Re: Click <-> Cayenne - multiselect <-> many to many relation

[Bob Schellink]

st...@gmx.de wrote:

thanks for the explanation and the example code.

Got it working, but i get an ognl.NoSuchPropertyException when 
form.saveChanges() is called.
I guess it's because, like you described, CayenneForm doesn't know about the 
to-many relation and is trying to access the normal setter for 
QuerySelect->name when the form is saved.

Is it save to ignore this Exeption or should/can i tell CayenneForm to ignore 
this particular field?


You *could* ignore it as the other properties are still copied, but 
you *should not* as your log will be filled with stack traces.

Form.copyTo and copyFrom maps fields to object properties based on 
their names. So you could either:

1 - rename the Field to not match the property e.g: 
QuerySelect("courseList") instead of QuerySelect("courses")

2 - override the Form.copyTo and copyFrom and exclude fields that 
should not be copied:

  public class MyPage extends BorderPage {

    private QuerySelect selectedCourses = new QuerySelect("courses");

    public MyPage() {
      CayenneForm form = new CayenneForm("form") {
        public void copyTo(Object object) {
          // Retrieve all fields for the Form and remove QuerySelect
          List fieldList = ContainerUtils.getInputFields(this);
          fieldList.remove(selectedCourses);

          ContainerUtils.copyContainerToObject(this, object, fieldList);
        }

        public void copyFrom(Object object) {
          // Retrieve all fields for the Form and remove QuerySelect
          List fieldList = ContainerUtils.getInputFields(this);
          fieldList.remove(selectedCourses);

          ContainerUtils.copyObjectToContainer(object, this, fieldList);
        }
      }

      ...
    }
  }

As you can see from #2 above, Form's copyTo and copyFrom methods 
delegates to ContainerUtils copying, so one can override these methods 
and manipulate the Fields before copying.


Hope this helps.

kind regards

bob