org.springframework.retry.support

Class RetryTemplate

java.lang.Object

org.springframework.retry.support.RetryTemplate

All Implemented Interfaces:

RetryOperations

public class RetryTemplate
extends Object
implements RetryOperations

Template class that simplifies the execution of operations with retry semantics.

Retryable operations are encapsulated in implementations of the RetryCallback interface and are executed using one of the supplied execute methods.

By default, an operation is retried if is throws any Exception or subclass of Exception. This behaviour can be changed by using the setRetryPolicy(RetryPolicy) method.

Also by default, each operation is retried for a maximum of three attempts with no back off in between. This behaviour can be configured using the setRetryPolicy(RetryPolicy) and setBackOffPolicy(BackOffPolicy) properties. The BackOffPolicy controls how long the pause is between each individual retry attempt.

A new instance can be fluently configured via builder(), e.g:

 
 RetryTemplate.builder()
                 .maxAttempts(10)
                 .fixedBackoff(1000)
                 .build();
 

See RetryTemplateBuilder for more examples and details.

This class is thread-safe and suitable for concurrent access when executing operations and when performing configuration changes. As such, it is possible to change the number of retries on the fly, as well as the BackOffPolicy used and no in progress retryable operations will be affected.

Author:

Rob Harrop, Dave Syer, Gary Russell, Artem Bilan, Josh Long, Aleksandr Shamukov

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.commons.logging.Log	logger

Constructor Summary

Constructors

Constructor and Description
RetryTemplate()

Method Summary

Modifier and Type	Method and Description
static RetryTemplateBuilder	builder() Main entry point to configure RetryTemplate using fluent API.
protected boolean	canRetry(RetryPolicy retryPolicy, RetryContext context) Decide whether to proceed with the ongoing retry attempt.
protected void	close(RetryPolicy retryPolicy, RetryContext context, RetryState state, boolean succeeded) Clean up the cache if necessary and close the context provided (if the flag indicates that processing was successful).
static RetryTemplate	defaultInstance() Creates a new default instance.
protected <T,E extends Throwable> T	doExecute(RetryCallback<T,E> retryCallback, RecoveryCallback<T> recoveryCallback, RetryState state) Execute the callback once if the policy dictates that we can, otherwise execute the recovery callback.
<T,E extends Throwable> T	execute(RetryCallback<T,E> retryCallback) Keep executing the callback until it either succeeds or the policy dictates that we stop, in which case the most recent exception thrown by the callback will be rethrown.
<T,E extends Throwable> T	execute(RetryCallback<T,E> retryCallback, RecoveryCallback<T> recoveryCallback) Keep executing the callback until it either succeeds or the policy dictates that we stop, in which case the recovery callback will be executed.
<T,E extends Throwable> T	execute(RetryCallback<T,E> retryCallback, RecoveryCallback<T> recoveryCallback, RetryState retryState) Execute the callback once if the policy dictates that we can, re-throwing any exception encountered so that clients can re-present the same task later.
<T,E extends Throwable> T	execute(RetryCallback<T,E> retryCallback, RetryState retryState) Execute the callback once if the policy dictates that we can, re-throwing any exception encountered so that clients can re-present the same task later.
protected <T> T	handleRetryExhausted(RecoveryCallback<T> recoveryCallback, RetryContext context, RetryState state) Actions to take after final attempt has failed.
boolean	hasListeners() Return true if at least one listener is registered.
protected RetryContext	open(RetryPolicy retryPolicy, RetryState state) Delegate to the RetryPolicy having checked in the cache for an existing value if the state is not null.
void	registerListener(RetryListener listener) Register an additional listener at the end of the list.
void	registerListener(RetryListener listener, int index) Register an additional listener at the specified index.
protected void	registerThrowable(RetryPolicy retryPolicy, RetryState state, RetryContext context, Throwable e)
protected <E extends Throwable> void	rethrow(RetryContext context, String message)
void	setBackOffPolicy(BackOffPolicy backOffPolicy) Setter for BackOffPolicy.
void	setListeners(RetryListener[] listeners) Setter for listeners.
void	setRetryContextCache(RetryContextCache retryContextCache) Public setter for the RetryContextCache.
void	setRetryPolicy(RetryPolicy retryPolicy) Setter for RetryPolicy.
void	setThrowLastExceptionOnExhausted(boolean throwLastExceptionOnExhausted)
protected boolean	shouldRethrow(RetryPolicy retryPolicy, RetryContext context, RetryState state) Extension point for subclasses to decide on behaviour after catching an exception in a RetryCallback.

