3.2 控制节点是否递归

查询动态实体

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()

如果当前树节点的名称等于Clothing则终止递归，否则继续递归。得到如下结果

[
    {
        "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"}
        ]
    }
]

信息

Clothing对象并非表现为childNodes属性为[]，而是根本没有childNodes属性。

这表示，Clothing对象是否有下级对象是未知的，因为递归过程因人为干预而被提前终止。

查询静态DTO

创建ChildNodesPropFilter类，实现org.babyfish.jimmer.sql.fetcher.RecursionStrategy<E>接口

Java

ChildNodesRecursionStrategy.java

package com.yourcompany.yourpackage.strategy;

...省略import语句...

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

...省略import语句...

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

在src/main/dto文件夹下新建任何一个扩展名为dto的文件，编辑代码如下

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

import com.yourcompany.yourpackage.strategy.ChildNodesRecursionStrategy

RecursiveTreeNodeView {
    #allScalars(this)
    
    !recursion(ChildNodesRecursionStrategy)
    childNodes*
}

编译项目，生成Java/Kotlin类型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()

得到如下结果

[
    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=[]
                            )
                        ]
                    )
                ]
            )
        ]
    )
]