/*
* 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.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.EvaluationException;
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.util.ClassUtils;
import org.springframework.util.ObjectUtils;
/**
* Represents projection, where a given operation is performed on all elements in some input sequence, returning
* a new sequence of the same size. For example:
* "{1,2,3,4,5,6,7,8,9,10}.!{#isEven(#this)}" returns "[n, y, n, y, n, y, n, y, n, y]"
*
* @author Andy Clement
* @author Mark Fisher
* @since 3.0
*/
public class Projection extends SpelNodeImpl {
private final boolean nullSafe;
public Projection(boolean nullSafe, int pos, SpelNodeImpl expression) {
super(pos, expression);
this.nullSafe = nullSafe;
}
@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
TypedValue op = state.getActiveContextObject();
Object operand = op.getValue();
boolean operandIsArray = ObjectUtils.isArray(operand);
// TypeDescriptor operandTypeDescriptor = op.getTypeDescriptor();
// When the input is a map, we push a special context object on the stack
// before calling the specified operation. This special context object
// has two fields 'key' and 'value' that refer to the map entries key
// and value, and they can be referenced in the operation
// eg. {'a':'y','b':'n'}.!{value=='y'?key:null}" == ['a', null]
if (operand instanceof Map) {
Map<?, ?> mapData = (Map<?, ?>) operand;
List<Object> result = new ArrayList<Object>();
for (Map.Entry entry : mapData.entrySet()) {
try {
state.pushActiveContextObject(new TypedValue(entry, TypeDescriptor.valueOf(Map.Entry.class)));
result.add(this.children[0].getValueInternal(state).getValue());
}
finally {
state.popActiveContextObject();
}
}
return new TypedValue(result,TypeDescriptor.valueOf(List.class)); // TODO unable to build correct type descriptor
}
else if (operand instanceof Collection || operandIsArray) {
Collection<?> data = (operand instanceof Collection ? (Collection<?>) operand :
Arrays.asList(ObjectUtils.toObjectArray(operand)));
List<Object> result = new ArrayList<Object>();
int idx = 0;
Class<?> arrayElementType = null;
for (Object element : data) {
try {
state.pushActiveContextObject(new TypedValue(element ,TypeDescriptor.valueOf(op.getTypeDescriptor().getType())));
state.enterScope("index", idx);
Object value = children[0].getValueInternal(state).getValue();
if (value != null && operandIsArray) {
arrayElementType = determineCommonType(arrayElementType, value.getClass());
}
result.add(value);
}
finally {
state.exitScope();
state.popActiveContextObject();
}
idx++;
}
if (operandIsArray) {
if (arrayElementType == null) {
arrayElementType = Object.class;
}
Object resultArray = Array.newInstance(arrayElementType, result.size());
System.arraycopy(result.toArray(), 0, resultArray, 0, result.size());
return new TypedValue(resultArray, op.getTypeDescriptor());
}
return new TypedValue(result, op.getTypeDescriptor());
}
else {
if (operand==null) {
if (this.nullSafe) {
return TypedValue.NULL;
}
else {
throw new SpelEvaluationException(getStartPosition(),
SpelMessage.PROJECTION_NOT_SUPPORTED_ON_TYPE, "null");
}
}
else {
throw new SpelEvaluationException(getStartPosition(),
SpelMessage.PROJECTION_NOT_SUPPORTED_ON_TYPE, operand.getClass().getName());
}
}
}
@Override
public String toStringAST() {
StringBuilder sb = new StringBuilder();
return sb.append("![").append(getChild(0).toStringAST()).append("]").toString();
}
private Class<?> determineCommonType(Class<?> oldType, Class<?> newType) {
if (oldType == null) {
return newType;
}
if (oldType.isAssignableFrom(newType)) {
return oldType;
}
Class<?> nextType = newType;
while (nextType != Object.class) {
if (nextType.isAssignableFrom(oldType)) {
return nextType;
}
nextType = nextType.getSuperclass();
}
Class<?>[] interfaces = ClassUtils.getAllInterfacesForClass(newType);
for (Class<?> nextInterface : interfaces) {
if (nextInterface.isAssignableFrom(oldType)) {
return nextInterface;
}
}
return Object.class;
}
}
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