/*
* Copyright 2002-2018 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.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.asm.Label;
import org.springframework.asm.MethodVisitor;
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.CodeFlow;
import org.springframework.expression.spel.CompilablePropertyAccessor;
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;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ReflectionUtils;
/**
* Represents a simple property or field reference.
*
* @author Andy Clement
* @author Juergen Hoeller
* @author Clark Duplichien
* @since 3.0
*/
public class PropertyOrFieldReference extends SpelNodeImpl {
private final boolean nullSafe;
private final String name;
@Nullable
private String originalPrimitiveExitTypeDescriptor;
@Nullable
private volatile PropertyAccessor cachedReadAccessor;
@Nullable
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 ValueRef getValueRef(ExpressionState state) throws EvaluationException {
return new AccessorLValue(this, state.getActiveContextObject(), state.getEvaluationContext(),
state.getConfiguration().isAutoGrowNullReferences());
}
@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
TypedValue tv = getValueInternal(state.getActiveContextObject(), state.getEvaluationContext(),
state.getConfiguration().isAutoGrowNullReferences());
PropertyAccessor accessorToUse = this.cachedReadAccessor;
if (accessorToUse instanceof CompilablePropertyAccessor) {
CompilablePropertyAccessor accessor = (CompilablePropertyAccessor) accessorToUse;
setExitTypeDescriptor(CodeFlow.toDescriptor(accessor.getPropertyType()));
}
return tv;
}
private TypedValue getValueInternal(TypedValue contextObject, EvaluationContext evalContext,
boolean isAutoGrowNullReferences) throws EvaluationException {
TypedValue result = readProperty(contextObject, evalContext, this.name);
// Dynamically create the objects if the user has requested that optional behavior
if (result.getValue() == null && isAutoGrowNullReferences &&
nextChildIs(Indexer.class, PropertyOrFieldReference.class)) {
TypeDescriptor resultDescriptor = result.getTypeDescriptor();
Assert.state(resultDescriptor != null, "No result type");
// Create a new collection or map ready for the indexer
if (List.class == resultDescriptor.getType()) {
if (isWritableProperty(this.name, contextObject, evalContext)) {
List<?> newList = new ArrayList<>();
writeProperty(contextObject, evalContext, this.name, newList);
result = readProperty(contextObject, evalContext, this.name);
}
}
else if (Map.class == resultDescriptor.getType()) {
if (isWritableProperty(this.name,contextObject, evalContext)) {
Map<?,?> newMap = new HashMap<>();
writeProperty(contextObject, evalContext, this.name, newMap);
result = readProperty(contextObject, evalContext, this.name);
}
}
else {
// 'simple' object
try {
if (isWritableProperty(this.name,contextObject, evalContext)) {
Class<?> clazz = result.getTypeDescriptor().getType();
Object newObject = ReflectionUtils.accessibleConstructor(clazz).newInstance();
writeProperty(contextObject, evalContext, this.name, newObject);
result = readProperty(contextObject, evalContext, this.name);
}
}
catch (InvocationTargetException ex) {
throw new SpelEvaluationException(getStartPosition(), ex.getTargetException(),
SpelMessage.UNABLE_TO_DYNAMICALLY_CREATE_OBJECT, result.getTypeDescriptor().getType());
}
catch (Throwable ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.UNABLE_TO_DYNAMICALLY_CREATE_OBJECT, result.getTypeDescriptor().getType());
}
}
}
return result;
}
@Override
public void setValue(ExpressionState state, @Nullable Object newValue) throws EvaluationException {
writeProperty(state.getActiveContextObject(), state.getEvaluationContext(), this.name, newValue);
}
@Override
public boolean isWritable(ExpressionState state) throws EvaluationException {
return isWritableProperty(this.name, state.getActiveContextObject(), state.getEvaluationContext());
}
@Override
public String toStringAST() {
return this.name;
}
/**
* Attempt to read the named property from the current context object.
