3.2 Limit Depth

Query Dynamic Entities

Java

TreeNodeTable table = TreeNodeTable.$;

List<TreeNode> rootNodes = sqlClient
    .createQuery(table)
    .where(table.parentId().isNull())
    .select(
        table.fetch(
            TreeNodeFetcher.$
                .allScalarFields()
                .recursiveChildNodes(
                    cfg -> cfg.depth(2)
                )
        )
    )
    .execute();

Kotlin

val rootNodes = sqlClient
    .createQuery(TreeNode::class) {
        where(table.parentId.isNull())
        select(
            table.fetchBy {
                allScalarFields()
                `childNodes*` {
                    depth(2)
                }
            }
        )
    }
    .execute()

The currently queried aggregate roots are defined as the 0th layer. On this basis, query two layers of child objects downwards to obtain the following data:

[
    {
        "id":1,
        "name":"Home",
        "childNodes":[
            {
                "id":2,
                "name":"Food",
                "childNodes":[
                    {"id":3,"name":"Drinks"},
                    {"id":6,"name":"Bread"}
                ]
            },
            {
                "id":9,
                "name":"Clothing",
                "childNodes":[
                    {"id":10,"name":"Woman"},
                    {"id":18,"name":"Man"}
                ]
            }
        ]
    }
]

info

The deepest 4 objects do not have the childNodes property as [], but do not have the childNodes property at all.

This means whether these 4 objects have subordinate objects is unknown, because the recursion process was prematurely terminated due to manual intervention.

Query Static DTO

Create a file with a .dto extension in the src/main/dto folder and edit the code as follows:

export com.yourcompany.yourproject.model.TreeNode
    -> package com.yourcompany.yourproject.model.dto

RecursiveTreeNodeView {
    #allScalars(this)
    
    !depth(2)
    childNodes*
}

Compile the project to generate the Java/Kotlin type RecursiveTreeNodeView

Java

TreeNodeTable table = TreeNodeTable.$;

List<RecursiveTreeNodeView> rootNodes = sqlClient
    .createQuery(table)
    .where(table.parentId().isNull())
    .select(
        table.fetch(RecursiveTreeNodeView.class)
    )
    .execute();

Kotlin

val rootNodes = sqlClient
    .createQuery(TreeNode::class) {
        where(table.parentId.isNull())
        select(
            table.fetch(RecursiveTreeNodeView::class)
        )
    }
    .execute()

You'll get the following result:

[
    RecursiveTreeNodeView(
        id=1, 
        name=Home, 
        childNodes=[
            RecursiveTreeNodeView(
                id=9, 
                name=Clothing, 
                childNodes=[
                    RecursiveTreeNodeView(
                        id=18, 
                        name=Man, 
                        childNodes=null
                    ), 
                    RecursiveTreeNodeView(
                        id=10, 
                        name=Woman, 
                        childNodes=null
                    )
                ]
            ), 
            RecursiveTreeNodeView(
                id=2, 
                name=Food, 
                childNodes=[
                    RecursiveTreeNodeView(
                        id=6, 
                        name=Bread, 
                        childNodes=null
                    ), 
                    RecursiveTreeNodeView(
                        id=3, 
                        name=Drinks, 
                        childNodes=null
                    )
                ]
            )
        ]
    )
]