JarCastingjddf-java 
Documentation on JavaDoc.io: https://javadoc.io/doc/io.jddf.gson/jddf-gson
This package is a Java implementation of JSON Data Definition Format. In particular, it lets you:
- Validate input data is valid against a JDDF schema,
- Get a list of validation errors from that input data, and
- Build your own tooling on top of JSON Data Definition Format
This package integrates with Google's gson, a popular JSON implementation for Java. If you would like support for another JSON implementation for Java, please open a GitHub ticket! Your request will be warmly welcomed.
Installation
If you're using Gradle:
dependencies {
implementation 'io.jddf.gson:jddf-gson:0.1.2'
}
Or Maven:
<dependency>
<groupId>io.jddf.gson</groupId>
<artifactId>jddf-gson</artifactId>
<version>0.1.2</version>
</dependency>
Usage
The three most important classes offered by this package are:
Schema, which represents a JDDF schemaValidator, which can find validation errors of JSON data against instances ofSchema, andValidationError, which represents a single validation problem with the input.Validator#validatereturns a list of these.
Here's an example of all of this in action:
// You can use Gson to convert JSON input into a JDDF schema.
//
// You can also just construct an instance of Schema directly, and use the
// getter/setter methods yourself.
String schemaJson = "{\"properties\":" +
"{\"name\": {\"type\": \"string\"}," +
"\"age\": {\"type\": \"uint32\"}," +
"\"phones\": {\"elements\": {\"type\": \"string\"}}}}";
Gson gson = new Gson();
Schema schema = gson.fromJson(schemaJson, Schema.class);
// JsonElement is a class from Gson. It represents generic JSON data.
//
// This input data is completely valid against the schema we just constructed.
String inputOkJson = "{\"name\": \"John Doe\", \"age\": 43, \"phones\": [\"+44 1234567\", \"+44 2345678\"]}";
JsonElement inputOk = gson.fromJson(inputOkJson, JsonElement.class);
// This input data has problems. "name" is missing, "age" has the wrong type,
// and "phones[1]" has the wrong type.
String inputBadJson = "{\"age\": \"43\", \"phones\": [\"+44 1234567\", 442345678]}";
JsonElement inputBad = gson.fromJson(inputBadJson, JsonElement.class);
Validator validator = new Validator();
List<ValidationError> errorsOk = validator.validate(schema, inputOk);
List<ValidationError> errorsBad = validator.validate(schema, inputBad);
// inputOk satsfies the schema we're using, so we don't get any validation
// errors from it.
System.out.println(errorsOk.size()) // 0
// inputBad had three validation problems, and so we get back three errors.
System.out.println(errorsBad.size()) // 3
// The first error indicates that "name" is missing.
//
// []
// [properties, name]
System.out.println(errorsBad.get(0).getInstancePath());
System.out.println(errorsBad.get(0).getSchemaPath());
// The second error indicates that "age" has the wrong type.
//
// [age]
// [properties, age, type]
System.out.println(errorsBad.get(1).getInstancePath());
System.out.println(errorsBad.get(1).getSchemaPath());
// The second error indicates that "phones[1]" has the wrong type.
//
// [phones, 1]
// [properties, phones, elements, type]
System.out.println(errorsBad.get(2).getInstancePath());
System.out.println(errorsBad.get(2).getSchemaPath());
