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This is a Java implementation of the JSON Schema Core Draft v4, v6, v7, v2019-09 and v2020-12 specification for JSON schema validation. This implementation supports Customizing Meta-Schemas, Vocabularies, Keywords and Formats.
In addition, OpenAPI 3 request/response validation is supported with the use of the appropriate meta-schema. For users who want to collect information from a JSON node based on the schema, the walkers can help. The JSON parser used is the Jackson parser. As it is a key component in our light-4j microservices framework to validate request/response against OpenAPI specification for light-rest-4j and RPC schema for light-hybrid-4j at runtime, performance is the most important aspect in the design.
Information on the compatibility support for each version, including known issues, can be found in the Compatibility with JSON Schema versions document.
Since Draft 2019-09 the format keyword only generates annotations by default and does not generate assertions.
This behavior can be overridden to generate assertions by setting the setFormatAssertionsEnabled to true in SchemaValidatorsConfig or ExecutionConfig.
This library can contain breaking changes in minor version releases that may require code changes.
Information on notable or breaking changes when upgrading the library can be found in the Upgrading to new versions document.
The Releases page will contain information on the latest versions.
The JSON Schema Validation Comparison project from Creek has an informative Comparison of JVM based Schema Validation Implementations which compares both the functional and performance characteristics of a number of different Java implementations.
The Bowtie project has a report that compares functional characteristics of different implementations, including non-Java implementations, but does not do any performance benchmarking.
This should be the fastest Java JSON Schema Validator implementation.
The following is the benchmark results from the JSON Schema Validator Perftest project that uses the Java Microbenchmark Harness.
Note that the benchmark results are highly dependent on the input data workloads and schemas used for the validation.
In this case this workload is using the Draft 4 specification and largely tests the performance of the evaluating the properties keyword. You may refer to Results of performance comparison of JVM based JSON Schema Validation Implementations for benchmark results for more typical workloads
If performance is an important consideration, the specific sample workloads should be benchmarked, as there are different performance characteristics when certain keywords are used. For instance the use of the unevaluatedProperties or unevaluatedItems keyword will trigger annotation collection in the related validators, such as the properties or items validators, and annotation collection will adversely affect performance.
Benchmark Mode Cnt Score Error Units
NetworkntBenchmark.testValidate thrpt 10 6776.693 ± 115.309 ops/s
NetworkntBenchmark.testValidate:·gc.alloc.rate thrpt 10 971.191 ± 16.420 MB/sec
NetworkntBenchmark.testValidate:·gc.alloc.rate.norm thrpt 10 165318.816 ± 0.459 B/op
NetworkntBenchmark.testValidate:·gc.churn.G1_Eden_Space thrpt 10 968.894 ± 51.234 MB/sec
NetworkntBenchmark.testValidate:·gc.churn.G1_Eden_Space.norm thrpt 10 164933.962 ± 8636.203 B/op
NetworkntBenchmark.testValidate:·gc.churn.G1_Survivor_Space thrpt 10 0.002 ± 0.001 MB/sec
NetworkntBenchmark.testValidate:·gc.churn.G1_Survivor_Space.norm thrpt 10 0.274 ± 0.218 B/op
NetworkntBenchmark.testValidate:·gc.count thrpt 10 89.000 counts
NetworkntBenchmark.testValidate:·gc.time thrpt 10 99.000 ms
Benchmark Mode Cnt Score Error Units
EveritBenchmark.testValidate thrpt 10 3719.192 ± 125.592 ops/s
EveritBenchmark.testValidate:·gc.alloc.rate thrpt 10 1448.208 ± 74.746 MB/sec
EveritBenchmark.testValidate:·gc.alloc.rate.norm thrpt 10 449621.927 ± 7400.825 B/op
EveritBenchmark.testValidate:·gc.churn.G1_Eden_Space thrpt 10 1446.397 ± 79.919 MB/sec
EveritBenchmark.testValidate:·gc.churn.G1_Eden_Space.norm thrpt 10 449159.799 ± 18614.931 B/op
EveritBenchmark.testValidate:·gc.churn.G1_Survivor_Space thrpt 10 0.001 ± 0.001 MB/sec
EveritBenchmark.testValidate:·gc.churn.G1_Survivor_Space.norm thrpt 10 0.364 ± 0.391 B/op
EveritBenchmark.testValidate:·gc.count thrpt 10 133.000 counts
EveritBenchmark.testValidate:·gc.time thrpt 10 148.000 ms
This implementation is tested against the JSON Schema Test Suite. As tests are continually added to the suite, these test results may not be current.
