Update documentation to explicitly mention that JSR-303 annotations won't be used when binding with ValueProvider.

[dve]

• Vaadin version : 8.0.2
• Description of the bug
  If you bind a field to a bean property with validation annotations, one has to use BeanValidationBinder.bind(String) instead of BeanValidationBinder.bind(ValueProvider, Setter) because the later ones ignores the validation annotations.
• If possible, minimal reproducible example

import javax.validation.constraints.Size;

import com.vaadin.data.BeanValidationBinder;
import com.vaadin.data.Binder;
import com.vaadin.ui.TextField;

public class Test {
	private TextField textField;
	private Bean value;

	public static class Bean {
		@Size(min = 3)
		private String property;

		public String getProperty() {
			return property;
		}

		public void setProperty(String property) {
			this.property = property;
		}
	}

	public void buildForm() {
		Binder<Bean> binder = new BeanValidationBinder<>(Bean.class);
		// this works:
		// binder.forField(textField).bind("property");

		// but not this:
		binder.forField(textField).bind(Bean::getProperty, Bean::setProperty);

		binder.setBean(value);
	}
}
`

[Legioth]

Cannot do anything about this. There's nothing in Java that allows us to find those annotations based on Bean::getProperty or Bean::setProperty because of type erasure. When using "property" instead, we can use reflection based on the bean type to find everything needed.

The only thing we could do is to somehow improve documentation about this limitation.

[dve]

What about guessing it:

1. strip is/set/get from method names
2. check if both striped method names are the same
3. make the first letter lower case
4. if there is a property with that name use it

The only thing we could do is to somehow improve documentation about this limitation

That should be definitely done: it took me some time to find out why validators are ignored.

[Legioth]

The method name is not known either. The Java compiler changes Bean::getProperty into something similar to bean -> bean.getProperty() which for the implementation of the bind method looks like any other implementation of the ValueProvider interface.

That should be definitely done: it took me some time to find out why validators are ignored.

Where in the documentation would it has been most useful to mention this? I'm just trying to figure out what would be the most impactful place(s) to add it.

[dve]

Ok, I did not know about the javac behavior .

It should be in the java doc of Binder#bind and in the Book of Vaadin.

[Legioth]

The problem with Binder#bind javadocs is that that the same javadocs are shared between the regular Binder and BeanValidationBinder. It might still make sense to add it there, but anything such would be only "overhead" from the perspective of someone who doesn't use bean validation annotations.

I was actually assuming that this was already covered by Book of Vaadin, but I cannot find it explicitly mentioned anywhere. I guess https://vaadin.com/docs/-/part/framework/datamodel/datamodel-forms.html#datamodel.forms.beans would be the natural place to mention it there.

[dve]

The link to the docs is where I would also place it. If you think its too much overhead for "non annotations user" then place it in the class level javadoc of BeanValidationBinder - I took a look into it ;-)

Is there at all a senece in using BeanValidationBinder.bind(ValueProvider, Setter)? If not maybe a waring in the log would be nice.

[Legioth]

BeanValidationBinder.bind(ValueProvider, Setter) is still useful if you also have a "computed property" that you want to bind, even though use is most likely quite uncommon.

[stadler]

+1 Please update the documentation. It is really frustrating to try to get this to work and in the end discover that it doesn't work due to a known limitation.

[NBau]

Additionally, it would be nice to allow the use of BeanValidationBinder.bind(ValueProvider, Setter, AnnotatedElement) for cases where the getter and setter need special handling (e.g. some JAXB generated beans do not follow strict bean rules).

[stale]

Hello there!

It looks like this issue hasn't progressed lately. There are so many issues that we just can't deal them all within a reasonable timeframe.

There are a couple of things you could help to get things rolling on this issue (this is an automated message, so expect that some of these are already in use):

• Check if the issue is still valid for the latest version. There are dozens of duplicates in our issue tracker, so it is possible that the issue is already tackled. If it appears to be fixed, close the issue, otherwise report to the issue that it is still valid.
• Provide more details how to reproduce the issue.
• Explain why it is important to get this issue fixed and politely draw others attention to it e.g. via the forum or social media.
• Add a reduced test case about the issue, so it is easier for somebody to start working on a solution.
• Try fixing the issue yourself and create a pull request that contains the test case and/or a fix for it. Handling the pull requests is the top priority for the core team.
• If the issue is clearly a bug, use the Warranty in your Vaadin subscription to raise its priority.

Thanks again for your contributions! Even though we haven't been able to get this issue fixed, we hope you to report your findings and enhancement ideas in the future too!