Clarify the use of exception in the conversion API [SPR-11500]

[spring-projects-issues]

Benjamin M opened SPR-11500 and commented

The Converters documentation ( http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html ) says:

"Your Converter may throw any Exception if conversion fails. An IllegalArgumentException should be thrown to report an invalid source value."

BUT: I cannot use ANY Exception, the Exception to use must be a RuntimeException.

This doesn't work:

public class MyConverter implements Converter<A, B> {
@Override
public B convert(A a) {
throw new Exception();
}
}

Eclipse says: "Unhandled exception type Exception"

But this works:

public class MyConverter implements Converter<A, B> {
@Override
public B convert(A a) {
throw new RuntimeException();
}
}

---

Affects: 4.0.2

Referenced from: commits 035d9d5

[spring-projects-issues]

Stéphane Nicoll commented

That's because the convert method does not declare any checked exception so you have to use an unchecked exception, RuntimeException being the root of unchecked exceptions.

I am not sure that this requires an update in the documentation as this is more a feature of the language, i.e. throw any Exception means any exception you're allowed in the context of the method. Maybe Exception should be written lower case to reduce the confusion.

I'll see what I can do. Note that IllegalArgumentException is an unchecked exception so that will work fine.

[spring-projects-issues]

Stéphane Nicoll commented

I've slightly updated the doc in 035d9d5af091

Thanks for the report.