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From "Luca Burgazzoli (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CAMEL-10548) Converter from List to String is not found when @EnableAutoConfiguration is used
Date Wed, 30 Nov 2016 17:47:59 GMT
Luca Burgazzoli created CAMEL-10548:
---------------------------------------

             Summary: Converter from List to String is not found when @EnableAutoConfiguration
is used
                 Key: CAMEL-10548
                 URL: https://issues.apache.org/jira/browse/CAMEL-10548
             Project: Camel
          Issue Type: Bug
          Components: camel-spring-boot
            Reporter: Luca Burgazzoli
            Assignee: Luca Burgazzoli
             Fix For: 2.19.0


This very simple spring-boot application :

{code:java}
@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 +
                '}';
        }
    }
}
{code}

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

{code}
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
{code}

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



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