3.2 Control Recursion Of Node

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.recursive(it -> {
                        return !it.getEntity().name().equals("Clothing");
                    });
                })
        )
    )
    .execute();

Kotlin

val rootNodes = sqlClient
    .createQuery(TreeNode::class) {
        where(table.parentId.isNull())
        select(
            table.fetchBy {
                allScalarFields()
                `childNodes*` {
                    recursive {
                        entity.name != "Clothing"
                    }
                }
            }
        )
    }
    .execute()

If the name of the current tree node is equal to Clothing, terminate the recursion, otherwise continue recursion. The result is as follows:

[
    {
        "id":1,
        "name":"Home",
        "childNodes":[
            {
                "id":2,
                "name":"Food",
                "childNodes":[
                    {
                        "id":3,
                        "name":"Drinks",
                        "childNodes":[
                            {
                                "id":4,
                                "name":"Coca Cola",
                                "childNodes":[]
                            },
                            {
                                "id":5,
                                "name":"Fanta",
                                "childNodes":[]
                            }
                        ]
                    },
                    {
                        "id":6,
                        "name":"Bread",
                        "childNodes":[
                            {
                                "id":7,
                                "name":"Baguette",
                                "childNodes":[]
                            },
                            {
                                "id":8,
                                "name":"Ciabatta",
                                "childNodes":[]
                            }
                        ]
                    }
                ]
            },
            {"id":9,"name":"Clothing"}
        ]
    }
]

info

The Clothing object does not have the childNodes property as [], but does not have the childNodes property at all.

This means whether the Clothing object has subordinate objects is unknown, because the recursion process was prematurely terminated due to manual intervention.

Query Static DTO

Create a ChildNodesPropFilter class that implements the org.babyfish.jimmer.sql.fetcher.RecursionStrategy<E> interface

Java

ChildNodesRecursionStrategy.java

package com.yourcompany.yourpackage.strategy;

...omitted import statements...

public class ChildNodesRecursionStrategy implements RecursionStrategy<TreeNode> {

    @Override
    public boolean isRecursive(Args<TreeNode> args) {
        return !args.getEntity().name().equals("Clothing");
    }
}

Kotlin

ChildNodesRecursionStrategy.kt

package com.yourcompany.yourpackage.strategy

...omitted import statements...

class ChildNodesRecursionStrategy : RecursionStrategy<TreeNode> {
    override fun isRecursive(args: RecursionStrategy.Args<TreeNode>): Boolean {
        return args.entity.name != "Clothing"
    }
}

In the src/main/dto folder, create a file with a .dto extension and edit the code as follows:

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

import com.yourcompany.yourpackage.strategy.ChildNodesRecursionStrategy

RecursiveTreeNodeView {
    #allScalars(this)
    
    !recursion(ChildNodesRecursionStrategy)
    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=null
            ), 
            RecursiveTreeNodeView(
                id=2, 
                name=Food, 
                childNodes=[
                    RecursiveTreeNodeView(
                        id=6, 
                        name=Bread, 
                        childNodes=[
                            RecursiveTreeNodeView(
                                id=7, 
                                name=Baguette, 
                                childNodes=[]
                            ), 
                            RecursiveTreeNodeView(
                                id=8, 
                                name=Ciabatta, 
                                childNodes=[]
                            )
                        ]
                    ), 
                    RecursiveTreeNodeView(
                        id=3, 
                        name=Drinks, 
                        childNodes=[
                            RecursiveTreeNodeView(
                                id=4, 
                                name=Coca Cola, 
                                childNodes=[]
                            ), 
                            RecursiveTreeNodeView(
                                id=5, 
                                name=Fanta, 
                                childNodes=[]
                            )
                        ]
                    )
                ]
            )
        ]
    )
]