/*
* Copyright 2002-2010 the original author or authors.
*
* 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.springframework.expression.spel.ast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
import org.springframework.expression.spel.support.ReflectivePropertyAccessor;
/**
* Represents a simple property or field reference.
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public class PropertyOrFieldReference extends SpelNodeImpl {
private final boolean nullSafe;
private final String name;
private volatile PropertyAccessor cachedReadAccessor;
private volatile PropertyAccessor cachedWriteAccessor;
public PropertyOrFieldReference(boolean nullSafe, String propertyOrFieldName, int pos) {
super(pos);
this.nullSafe = nullSafe;
this.name = propertyOrFieldName;
}
public boolean isNullSafe() {
return this.nullSafe;
}
public String getName() {
return this.name;
}
@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
TypedValue result = readProperty(state, this.name);
// Dynamically create the objects if the user has requested that optional behaviour
if (result.getValue() == null && state.getConfiguration().isAutoGrowNullReferences() &&
nextChildIs(Indexer.class, PropertyOrFieldReference.class)) {
TypeDescriptor resultDescriptor = result.getTypeDescriptor();
// Creating lists and maps
if ((resultDescriptor.getType().equals(List.class) || resultDescriptor.getType().equals(Map.class))) {
// Create a new collection or map ready for the indexer
if (resultDescriptor.getType().equals(List.class)) {
try {
if (isWritable(state)) {
List newList = ArrayList.class.newInstance();
writeProperty(state, this.name, newList);
result = readProperty(state, this.name);
}
}
catch (InstantiationException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_CREATE_LIST_FOR_INDEXING);
}
catch (IllegalAccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_CREATE_LIST_FOR_INDEXING);
}
}
else {
try {
if (isWritable(state)) {
Map newMap = HashMap.class.newInstance();
writeProperty(state, name, newMap);
result = readProperty(state, this.name);
}
}
catch (InstantiationException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_CREATE_MAP_FOR_INDEXING);
}
catch (IllegalAccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_CREATE_MAP_FOR_INDEXING);
}
}
}
else {
// 'simple' object
try {
if (isWritable(state)) {
Object newObject = result.getTypeDescriptor().getType().newInstance();
writeProperty(state, name, newObject);
result = readProperty(state, this.name);
}
}
catch (InstantiationException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_DYNAMICALLY_CREATE_OBJECT, result.getTypeDescriptor().getType());
}
catch (IllegalAccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_DYNAMICALLY_CREATE_OBJECT, result.getTypeDescriptor().getType());
}
}
}
return result;
}
@Override
public void setValue(ExpressionState state, Object newValue) throws SpelEvaluationException {
writeProperty(state, this.name, newValue);
}
@Override
public boolean isWritable(ExpressionState state) throws SpelEvaluationException {
return isWritableProperty(this.name, state);
}
@Override
public String toStringAST() {
return this.name;
}
/**
* Attempt to read the named property from the current context object.
* @param state the evaluation state
* @param name the name of the property
* @return the value of the property
* @throws SpelEvaluationException if any problem accessing the property or it cannot be found
*/
private TypedValue readProperty(ExpressionState state, String name) throws EvaluationException {
TypedValue contextObject = state.getActiveContextObject();
Object targetObject = contextObject.getValue();
if (targetObject == null && this.nullSafe) {
return TypedValue.NULL;
}
PropertyAccessor accessorToUse = this.cachedReadAccessor;
if (accessorToUse != null) {
try {
return accessorToUse.read(state.getEvaluationContext(), contextObject.getValue(), name);
}
catch (AccessException ae) {
// this is OK - it may have gone stale due to a class change,
// let's try to get a new one and call it before giving up
this.cachedReadAccessor = null;
}
}
Class<?> contextObjectClass = getObjectClass(contextObject.getValue());
List<PropertyAccessor> accessorsToTry = getPropertyAccessorsToTry(contextObjectClass, state);
EvaluationContext eContext = state.getEvaluationContext();
// Go through the accessors that may be able to resolve it. If they are a cacheable accessor then
// get the accessor and use it. If they are not cacheable but report they can read the property
// then ask them to read it
if (accessorsToTry != null) {
try {
for (PropertyAccessor accessor : accessorsToTry) {
if (accessor.canRead(eContext, contextObject.getValue(), name)) {
if (accessor instanceof ReflectivePropertyAccessor) {
accessor = ((ReflectivePropertyAccessor) accessor).createOptimalAccessor(
