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Document RetryTemplate#invoke variants in reference manual
Closes gh-36452
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@@ -25,7 +25,8 @@ public void sendNotification() {
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By default, the method invocation will be retried for any exception thrown: with at most
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3 retry attempts (`maxRetries = 3`) after an initial failure, and a delay of 1 second
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between attempts.
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between attempts. If all attempts have failed and the retry policy has been exhausted,
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the last original exception from the target method will be propagated to the caller.
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[NOTE]
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====
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@@ -99,6 +100,13 @@ TIP: Several attributes in `@Retryable` have `String` variants that provide prop
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placeholder and SpEL support, as an alternative to the specifically typed annotation
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attributes used in the above examples.
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[TIP]
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====
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During `@Retryable` processing, Spring publishes a `MethodRetryEvent` for every exception
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coming out of the target method. This can be used to track/log all original exceptions
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whereas the caller of the `@Retryable` method will only ever see the last exception.
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====
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[[resilience-annotations-concurrencylimit]]
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== `@ConcurrencyLimit`
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@@ -174,7 +182,7 @@ configured {spring-framework-api}/core/retry/RetryPolicy.html[`RetryPolicy`].
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----
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var retryTemplate = new RetryTemplate(); // <1>
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retryTemplate.execute(
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retryTemplate.invoke(
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() -> jmsClient.destination("notifications").send(...));
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----
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<1> Implicitly uses `RetryPolicy.withDefaults()`.
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@@ -200,7 +208,7 @@ If you only need to customize the number of retry attempts, you can use the
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----
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var retryTemplate = new RetryTemplate(RetryPolicy.withMaxRetries(4)); // <1>
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retryTemplate.execute(
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retryTemplate.invoke(
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() -> jmsClient.destination("notifications").send(...));
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----
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<1> Explicitly uses `RetryPolicy.withMaxRetries(4)`.
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@@ -218,7 +226,7 @@ matched against an exception thrown by a failed operation as well as nested caus
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var retryTemplate = new RetryTemplate(retryPolicy);
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retryTemplate.execute(
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retryTemplate.invoke(
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() -> jmsClient.destination("notifications").send(...));
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----
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<1> Specify one or more exception types to include.
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@@ -251,21 +259,96 @@ and an exponential back-off strategy with a bit of jitter.
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var retryTemplate = new RetryTemplate(retryPolicy);
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retryTemplate.execute(
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retryTemplate.invoke(
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() -> jmsClient.destination("notifications").send(...));
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----
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[TIP]
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====
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A {spring-framework-api}/core/retry/RetryListener.html[`RetryListener`] can be registered
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with a `RetryTemplate` to react to events published during key retry phases (before a
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retry attempt, after a retry attempt, etc.), and you can compose multiple listeners via a
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{spring-framework-api}/core/retry/support/CompositeRetryListener.html[`CompositeRetryListener`].
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====
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Although the factory methods and builder API for `RetryPolicy` cover most common
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configuration scenarios, you can implement a custom `RetryPolicy` for complete control
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over the types of exceptions that should trigger a retry as well as the
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{spring-framework-api}/util/backoff/BackOff.html[`BackOff`] strategy to use. Note that you
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can also configure a customized `BackOff` strategy via the `backOff()` method in the
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`RetryPolicy.Builder`.
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{spring-framework-api}/util/backoff/BackOff.html[`BackOff`] strategy to use. Note that
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you can also configure a customized `BackOff` strategy via the `backOff()` method in
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the `RetryPolicy.Builder`.
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====
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Note that the examples above apply a pattern similar to `@Retryable` method invocations
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where the last original exception will be propagated to the caller, using the `invoke`
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variants on `RetryTemplate` which are available with and without a return value.
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The callback may throw unchecked exceptions, the last one of which is exposed for
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direct handling on the caller side:
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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try {
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retryTemplate.invoke(
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() -> jmsClient.destination("notifications").send(...));
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}
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catch (MessageDeliveryException ex) {
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// coming out of the original JmsClient send method
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}
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----
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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try {
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var result = retryTemplate.invoke(() -> {
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jmsClient.destination("notifications").send(...);
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return "result";
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});
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}
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catch (MessageDeliveryException ex) {
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// coming out of the original JmsClient send method
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}
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----
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`RetryTemplate` instances are very light and can be created on the fly,
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potentially with a specific retry policy to use for a given invocation:
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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try {
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new RetryTemplate(RetryPolicy.withMaxRetries(4)).invoke(
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() -> jmsClient.destination("notifications").send(...));
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}
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catch (MessageDeliveryException ex) {
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// coming out of the original JmsClient send method
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}
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----
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For deeper interaction, you may use RetryTemplate's `execute` method. The caller will
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have to handle the checked `RetryException` thrown by `RetryTemplate`, exposing the
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outcome of all attempts:
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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try {
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var result = new RetryTemplate().execute(() -> {
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jmsClient.destination("notifications").send(...);
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return "result";
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});
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}
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catch (RetryException ex) {
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// ex.getExceptions() / ex.getLastException() ...
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}
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----
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A {spring-framework-api}/core/retry/RetryListener.html[`RetryListener`] can be registered
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with a `RetryTemplate` to react to events published during key retry phases (before a
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retry attempt, after a retry attempt, etc.), being able to track all invocation attempts
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and all exceptions coming out of the callback. This is particularly useful when using
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`invoke` where no retry state other than the last original exception is exposed otherwise:
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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var retryTemplate = new RetryTemplate();
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retryTemplate.setRetryPolicy(...);
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retryTemplate.setRetryListener(...);
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retryTemplate.invoke(
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() -> jmsClient.destination("notifications").send(...));
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----
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You can also compose multiple listeners via a
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{spring-framework-api}/core/retry/support/CompositeRetryListener.html[`CompositeRetryListener`].
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