org.yaml.snakeyaml.composer.Composer Maven / Gradle / Ivy
/**
* Copyright (c) 2008, 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.yaml.snakeyaml.composer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.yaml.snakeyaml.LoaderOptions;
import org.yaml.snakeyaml.error.Mark;
import org.yaml.snakeyaml.error.YAMLException;
import org.yaml.snakeyaml.events.AliasEvent;
import org.yaml.snakeyaml.events.Event;
import org.yaml.snakeyaml.events.MappingStartEvent;
import org.yaml.snakeyaml.events.NodeEvent;
import org.yaml.snakeyaml.events.ScalarEvent;
import org.yaml.snakeyaml.events.SequenceStartEvent;
import org.yaml.snakeyaml.nodes.MappingNode;
import org.yaml.snakeyaml.nodes.Node;
import org.yaml.snakeyaml.nodes.NodeId;
import org.yaml.snakeyaml.nodes.NodeTuple;
import org.yaml.snakeyaml.nodes.ScalarNode;
import org.yaml.snakeyaml.nodes.SequenceNode;
import org.yaml.snakeyaml.nodes.Tag;
import org.yaml.snakeyaml.parser.Parser;
import org.yaml.snakeyaml.resolver.Resolver;
/**
* Creates a node graph from parser events.
*
* Corresponds to the 'Compose' step as described in chapter 3.1 of the
* YAML Specification.
*
*/
public class Composer {
protected final Parser parser;
private final Resolver resolver;
private final Map anchors;
private final Set recursiveNodes;
private int nonScalarAliasesCount = 0;
private final LoaderOptions loadingConfig;
public Composer(Parser parser, Resolver resolver) {
this(parser, resolver, new LoaderOptions());
}
public Composer(Parser parser, Resolver resolver, LoaderOptions loadingConfig) {
this.parser = parser;
this.resolver = resolver;
this.anchors = new HashMap();
this.recursiveNodes = new HashSet();
this.loadingConfig = loadingConfig;
}
/**
* Checks if further documents are available.
*
* @return true if there is at least one more document.
*/
public boolean checkNode() {
// Drop the STREAM-START event.
if (parser.checkEvent(Event.ID.StreamStart)) {
parser.getEvent();
}
// If there are more documents available?
return !parser.checkEvent(Event.ID.StreamEnd);
}
/**
* Reads and composes the next document.
*
* @return The root node of the document or null if no more
* documents are available.
*/
public Node getNode() {
// Drop the DOCUMENT-START event.
parser.getEvent();
// Compose the root node.
Node node = composeNode(null);
// Drop the DOCUMENT-END event.
parser.getEvent();
//clean up resources
this.anchors.clear();
this.recursiveNodes.clear();
return node;
}
/**
* 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 null if no document
* is available.
*/
public Node getSingleNode() {
// Drop the STREAM-START event.
parser.getEvent();
// Compose a document if the stream is not empty.
Node document = null;
if (!parser.checkEvent(Event.ID.StreamEnd)) {
document = getNode();
}
// Ensure that the stream contains no more documents.
if (!parser.checkEvent(Event.ID.StreamEnd)) {
Event event = parser.getEvent();
Mark contextMark = document != null ? document.getStartMark(): null;
throw new ComposerException("expected a single document in the stream",
contextMark, "but found another document", event.getStartMark());
}
// Drop the STREAM-END event.
parser.getEvent();
return document;
}
private Node composeNode(Node parent) {
if (parent != null) recursiveNodes.add(parent);
final Node node;
if (parser.checkEvent(Event.ID.Alias)) {
AliasEvent event = (AliasEvent) parser.getEvent();
String anchor = event.getAnchor();
if (!anchors.containsKey(anchor)) {
throw new ComposerException(null, null, "found undefined alias " + anchor,
event.getStartMark());
}
node = anchors.get(anchor);
if (!(node instanceof ScalarNode)) {
this.nonScalarAliasesCount++;
if (this.nonScalarAliasesCount > loadingConfig.getMaxAliasesForCollections()) {
throw new YAMLException("Number of aliases for non-scalar nodes exceeds the specified max=" + loadingConfig.getMaxAliasesForCollections());
}
}
if (recursiveNodes.remove(node)) {
node.setTwoStepsConstruction(true);
}
} else {
NodeEvent event = (NodeEvent) parser.peekEvent();
String 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);
}
}
recursiveNodes.remove(parent);
return node;
}
protected Node composeScalarNode(String anchor) {
ScalarEvent ev = (ScalarEvent) parser.getEvent();
String tag = ev.getTag();
boolean resolved = false;
Tag nodeTag;
if (tag == null || tag.equals("!")) {
nodeTag = resolver.resolve(NodeId.scalar, ev.getValue(),
ev.getImplicit().canOmitTagInPlainScalar());
resolved = true;
} else {
nodeTag = new Tag(tag);
}
Node node = new ScalarNode(nodeTag, resolved, ev.getValue(), ev.getStartMark(),
ev.getEndMark(), ev.getScalarStyle());
if (anchor != null) {
node.setAnchor(anchor);
anchors.put(anchor, node);
}
return node;
}
protected Node composeSequenceNode(String anchor) {
SequenceStartEvent startEvent = (SequenceStartEvent) parser.getEvent();
String tag = startEvent.getTag();
Tag nodeTag;
boolean resolved = false;
if (tag == null || tag.equals("!")) {
nodeTag = resolver.resolve(NodeId.sequence, null, startEvent.getImplicit());
resolved = true;
} else {
nodeTag = new Tag(tag);
}
final ArrayList children = new ArrayList();
SequenceNode node = new SequenceNode(nodeTag, resolved, children, startEvent.getStartMark(),
null, startEvent.getFlowStyle());
if (anchor != null) {
node.setAnchor(anchor);
anchors.put(anchor, node);
}
while (!parser.checkEvent(Event.ID.SequenceEnd)) {
children.add(composeNode(node));
}
Event endEvent = parser.getEvent();
node.setEndMark(endEvent.getEndMark());
return node;
}
protected Node composeMappingNode(String anchor) {
MappingStartEvent startEvent = (MappingStartEvent) parser.getEvent();
String tag = startEvent.getTag();
Tag nodeTag;
boolean resolved = false;
if (tag == null || tag.equals("!")) {
nodeTag = resolver.resolve(NodeId.mapping, null, startEvent.getImplicit());
resolved = true;
} else {
nodeTag = new Tag(tag);
}
final List children = new ArrayList();
MappingNode node = new MappingNode(nodeTag, resolved, children, startEvent.getStartMark(),
null, startEvent.getFlowStyle());
if (anchor != null) {
node.setAnchor(anchor);
anchors.put(anchor, node);
}
while (!parser.checkEvent(Event.ID.MappingEnd)) {
composeMappingChildren(children, node);
}
Event endEvent = parser.getEvent();
node.setEndMark(endEvent.getEndMark());
return node;
}
protected void composeMappingChildren(List children, MappingNode node) {
Node itemKey = composeKeyNode(node);
if (itemKey.getTag().equals(Tag.MERGE)) {
node.setMerged(true);
}
Node itemValue = composeValueNode(node);
children.add(new NodeTuple(itemKey, itemValue));
}
protected Node composeKeyNode(MappingNode node) {
return composeNode(node);
}
protected Node composeValueNode(MappingNode node) {
return composeNode(node);
}
}