throwable is propagated to the application.

The time argument is unused - this interceptor does no timing. If building the proxy fails, the failure is logged and the unproxied driver statement is returned, so a failure degrades the connection hiding rather than failing the application's call.

Specified by:

createStatement in class AbstractCreateStatementInterceptor

Parameters:

proxy - the actual proxy object

method - the method that was called. It will be one of the methods defined in AbstractCreateStatementInterceptor.STATEMENT_TYPES

args - the arguments to the method

statement - the statement that the underlying connection created

time - elapsed time in milliseconds, measured with the monotonic clock

Returns:

a Statement object

createDecorator

protected Object createDecorator(Object proxy,
 Method method,
 Object[] args,
 Object statement,
 Constructor<?> constructor,
 String sql)
                          throws InstantiationException,
IllegalAccessException,
InvocationTargetException

Creates a proxy for a Statement.

Parameters:

proxy - The proxy object on which the method that triggered the creation of the statement was called.

method - The method that was called on the proxy

args - The arguments passed as part of the method call to the proxy

statement - The statement object that is to be proxied

constructor - The constructor for the desired proxy

sql - The sql of the statement

Returns:

A new proxy for the Statement

Throws:

InstantiationException - Couldn't instantiate object

IllegalAccessException - Inaccessible constructor

InvocationTargetException - Exception thrown from constructor

isResultSet

protected boolean isResultSet(Method method,
 boolean process)

Checks if the given method returns a ResultSet. This, not any executeQuery-specific test, is the dispatch predicate the proxies consult.

Parameters:

method - the method to check

process - whether processing is already enabled

Returns:

true if the method returns a ResultSet