| Implementations | Overall | DRAFT_03 | DRAFT_04 | DRAFT_06 | DRAFT_07 | DRAFT_2019_09 | DRAFT_2020_12 |
|---|---|---|---|---|---|---|---|
| NetworkNt | pass: r:4703 (100.0%) o:2369 (100.0%) fail: r:0 (0.0%) o:1 (0.0%) |
pass: r:600 (100.0%) o:251 (100.0%) fail: r:0 (0.0%) o:0 (0.0%) |
pass: r:796 (100.0%) o:318 (100.0%) fail: r:0 (0.0%) o:0 (0.0%) |
pass: r:880 (100.0%) o:541 (100.0%) fail: r:0 (0.0%) o:0 (0.0%) |
pass: r:1201 (100.0%) o:625 (100.0%) fail: r:0 (0.0%) o:0 (0.0%) |
pass: r:1226 (100.0%) o:634 (99.8%) fail: r:0 (0.0%) o:1 (0.2%) |
- Note that this uses the ECMA 262 Validator option turned on for the
patterntests.
This library uses Jackson which is a Java JSON parser that is widely used in other projects. If you are already using the Jackson parser in your project, it is natural to choose this library over others for schema validation.
The library works with JSON and YAML on both schema definitions and input data.
The OpenAPI 3.0 specification is using JSON schema to validate the request/response, but there are some differences. With a configuration file, you can enable the library to work with OpenAPI 3.0 validation.
Following the design principle of the Light Platform, this library has minimal dependencies to ensure there are no dependency conflicts when using it.
The following are the dependencies that will automatically be included when this library is included.
<dependency>
<!-- Used for logging -->
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>${version.slf4j}</version>
</dependency>
<dependency>
<!-- Used to process JSON -->
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${version.jackson}</version>
</dependency>
<dependency>
<!-- Used to process YAML -->
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-yaml</artifactId>
<version>${version.jackson}</version>
</dependency>
<dependency>
<!-- Used to validate RFC 3339 date and date-time -->
<groupId>com.ethlo.time</groupId>
<artifactId>itu</artifactId>
<version>${version.itu}</version>
</dependency>The following are the optional dependencies that may be required for certain options.
These are not automatically included and setting the relevant option without adding the library will result in a ClassNotFoundException.
<!-- This is required when setting setEcma262Validator(true) -->
<dependency>
<!-- Used to validate ECMA 262 regular expressions -->
<groupId>org.jruby.joni</groupId>
<artifactId>joni</artifactId>
<version>${version.joni}</version>
<optional>true</optional>
</dependency>The following are required dependencies that are automatically included, but can be explicitly excluded if they are not required.
The YAML dependency can be excluded if this is not required. Attempting to process schemas or input that are YAML will result in a ClassNotFoundException.
<dependency>
<groupId>com.networknt</groupId>
<artifactId>json-schema-validator</artifactId>
<exclusions>
<exclusion>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-yaml</artifactId>
</exclusion>
</exclusions>
</dependency>The Ethlo Time dependency can be excluded if accurate validation of the date-time format is not required. The date-time format will then use java.time.OffsetDateTime to determine if the date-time is valid .
<dependency>
<groupId>com.networknt</groupId>
<artifactId>json-schema-validator</artifactId>
<exclusions>
<exclusion>
<groupId>com.ethlo.time</groupId>
<artifactId>itu</artifactId>
</exclusion>
</exclusions>
</dependency>This library is very active with a lot of contributors. New features and bug fixes are handled quickly by the team members. Because it is an essential dependency of the light-4j framework in the same GitHub organization, it will be evolved and maintained along with the framework.
The library supports Java 8 and up. If you want to build from the source code, you need to install JDK 8 locally. To support multiple version of JDK, you can use SDKMAN
This package is available on Maven central.
<dependency>
<groupId>com.networknt</groupId>
<artifactId>json-schema-validator</artifactId>
<version>1.4.0</version>
</dependency>dependencies {
implementation(group: 'com.networknt', name: 'json-schema-validator', version: '1.4.0');
}The following example demonstrates how inputs are validated against a schema. It comprises the following steps.
- Creating a schema factory with the default schema dialect and how the schemas can be retrieved.
- Configuring mapping the
$idto a retrieval URI usingschemaMappers. - Configuring how the schemas are loaded using the retrieval URI using
schemaLoaders. For instance aMap<String, String> schemascontaining a mapping of retrieval URI to schema data as aStringcan by configured usingbuilder.schemaLoaders(schemaLoaders -> schemaLoaders.schemas(schemas)). This also accepts aFunction<String, String> schemaRetrievalFunction.
- Configuring mapping the
- Creating a configuration for controlling validator behavior.
