org.snakeyaml.engine.v2.composer.Composer Maven / Gradle / Ivy
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/**
* Copyright (c) 2018, http://www.snakeyaml.org
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.snakeyaml.engine.v2.composer;
import org.snakeyaml.engine.v2.api.LoadSettings;
import org.snakeyaml.engine.v2.common.Anchor;
import org.snakeyaml.engine.v2.events.AliasEvent;
import org.snakeyaml.engine.v2.events.Event;
import org.snakeyaml.engine.v2.events.MappingStartEvent;
import org.snakeyaml.engine.v2.events.NodeEvent;
import org.snakeyaml.engine.v2.events.ScalarEvent;
import org.snakeyaml.engine.v2.events.SequenceStartEvent;
import org.snakeyaml.engine.v2.exceptions.ComposerException;
import org.snakeyaml.engine.v2.exceptions.Mark;
import org.snakeyaml.engine.v2.exceptions.YamlEngineException;
import org.snakeyaml.engine.v2.nodes.MappingNode;
import org.snakeyaml.engine.v2.nodes.Node;
import org.snakeyaml.engine.v2.nodes.NodeTuple;
import org.snakeyaml.engine.v2.nodes.NodeType;
import org.snakeyaml.engine.v2.nodes.ScalarNode;
import org.snakeyaml.engine.v2.nodes.SequenceNode;
import org.snakeyaml.engine.v2.nodes.Tag;
import org.snakeyaml.engine.v2.parser.Parser;
import org.snakeyaml.engine.v2.resolver.ScalarResolver;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
/**
* Creates a node graph from parser events.
*
* Corresponds to the 'Composer' step as described in chapter 3.1.2 of the
* YAML Specification.
*
*/
public class Composer implements Iterator {
protected final Parser parser;
private final ScalarResolver scalarResolver;
private final Map anchors;
private final Set recursiveNodes;
private int nonScalarAliasesCount = 0;
private final LoadSettings settings;
public Composer(Parser parser, LoadSettings settings) {
this.parser = parser;
this.scalarResolver = settings.getScalarResolver();
this.settings = settings;
this.anchors = new HashMap();
this.recursiveNodes = new HashSet();
}
/**
* Checks if further documents are available.
*
* @return true if there is at least one more document.
*/
public boolean hasNext() {
// Drop the STREAM-START event.
if (parser.checkEvent(Event.ID.StreamStart)) {
parser.next();
}
// If there are more documents available?
return !parser.checkEvent(Event.ID.StreamEnd);
}
/**
* Reads a document from a source that contains only one document.
*
* If the stream contains more than one document an exception is thrown.
*
*
* @return The root node of the document or Optional.empty() if no document
* is available.
*/
public Optional getSingleNode() {
// Drop the STREAM-START event.
parser.next();
// Compose a document if the stream is not empty.
Optional document = Optional.empty();
if (!parser.checkEvent(Event.ID.StreamEnd)) {
document = Optional.of(next());
}
// Ensure that the stream contains no more documents.
if (!parser.checkEvent(Event.ID.StreamEnd)) {
Event event = parser.next();
Optional previousDocMark = document.flatMap(Node::getStartMark);
throw new ComposerException("expected a single document in the stream", previousDocMark,
"but found another document", event.getStartMark());
}
// Drop the STREAM-END event.
parser.next();
return document;
}
/**
* Reads and composes the next document.
*
* @return The root node of the document or null if no more
* documents are available.
*/
public Node next() {
// Drop the DOCUMENT-START event.
parser.next();
// Compose the root node.
