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/*
 * 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.activiti.engine.impl.el;

import java.beans.FeatureDescriptor;
import java.math.BigDecimal;
import java.util.Iterator;
import java.util.List;

import javax.el.CompositeELResolver;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.PropertyNotWritableException;

import org.activiti.engine.impl.context.Context;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * Defines property resolution behavior on JsonNodes.
 *
 * @see CompositeELResolver
 * @see ELResolver
 */
public class JsonNodeELResolver extends ELResolver {

	private final boolean readOnly;

	/**
	 * Creates a new read/write BeanELResolver.
	 */
	public JsonNodeELResolver() {
		this(false);
	}

	/**
	 * Creates a new BeanELResolver whose read-only status is determined by the
	 * given parameter.
	 */
	public JsonNodeELResolver(boolean readOnly) {
		this.readOnly = readOnly;
	}

	/**
	 * If the base object is not null, returns the most general type that this
	 * resolver accepts for the property argument. Otherwise, returns null.
	 * Assuming the base is not null, this method will always return
	 * Object.class. This is because any object is accepted as a key and is
	 * coerced into a string.
	 * 
	 * @param context
	 *            The context of this evaluation.
	 * @param base
	 *            The bean to analyze.
	 * @return null if base is null; otherwise Object.class.
	 */
	@Override
	public Class getCommonPropertyType(ELContext context, Object base) {
		return isResolvable(base) ? Object.class : null;
	}

