src/main/java/org/yaml/snakeyaml/representer/Representer.java

/**
 * Copyright (c) 2008, SnakeYAML
 *
 * 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.representer;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.yaml.snakeyaml.DumperOptions;
import org.yaml.snakeyaml.DumperOptions.FlowStyle;
import org.yaml.snakeyaml.TypeDescription;
import org.yaml.snakeyaml.introspector.Property;
import org.yaml.snakeyaml.introspector.PropertyUtils;
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;

/**
 * Represent JavaBeans
 */
public class Representer extends SafeRepresenter {

  protected Map<Class<? extends Object>, TypeDescription> typeDefinitions = Collections.emptyMap();

  public Representer() {
    this.representers.put(null, new RepresentJavaBean());
  }

  public Representer(DumperOptions options) {
    super(options);
    this.representers.put(null, new RepresentJavaBean());
  }

  public TypeDescription addTypeDescription(TypeDescription td) {
    if (Collections.EMPTY_MAP == typeDefinitions) {
      typeDefinitions = new HashMap<Class<? extends Object>, TypeDescription>();
    }
    if (td.getTag() != null) {
      addClassTag(td.getType(), td.getTag());
    }
    td.setPropertyUtils(getPropertyUtils());
    return typeDefinitions.put(td.getType(), td);
  }

  @Override
  public void setPropertyUtils(PropertyUtils propertyUtils) {
    super.setPropertyUtils(propertyUtils);
    Collection<TypeDescription> tds = typeDefinitions.values();
    for (TypeDescription typeDescription : tds) {
      typeDescription.setPropertyUtils(propertyUtils);
    }
  }

  protected class RepresentJavaBean implements Represent {

    public Node representData(Object data) {
      return representJavaBean(getProperties(data.getClass()), data);
    }
  }

  /**
   * Tag logic: - explicit root tag is set in serializer - if there is a predefined class tag it is
   * used - a global tag with class name is always used as tag. The JavaBean parent of the specified
   * JavaBean may set another tag (tag:yaml.org,2002:map) when the property class is the same as
   * runtime class
   *
   * @param properties JavaBean getters
   * @param javaBean instance for Node
   * @return Node to get serialized
   */
  protected MappingNode representJavaBean(Set<Property> properties, Object javaBean) {
    List<NodeTuple> value = new ArrayList<NodeTuple>(properties.size());
    Tag tag;
    Tag customTag = classTags.get(javaBean.getClass());
    tag = customTag != null ? customTag : new Tag(javaBean.getClass());
    // flow style will be chosen by BaseRepresenter
    MappingNode node = new MappingNode(tag, value, FlowStyle.AUTO);
    representedObjects.put(javaBean, node);
    DumperOptions.FlowStyle bestStyle = FlowStyle.FLOW;
    for (Property property : properties) {
      Object memberValue = property.get(javaBean);
      Tag customPropertyTag = memberValue == null ? null : classTags.get(memberValue.getClass());
      NodeTuple tuple =
          representJavaBeanProperty(javaBean, property, memberValue, customPropertyTag);
      if (tuple == null) {
        continue;
      }
      if (!((ScalarNode) tuple.getKeyNode()).isPlain()) {
        bestStyle = FlowStyle.BLOCK;
      }
      Node nodeValue = tuple.getValueNode();
      if (!(nodeValue instanceof ScalarNode && ((ScalarNode) nodeValue).isPlain())) {
        bestStyle = FlowStyle.BLOCK;
      }
      value.add(tuple);
    }
    if (defaultFlowStyle != FlowStyle.AUTO) {
      node.setFlowStyle(defaultFlowStyle);
    } else {
      node.setFlowStyle(bestStyle);
    }
    return node;
  }

  /**
   * Represent one JavaBean property.
   *
   * @param javaBean - the instance to be represented
   * @param property - the property of the instance
   * @param propertyValue - value to be represented
   * @param customTag - user defined Tag
   * @return NodeTuple to be used in a MappingNode. Return null to skip the property
   */
  protected NodeTuple representJavaBeanProperty(Object javaBean, Property property,
      Object propertyValue, Tag customTag) {
    ScalarNode nodeKey = (ScalarNode) representData(property.getName());
    // the first occurrence of the node must keep the tag
    boolean hasAlias = this.representedObjects.containsKey(propertyValue);

