[CAMEL-10548] Converter from List to String is not found when @EnableAutoConfiguration is used

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.18.2, 2.19.0
• Component/s: camel-spring-boot
• Estimated Complexity: Unknown
• Assignee: Luca Burgazzoli
• Reporter: Luca Burgazzoli
• Created: 30/Nov/16 17:47
• Updated: 01/Dec/16 15:52
• Resolved: 01/Dec/16 15:52

Description

This very simple spring-boot application :

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Component
    public class MyRouteBuilder extends RouteBuilder {
        @Override
        public void configure() throws Exception {
            from("timer:person")
                .setBody().constant(Arrays.asList(
                    new Person("Peter", 25),
                    new Person("John", 33)
                ))
                .log("Body is ${body}");
        }
    }

    public static class Person {
        private String name;
        private int age;

        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        @Override
        public String toString() {
            return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
        }
    }
}

Fails to resolve the simple expression ${body} because of the following exception:

org.apache.camel.TypeConversionException: Error during type conversion from type: java.lang.String to the required type: java.lang.String with value [Person{name='Peter', age=25}, Person{name='John', age=33}] due Failed to convert from type [java.util.Arrays$ArrayList<?>] to type [java.lang.String] for value '[Person{name='Peter', age=25}, Person{name='John', age=33}]'; nested exception is org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.util.Arrays$ArrayList<?>] to type [java.lang.String]
	at org.apache.camel.impl.converter.BaseTypeConverterRegistry.createTypeConversionException(BaseTypeConverterRegistry.java:629) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.impl.converter.BaseTypeConverterRegistry.convertTo(BaseTypeConverterRegistry.java:150) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.support.ExpressionAdapter.evaluate(ExpressionAdapter.java:41) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.builder.ExpressionBuilder$75.evaluate(ExpressionBuilder.java:1795) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.support.ExpressionAdapter.evaluate(ExpressionAdapter.java:36) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.processor.LogProcessor.process(LogProcessor.java:53) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:77) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:542) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:197) [camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:120) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:83) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:197) [camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.component.timer.TimerConsumer.sendTimerExchange(TimerConsumer.java:192) [camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.component.timer.TimerConsumer$1.run(TimerConsumer.java:76) [camel-core-2.18.0.jar:2.18.0]
	at java.util.TimerThread.mainLoop(Timer.java:555) [na:1.8.0_112]
	at java.util.TimerThread.run(Timer.java:505) [na:1.8.0_112]
Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.util.Arrays$ArrayList<?>] to type [java.lang.String] for value '[Person{name='Peter', age=25}, Person{name='John', age=33}]'; nested exception is org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.util.Arrays$ArrayList<?>] to type [java.lang.String]
	at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:42) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:192) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:176) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	at org.apache.camel.spring.boot.SpringTypeConverter.convertTo(SpringTypeConverter.java:46) ~[camel-spring-boot-2.18.0.jar:2.18.0]
	at org.apache.camel.impl.converter.BaseTypeConverterRegistry.doConvertTo(BaseTypeConverterRegistry.java:346) ~[camel-core-2.18.0.jar:2.18.0]
	at org.apache.camel.impl.converter.BaseTypeConverterRegistry.convertTo(BaseTypeConverterRegistry.java:133) ~[camel-core-2.18.0.jar:2.18.0]
	... 14 common frames omitted
Caused by: org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.util.Arrays$ArrayList<?>] to type [java.lang.String]
	at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:313) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	at org.springframework.core.convert.support.CollectionToStringConverter.convert(CollectionToStringConverter.java:68) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:36) ~[spring-core-4.3.3.RELEASE.jar:4.3.3.RELEASE]
	... 19 common frames omitted

The root cause is spring failing to find a converter for Person --> String and as the SpringTypeConverter registered by camel-spring-boot is one of the fallback converters used by BaseTypeConverterRegistry, it leads Camel to fail too.

As today is a Camel TypeConverter fails with an exception while looping over fallback converters, the loops ends and the conversion fails too. It may turn out that the bug is caused by the way camel uses Spring's type converters but it may be good to catch exceptions and try the next converter, davsclaus make sense ?

A workaround is to create a custom converter for the class:

    @Component
    public class PersonConverter implements Converter<Person, String> {
        @Override
        public String convert(Person source) {
            return source.toString();
        }
    }

Issue Links

• links to: Spring Framework SPR-14971