@ConfigurationProperties bug when a property is a list of classes

[mkopylec]

I'm using 1.3.5.RELEASE version.
I have a configuration class:

@ConfigurationProperties("sample")
public class SampleProperties {

    public static final List<Class<? extends Throwable>> DEFAULT_CLASSES = asList(Exception.class, RuntimeException.class);

    private List<Class<? extends Throwable>> classes = new ArrayList<>(DEFAULT_CLASSES);

    public List<Class<? extends Throwable>> getClasses() {
        return classes;
    }

    public void setClasses(List<Class<? extends Throwable>> classes) {
        this.classes = classes;
    }
}

and application.yml file:

sample.classes: java.io.IOException, java.lang.IllegalArgumentException

Now I expect classes to be [java.io.IOException, java.lang.IllegalArgumentException] but they are [java.lang.Exception, java.lang.RuntimeException]

See the demo project for more details.

[wilkinsona]

Thanks for the sample. I see what's going on now.

The problem is that the underlying support in Spring Framework for property conversion can't convert a comma-separate String into a List of classes. Instead, it tries to load a class named java.io.IOException, java.lang.IllegalArgumentException. This happens silently as there's no Validator. If you add Hibernate Validator to the classpath, a failure is reported and the app fails to start:

Caused by: org.springframework.validation.BindException: org.springframework.boot.bind.RelaxedDataBinder$RelaxedBeanPropertyBindingResult: 1 errors
Field error in object 'sample' on field 'classes': rejected value [java.io.IOException, java.lang.IllegalArgumentException]; codes [typeMismatch.sample.classes,typeMismatch.classes,typeMismatch.java.util.List,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [sample.classes,classes]; arguments []; default message [classes]]; default message [Failed to convert property value of type [java.lang.String] to required type [java.util.List] for property 'classes'; nested exception is java.lang.IllegalArgumentException: Cannot find class [java.io.IOException, java.lang.IllegalArgumentException]]
    at org.springframework.boot.bind.PropertiesConfigurationFactory.validate(PropertiesConfigurationFactory.java:362) ~[spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE]
    at org.springframework.boot.bind.PropertiesConfigurationFactory.doBindPropertiesToTarget(PropertiesConfigurationFactory.java:271) ~[spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE]
    at org.springframework.boot.bind.PropertiesConfigurationFactory.bindPropertiesToTarget(PropertiesConfigurationFactory.java:241) ~[spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE]
    at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.postProcessBeforeInitialization(ConfigurationPropertiesBindingPostProcessor.java:334) ~[spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE]
    ... 31 common frames omitted

If you'd like Spring Framework to be able to support this comma-separated String to List<Class> conversion then you could raise a JIRA ticket requesting it.

In the meantime, you could add your own converter:

    @ConfigurationPropertiesBinding
    @Bean
    public Converter<String, List<Class<? extends Throwable>>> customConverter() {
        return new Converter<String, List<Class<? extends Throwable>>>() {

            @SuppressWarnings("unchecked")
            @Override
            public List<Class<? extends Throwable>> convert(String source) {
                try {
                    List<Class<? extends Throwable>> classes = new ArrayList<>();
                    for (String className: StringUtils.commaDelimitedListToStringArray(source)) {
                        classes.add((Class<? extends Throwable>)ClassUtils.forName(className.trim(),
                                getClass().getClassLoader()));
                    }
                    return classes;
                } catch (ClassNotFoundException ex) {
                    ex.printStackTrace();
                    throw new IllegalStateException(ex);
                }
            }

        };

    }

[mkopylec]

Thanks again!

[yuhuanxi]

thanks

[philwebb]

This looks very similar to #12166 so you might want to consider upgrading to Spring Boot 2.0