    Node nodeValue = representData(propertyValue);

    if (propertyValue != null && !hasAlias) {
      NodeId nodeId = nodeValue.getNodeId();
      if (customTag == null) {
        if (nodeId == NodeId.scalar) {
          // generic Enum requires the full tag
          if (property.getType() != java.lang.Enum.class) {
            if (propertyValue instanceof Enum<?>) {
              nodeValue.setTag(Tag.STR);
            }
          }
        } else {
          if (nodeId == NodeId.mapping) {
            if (property.getType() == propertyValue.getClass()) {
              if (!(propertyValue instanceof Map<?, ?>)) {
                if (!nodeValue.getTag().equals(Tag.SET)) {
                  nodeValue.setTag(Tag.MAP);
                }
              }
            }
          }
          checkGlobalTag(property, nodeValue, propertyValue);
        }
      }
    }

    return new NodeTuple(nodeKey, nodeValue);
  }

  /**
   * Remove redundant global tag for a type safe (generic) collection if it is the same as defined
   * by the JavaBean property
   *
   * @param property - JavaBean property
   * @param node - representation of the property
   * @param object - instance represented by the node
   */
  @SuppressWarnings("unchecked")
  protected void checkGlobalTag(Property property, Node node, Object object) {
    // Skip primitive arrays.
    if (object.getClass().isArray() && object.getClass().getComponentType().isPrimitive()) {
      return;
    }

    Class<?>[] arguments = property.getActualTypeArguments();
    if (arguments != null) {
      if (node.getNodeId() == NodeId.sequence) {
        // apply map tag where class is the same
        Class<? extends Object> t = arguments[0];
        SequenceNode snode = (SequenceNode) node;
        Iterable<Object> memberList = Collections.EMPTY_LIST;
        if (object.getClass().isArray()) {
          memberList = Arrays.asList((Object[]) object);
        } else if (object instanceof Iterable<?>) {
          // list
          memberList = (Iterable<Object>) object;
        }
        Iterator<Object> iter = memberList.iterator();
        if (iter.hasNext()) {
          for (Node childNode : snode.getValue()) {
            Object member = iter.next();
            if (member != null) {
              if (t.equals(member.getClass())) {
                if (childNode.getNodeId() == NodeId.mapping) {
                  childNode.setTag(Tag.MAP);
                }
              }
            }
          }
        }
      } else if (object instanceof Set) {
        Class<?> t = arguments[0];
        MappingNode mnode = (MappingNode) node;
        Iterator<NodeTuple> iter = mnode.getValue().iterator();
        Set<?> set = (Set<?>) object;
        for (Object member : set) {
          NodeTuple tuple = iter.next();
          Node keyNode = tuple.getKeyNode();
          if (t.equals(member.getClass())) {
            if (keyNode.getNodeId() == NodeId.mapping) {
              keyNode.setTag(Tag.MAP);
            }
          }
        }
      } else if (object instanceof Map) { // NodeId.mapping ends-up here
        Class<?> keyType = arguments[0];
        Class<?> valueType = arguments[1];
        MappingNode mnode = (MappingNode) node;
        for (NodeTuple tuple : mnode.getValue()) {
          resetTag(keyType, tuple.getKeyNode());
          resetTag(valueType, tuple.getValueNode());
        }
      } else {
        // the type for collection entries cannot be
        // detected
      }
    }
  }

  private void resetTag(Class<? extends Object> type, Node node) {
    Tag tag = node.getTag();
    if (tag.matches(type)) {
      if (Enum.class.isAssignableFrom(type)) {
        node.setTag(Tag.STR);
      } else {
        node.setTag(Tag.MAP);
      }
    }
  }

  /**
   * Get JavaBean properties to be serialised. The order is respected. This method may be overridden
   * to provide custom property selection or order.
   *
   * @param type - JavaBean to inspect the properties
   * @return properties to serialise
   */
  protected Set<Property> getProperties(Class<? extends Object> type) {
    if (typeDefinitions.containsKey(type)) {
      return typeDefinitions.get(type).getProperties();
    }
    return getPropertyUtils().getProperties(type);
  }
}