FreeMarker-包含int的Handeling Json

Question

我正在尝试创建一个脚本，该脚本将检查id并导出其名称，但遇到以下情况；

---

FTL堆栈跟踪（“〜”表示与嵌套相关：]

-在以下位置失败：#assign services = {“ externalId”：1 [在第1行第1列的无名模板中]

<#list [services] as st><#if st.externalId == externalId>${st.name}</#if>
<#list st.children as nd<#if nd.externalId == externalId>${nd.name}</#if>
<#list nd.children as rd><#if rd.externalId == externalId>${rd.name}</#if>
<#list rd.children as th><#if th.externalId == externalId>${th.name}</#if>
<#list th.children as ths><#if ths.externalId == externalId>${ths.name}</#if>
<#list ths.children as thb><#if thb.externalId == externalId>${thb.name}</#if>
</#list></#list></#list></#list></#list></#list>`    

如果所有externalID都有数字，该脚本就可以正常工作，但是当它为null时也可以为null，但我得到一个错误；

<#assign services=
{
"externalId": 1,
"name": "one",
"children": [
    {
        "externalId": 2,
        "name": "two",
        "children": [ 
            {
                "externalId": null,
                "name": "three",
                "children": [
                   {
                             "externalId": 4,
                             "name": "four",
                             "children": [
                                {
                                         "externalId": 5,
                                         "name": "five",
                                         "children": []
                                }         ]
                    }       ]
            }]
     }]
}>      

我正在测试https://try.freemarker.apache.org/

请帮助！

Answer 1

在FreeMarker中，您（几乎）总是必须指定一个期望出现null -s的默认值。像：nd.externalId! == external会将nd.externalId视为空字符串。或者，当null为${th.name!'null'}时，null将打印th.name。