How to Successfully Navigate RepeatException in Spring: Unraveling the Mystery with Code Examples
If you’re building applications with the Spring framework, chances are you’ve encountered or will meet the ubiquitous RepeatException. This exception is thrown specifically by Spring Batch - a framework used within Spring for batch processing. This write-up aims to provide a comprehensive understanding of RepeatException in Spring, it’s scenarios, savvily handling them, and enhancing your codebase efficiently.
Introduction to RepeatException
Before diving into the main topic, we need to understand what exactly is RepeatException. It’s a runtime exception in Spring Batch used to report errors during the execution of repetitive operations.
Here’s an example of how the RepeatException is typically used in code:
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RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception{
try {
// code that might throw an exception
}
catch (SomeSpecificException ex) {
throw new RepeatException("An error occurred", ex);
}
}
After encountering the RepeatException the spring batch framework can decide whether to retry the operation or not based on the provided policies.
When Does RepeatException Occur?
A RepeatException is thrown mainly in two instances:
During a Repeat Operation: When an unrecoverable error occurs during the execution of a repeat operation.
After a Retry Exhausted: Once a retry operation has exhausted all attempts to execute a specific operation, Spring Batch throws the last
RetryExceptionas aRepeatException.
Practical Application of RepeatException - Code Examples
Let’s deepen the understanding of RepeatException through intertwined understanding of Spring Batch’s three main features: Retry, Repeat, and Skip.
1. Repeat Exception in Retry Policy:
To demonstrate, let’s consider an example involving batch processing that includes a simple Retry Policy. Sometimes during a batch operation, if a non-Spring exception is thrown, you may decide to retry the operation. The Retry Policy dictates how many times the operation should be retried before giving up and throwing a RepeatException.
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public ItemReader reader() {
return new MyItemReader()
.retryLimit(3)
.retry(SomeSpecificException.class)
.noRetry(AnotherSpecificException.class);
}
class MyItemReader implements ItemReader {
private RetryTemplate retryTemplate;
@Override
public RepeatStatus read() {
try {
retryTemplate.execute(retryContext -> {
// code that might throw an exception
return RepeatStatus.FINISHED;
});
} catch(RetryException ex) {
throw new RepeatException("Failed after retries", ex);
}
return RepeatStatus.FINISHED;
}
}
2. Repeat Exception during Skip:
Spring Batch also offers a ‘skip’ feature that you can incorporate, which bypasses problematic records while processing. When you define a SkipPolicy along with the no. of allowable skips, the SkipLimitExceededException is thrown when the limit is exceeded, which is usually caught and wrapped in a RepeatException.
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public ItemProcessor processor() {
return new MySkipableItemProcessor().skipLimit(5)
.skip(SomeSpecificException.class);
}
class MySkipableItemProcessor implements ItemProcessor {
private SkipPolicy skipPolicy;
@Override
public RepeatStatus process() {
try {
// Code that might throw an exception
} catch (SomeSpecificException ex) {
if (!skipPolicy.shouldSkip(ex, 0)) {
throw new RepeatException("Failed while skipping", ex);
}
}
return RepeatStatus.FINISHED;
}
}
Your Spring Batch application needs to handle RepeatException. A simple way to handle this is by using a try-catch block and creating a custom error response:
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@Override
public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) {
try {
// code that might throw an exception
} catch (RepeatException ex) {
contribution.incrementWriteSkipCount();
return RepeatStatus.CONTINUABLE;
}
}
Workaround for RepeatException
Think of RepeatException as a stop sign- an indicator something has gone wrong that needs halting or retrying. Like with stop signs, it might be tempting to bypass this indicator, but this hampers performance and leads to more debugging.
This exploration of RepeatException should help you understand its occurrence, causes, and most importantly, how to handle it in your Spring Batch applications. Remember that tackling exceptions like these is elemental towards debugging and optimizing your code.