org.springframework.expression.spel.ExpressionState Maven / Gradle / Ivy
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/*
* 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;
import java.util.ArrayDeque;
import java.util.Collections;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
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.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
/**
* An 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 for to define common utility routines that the various AST
* nodes might need.
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public class ExpressionState {
private final EvaluationContext relatedContext;
private final TypedValue rootObject;
private final SpelParserConfiguration configuration;
@Nullable
private Deque contextObjects;
@Nullable
private Deque variableScopes;
// 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
@Nullable
private ArrayDeque 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(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) {
if (this.contextObjects == null) {
this.contextObjects = new ArrayDeque<>();
}
this.contextObjects.push(obj);
}
public void popActiveContextObject() {
if (this.contextObjects == null) {
this.contextObjects = new ArrayDeque<>();
}
try {
this.contextObjects.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();
}
public void setVariable(String name, @Nullable Object value) {
this.relatedContext.setVariable(name, value);
}
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 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 TypeConverter getTypeConverter() {
return this.relatedContext.getTypeConverter();
}
@Nullable
public Object convertValue(TypedValue value, TypeDescriptor targetTypeDescriptor) throws EvaluationException {
Object val = value.getValue();
return this.relatedContext.getTypeConverter().convertValue(
val, TypeDescriptor.forObject(val), targetTypeDescriptor);
}
/*
* A new scope is entered when a function is invoked.
*/
public void enterScope(Map argMap) {
initVariableScopes().push(new VariableScope(argMap));
initScopeRootObjects().push(getActiveContextObject());
}
public void enterScope() {
initVariableScopes().push(new VariableScope(Collections.emptyMap()));
initScopeRootObjects().push(getActiveContextObject());
}
public void enterScope(String name, Object value) {
initVariableScopes().push(new VariableScope(name, value));
initScopeRootObjects().push(getActiveContextObject());
}
public void exitScope() {
initVariableScopes().pop();
initScopeRootObjects().pop();
}
public void setLocalVariable(String name, Object value) {
initVariableScopes().element().setVariable(name, value);
}
@Nullable
public Object lookupLocalVariable(String name) {
for (VariableScope scope : initVariableScopes()) {
if (scope.definesVariable(name)) {
return scope.lookupVariable(name);
}
}
return null;
}
private Deque initVariableScopes() {
if (this.variableScopes == null) {
this.variableScopes = new ArrayDeque<>();
// top-level empty variable scope
this.variableScopes.add(new VariableScope());
}
return this.variableScopes;
}
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;
}
/**
* A new scope is entered when a function is called and it is used to hold the
* parameters to the function call. If the names of the parameters clash with
* those in a higher level scope, those in the higher level scope will not be
* accessible whilst the function is executing. When the function returns,
* the scope is exited.
*/
private static class VariableScope {
private final Map vars = new HashMap<>();
public VariableScope() {
}
public VariableScope(@Nullable Map arguments) {
if (arguments != null) {
this.vars.putAll(arguments);
}
}
public VariableScope(String name, Object value) {
this.vars.put(name,value);
}
public Object lookupVariable(String name) {
return this.vars.get(name);
}
public void setVariable(String name, Object value) {
this.vars.put(name,value);
}
public boolean definesVariable(String name) {
return this.vars.containsKey(name);
}
}
}