使用patternProperties进行JSON Schema校验失效问题求助

Hey Klaus, let's break down why your patternProperties rule isn't enforcing the key format you expect—there are a few small but critical issues in your schema that are causing the problem:

1. You're missing additionalProperties: false for the falMedia object #

When using patternProperties to define allowed key patterns, JSON Schema allows any extra keys that don't match the pattern by default (since additionalProperties defaults to true). To block non-matching keys, you need to explicitly set additionalProperties: false in the falMedia object schema. This tells the validator that only keys matching your regex are permitted.

2. additionalProperties is misplaced in the processedFile schema #

In your current schema, you've nested additionalProperties: false inside the properties block of processedFile—this is incorrect. It should be at the same level as type and properties to take effect.

3. The title field in falMedia sub-objects doesn't allow null #

Your schema defines "title": { "type": "string" }, but the first news item has title: null in its falMedia entries. This would cause a validation failure, so you need to update this to allow both string and null values, just like you did for the alternative field.

Corrected Schema #

Here's the fixed version of your schema with all these issues addressed:

{
  "$schema": "http://json-schema.org/draft-04/schema",
  "title": "FPÖ News",
  "description": "Schema for FPÖ News articles accessed by the mobile apps",
  "type": "array",
  "items": {
    "additionalProperties": false,
    "properties": {
      "bodytext": { "type": "string" },
      "datetime": { "type": "string" },
      "falMedia": {
        "anyOf": [
          {
            "type": "object",
            "patternProperties": {
              "^[0-9abcde]*$": {
                "type": "object",
                "properties": {
                  "alternative": { "type": ["null", "string"] },
                  "description": { "type": "string" },
                  "link": { "type": "string" },
                  "pid": { "type": "integer" },
                  "processedFile": {
                    "type": "object",
                    "properties": {
                      "publicUrl": { "type": "string" }
                    },
                    "additionalProperties": false
                  },
                  "title": { "type": ["string", "null"] },
                  "uid": { "type": "integer" }
                },
                "additionalProperties": false
              }
            },
            "additionalProperties": false
          },
          { "type": "array" }
        ]
      },
      "falRelatedFiles": { "type": "array" },
      "istopnews": { "type": "boolean" },
      "pid": { "type": "integer" },
      "teaser": { "type": ["string", "null"] },
      "title": { "type": "string" },
      "uid": { "type": "integer" }
    },
    "required": [ "bodytext", "datetime", "istopnews", "pid", "teaser", "title", "uid" ]
  }
}

How This Fixes Your Issue #

• Now, if you use a falMedia key that doesn't match ^[0-9abcde]*$ (like "invalid-key"), the validator will correctly reject the JSON because additionalProperties: false blocks unrecognized keys.
• The processedFile schema now properly enforces that only the publicUrl field is allowed.
• The title field in falMedia entries will accept null values, matching your sample JSON.

内容的提问来源于stack exchange，提问作者Klaus Hörmann-Engl