- Loading a schema from a schema location along with the validator configuration.
- Using the schema to validate the data along with setting any execution specific configuration like for instance the locale or whether format assertions are enabled.
// This creates a schema factory that will use Draft 2020-12 as the default if $schema is not specified
// in the schema data. If $schema is specified in the schema data then that schema dialect will be used
// instead and this version is ignored.
JsonSchemaFactory jsonSchemaFactory = JsonSchemaFactory.getInstance(VersionFlag.V202012, builder ->
// This creates a mapping from $id which starts with https://www.example.org/ to the retrieval URI classpath:schema/
builder.schemaMappers(schemaMappers -> schemaMappers.mapPrefix("https://www.example.org/", "classpath:schema/"))
);
SchemaValidatorsConfig config = new SchemaValidatorsConfig();
// By default JSON Path is used for reporting the instance location and evaluation path
config.setPathType(PathType.JSON_POINTER);
// By default the JDK regular expression implementation which is not ECMA 262 compliant is used
// Note that setting this to true requires including the optional joni dependency
// config.setEcma262Validator(true);
// Due to the mapping the schema will be retrieved from the classpath at classpath:schema/example-main.json.
// If the schema data does not specify an $id the absolute IRI of the schema location will be used as the $id.
JsonSchema schema = jsonSchemaFactory.getSchema(SchemaLocation.of("https://www.example.org/example-main.json"), config);
String input = "{\r\n"
+ " \"main\": {\r\n"
+ " \"common\": {\r\n"
+ " \"field\": \"invalidfield\"\r\n"
+ " }\r\n"
+ " }\r\n"
+ "}";
Set<ValidationMessage> assertions = schema.validate(input, InputFormat.JSON, executionContext -> {
// By default since Draft 2019-09 the format keyword only generates annotations and not assertions
executionContext.getExecutionConfig().setFormatAssertionsEnabled(true);
});The following example demonstrates how a schema is validated against a meta-schema.
This is actually the same as validating inputs against a schema except in this case the input is the schema and the schema used is the meta-schema.
Note that the meta-schemas for Draft 4, Draft 6, Draft 7, Draft 2019-09 and Draft 2020-12 are bundled with the library and these classpath resources will be used by default.
JsonSchemaFactory jsonSchemaFactory = JsonSchemaFactory.getInstance(VersionFlag.V202012);
SchemaValidatorsConfig config = new SchemaValidatorsConfig();
// By default JSON Path is used for reporting the instance location and evaluation path
config.setPathType(PathType.JSON_POINTER);
// By default the JDK regular expression implementation which is not ECMA 262 compliant is used
// Note that setting this to true requires including the optional joni dependency
// config.setEcma262Validator(true);
// Due to the mapping the meta-schema will be retrieved from the classpath at classpath:draft/2020-12/schema.
JsonSchema schema = jsonSchemaFactory.getSchema(SchemaLocation.of(SchemaId.V202012), config);
String input = "{\r\n"
+ " \"type\": \"object\",\r\n"
+ " \"properties\": {\r\n"
+ " \"key\": {\r\n"
+ " \"title\" : \"My key\",\r\n"
+ " \"type\": \"invalidtype\"\r\n"
+ " }\r\n"
+ " }\r\n"
+ "}";
Set<ValidationMessage> assertions = schema.validate(input, InputFormat.JSON, executionContext -> {
// By default since Draft 2019-09 the format keyword only generates annotations and not assertions
executionContext.getConfig().setFormatAssertionsEnabled(true);
});The following types of results are generated by the library.
| Type | Description |
|---|---|
| Assertions | Validation errors generated by a keyword on a particular input data instance. This is generally described in a ValidationMessage or in a OutputUnit. Note that since Draft 2019-09 the format keyword no longer generates assertions by default and instead generates only annotations unless configured otherwise using a configuration option or by using a meta-schema that uses the appropriate vocabulary. |
| Annotations | Additional information generated by a keyword for a particular input data instance. This is generally described in a OutputUnit. Annotation collection and reporting is turned off by default. Annotations required by keywords such as unevaluatedProperties or unevaluatedItems are always collected for evaluation purposes and cannot be disabled but will not be reported unless configured to do so. |
The following information is used to describe both types of results.
