YamlPropertySourceFactory fails to load 'S&P', and instead loads 'SP'

I am using Spring Boot 3.2 with Java 21, along with SnakeYAML 2.2.

I am trying to load yaml file sources.yaml. This is how my YAML looks like:

sources:
    "S&P":
        cron: '0 30 1 * * SUN-SAT'
        calculateCA: 'true'
        modifyOhlc: 'true'

And this is how SourcesConfig class looks like:

@Configuration
@EnableConfigurationProperties
@ConfigurationProperties
@Slf4j
@PropertySource(value = "file:config/sources.yml", factory = YamlPropertySourceFactory.class)
public class SourcesConfig2 {

    @Getter
    @Setter
    private Map<String, MetaData> sources;

    @Data
    public static class MetaData {
        private String cron;
        private boolean calculateCA;
        private boolean modifyOhlc;
        private String lastUpdatedTime;
        private ZoneOffset gmtOffset;
    }
}

public class YamlPropertySourceFactory implements PropertySourceFactory {

    @Override
    public PropertySource<?> createPropertySource(String name, EncodedResource encodedResource) {
        YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
        factory.setResources(encodedResource.getResource());

        Properties properties = factory.getObject();
        String fileName = encodedResource.getResource().getFilename();

        Objects.requireNonNull(fileName);
        Objects.requireNonNull(properties);
        return new PropertiesPropertySource(fileName, properties);
    }
}

I have removed other methods for brevity. At initial loadup, I have noticed an error popping up and went to debug. S&P is loaded as SP.

While debugging I noticed that the file is correctly loading. Something changed after its loadup and I cannot pinpoint what went wrong exactly.

What is wrong here? I have tried with other combinations like 'S$P', 'S@P' etc. and for some reason any special character is missed.

I believe you are running into this issue. You need to surround the S&P config/map key with square brackets as suggested here, so that the key becomes "[S&P]" from "S&P"