* @return the value of the property
* @throws EvaluationException if any problem accessing the property or it cannot be found
*/
private TypedValue readProperty(TypedValue contextObject, EvaluationContext evalContext, String name)
throws EvaluationException {
Object targetObject = contextObject.getValue();
if (targetObject == null && this.nullSafe) {
return TypedValue.NULL;
}
PropertyAccessor accessorToUse = this.cachedReadAccessor;
if (accessorToUse != null) {
if (evalContext.getPropertyAccessors().contains(accessorToUse)) {
try {
return accessorToUse.read(evalContext, contextObject.getValue(), name);
}
catch (Exception ex) {
// 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;
}
List<PropertyAccessor> accessorsToTry =
getPropertyAccessorsToTry(contextObject.getValue(), evalContext.getPropertyAccessors());
// 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
try {
for (PropertyAccessor accessor : accessorsToTry) {
if (accessor.canRead(evalContext, contextObject.getValue(), name)) {
if (accessor instanceof ReflectivePropertyAccessor) {
accessor = ((ReflectivePropertyAccessor) accessor).createOptimalAccessor(
evalContext, contextObject.getValue(), name);
}
this.cachedReadAccessor = accessor;
return accessor.read(evalContext, contextObject.getValue(), name);
}
}
}
catch (Exception ex) {
throw new SpelEvaluationException(ex, SpelMessage.EXCEPTION_DURING_PROPERTY_READ, name, ex.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(getObjectClass(contextObject.getValue())));
}
}
private void writeProperty(
TypedValue contextObject, EvaluationContext evalContext, String name, @Nullable Object newValue)
throws EvaluationException {
if (contextObject.getValue() == null && this.nullSafe) {
return;
}
if (contextObject.getValue() == null) {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.PROPERTY_OR_FIELD_NOT_WRITABLE_ON_NULL, name);
}
PropertyAccessor accessorToUse = this.cachedWriteAccessor;
if (accessorToUse != null) {
if (evalContext.getPropertyAccessors().contains(accessorToUse)) {
try {
accessorToUse.write(evalContext, contextObject.getValue(), name, newValue);
return;
}
catch (Exception ex) {
// 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;
}
List<PropertyAccessor> accessorsToTry =
getPropertyAccessorsToTry(contextObject.getValue(), evalContext.getPropertyAccessors());
try {
for (PropertyAccessor accessor : accessorsToTry) {
if (accessor.canWrite(evalContext, contextObject.getValue(), name)) {
this.cachedWriteAccessor = accessor;
accessor.write(evalContext, contextObject.getValue(), name, newValue);
return;
}
}
}
catch (AccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex, SpelMessage.EXCEPTION_DURING_PROPERTY_WRITE,
name, ex.getMessage());
}
throw new SpelEvaluationException(getStartPosition(), SpelMessage.PROPERTY_OR_FIELD_NOT_WRITABLE, name,
FormatHelper.formatClassNameForMessage(getObjectClass(contextObject.getValue())));
}
public boolean isWritableProperty(String name, TypedValue contextObject, EvaluationContext evalContext)
throws EvaluationException {
Object value = contextObject.getValue();
if (value != null) {
List<PropertyAccessor> accessorsToTry =
getPropertyAccessorsToTry(contextObject.getValue(), evalContext.getPropertyAccessors());
for (PropertyAccessor accessor : accessorsToTry) {
try {
if (accessor.canWrite(evalContext, value, name)) {
return true;
}
}
catch (AccessException ex) {
// let others try
}
}
}
return false;
}
/**
* 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 contextObject the object 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(
@Nullable Object contextObject, List<PropertyAccessor> propertyAccessors) {
Class<?> targetType = (contextObject != null ? contextObject.getClass() : null);