| Type | Description |
|---|---|
| Evaluation Path | This is the set of keys from the root through which evaluation passes to reach the schema for evaluating the instance. This includes $ref and $dynamicRef. eg. /properties/bar/$ref/properties/bar-prop |
| Schema Location | This is the canonical IRI of the schema plus the JSON pointer fragment to the schema that was used for evaluating the instance. eg. https://json-schema.org/schemas/example#/$defs/bar/properties/bar-prop |
| Instance Location | This is the JSON pointer fragment to the instance data that was being evaluated. eg. /bar/bar-prop |
Assertions contains the following additional information
| Type | Description |
|---|---|
| Message | The validation error message. |
| Code | The error code. |
| Message Key | The message key used for generating the message for localization. |
| Arguments | The arguments used for generating the message. |
| Type | The keyword that generated the message. |
| Property | The property name that caused the validation error for example for the required keyword. Note that this is not part of the instance location as that points to the instance node. |
| Schema Node | The JsonNode pointed to by the Schema Location. |
| Instance Node | The JsonNode pointed to by the Instance Location. |
| Details | Additional details that can be set by custom keyword validator implementations. This is not used by the library. |
Annotations contains the following additional information
| Type | Description |
|---|---|
| Value | The annotation value generated |
This library implements the Flag, List and Hierarchical output formats defined in the Specification for Machine-Readable Output for JSON Schema Validation and Annotation.
The List and Hierarchical output formats are particularly helpful for understanding how the system arrived at a particular result.
| Output Format | Description |
|---|---|
| Default | Generates the list of assertions. |
| Boolean | Returns true if the validation is successful. Note that the fail fast option is turned on by default for this output format. |
| Flag | Returns an OutputFlag object with valid having true if the validation is successful. Note that the fail fast option is turned on by default for this output format. |
| List | Returns an OutputUnit object with details with a list of OutputUnit objects with the assertions and annotations. Note that annotations are not collected by default and it has to be enabled as it will impact performance. |
| Hierarchical | Returns an OutputUnit object with a hierarchy of OutputUnit objects for the evaluation path with the assertions and annotations. Note that annotations are not collected by default and it has to be enabled as it will impact performance. |
The following example shows how to generate the hierarchical output format with annotation collection and reporting turned on and format assertions turned on.
JsonSchemaFactory factory = JsonSchemaFactory.getInstance(VersionFlag.V202012);
SchemaValidatorsConfig config = new SchemaValidatorsConfig();
config.setPathType(PathType.JSON_POINTER);
config.setFormatAssertionsEnabled(true);
JsonSchema schema = factory.getSchema(SchemaLocation.of("https://json-schema.org/schemas/example"), config);
OutputUnit outputUnit = schema.validate(inputData, InputFormat.JSON, OutputFormat.HIERARCHICAL, executionContext -> {
executionContext.getExecutionConfig().setAnnotationCollectionEnabled(true);
executionContext.getExecutionConfig().setAnnotationCollectionFilter(keyword -> true);
});The following is sample output from the Hierarchical format.
{
"valid" : false,
"evaluationPath" : "",
"schemaLocation" : "https://json-schema.org/schemas/example#",
"instanceLocation" : "",
"droppedAnnotations" : {
"properties" : [ "foo", "bar" ],
"title" : "root"
},
"details" : [ {
"valid" : false,
"evaluationPath" : "/properties/foo/allOf/0",
"schemaLocation" : "https://json-schema.org/schemas/example#/properties/foo/allOf/0",
"instanceLocation" : "/foo",
"errors" : {
"required" : "required property 'unspecified-prop' not found"
}
}, {
"valid" : false,
"evaluationPath" : "/properties/foo/allOf/1",
"schemaLocation" : "https://json-schema.org/schemas/example#/properties/foo/allOf/1",
"instanceLocation" : "/foo",
"droppedAnnotations" : {
"properties" : [ "foo-prop" ],
"title" : "foo-title",
"additionalProperties" : [ "foo-prop", "other-prop" ]
},
"details" : [ {
"valid" : false,
"evaluationPath" : "/properties/foo/allOf/1/properties/foo-prop",
"schemaLocation" : "https://json-schema.org/schemas/example#/properties/foo/allOf/1/properties/foo-prop",
"instanceLocation" : "/foo/foo-prop",
"errors" : {
"const" : "must be a constant value 1"
},
"droppedAnnotations" : {
"title" : "foo-prop-title"
}
} ]
}, {
"valid" : false,
"evaluationPath" : "/properties/bar/$ref",
"schemaLocation" : "https://json-schema.org/schemas/example#/$defs/bar",
"instanceLocation" : "/bar",
"droppedAnnotations" : {
"properties" : [ "bar-prop" ],
"title" : "bar-title"
},
"details" : [ {
"valid" : false,
"evaluationPath" : "/properties/bar/$ref/properties/bar-prop",
"schemaLocation" : "https://json-schema.org/schemas/example#/$defs/bar/properties/bar-prop",
"instanceLocation" : "/bar/bar-prop",
"errors" : {
"minimum" : "must have a minimum value of 10"
},
"droppedAnnotations" : {
"title" : "bar-prop-title"
}
} ]
} ]
}| Name | Description | Default Value |
|---|---|---|
annotationCollectionEnabled |
