SqsAutoConfiguration#configureProperties NPEs/throws when listener.* properties are left unset (regression from 3.x's alwaysApplyingWhenNonNull()) #1705

Type: Bug

Component: SQS

Describe the bug

SqsAutoConfiguration.configureProperties() maps SqsProperties.Listener's
maxConcurrentMessages, maxMessagesPerPoll, pollTimeout, maxDelayBetweenPolls,
and autoStartup unconditionally:

private void configureProperties(SqsContainerOptionsBuilder options) {
    PropertyMapper mapper = PropertyMapper.get();
    mapper.from(this.sqsProperties.getQueueNotFoundStrategy()).to(options::queueNotFoundStrategy);
    mapper.from(this.sqsProperties.getListener().getMaxConcurrentMessages()).to(options::maxConcurrentMessages);
    ...

All five Listener fields are @Nullable with no default, so an application that doesn't
explicitly set any of them (reasonable, since they all have sensible built-in defaults in
AbstractContainerOptions.Builder) gets a crash on every context startup:

• a NullPointerException from unboxing null into the primitive int/boolean setters
  (maxConcurrentMessages, maxMessagesPerPoll, autoStartup), or
• an IllegalArgumentException from the Assert.notNull guards inside
  AbstractContainerOptions.Builder (pollTimeout, maxDelayBetweenPolls)

-- whichever field the mapper reaches first.

This is a regression from 3.4.2, whose equivalent method guarded the whole block:

private void configureProperties(SqsContainerOptionsBuilder options) {
    PropertyMapper mapper = PropertyMapper.get().alwaysApplyingWhenNonNull();
    ...

That .alwaysApplyingWhenNonNull() call is missing in every 4.x release checked directly
against the Maven Central sources jars: 4.0.0, 4.0.1, 4.0.2, 4.1.0, 4.1.1 (latest).

Observed stack trace (with spring.cloud.aws.sqs.queue-not-found-strategy set, everything
else left at its default):

Caused by: java.lang.NullPointerException
    at org.springframework.boot.context.properties.PropertyMapper$Source.to(PropertyMapper.java:294)
    at io.awspring.cloud.autoconfigure.sqs.SqsAutoConfiguration.configureProperties(SqsAutoConfiguration.java:214)
    at io.awspring.cloud.sqs.config.AbstractMessageListenerContainerFactory.configure(AbstractMessageListenerContainerFactory.java:174)
    at io.awspring.cloud.autoconfigure.sqs.SqsAutoConfiguration.defaultSqsListenerContainerFactory(SqsAutoConfiguration.java:192)

Expected: unset listener properties should fall back to AbstractContainerOptions.Builder's
own defaults, as they did in 3.x, rather than crashing context startup.

Suggested fix: restore PropertyMapper.get().alwaysApplyingWhenNonNull() (or add
.whenNonNull() per mapping) in SqsAutoConfiguration.configureProperties().

Versions:

• spring-cloud-aws-dependencies: 4.1.1 (also present in 4.0.0-4.1.0)
• Spring Boot: 3.5.16
• Java: 21 / 25

Sample

Minimal Spring Boot app that reproduces this on context startup. Only dependency beyond
spring-boot-starter is spring-cloud-aws-starter-sqs (version managed by the
spring-cloud-aws-dependencies:4.1.1 BOM); no spring.cloud.aws.sqs.listener.*
properties are set.

pom.xml (relevant sections):

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>io.awspring.cloud</groupId>
      <artifactId>spring-cloud-aws-dependencies</artifactId>
      <version>4.1.1</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>
<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
  </dependency>
  <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
  </dependency>
  <dependency>
    <groupId>io.awspring.cloud</groupId>
    <artifactId>spring-cloud-aws-starter-sqs</artifactId>
  </dependency>
</dependencies>

application.properties:

spring.cloud.aws.region.static=us-east-1
spring.cloud.aws.sqs.queue-not-found-strategy=fail

Test (the mocked SqsAsyncClient bean only exists to isolate this from real network/event-loop
setup, which is unrelated to the bug):

@SpringBootTest
class ReproApplicationTests {

    @TestConfiguration
    static class MockSqsClientConfig {
        @Bean
        SqsAsyncClient sqsAsyncClient() {
            return mock(SqsAsyncClient.class);
        }
    }

    @Test
    void contextLoads() {
    }
}

Running this test throws the NullPointerException above immediately on context startup.