org.springframework.expression.spel.ExpressionState Maven / Gradle / Ivy
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/*
* Copyright 2002-2024 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
*
* https://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;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.function.Supplier;
import org.jspecify.annotations.Nullable;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.Operation;
import org.springframework.expression.OperatorOverloader;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypeComparator;
import org.springframework.expression.TypeConverter;
import org.springframework.expression.TypedValue;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
/**
* ExpressionState is for maintaining per-expression-evaluation state: any changes to
* it are not seen by other expressions, but it gives a place to hold local variables and
* for component expressions in a compound expression to communicate state. This is in
* contrast to the EvaluationContext, which is shared amongst expression evaluations, and
* any changes to it will be seen by other expressions or any code that chooses to ask
* questions of the context.
*
* It also acts as a place to define common utility routines that the various AST
* nodes might need.
*
* @author Andy Clement
* @author Juergen Hoeller
* @author Sam Brannen
* @since 3.0
*/
public class ExpressionState {
private final EvaluationContext relatedContext;
private final TypedValue rootObject;
private final SpelParserConfiguration configuration;
private @Nullable Deque contextObjects;
// When entering a new scope there is a new base object which should be used
// for '#this' references (or to act as a target for unqualified references).
// This ArrayDeque captures those objects at each nested scope level.
// For example:
// #list1.?[#list2.contains(#this)]
// On entering the selection we enter a new scope, and #this is now the
// element from list1.
private @Nullable Deque scopeRootObjects;
public ExpressionState(EvaluationContext context) {
this(context, context.getRootObject(), new SpelParserConfiguration(false, false));
}
public ExpressionState(EvaluationContext context, SpelParserConfiguration configuration) {
this(context, context.getRootObject(), configuration);
}
public ExpressionState(EvaluationContext context, TypedValue rootObject) {
this(context, rootObject, new SpelParserConfiguration(false, false));
}
public ExpressionState(EvaluationContext context, TypedValue rootObject, SpelParserConfiguration configuration) {
Assert.notNull(context, "EvaluationContext must not be null");
Assert.notNull(rootObject, "'rootObject' must not be null");
Assert.notNull(configuration, "SpelParserConfiguration must not be null");
this.relatedContext = context;
this.rootObject = rootObject;
this.configuration = configuration;
}
/**
* The active context object is what unqualified references to properties/etc are resolved against.
*/
public TypedValue getActiveContextObject() {
if (CollectionUtils.isEmpty(this.contextObjects)) {
return this.rootObject;
}
return this.contextObjects.element();
}
public void pushActiveContextObject(TypedValue obj) {
initContextObjects().push(obj);
}
public void popActiveContextObject() {
try {
initContextObjects().pop();
}
catch (NoSuchElementException ex) {
throw new IllegalStateException("Cannot pop active context object: stack is empty");
}
}
public TypedValue getRootContextObject() {
return this.rootObject;
}
public TypedValue getScopeRootContextObject() {
if (CollectionUtils.isEmpty(this.scopeRootObjects)) {
return this.rootObject;
}
return this.scopeRootObjects.element();
}
/**
* Assign the value created by the specified {@link Supplier} to a named variable
* within the evaluation context.
* In contrast to {@link #setVariable(String, Object)}, this method should
* only be invoked to support assignment within an expression.
* @param name the name of the variable to assign
* @param valueSupplier the supplier of the value to be assigned to the variable
* @return a {@link TypedValue} wrapping the assigned value
* @since 5.2.24
* @see EvaluationContext#assignVariable(String, Supplier)
*/
public TypedValue assignVariable(String name, Supplier valueSupplier) {
return this.relatedContext.assignVariable(name, valueSupplier);
}
/**
* Set a named variable in the evaluation context to a specified value.
* In contrast to {@link #assignVariable(String, Supplier)}, this method
* should only be invoked programmatically.
* @param name the name of the variable to set
* @param value the value to be placed in the variable
* @see EvaluationContext#setVariable(String, Object)
*/
public void setVariable(String name, @Nullable Object value) {
this.relatedContext.setVariable(name, value);
}
/**
* Look up a named global variable in the evaluation context.
* @param name the name of the variable to look up
* @return a {@link TypedValue} containing the value of the variable, or
* {@link TypedValue#NULL} if the variable does not exist
* @see #assignVariable(String, Supplier)
* @see #setVariable(String, Object)
*/
public TypedValue lookupVariable(String name) {
Object value = this.relatedContext.lookupVariable(name);
return (value != null ? new TypedValue(value) : TypedValue.NULL);
}
public TypeComparator getTypeComparator() {
return this.relatedContext.getTypeComparator();
}
public Class findType(String type) throws EvaluationException {
return this.relatedContext.getTypeLocator().findType(type);
}
public TypeConverter getTypeConverter() {
return this.relatedContext.getTypeConverter();
}
public Object convertValue(Object value, TypeDescriptor targetTypeDescriptor) throws EvaluationException {
Object result = this.relatedContext.getTypeConverter().convertValue(
value, TypeDescriptor.forObject(value), targetTypeDescriptor);
if (result == null) {
throw new IllegalStateException("Null conversion result for value [" + value + "]");
}
return result;
}
public @Nullable Object convertValue(TypedValue value, TypeDescriptor targetTypeDescriptor) throws EvaluationException {
Object val = value.getValue();
return this.relatedContext.getTypeConverter().convertValue(
val, TypeDescriptor.forObject(val), targetTypeDescriptor);
}
/**
* Enter a new scope with a new {@linkplain #getActiveContextObject() root
* context object} and a new local variable scope.
*/
public void enterScope() {
initScopeRootObjects().push(getActiveContextObject());
}
public void exitScope() {
initScopeRootObjects().pop();
}
private Deque initContextObjects() {
if (this.contextObjects == null) {
this.contextObjects = new ArrayDeque<>();
}
return this.contextObjects;
}
private Deque initScopeRootObjects() {
if (this.scopeRootObjects == null) {
this.scopeRootObjects = new ArrayDeque<>();
}
return this.scopeRootObjects;
}
public TypedValue operate(Operation op, @Nullable Object left, @Nullable Object right) throws EvaluationException {
OperatorOverloader overloader = this.relatedContext.getOperatorOverloader();
if (overloader.overridesOperation(op, left, right)) {
Object returnValue = overloader.operate(op, left, right);
return new TypedValue(returnValue);
}
else {
String leftType = (left == null ? "null" : left.getClass().getName());
String rightType = (right == null? "null" : right.getClass().getName());
throw new SpelEvaluationException(SpelMessage.OPERATOR_NOT_SUPPORTED_BETWEEN_TYPES, op, leftType, rightType);
}
}
public List getPropertyAccessors() {
return this.relatedContext.getPropertyAccessors();
}
public EvaluationContext getEvaluationContext() {
return this.relatedContext;
}
public SpelParserConfiguration getConfiguration() {
return this.configuration;
}
}