Controls whether annotations are collected during processing. Note that collecting annotations will adversely affect performance. | false |
annotationCollectionFilter |
The predicate used to control which keyword to collect and report annotations for. This requires annotationCollectionEnabled to be true. |
keyword -> false |
locale |
The locale to use for generating messages in the ValidationMessage. Note that this value is copied from SchemaValidatorsConfig for each execution. |
Locale.getDefault() |
failFast |
Whether to return failure immediately when an assertion is generated. Note that this value is copied from SchemaValidatorsConfig for each execution but is automatically set to true for the Boolean and Flag output formats. |
false |
formatAssertionsEnabled |
The default is to generate format assertions from Draft 4 to Draft 7 and to only generate annotations from Draft 2019-09. Setting to true or false will override the default behavior. |
null |
| Name | Description | Default Value |
|---|---|---|
pathType |
The path type to use for reporting the instance location and evaluation path. Set to PathType.JSON_POINTER to use JSON Pointer. |
PathType.DEFAULT |
ecma262Validator |
Whether to use the ECMA 262 joni library to validate the pattern keyword. This requires the dependency to be manually added to the project or a ClassNotFoundException will be thrown. |
false |
executionContextCustomizer |
This can be used to customize the ExecutionContext generated by the JsonSchema for each validation run. |
null |
schemaIdValidator |
This is used to customize how the $id values are validated. Note that the default implementation allows non-empty fragments where no base IRI is specified and also allows non-absolute IRI $id values in the root schema. |
JsonSchemaIdValidator.DEFAULT |
messageSource |
This is used to retrieve the locale specific messages. | DefaultMessageSource.getInstance() |
preloadJsonSchema |
Whether the schema will be preloaded before processing any input. This will use memory but the execution of the validation will be faster. | true |
preloadJsonSchemaRefMaxNestingDepth |
The max depth of the evaluation path to preload when preloading refs. | 40 |
cacheRefs |
Whether the schemas loaded from refs will be cached and reused for subsequent runs. Setting this to false will affect performance but may be neccessary to prevent high memory usage for the cache if multiple nested applicators like anyOf, oneOf and allOf are used. |
true |
locale |
The locale to use for generating messages in the ValidationMessage. |
Locale.getDefault() |
failFast |
Whether to return failure immediately when an assertion is generated. | false |
formatAssertionsEnabled |
The default is to generate format assertions from Draft 4 to Draft 7 and to only generate annotations from Draft 2019-09. Setting to true or false will override the default behavior. |
null |
When the library creates a schema from the schema factory, it creates a distinct validator instance for each location on the evaluation path. This means if there are different $ref that reference the same schema location, different validator instances are created for each evaluation path.
When the schema is created, the library will automatically preload all the validators needed and resolve references. At this point, no exceptions will be thrown if a reference cannot be resolved. If there are references that are cyclic, only the first cycle will be preloaded. If you wish to ensure that remote references can all be resolved, the initializeValidators method needs to be called on the JsonSchema which will throw an exception if there are references that cannot be resolved.
The JsonSchema created from the factory should be cached and reused. Not reusing the JsonSchema means that the schema data needs to be repeated parsed with validator instances created and references resolved.
Collecting annotations will adversely affect validation performance.
The earlier draft specifications contain less keywords that can potentially impact performance. For instance the use of the unevaluatedProperties or unevaluatedItems keyword will trigger annotation collection in the related validators, such as the properties or items validators.
This does not mean that using a schema with a later draft specification will automatically cause a performance impact. For instance, the properties validator will perform checks to determine if annotations need to be collected, and checks if the meta-schema contains the unevaluatedProperties keyword and whether the unevaluatedProperties keyword exists adjacent the evaluation path.
The light-rest-4j, light-graphql-4j and light-hybrid-4j use this library to validate the request and response based on the specifications. If you are using other frameworks like Spring Boot, you can use the OpenApiValidator, a generic OpenAPI 3.0 validator based on the OpenAPI 3.0 specification.
If you have a project using this library, please submit a PR to add your project below.
Thanks to the following people who have contributed to this project. If you are using this library, please consider to be a sponsor for one of the contributors.
For all contributors, please visit https://github.com/networknt/json-schema-validator/graphs/contributors
If you are a contributor, please join the GitHub Sponsors and switch the link to your sponsors dashboard via a PR.
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