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected final org.apache.commons.logging.Log logger

Constructor Detail

RetryTemplate

public RetryTemplate()

Method Detail

builder

public static RetryTemplateBuilder builder()

Main entry point to configure RetryTemplate using fluent API. See RetryTemplateBuilder for usage examples and details.

Returns:

a new instance of RetryTemplateBuilder with preset default behaviour, that can be overwritten during manual configuration

Since:

1.3

defaultInstance

public static RetryTemplate defaultInstance()

Creates a new default instance. The properties of default instance are described in RetryTemplateBuilder documentation.

Returns:

a new instance of RetryTemplate with default behaviour

Since:

1.3

setThrowLastExceptionOnExhausted

public void setThrowLastExceptionOnExhausted(boolean throwLastExceptionOnExhausted)

Parameters:

throwLastExceptionOnExhausted - the throwLastExceptionOnExhausted to set

setRetryContextCache

public void setRetryContextCache(RetryContextCache retryContextCache)

Public setter for the RetryContextCache.

Parameters:

retryContextCache - the RetryContextCache to set.

setListeners

public void setListeners(RetryListener[] listeners)

Setter for listeners. The listeners are executed before and after a retry block (i.e. before and after all the attempts), and on an error (every attempt).

Parameters:

listeners - the RetryListeners

See Also:

RetryListener

registerListener

public void registerListener(RetryListener listener)

Register an additional listener at the end of the list.

Parameters:

listener - the RetryListener

See Also:

setListeners(RetryListener[])

registerListener

public void registerListener(RetryListener listener,
                             int index)

Register an additional listener at the specified index.

Parameters:

listener - the RetryListener

index - the position in the list.

Since:

1.3

See Also:

setListeners(RetryListener[])

hasListeners

public boolean hasListeners()

Return true if at least one listener is registered.

Returns:

true if listeners present.

Since:

1.3

setBackOffPolicy

public void setBackOffPolicy(BackOffPolicy backOffPolicy)

Setter for BackOffPolicy.

Parameters:

backOffPolicy - the BackOffPolicy

setRetryPolicy

public void setRetryPolicy(RetryPolicy retryPolicy)

Setter for RetryPolicy.

Parameters:

retryPolicy - the RetryPolicy

execute

public final <T,E extends Throwable> T execute(RetryCallback<T,E> retryCallback)
                                        throws E extends Throwable

Keep executing the callback until it either succeeds or the policy dictates that we stop, in which case the most recent exception thrown by the callback will be rethrown.

Specified by:

execute in interface RetryOperations

Type Parameters:

T - the return value

E - the exception to throw

Parameters:

retryCallback - the RetryCallback

Returns:

the value returned by the RetryCallback upon successful invocation.

Throws:

TerminatedRetryException - if the retry has been manually terminated by a listener.

E - any Exception raised by the RetryCallback upon unsuccessful retry.

E extends Throwable

See Also:

RetryOperations.execute(RetryCallback)

execute

public final <T,E extends Throwable> T execute(RetryCallback<T,E> retryCallback,
                                               RecoveryCallback<T> recoveryCallback)
                                        throws E extends Throwable

Keep executing the callback until it either succeeds or the policy dictates that we stop, in which case the recovery callback will be executed.

Specified by:

execute in interface RetryOperations

Type Parameters:

T - the type to return

E - the type of the exception

Parameters:

retryCallback - the RetryCallback

recoveryCallback - the RecoveryCallback

Returns:

the value returned by the RetryCallback upon successful invocation, and that returned by the RecoveryCallback otherwise.

Throws:

TerminatedRetryException - if the retry has been manually terminated by a listener.

E - any Exception raised by the unsuccessful retry.

E extends Throwable

See Also:

RetryOperations.execute(RetryCallback, RecoveryCallback)

execute

public final <T,E extends Throwable> T execute(RetryCallback<T,E> retryCallback,
                                               RetryState retryState)
                                        throws E extends Throwable,
                                               ExhaustedRetryException

Execute the callback once if the policy dictates that we can, re-throwing any exception encountered so that clients can re-present the same task later.

Specified by:

execute in interface RetryOperations

Type Parameters:

T - the type of the return value

E - the type of the exception to return

Parameters:

retryCallback - the RetryCallback

retryState - the RetryState

Returns:

the value returned by the RetryCallback upon successful invocation, and that returned by the RecoveryCallback otherwise.