Node node = composeNode(Optional.empty());
// Drop the DOCUMENT-END event.
parser.next();
this.anchors.clear();
this.recursiveNodes.clear();
this.nonScalarAliasesCount = 0;
return node;
}
private Node composeNode(Optional parent) {
parent.ifPresent(recursiveNodes::add);//TODO add unit test for this line
final Node node;
if (parser.checkEvent(Event.ID.Alias)) {
AliasEvent event = (AliasEvent) parser.next();
Anchor anchor = event.getAlias();
if (!anchors.containsKey(anchor)) {
throw new ComposerException("found undefined alias " + anchor, event.getStartMark());
}
node = anchors.get(anchor);
if (node.getNodeType() != NodeType.SCALAR) {
this.nonScalarAliasesCount++;
if (this.nonScalarAliasesCount > settings.getMaxAliasesForCollections()) {
throw new YamlEngineException("Number of aliases for non-scalar nodes exceeds the specified max=" + settings.getMaxAliasesForCollections());
}
}
if (recursiveNodes.remove(node)) {
node.setRecursive(true);
}
} else {
NodeEvent event = (NodeEvent) parser.peekEvent();
Optional anchor = event.getAnchor();
// the check for duplicate anchors has been removed (issue 174)
if (parser.checkEvent(Event.ID.Scalar)) {
node = composeScalarNode(anchor);
} else if (parser.checkEvent(Event.ID.SequenceStart)) {
node = composeSequenceNode(anchor);
} else {
node = composeMappingNode(anchor);
}
}
parent.ifPresent(recursiveNodes::remove);//TODO add unit test for this line
return node;
}
private void registerAnchor(Anchor anchor, Node node) {
anchors.put(anchor, node);
node.setAnchor(Optional.of(anchor));
}
protected Node composeScalarNode(Optional anchor) {
ScalarEvent ev = (ScalarEvent) parser.next();
Optional tag = ev.getTag();
boolean resolved = false;
Tag nodeTag;
if (!tag.isPresent() || tag.get().equals("!")) {
nodeTag = scalarResolver.resolve(ev.getValue(), ev.getImplicit().canOmitTagInPlainScalar());
resolved = true;
} else {
nodeTag = new Tag(tag.get());
}
Node node = new ScalarNode(nodeTag, resolved, ev.getValue(), ev.getScalarStyle(), ev.getStartMark(), ev.getEndMark());
anchor.ifPresent(a -> registerAnchor(a, node));
return node;
}
protected Node composeSequenceNode(Optional anchor) {
SequenceStartEvent startEvent = (SequenceStartEvent) parser.next();
Optional tag = startEvent.getTag();
Tag nodeTag;
boolean resolved = false;
if (!tag.isPresent() || tag.get().equals("!")) {
nodeTag = Tag.SEQ;
resolved = true;
} else {
nodeTag = new Tag(tag.get());
}
final ArrayList children = new ArrayList();
SequenceNode node = new SequenceNode(nodeTag, resolved, children, startEvent.getFlowStyle(), startEvent.getStartMark(),
Optional.empty());
anchor.ifPresent(a -> registerAnchor(a, node));
while (!parser.checkEvent(Event.ID.SequenceEnd)) {
children.add(composeNode(Optional.of(node)));
}
Event endEvent = parser.next();
node.setEndMark(endEvent.getEndMark());
return node;
}
protected Node composeMappingNode(Optional anchor) {
MappingStartEvent startEvent = (MappingStartEvent) parser.next();
Optional tag = startEvent.getTag();
Tag nodeTag;
boolean resolved = false;
if (!tag.isPresent() || tag.get().equals("!")) {
nodeTag = Tag.MAP;
resolved = true;
} else {
nodeTag = new Tag(tag.get());
}
final List children = new ArrayList<>();
MappingNode node = new MappingNode(nodeTag, resolved, children, startEvent.getFlowStyle(), startEvent.getStartMark(), Optional.empty());
anchor.ifPresent(a -> registerAnchor(a, node));
while (!parser.checkEvent(Event.ID.MappingEnd)) {
composeMappingChildren(children, node);
}
Event endEvent = parser.next();
node.setEndMark(endEvent.getEndMark());
return node;
}
protected void composeMappingChildren(List children, MappingNode node) {
Node itemKey = composeKeyNode(node);
Node itemValue = composeValueNode(node);
children.add(new NodeTuple(itemKey, itemValue));
}
protected Node composeKeyNode(MappingNode node) {
return composeNode(Optional.of(node));
}
protected Node composeValueNode(MappingNode node) {
return composeNode(Optional.of(node));
}
}