org.activiti.engine.impl.javax.el.MapELResolver Maven / Gradle / Ivy
/*
* Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
*
* 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.javax.el;
import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.Map;
/**
* Defines property resolution behavior on instances of java.util.Map. This resolver handles base objects of type java.util.Map. It accepts any object as a property and uses that object as a key in
* the map. The resulting value is the value in the map that is associated with that key. This resolver can be constructed in read-only mode, which means that isReadOnly will always return true and
* {@link #setValue(ELContext, Object, Object, Object)} will always throw PropertyNotWritableException. ELResolvers are combined together using {@link CompositeELResolver} s, to define rich semantics
* for evaluating an expression. See the javadocs for {@link ELResolver} for details.
*/
public class MapELResolver extends ELResolver {
private final boolean readOnly;
/**
* Creates a new read/write MapELResolver.
*/
public MapELResolver() {
this(false);
}
/**
* Creates a new MapELResolver whose read-only status is determined by the given parameter.
*/
public MapELResolver(boolean readOnly) {
this.readOnly = readOnly;
}
/**
* If the base object is a map, returns the most general type that this resolver accepts for the property argument. Otherwise, returns null. Assuming the base is a Map, this method will always
* return Object.class. This is because Maps accept any object as a key.
*
* @param context
* The context of this evaluation.
* @param base
* The map to analyze. Only bases of type Map are handled by this resolver.
* @return null if base is not a Map; otherwise Object.class.
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
return isResolvable(base) ? Object.class : null;
}
/**
* If the base object is a map, returns an Iterator containing the set of keys available in the Map. Otherwise, returns null. The Iterator returned must contain zero or more instances of
* java.beans.FeatureDescriptor. Each info object contains information about a key in the Map, and is initialized as follows:
*
* - displayName - The return value of calling the toString method on this key, or "null" if the key is null
* - name - Same as displayName property
* - shortDescription - Empty string
* - expert - false
* - hidden - false
* - preferred - true
*
* In addition, the following named attributes must be set in the returned FeatureDescriptors:
*
* - {@link ELResolver#TYPE} - The return value of calling the getClass() method on this key, or null if the key is null.
* - {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true
*
*
* @param context
* The context of this evaluation.
* @param base
* The map to analyze. Only bases of type Map are handled by this resolver.
* @return An Iterator containing zero or more (possibly infinitely more) FeatureDescriptor objects, each representing a key in this map, or null if the base object is not a map.
*/
@Override
public Iterator getFeatureDescriptors(ELContext context, Object base) {
if (isResolvable(base)) {
Map map = (Map) base;
final Iterator keys = map.keySet().iterator();
return new Iterator() {
public boolean hasNext() {
return keys.hasNext();
}
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;
}
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)) {
result = ((Map) base).get(property);
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
@SuppressWarnings("unchecked")
public void setValue(ELContext context, Object base, Object property, Object value) {
if (context == null) {
throw new NullPointerException("context is null");
}
if (isResolvable(base)) {
if (readOnly) {
throw new PropertyNotWritableException("resolver is read-only");
}
((Map) base).put(property, value);
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 instanceof Map
*/
private final boolean isResolvable(Object base) {
return base instanceof Map;
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy