Package jsonschema provides json-schema compilation and validation.

Benchmarks

• implements draft 2020-12, draft 2019-09, draft-7, draft-6, draft-4
• fully compliant with JSON-Schema-Test-Suite, (excluding some optional)
  • list of optional tests that are excluded can be found in schema_test.go(variable skipTests)
• validates schemas against meta-schema
• full support of remote references
• support of recursive references between schemas
• detects infinite loop in schemas
• thread safe validation
• rich, intuitive hierarchial error messages with json-pointers to exact location
• supports output formats flag, basic and detailed
• supports enabling format and content Assertions in draft2019-09 or above
  • change Compiler.AssertFormat, Compiler.AssertContent to true
• compiled schema can be introspected. easier to develop tools like generating go structs given schema
• supports user-defined keywords via extensions
• implements following formats (supports user-defined)
  • date-time, date, time, duration, period (supports leap-second)
  • uuid, hostname, email
  • ip-address, ipv4, ipv6
  • uri, uriref, uri-template(limited validation)
  • json-pointer, relative-json-pointer
  • regex, format
• implements following contentEncoding (supports user-defined)
  • base64
• implements following contentMediaType (supports user-defined)
  • application/json
• can load from files/http/https/string/[]byte/io.Reader (supports user-defined)

see examples in godoc

The schema is compiled against the version specified in $schema property. If "$schema" property is missing, it uses latest draft which currently implemented by this library.

You can force to use specific version, when $schema is missing, as follows:

compiler := jsonschema.NewCompiler()
compiler.Draft = jsonschema.Draft4

This package supports loading json-schema from filePath and fileURL.

To load json-schema from HTTPURL, add following import:

import _ "github.com/santhosh-tekuri/jsonschema/v5/httploader"

The ValidationError returned by Validate method contains detailed context to understand why and where the error is.

schema.json:

{
      "$ref": "t.json#/definitions/employee"
}

t.json:

{
    "definitions": {
        "employee": {
            "type": "string"
        }
    }
}

doc.json:

1

assuming err is the ValidationError returned when doc.json validated with schema.json,

fmt.Printf("%#v\n", err) // using %#v prints errors hierarchy

Prints:

[I#] [S#] doesn't validate with file:///Users/santhosh/jsonschema/schema.json#
  [I#] [S#/$ref] doesn't validate with 'file:///Users/santhosh/jsonschema/t.json#/definitions/employee'
    [I#] [S#/definitions/employee/type] expected string, but got number

Here I stands for instance document and S stands for schema document.
The json-fragments that caused error in instance and schema documents are represented using json-pointer notation.
Nested causes are printed with indent.

To output err in flag output format:

b, _ := json.MarshalIndent(err.FlagOutput(), "", "  ")
fmt.Println(string(b))

Prints:

{
  "valid": false
}

To output err in basic output format:

b, _ := json.MarshalIndent(err.BasicOutput(), "", "  ")
fmt.Println(string(b))

Prints:

{
  "valid": false,
  "errors": [
    {
      "keywordLocation": "",
      "absoluteKeywordLocation": "file:///Users/santhosh/jsonschema/schema.json#",
      "instanceLocation": "",
      "error": "doesn't validate with file:///Users/santhosh/jsonschema/schema.json#"
    },
    {
      "keywordLocation": "/$ref",
      "absoluteKeywordLocation": "file:///Users/santhosh/jsonschema/schema.json#/$ref",
      "instanceLocation": "",
      "error": "doesn't validate with 'file:///Users/santhosh/jsonschema/t.json#/definitions/employee'"
    },
    {
      "keywordLocation": "/$ref/type",
      "absoluteKeywordLocation": "file:///Users/santhosh/jsonschema/t.json#/definitions/employee/type",
      "instanceLocation": "",
      "error": "expected string, but got number"
    }
  ]
}

To output err in detailed output format:

b, _ := json.MarshalIndent(err.DetailedOutput(), "", "  ")
fmt.Println(string(b))

Prints:

{
  "valid": false,
  "keywordLocation": "",
  "absoluteKeywordLocation": "file:///Users/santhosh/jsonschema/schema.json#",
  "instanceLocation": "",
  "errors": [
    {
      "valid": false,
      "keywordLocation": "/$ref",
      "absoluteKeywordLocation": "file:///Users/santhosh/jsonschema/schema.json#/$ref",
      "instanceLocation": "",
      "errors": [
        {
          "valid": false,
          "keywordLocation": "/$ref/type",
          "absoluteKeywordLocation": "file:///Users/santhosh/jsonschema/t.json#/definitions/employee/type",
          "instanceLocation": "",
          "error": "expected string, but got number"
        }
      ]
    }
  ]
}

to install go install github.com/santhosh-tekuri/jsonschema/cmd/jv@latest

jv [-draft INT] [-output FORMAT] [-assertformat] [-assertcontent] <json-schema> [<json-or-yaml-doc>]...
  -assertcontent
    	enable content assertions with draft >= 2019
  -assertformat
    	enable format assertions with draft >= 2019
  -draft int
    	draft used when '$schema' attribute is missing. valid values 4, 5, 7, 2019, 2020 (default 2020)
  -output string
    	output format. valid values flag, basic, detailed

if no <json-or-yaml-doc> arguments are passed, it simply validates the <json-schema>.
if $schema attribute is missing in schema, it uses latest version. this can be overridden by passing -draft flag

exit-code is 1, if there are any validation errors

jv can also validate yaml files. It also accepts schema from yaml files.

since yaml supports non-string keys, such yaml documents are rendered as invalid json documents.

most yaml parser use map[interface{}]interface{} for object,
whereas json parser uses map[string]interface{}.

so we need to manually convert them to map[string]interface{}.
below code shows such conversion by toStringKeys function.

https://play.golang.org/p/Hhax3MrtD8r

NOTE: if you are using gopkg.in/yaml.v3, then you do not need such conversion. since this library returns map[string]interface{} if all keys are strings.