	/**
	 * If the base object is not null, returns an Iterator containing the set of
	 * JavaBeans properties available on the given object. Otherwise, returns
	 * null. The Iterator returned must contain zero or more instances of
	 * java.beans.FeatureDescriptor. Each info object contains information about
	 * a property in the bean, as obtained by calling the
	 * BeanInfo.getPropertyDescriptors method. The FeatureDescriptor is
	 * initialized using the same fields as are present in the
	 * PropertyDescriptor, with the additional required named attributes "type"
	 * and "resolvableAtDesignTime" set as follows:
	 * 
    *
  • {@link ELResolver#TYPE} - The runtime type of the property, from * PropertyDescriptor.getPropertyType().
  • *
  • {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true.
  • *
* * @param context * The context of this evaluation. * @param base * The bean to analyze. * @return An Iterator containing zero or more FeatureDescriptor objects, * each representing a property on this bean, or null if the base * object is null. */ @Override public Iterator getFeatureDescriptors(ELContext context, Object base) { if (isResolvable(base)) { JsonNode node = (JsonNode) base; final Iterator keys = node.fieldNames(); return new Iterator() { @Override public boolean hasNext() { return keys.hasNext(); } @Override public FeatureDescriptor next() { Object key = keys.next(); FeatureDescriptor feature = new FeatureDescriptor(); feature.setDisplayName(key == null ? "null" : key.toString()); feature.setName(feature.getDisplayName()); feature.setShortDescription(""); feature.setExpert(true); feature.setHidden(false); feature.setPreferred(true); feature.setValue(TYPE, key == null ? "null" : key.getClass()); feature.setValue(RESOLVABLE_AT_DESIGN_TIME, true); return feature; } @Override public void remove() { throw new UnsupportedOperationException("cannot remove"); } }; } return null; } /** * If the base object is a map, returns the most general acceptable type for * a value in this map. If the base is a Map, the propertyResolved property * of the ELContext object must be set to true by this resolver, before * returning. If this property is not true after this method is called, the * caller should ignore the return value. Assuming the base is a Map, this * method will always return Object.class. This is because Maps accept any * object as the value for a given key. * * @param context * The context of this evaluation. * @param base * The map to analyze. Only bases of type Map are handled by this * resolver. * @param property * The key to return the acceptable type for. Ignored by this * resolver. * @return If the propertyResolved property of ELContext was set to true, * then the most general acceptable type; otherwise undefined. * @throws NullPointerException * if context is null * @throws ELException * if an exception was thrown while performing the property or * variable resolution. The thrown exception must be included as * the cause property of this exception, if available. */ @Override public Class getType(ELContext context, Object base, Object property) { if (context == null) { throw new NullPointerException("context is null"); } Class result = null; if (isResolvable(base)) { result = Object.class; context.setPropertyResolved(true); } return result; } /** * If the base object is a map, returns the value associated with the given * key, as specified by the property argument. If the key was not found, * null is returned. If the base is a Map, the propertyResolved property of * the ELContext object must be set to true by this resolver, before * returning. If this property is not true after this method is called, the * caller should ignore the return value. Just as in * java.util.Map.get(Object), just because null is returned doesn't mean * there is no mapping for the key; it's also possible that the Map * explicitly maps the key to null. * * @param context * The context of this evaluation. * @param base * The map to analyze. Only bases of type Map are handled by this * resolver. * @param property * The key to return the acceptable type for. Ignored by this * resolver. * @return If the propertyResolved property of ELContext was set to true, * then the value associated with the given key or null if the key * was not found. Otherwise, undefined. * @throws ClassCastException * if the key is of an inappropriate type for this map * (optionally thrown by the underlying Map). * @throws NullPointerException * if context is null, or if the key is null and this map does * not permit null keys (the latter is optionally thrown by the * underlying Map). * @throws ELException * if an exception was thrown while performing the property or * variable resolution. The thrown exception must be included as * the cause property of this exception, if available. */ @Override public Object getValue(ELContext context, Object base, Object property) { if (context == null) { throw new NullPointerException("context is null"); } Object result = null; if (isResolvable(base)) { JsonNode resultNode = ((JsonNode) base).get(property.toString()); if (resultNode != null && resultNode.isValueNode()) { if (resultNode.isBoolean()) { result = resultNode.asBoolean(); } else if (resultNode.isLong()) { result = resultNode.asLong(); } else if (resultNode.isBigDecimal() || resultNode.isDouble()) { result = resultNode.asDouble(); } else if (resultNode.isTextual()) { result = resultNode.asText(); } else { result = resultNode.toString(); } } else { if (resultNode.isArray()) { result = Context.getProcessEngineConfiguration().getObjectMapper().convertValue(resultNode, List.class); } else { result = resultNode; } } context.setPropertyResolved(true); } return result; } /** * If the base object is a map, returns whether a call to * {@link #setValue(ELContext, Object, Object, Object)} will always fail. If * the base is a Map, the propertyResolved property of the ELContext object * must be set to true by this resolver, before returning. If this property * is not true after this method is called, the caller should ignore the * return value. If this resolver was constructed in read-only mode, this * method will always return true. If a Map was created using * java.util.Collections.unmodifiableMap(Map), this method must return true. * Unfortunately, there is no Collections API method to detect this. * However, an implementation can create a prototype unmodifiable Map and * query its runtime type to see if it matches the runtime type of the base * object as a workaround. * * @param context * The context of this evaluation. * @param base * The map to analyze. Only bases of type Map are handled by this * resolver. * @param property * The key to return the acceptable type for. Ignored by this * resolver. * @return If the propertyResolved property of ELContext was set to true, * then true if calling the setValue method will always fail or * false if it is possible that such a call may succeed; otherwise * undefined. * @throws NullPointerException * if context is null. * @throws ELException * if an exception was thrown while performing the property or * variable resolution. The thrown exception must be included as * the cause property of this exception, if available. */ @Override public boolean isReadOnly(ELContext context, Object base, Object property) { if (context == null) { throw new NullPointerException("context is null"); } if (isResolvable(base)) { context.setPropertyResolved(true); } return readOnly; } /** * If the base object is a map, attempts to set the value associated with * the given key, as specified by the property argument. If the base is a * Map, the propertyResolved property of the ELContext object must be set to * true by this resolver, before returning. If this property is not true * after this method is called, the caller can safely assume no value was * set. If this resolver was constructed in read-only mode, this method will * always throw PropertyNotWritableException. If a Map was created using * java.util.Collections.unmodifiableMap(Map), this method must throw * PropertyNotWritableException. Unfortunately, there is no Collections API * method to detect this. However, an implementation can create a prototype * unmodifiable Map and query its runtime type to see if it matches the * runtime type of the base object as a workaround. * * @param context * The context of this evaluation. * @param base * The map to analyze. Only bases of type Map are handled by this * resolver. * @param property * The key to return the acceptable type for. Ignored by this * resolver. * @param value * The value to be associated with the specified key. * @throws ClassCastException * if the class of the specified key or value prevents it from * being stored in this map. * @throws NullPointerException * if context is null, or if this map does not permit null keys * or values, and the specified key or value is null. * @throws IllegalArgumentException * if some aspect of this key or value prevents it from being * stored in this map. * @throws PropertyNotWritableException * if this resolver was constructed in read-only mode, or if the * put operation is not supported by the underlying map. * @throws ELException * if an exception was thrown while performing the property or * variable resolution. The thrown exception must be included as * the cause property of this exception, if available. */ @Override public void setValue(ELContext context, Object base, Object property, Object value) { if (context == null) { throw new NullPointerException("context is null"); } if (base instanceof ObjectNode) { if (readOnly) { throw new PropertyNotWritableException("resolver is read-only"); } ObjectNode node = (ObjectNode) base; if (value instanceof BigDecimal) { node.put(property.toString(), (BigDecimal) value); } else if (value instanceof Boolean) { node.put(property.toString(), (Boolean) value); } else if (value instanceof Long) { node.put(property.toString(), (Long) value); } else if (value instanceof Double) { node.put(property.toString(), (Double) value); } else if (value != null) { node.put(property.toString(), value.toString()); } else { node.putNull(property.toString()); } context.setPropertyResolved(true); } } /** * Test whether the given base should be resolved by this ELResolver. * * @param base * The bean to analyze. * @param property * The name of the property to analyze. Will be coerced to a * String. * @return base != null */ private final boolean isResolvable(Object base) { return base instanceof JsonNode; } }




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