List<PropertyAccessor> specificAccessors = new ArrayList<>();
List<PropertyAccessor> generalAccessors = new ArrayList<>();
for (PropertyAccessor resolver : propertyAccessors) {
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) {
for (Class<?> clazz : targets) {
if (clazz == targetType) {
specificAccessors.add(resolver);
break;
}
else if (clazz.isAssignableFrom(targetType)) {
generalAccessors.add(resolver);
}
}
}
}
List<PropertyAccessor> resolvers = new ArrayList<>(specificAccessors);
generalAccessors.removeAll(specificAccessors);
resolvers.addAll(generalAccessors);
return resolvers;
}
@Override
public boolean isCompilable() {
PropertyAccessor accessorToUse = this.cachedReadAccessor;
return (accessorToUse instanceof CompilablePropertyAccessor &&
((CompilablePropertyAccessor) accessorToUse).isCompilable());
}
@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
PropertyAccessor accessorToUse = this.cachedReadAccessor;
if (!(accessorToUse instanceof CompilablePropertyAccessor)) {
throw new IllegalStateException("Property accessor is not compilable: " + accessorToUse);
}
Label skipIfNull = null;
if (this.nullSafe) {
mv.visitInsn(DUP);
skipIfNull = new Label();
Label continueLabel = new Label();
mv.visitJumpInsn(IFNONNULL, continueLabel);
CodeFlow.insertCheckCast(mv, this.exitTypeDescriptor);
mv.visitJumpInsn(GOTO, skipIfNull);
mv.visitLabel(continueLabel);
}
((CompilablePropertyAccessor) accessorToUse).generateCode(this.name, mv, cf);
cf.pushDescriptor(this.exitTypeDescriptor);
if (this.originalPrimitiveExitTypeDescriptor != null) {
// The output of the accessor is a primitive but from the block above it might be null,
// so to have a common stack element type at skipIfNull target it is necessary
// to box the primitive
CodeFlow.insertBoxIfNecessary(mv, this.originalPrimitiveExitTypeDescriptor);
}
if (skipIfNull != null) {
mv.visitLabel(skipIfNull);
}
}
void setExitTypeDescriptor(String descriptor) {
// If this property or field access would return a primitive - and yet
// it is also marked null safe - then the exit type descriptor must be
// promoted to the box type to allow a null value to be passed on
if (this.nullSafe && CodeFlow.isPrimitive(descriptor)) {
this.originalPrimitiveExitTypeDescriptor = descriptor;
this.exitTypeDescriptor = CodeFlow.toBoxedDescriptor(descriptor);
}
else {
this.exitTypeDescriptor = descriptor;
}
}
private static class AccessorLValue implements ValueRef {
private final PropertyOrFieldReference ref;
private final TypedValue contextObject;
private final EvaluationContext evalContext;
private final boolean autoGrowNullReferences;
public AccessorLValue(PropertyOrFieldReference propertyOrFieldReference, TypedValue activeContextObject,
EvaluationContext evalContext, boolean autoGrowNullReferences) {
this.ref = propertyOrFieldReference;
this.contextObject = activeContextObject;
this.evalContext = evalContext;
this.autoGrowNullReferences = autoGrowNullReferences;
}
@Override
public TypedValue getValue() {
TypedValue value =
this.ref.getValueInternal(this.contextObject, this.evalContext, this.autoGrowNullReferences);
PropertyAccessor accessorToUse = this.ref.cachedReadAccessor;
if (accessorToUse instanceof CompilablePropertyAccessor) {
this.ref.setExitTypeDescriptor(CodeFlow.toDescriptor(((CompilablePropertyAccessor) accessorToUse).getPropertyType()));
}
return value;
}
@Override
public void setValue(@Nullable Object newValue) {
this.ref.writeProperty(this.contextObject, this.evalContext, this.ref.name, newValue);
}
@Override
public boolean isWritable() {
return this.ref.isWritableProperty(this.ref.name, this.contextObject, this.evalContext);
}
}
}