Throws:

ExhaustedRetryException - if the retry has been exhausted.

E - any Exception raised by the RecoveryCallback.

E extends Throwable

See Also:

RetryOperations.execute(RetryCallback, RetryState)

execute

public final <T,E extends Throwable> T execute(RetryCallback<T,E> retryCallback,
                                               RecoveryCallback<T> recoveryCallback,
                                               RetryState retryState)
                                        throws E extends Throwable,
                                               ExhaustedRetryException

Execute the callback once if the policy dictates that we can, re-throwing any exception encountered so that clients can re-present the same task later.

Specified by:

execute in interface RetryOperations

Type Parameters:

T - the return value type

E - the exception type

Parameters:

retryCallback - the RetryCallback

recoveryCallback - the RecoveryCallback

retryState - the RetryState

Returns:

the value returned by the RetryCallback upon successful invocation, and that returned by the RecoveryCallback otherwise.

Throws:

E - any Exception raised by the RecoveryCallback upon unsuccessful retry.

E extends Throwable

ExhaustedRetryException

See Also:

RetryOperations.execute(RetryCallback, RetryState)

doExecute

protected <T,E extends Throwable> T doExecute(RetryCallback<T,E> retryCallback,
                                              RecoveryCallback<T> recoveryCallback,
                                              RetryState state)
                                       throws E extends Throwable,
                                              ExhaustedRetryException

Execute the callback once if the policy dictates that we can, otherwise execute the recovery callback.

Type Parameters:

T - the type of the return value

E - the exception type to throw

Parameters:

recoveryCallback - the RecoveryCallback

retryCallback - the RetryCallback

state - the RetryState

Returns:

T the retried value

Throws:

ExhaustedRetryException - if the retry has been exhausted.

E - an exception if the retry operation fails

E extends Throwable

See Also:

RetryOperations.execute(RetryCallback, RecoveryCallback, RetryState)

canRetry

protected boolean canRetry(RetryPolicy retryPolicy,
                           RetryContext context)

Decide whether to proceed with the ongoing retry attempt. This method is called before the RetryCallback is executed, but after the backoff and open interceptors.

Parameters:

retryPolicy - the policy to apply

context - the current retry context

Returns:

true if we can continue with the attempt

close

protected void close(RetryPolicy retryPolicy,
                     RetryContext context,
                     RetryState state,
                     boolean succeeded)

Clean up the cache if necessary and close the context provided (if the flag indicates that processing was successful).

Parameters:

retryPolicy - the RetryPolicy

context - the RetryContext

state - the RetryState

succeeded - whether the close succeeded

registerThrowable

protected void registerThrowable(RetryPolicy retryPolicy,
                                 RetryState state,
                                 RetryContext context,
                                 Throwable e)

open

protected RetryContext open(RetryPolicy retryPolicy,
                            RetryState state)

Delegate to the RetryPolicy having checked in the cache for an existing value if the state is not null.

Parameters:

state - a RetryState

retryPolicy - a RetryPolicy to delegate the context creation

Returns:

a retry context, either a new one or the one used last time the same state was encountered

handleRetryExhausted

protected <T> T handleRetryExhausted(RecoveryCallback<T> recoveryCallback,
                                     RetryContext context,
                                     RetryState state)
                              throws Throwable

Actions to take after final attempt has failed. If there is state clean up the cache. If there is a recovery callback, execute that and return its result. Otherwise throw an exception.

Type Parameters:

T - the type to classify

Parameters:

recoveryCallback - the callback for recovery (might be null)

context - the current retry context

state - the RetryState

Returns:

T the payload to return

Throws:

Exception - if the callback does, and if there is no callback and the state is null then the last exception from the context

ExhaustedRetryException - if the state is not null and there is no recovery callback

Throwable - if there is an error

rethrow

protected <E extends Throwable> void rethrow(RetryContext context,
                                             String message)
                                      throws E extends Throwable

Throws:

E extends Throwable

shouldRethrow

protected boolean shouldRethrow(RetryPolicy retryPolicy,
                                RetryContext context,
                                RetryState state)

Extension point for subclasses to decide on behaviour after catching an exception in a RetryCallback. Normal stateless behaviour is not to rethrow, and if there is state we rethrow.

Parameters:

retryPolicy - the retry policy

context - the current context

state - the current retryState

Returns:

true if the state is not null but subclasses might choose otherwise