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JsonLdTreeBuilder.java
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JsonLdTreeBuilder.java
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/**
* Copyright (C) 2022 Czech Technical University in Prague
* <p>
* This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later
* version.
* <p>
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details. You should have received a copy of the GNU General Public License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
*/
package cz.cvut.kbss.jsonld.serialization;
import cz.cvut.kbss.jsonld.serialization.context.JsonLdContextFactory;
import cz.cvut.kbss.jsonld.serialization.model.CollectionNode;
import cz.cvut.kbss.jsonld.serialization.model.CompositeNode;
import cz.cvut.kbss.jsonld.serialization.model.JsonNode;
import cz.cvut.kbss.jsonld.serialization.model.ObjectNode;
import cz.cvut.kbss.jsonld.serialization.serializer.ValueSerializer;
import cz.cvut.kbss.jsonld.serialization.serializer.ValueSerializers;
import cz.cvut.kbss.jsonld.serialization.traversal.InstanceVisitor;
import cz.cvut.kbss.jsonld.serialization.traversal.SerializationContext;
import java.util.Collection;
import java.util.Set;
import java.util.Stack;
/**
* Builds an abstract representation of a JSON-LD tree, which is a result of object graph traversal by {@link
* cz.cvut.kbss.jsonld.serialization.traversal.ObjectGraphTraverser}.
*/
public class JsonLdTreeBuilder implements InstanceVisitor {
private final Stack<CompositeNode<?>> nodeStack = new Stack<>();
private CompositeNode<?> currentNode;
private final ValueSerializers serializers;
private final JsonLdContextFactory jsonLdContextFactory;
public JsonLdTreeBuilder(ValueSerializers serializers, JsonLdContextFactory jsonLdContextFactory) {
this.serializers = serializers;
this.jsonLdContextFactory = jsonLdContextFactory;
}
@Override
public boolean visitObject(SerializationContext<?> ctx) {
if (serializers.hasCustomSerializer(ctx.getValue().getClass())) {
final ValueSerializer serializer = serializers.getSerializer(ctx).get();
final JsonNode node = serializer.serialize(ctx.getValue(), ctx);
if (node != null) {
if (currentNode != null) {
currentNode.addItem(node);
} else {
assert node instanceof CompositeNode;
currentNode = (CompositeNode<?>) node;
}
}
return false;
}
return true;
}
@Override
public void openObject(SerializationContext<?> ctx) {
final ObjectNode newCurrent = ctx.getTerm() != null ? JsonNodeFactory.createObjectNode(ctx.getTerm()) :
JsonNodeFactory.createObjectNode();
openNewNode(newCurrent);
// Prepare to create new JSON-LD context when an object is open
ctx.setJsonLdContext(jsonLdContextFactory.createJsonLdContext(ctx.getJsonLdContext()));
}
private void openNewNode(CompositeNode<?> newNode) {
if (currentNode != null) {
if (currentNode.isOpen()) {
nodeStack.push(currentNode);
}
currentNode.addItem(newNode);
}
this.currentNode = newNode;
}
@Override
public void closeObject(SerializationContext<?> ctx) {
if (!ctx.isCurrentEmpty()) {
currentNode.prependItem(ctx.getContextNode());
}
closeCurrentNode();
}
private void closeCurrentNode() {
currentNode.close();
if (!nodeStack.empty()) {
this.currentNode = nodeStack.pop();
}
}
@Override
public void visitIdentifier(SerializationContext<String> idCtx) {
assert currentNode.isOpen();
currentNode.addItem(serializers.getIdentifierSerializer().serialize(idCtx.getValue(), idCtx));
}
@Override
public void visitTypes(SerializationContext<Set<String>> typesCtx) {
currentNode.addItem(serializers.getTypesSerializer().serialize(typesCtx.getValue(), typesCtx));
}
@Override
public void visitAttribute(SerializationContext<?> ctx) {
if (ctx.getValue() != null) {
assert currentNode != null;
final ValueSerializer serializer = serializers.getOrDefault(ctx);
final JsonNode node = serializer.serialize(ctx.getValue(), ctx);
if (node != null) {
currentNode.addItem(node);
}
}
}
@Override
public void openCollection(SerializationContext<? extends Collection<?>> ctx) {
final CollectionNode<?> newCurrent =
ctx.getTerm() != null ? JsonNodeFactory.createCollectionNode(ctx.getTerm(),
ctx.getValue()) :
JsonNodeFactory.createCollectionNode(ctx.getValue());
openNewNode(newCurrent);
}
@Override
public void closeCollection(SerializationContext<?> ctx) {
assert currentNode instanceof CollectionNode;
closeCurrentNode();
}
public CompositeNode<?> getTreeRoot() {
return currentNode;
}
}