eContext, contextObject.getValue(), name);
}
this.cachedReadAccessor = accessor;
return accessor.read(eContext, contextObject.getValue(), name);
}
}
}
catch (AccessException ae) {
throw new SpelEvaluationException(ae, SpelMessage.EXCEPTION_DURING_PROPERTY_READ, name, ae.getMessage());
}
}
if (contextObject.getValue() == null) {
throw new SpelEvaluationException(SpelMessage.PROPERTY_OR_FIELD_NOT_READABLE_ON_NULL, name);
}
else {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.PROPERTY_OR_FIELD_NOT_READABLE, name,
FormatHelper.formatClassNameForMessage(contextObjectClass));
}
}
private void writeProperty(ExpressionState state, String name, Object newValue) throws SpelEvaluationException {
TypedValue contextObject = state.getActiveContextObject();
EvaluationContext eContext = state.getEvaluationContext();
if (contextObject.getValue() == null && nullSafe) {
return;
}
PropertyAccessor accessorToUse = this.cachedWriteAccessor;
if (accessorToUse != null) {
try {
accessorToUse.write(state.getEvaluationContext(), contextObject.getValue(), name, newValue);
return;
}
catch (AccessException ae) {
// this is OK - it may have gone stale due to a class change,
// let's try to get a new one and call it before giving up
this.cachedWriteAccessor = null;
}
}
Class<?> contextObjectClass = getObjectClass(contextObject.getValue());
List<PropertyAccessor> accessorsToTry = getPropertyAccessorsToTry(contextObjectClass, state);
if (accessorsToTry != null) {
try {
for (PropertyAccessor accessor : accessorsToTry) {
if (accessor.canWrite(eContext, contextObject.getValue(), name)) {
this.cachedWriteAccessor = accessor;
accessor.write(eContext, contextObject.getValue(), name, newValue);
return;
}
}
}
catch (AccessException ae) {
throw new SpelEvaluationException(getStartPosition(), ae, SpelMessage.EXCEPTION_DURING_PROPERTY_WRITE,
name, ae.getMessage());
}
}
if (contextObject.getValue()==null) {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.PROPERTY_OR_FIELD_NOT_WRITABLE_ON_NULL, name);
}
else {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.PROPERTY_OR_FIELD_NOT_WRITABLE, name,
FormatHelper.formatClassNameForMessage(contextObjectClass));
}
}
public boolean isWritableProperty(String name, ExpressionState state) throws SpelEvaluationException {
Object contextObject = state.getActiveContextObject().getValue();
// TypeDescriptor td = state.getActiveContextObject().getTypeDescriptor();
EvaluationContext eContext = state.getEvaluationContext();
List<PropertyAccessor> resolversToTry = getPropertyAccessorsToTry(getObjectClass(contextObject), state);
if (resolversToTry != null) {
for (PropertyAccessor pfResolver : resolversToTry) {
try {
if (pfResolver.canWrite(eContext, contextObject, name)) {
return true;
}
}
catch (AccessException ae) {
// let others try
}
}
}
return false;
}
// TODO when there is more time, remove this and use the version in AstUtils
/**
* Determines the set of property resolvers that should be used to try and access a property on the specified target
* type. The resolvers are considered to be in an ordered list, however in the returned list any that are exact
* matches for the input target type (as opposed to 'general' resolvers that could work for any type) are placed at
* the start of the list. In addition, there are specific resolvers that exactly name the class in question and
* resolvers that name a specific class but it is a supertype of the class we have. These are put at the end of the
* specific resolvers set and will be tried after exactly matching accessors but before generic accessors.
* @param targetType the type upon which property access is being attempted
* @return a list of resolvers that should be tried in order to access the property
*/
private List<PropertyAccessor> getPropertyAccessorsToTry(Class<?> targetType, ExpressionState state) {
List<PropertyAccessor> specificAccessors = new ArrayList<PropertyAccessor>();
List<PropertyAccessor> generalAccessors = new ArrayList<PropertyAccessor>();
for (PropertyAccessor resolver : state.getPropertyAccessors()) {
Class<?>[] targets = resolver.getSpecificTargetClasses();
if (targets == null) { // generic resolver that says it can be used for any type
generalAccessors.add(resolver);
}
else {
if (targetType != null) {
int pos = 0;
for (Class<?> clazz : targets) {
if (clazz == targetType) { // put exact matches on the front to be tried first?
specificAccessors.add(pos++, resolver);
}
else if (clazz.isAssignableFrom(targetType)) { // put supertype matches at the end of the
// specificAccessor list
generalAccessors.add(resolver);
}
}
}
}
}
List<PropertyAccessor> resolvers = new ArrayList<PropertyAccessor>();
resolvers.addAll(specificAccessors);
resolvers.addAll(generalAccessors);
return resolvers;
}
}
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