TreeGrid and multiple dataproviders Vaadin 8.1

Vaadin 6 / 7 / 8
1

Been fiddling past few days with the TreeGrid and I was wondering if there is a way to represent let’s say 2 different classes in a one Grid in a way that Class A is the root object and Class B is their parent. The amount of Class B may vary. Example:

Lets say that Class A is a workstation and Class B are the employees and I’d like to show data as follows:

  • Workstation Alpha
    [list]
  • Employer 1
  • Employer 2

    [/list]
  • Workstation Bravo
    [list]
  • ​Employer 1
  • Employer 2
  • Employer 3

    [/list]

I’m not even completely sure if TreeGrid is the proper way to show such data, but I as well tried the Tree component and it seems to have same limitations where I can only use one dataprovider and then the other class can’t be used since the dataprovider is for, lets say Class A. Any ideas?

EDIT: Made some progress. Now tackled with “java.lang.IllegalArgumentException: Cannot add the same item multiple times: Document name” Error message. Code below:

Tree<String> overviewTree = new Tree<>("ID-LIST");
        TreeData<String> dataReal = new TreeData<>();
        Attribute attribute = new Attribute();
        for (Metaclass m: metaclassList) {
        m.getId();
        m.getNimike();
        dataReal.addItems(null, m.getNimike());
       
        try {
for (Attribute a:DBcore.getInstance().loadAttributesALL()) {
a.getMcid();
a.getMaid();
if (a.getMcid() == m.getId()) {
dataReal.addItems(m.getNimike(), a.getNimike());
}
}
} catch (SQLException e) {
}
        }
        
        overviewTree.setDataProvider(new TreeDataProvider<>(dataReal));
mainlayout.addComponent(overviewTree);
2

As Java doesn’t (still :frowning: ) support proper union types, the only suggestions I can think of right now are either using a wrapper class or some typechecking / typecasting.

-Olli

3

Thank you for your response. I managed to actually have a workaround once again ^^. I fiddled with the Tree component, collected my 2 classes to different lists, List and List where A and B are the classnames. Once they are lists I just go through them, pick the info I want to display and convert it to string and dispaly it in the Tree treename. However, the problem I am now facing is that Tree-component cannot add the same item multiple times. For example I have a field named “Document name” in several different objects in class B. Once I try to list all of the class B objects in the tree, I get the error “Cannot add the same item multiple times: Document name” I wonder if there is a way to allow this?

Edited: To be precise, I get the following error message: java.lang.IllegalArgumentException: Cannot add the same item multiple times: Document name.

And the code I work with is the following :

 Tree<String> overviewTree = new Tree<>("ID-LISTA FOR REAL");
        TreeData<String> dataReal = new TreeData<>();
        Attribute attribute = new Attribute();
        for (Metaclass m: metaclassList) {
        m.getId();
        m.getNimike();
        dataReal.addItems(null, m.getNimike());
       
        try {
for (Attribute a:DBcore.getInstance().loadAttributesALL()) {
a.getMcid();
a.getMaid();
if (a.getMcid() == m.getId()) {
dataReal.addItems(m.getNimike(), a.getNimike());
}
}
} catch (SQLException e) {
}
        }
        
        overviewTree.setDataProvider(new TreeDataProvider<>(dataReal));

mainlayout.addComponent(overviewTree);
4

Nevermind… Figured it out. Just added an id field to the item → no duplicates.

5

EDIT: I was in the middle of typing a response, which wasn’t needed anymore, but just for completeness’s sake:

The exception comes from here:
https://github.com/vaadin/framework/blob/master/server/src/main/java/com/vaadin/data/TreeData.java#L179
 and the implementation of the contains method is here:
https://github.com/vaadin/framework/blob/master/server/src/main/java/com/vaadin/data/TreeData.java#L480
 - I think because two different String objects have the same hashcode, Strings won’t work as the TreeData type very well if you can have multiple entries with the same value.

6

Thank you Olli. Really appreciate your effort :slight_smile: