private void writeActionDescriptors(
JsonGenerator jgen, String currentVocab, List<ActionDescriptor> actionDescriptors)
throws IOException, IntrospectionException {
for (ActionDescriptor actionDescriptor : actionDescriptors) {
jgen.writeStartObject(); // begin a hydra:Operation
final String semanticActionType = actionDescriptor.getSemanticActionType();
if (semanticActionType != null) {
jgen.writeStringField("@type", semanticActionType);
}
jgen.writeStringField("hydra:method", actionDescriptor.getHttpMethod());
final ActionInputParameter requestBodyInputParameter = actionDescriptor.getRequestBody();
if (requestBodyInputParameter != null) {
jgen.writeObjectFieldStart("hydra:expects"); // begin hydra:expects
final Class<?> clazz = requestBodyInputParameter.getParameterType();
final Expose classExpose = clazz.getAnnotation(Expose.class);
final String typeName;
if (classExpose != null) {
typeName = classExpose.value();
} else {
typeName = requestBodyInputParameter.getParameterType().getSimpleName();
}
jgen.writeStringField("@type", typeName);
jgen.writeArrayFieldStart("hydra:supportedProperty"); // begin hydra:supportedProperty
// TODO check need for actionDescriptor and requestBodyInputParameter here:
recurseSupportedProperties(
jgen,
currentVocab,
clazz,
actionDescriptor,
requestBodyInputParameter,
requestBodyInputParameter.getCallValue());
jgen.writeEndArray(); // end hydra:supportedProperty
jgen.writeEndObject(); // end hydra:expects
}
jgen.writeEndObject(); // end hydra:Operation
}
}
private void writeHydraVariableMapping(
JsonGenerator jgen,
@Nullable ActionDescriptor actionDescriptor,
Collection<String> variableNames)
throws IOException {
for (String requestParamName : variableNames) {
jgen.writeStartObject();
jgen.writeStringField("@type", "hydra:IriTemplateMapping");
jgen.writeStringField("hydra:variable", requestParamName);
if (actionDescriptor != null) {
jgen.writeBooleanField(
"hydra:required",
actionDescriptor.getAnnotatedParameter(requestParamName).isRequired());
jgen.writeStringField(
"hydra:property",
getExposedPropertyOrParamName(
actionDescriptor.getAnnotatedParameter(requestParamName)));
}
jgen.writeEndObject();
}
}
@Override
public void serialize(List<Link> links, JsonGenerator jgen, SerializerProvider serializerProvider)
throws IOException {
try {
Collection<Link> simpleLinks = new ArrayList<Link>();
Collection<Affordance> affordances = new ArrayList<Affordance>();
Collection<Link> templatedLinks = new ArrayList<Link>();
Collection<Affordance> templatedAffordances = new ArrayList<Affordance>();
Collection<Affordance> collectionAffordances = new ArrayList<Affordance>();
Link selfRel = null;
for (Link link : links) {
if (link instanceof Affordance) {
final Affordance affordance = (Affordance) link;
final List<ActionDescriptor> actionDescriptors = affordance.getActionDescriptors();
if (!actionDescriptors.isEmpty()) {
if (affordance.isTemplated()) {
templatedAffordances.add(affordance);
} else {
if (!affordance.isSelfRel()
&& Cardinality.COLLECTION == affordance.getCardinality()) {
collectionAffordances.add(affordance);
} else {
affordances.add(affordance);
}
}
} else {
if (affordance.isTemplated()) {
templatedLinks.add(affordance);
} else {
simpleLinks.add(affordance);
}
}
} else if (link.isTemplated()) {
templatedLinks.add(link);
} else {
simpleLinks.add(link);
}
if ("self".equals(link.getRel())) {
selfRel = link;
}
}
for (Affordance templatedAffordance : templatedAffordances) {
jgen.writeObjectFieldStart(templatedAffordance.getRel());
jgen.writeStringField("@type", "hydra:IriTemplate");
jgen.writeStringField("hydra:template", templatedAffordance.getHref());
final List<ActionDescriptor> actionDescriptors = templatedAffordance.getActionDescriptors();
ActionDescriptor actionDescriptor = actionDescriptors.get(0);
jgen.writeArrayFieldStart("hydra:mapping");
writeHydraVariableMapping(jgen, actionDescriptor, actionDescriptor.getPathVariableNames());
writeHydraVariableMapping(jgen, actionDescriptor, actionDescriptor.getRequestParamNames());
jgen.writeEndArray();
jgen.writeEndObject();
}
for (Link templatedLink : templatedLinks) {
// we only have the template, no access to method params
jgen.writeObjectFieldStart(templatedLink.getRel());
jgen.writeStringField("@type", "hydra:IriTemplate");
jgen.writeStringField("hydra:template", templatedLink.getHref());
jgen.writeArrayFieldStart("hydra:mapping");
writeHydraVariableMapping(jgen, null, templatedLink.getVariableNames());
jgen.writeEndArray();
jgen.writeEndObject();
}
@SuppressWarnings("unchecked")
Deque<LdContext> contextStack =
(Deque<LdContext>) serializerProvider.getAttribute(JacksonHydraSerializer.KEY_LD_CONTEXT);
String currentVocab =
(contextStack != null && !contextStack.isEmpty()) ? contextStack.peek().vocab : null;
// related collections
if (!collectionAffordances.isEmpty()) {
jgen.writeArrayFieldStart("hydra:collection");
for (Affordance collectionAffordance : collectionAffordances) {
jgen.writeStartObject();
jgen.writeStringField(JsonLdKeywords.AT_TYPE, "hydra:Collection");
jgen.writeStringField(JsonLdKeywords.AT_ID, collectionAffordance.getHref());
jgen.writeObjectFieldStart("hydra:manages");
jgen.writeStringField("hydra:property", collectionAffordance.getRel());
// a) in the case of </Alice> :knows /bob the subject must be /Alice
// b) in the case of <> orderedItem /latte-1 the subject is an anonymous resource of type
// Order
// c) in the case of </order/1> :seller </store> the object must be the store
// 1. where is the information *about* the subject or object: the type or @id
// 2. how to decide if the collection manages items for a subject or object?
// ad 1.)
// ad a) self rel of the Resource that has the collection affordance: looking through link
// list
// at serialization time is possible
// ad b) a candidate is the class given as value of @ExposesResourceFor on the controller
// that defines the method which leads us to believe we have a collection:
// either a GET /orders handler having a collection return type or the POST /orders.
// Works only if the GET or POST has no request mapping path of its own
// an alternative is to use {} without type if @ExposesResourceFor is not present
// ad c) like a
// ad 2.)
// we know the affordance is a collection
// * we could pass information into build(rel), like
// .rel().reverseRel("schema:seller").build()
// * we could use build("myReversedTerm") and look at the @context to see if it is
// reversed,
// if so, we know that the manages block must use object not subject. However weird if
// the
// reverse term is never really used in the json-ld
// * we could have a registry which says if a property is meant to be reversed in a
// certain context
// and use that to find out if we need subject or object, like :seller ->
if (selfRel != null) {
// prefer rev over rel, assuming that rev exists to be used by RDF serialization
if (collectionAffordance.getRev() != null) {
jgen.writeStringField("hydra:object", selfRel.getHref());
} else if (collectionAffordance.getRel() != null) {
jgen.writeStringField("hydra:subject", selfRel.getHref());
}
} else {
// prefer rev over rel, assuming that rev exists to be used by RDF serialization
if (collectionAffordance.getRev() != null) {
jgen.writeObjectFieldStart("hydra:object");
jgen.writeEndObject();
} else if (collectionAffordance.getRel() != null) {
jgen.writeObjectFieldStart("hydra:subject");
jgen.writeEndObject();
}
}
jgen.writeEndObject(); // end manages
List<ActionDescriptor> actionDescriptors = collectionAffordance.getActionDescriptors();
if (!actionDescriptors.isEmpty()) {
jgen.writeArrayFieldStart("hydra:operation");
}
writeActionDescriptors(jgen, currentVocab, actionDescriptors);
if (!actionDescriptors.isEmpty()) {
jgen.writeEndArray(); // end hydra:operation
}
jgen.writeEndObject(); // end collection
}
jgen.writeEndArray();
}
for (Affordance affordance : affordances) {
final String rel = affordance.getRel();
List<ActionDescriptor> actionDescriptors = affordance.getActionDescriptors();
if (!actionDescriptors.isEmpty()) {
if (!Link.REL_SELF.equals(rel)) {
jgen.writeObjectFieldStart(rel); // begin rel
}
jgen.writeStringField(JsonLdKeywords.AT_ID, affordance.getHref());
jgen.writeArrayFieldStart("hydra:operation");
}
writeActionDescriptors(jgen, currentVocab, actionDescriptors);
if (!actionDescriptors.isEmpty()) {
jgen.writeEndArray(); // end hydra:operation
if (!Link.REL_SELF.equals(rel)) {
jgen.writeEndObject(); // end rel
}
}
}
for (Link simpleLink : simpleLinks) {
final String rel = simpleLink.getRel();
if (Link.REL_SELF.equals(rel)) {
jgen.writeStringField("@id", simpleLink.getHref());
} else {
String linkAttributeName = IanaRels.isIanaRel(rel) ? IANA_REL_PREFIX + rel : rel;
jgen.writeObjectFieldStart(linkAttributeName);
jgen.writeStringField("@id", simpleLink.getHref());
jgen.writeEndObject();
}
}
} catch (IntrospectionException e) {
throw new RuntimeException(e);
}
}