如何使用if/then/else实现JSON Schema依赖属性的对象/null条件校验

问题原因 #

你编写的Schema存在两个核心问题导致校验不生效：

• 错误使用topObj.ineligibleReason这种点路径作为properties的键，JSON Schema的properties仅识别当前校验层级的属性名，不支持跨层级路径写法
• else分支的myObject规则写在了根Schema层级，实际该属性隶属于topObj下，规则完全未命中

正确Schema配置 #

推荐将条件判断写到topObj的Schema定义内部，避免层级混淆，完整代码如下，兼容Postman内置的AJV校验规则：

{
  "type": "object",
  "properties": {
    "topObj": {
      "type": "object",
      "properties": {
        "subItem1": { "type": "string" },
        "subItem2": { "type": "string" },
        "ineligibleReason": { "type": "string" },
        "myObject": { "type": ["object", "null"] }
      },
      "required": ["subItem1", "subItem2", "ineligibleReason", "myObject"],
      "additionalProperties": false,
      // 条件判断直接写在topObj层级下，直接引用当前层级属性即可
      "if": {
        "properties": {
          "ineligibleReason": { "const": "" }
        },
        "required": ["ineligibleReason"]
      },
      "then": {
        "properties": {
          "myObject": {
            "type": "object",
            "properties": {
              "subObject1": { "type": "boolean" },
              "subObject2": { "type": "string" }
            },
            "required": ["subObject1", "subObject2"],
            "additionalProperties": false
          }
        }
      },
      "else": {
        "properties": {
          "myObject": { "type": "null" }
        }
      }
    }
  },
  "required": ["topObj"],
  "additionalProperties": false
}

校验逻辑说明 #

• 当ineligibleReason为空字符串时，触发then规则，要求myObject必须是包含指定子属性的对象，为null会校验失败
• 当ineligibleReason为非空字符串时，触发else规则，要求myObject必须为null，为对象会校验失败
  完全匹配你列出的校验规则要求。

内容的提问来源于stack exchange，提问作者Jim