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Disable variable assignment in SimpleEvaluationContext
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This commit introduces infrastructure to differentiate between
programmatic setting of a variable in an EvaluationContext versus the
assignment of a variable within a SpEL expression using the assignment
operator (=). In addition, this commit disables variable assignment
within expressions when using the SimpleEvaluationContext.

Closes gh-30327
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sbrannen authored and bclozel committed Apr 13, 2023
1 parent ebc8265 commit 6bfb94a
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Showing 11 changed files with 180 additions and 41 deletions.
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/*
* Copyright 2002-2018 the original author or authors.
* Copyright 2002-2023 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.
Expand All @@ -17,19 +17,29 @@
package org.springframework.expression;

import java.util.List;
import java.util.function.Supplier;

import org.springframework.lang.Nullable;

/**
* Expressions are executed in an evaluation context. It is in this context that
* references are resolved when encountered during expression evaluation.
*
* <p>There is a default implementation of this EvaluationContext interface:
* {@link org.springframework.expression.spel.support.StandardEvaluationContext}
* which can be extended, rather than having to implement everything manually.
* <p>There are two default implementations of this interface.
* <ul>
* <li>{@link org.springframework.expression.spel.support.SimpleEvaluationContext
* SimpleEvaluationContext}: a simpler builder-style {@code EvaluationContext}
* variant for data-binding purposes, which allows for opting into several SpEL
* features as needed.</li>
* <li>{@link org.springframework.expression.spel.support.StandardEvaluationContext
* StandardEvaluationContext}: a powerful and highly configurable {@code EvaluationContext}
* implementation, which can be extended, rather than having to implement everything
* manually.</li>
* </ul>
*
* @author Andy Clement
* @author Juergen Hoeller
* @author Sam Brannen
* @since 3.0
*/
public interface EvaluationContext {
Expand Down Expand Up @@ -85,15 +95,38 @@ public interface EvaluationContext {
OperatorOverloader getOperatorOverloader();

/**
* Set a named variable within this evaluation context to a specified value.
* Assign the value created by the specified {@link Supplier} to a named variable
* within this evaluation context.
* <p>In contrast to {@link #setVariable(String, Object)}, this method should only
* be invoked to support the assignment operator ({@code =}) within an expression.
* <p>By default, this method delegates to {@code setVariable(String, Object)},
* providing the value created by the {@code valueSupplier}. Concrete implementations
* may override this <em>default</em> method to provide different semantics.
* @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
*/
default TypedValue assignVariable(String name, Supplier<TypedValue> valueSupplier) {
TypedValue typedValue = valueSupplier.get();
setVariable(name, typedValue.getValue());
return typedValue;
}

/**
* Set a named variable in this evaluation context to a specified value.
* <p>In contrast to {@link #assignVariable(String, Supplier)}, this method
* should only be invoked programmatically when interacting directly with the
* {@code EvaluationContext} &mdash; for example, to provide initial
* configuration for the context.
* @param name the name of the variable to set
* @param value the value to be placed in the variable
*/
void setVariable(String name, @Nullable Object value);

/**
* Look up a named variable within this evaluation context.
* @param name variable to lookup
* @param name the name of the variable to look up
* @return the value of the variable, or {@code null} if not found
*/
@Nullable
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2018 the original author or authors.
* Copyright 2002-2023 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.
Expand All @@ -23,6 +23,7 @@
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.function.Supplier;

import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.EvaluationContext;
Expand All @@ -38,18 +39,19 @@
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
* 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.
*
* <p>It also acts as a place for to define common utility routines that the various AST
* <p>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 {
Expand Down Expand Up @@ -138,6 +140,29 @@ public TypedValue getScopeRootContextObject() {
return this.scopeRootObjects.element();
}

/**
* Assign the value created by the specified {@link Supplier} to a named variable
* within the evaluation context.
* <p>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<TypedValue> valueSupplier) {
return this.relatedContext.assignVariable(name, valueSupplier);
}

/**
* Set a named variable in the evaluation context to a specified value.
* <p>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);
}
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Expand Up @@ -280,7 +280,11 @@ public enum SpelMessage {

/** @since 5.2.24 */
MAX_EXPRESSION_LENGTH_EXCEEDED(Kind.ERROR, 1079,
"SpEL expression is too long, exceeding the threshold of ''{0}'' characters");
"SpEL expression is too long, exceeding the threshold of ''{0}'' characters"),

/** @since 5.2.24 */
VARIABLE_ASSIGNMENT_NOT_SUPPORTED(Kind.ERROR, 1080,
"Assignment to variable ''{0}'' is not supported");


private final Kind kind;
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2019 the original author or authors.
* Copyright 2002-2023 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.
Expand Down Expand Up @@ -27,6 +27,7 @@
* <p>Example: 'someNumberProperty=42'
*
* @author Andy Clement
* @author Sam Brannen
* @since 3.0
*/
public class Assign extends SpelNodeImpl {
Expand All @@ -38,9 +39,7 @@ public Assign(int startPos, int endPos, SpelNodeImpl... operands) {

@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
TypedValue newValue = this.children[1].getValueInternal(state);
getChild(0).setValue(state, newValue.getValue());
return newValue;
return this.children[0].setValueInternal(state, () -> this.children[1].getValueInternal(state));
}

@Override
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2019 the original author or authors.
* Copyright 2002-2023 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.
Expand All @@ -17,20 +17,21 @@
package org.springframework.expression.spel.ast;

import java.util.StringJoiner;
import java.util.function.Supplier;

import org.springframework.asm.MethodVisitor;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.CodeFlow;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.lang.Nullable;

/**
* Represents a DOT separated expression sequence, such as
* {@code 'property1.property2.methodOne()'}.
*
* @author Andy Clement
* @author Sam Brannen
* @since 3.0
*/
public class CompoundExpression extends SpelNodeImpl {
Expand Down Expand Up @@ -95,8 +96,12 @@ public TypedValue getValueInternal(ExpressionState state) throws EvaluationExcep
}

@Override
public void setValue(ExpressionState state, @Nullable Object value) throws EvaluationException {
getValueRef(state).setValue(value);
public TypedValue setValueInternal(ExpressionState state, Supplier<TypedValue> valueSupplier)
throws EvaluationException {

TypedValue typedValue = valueSupplier.get();
getValueRef(state).setValue(typedValue.getValue());
return typedValue;
}

@Override
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2020 the original author or authors.
* Copyright 2002-2023 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.
Expand All @@ -25,6 +25,7 @@
import java.util.List;
import java.util.Map;
import java.util.StringJoiner;
import java.util.function.Supplier;

import org.springframework.asm.MethodVisitor;
import org.springframework.core.convert.TypeDescriptor;
Expand All @@ -45,11 +46,12 @@

/**
* An Indexer can index into some proceeding structure to access a particular piece of it.
* Supported structures are: strings / collections (lists/sets) / arrays.
* <p>Supported structures are: strings / collections (lists/sets) / arrays.
*
* @author Andy Clement
* @author Phillip Webb
* @author Stephane Nicoll
* @author Sam Brannen
* @since 3.0
*/
// TODO support multidimensional arrays
Expand Down Expand Up @@ -102,8 +104,12 @@ public TypedValue getValueInternal(ExpressionState state) throws EvaluationExcep
}

@Override
public void setValue(ExpressionState state, @Nullable Object newValue) throws EvaluationException {
getValueRef(state).setValue(newValue);
public TypedValue setValueInternal(ExpressionState state, Supplier<TypedValue> valueSupplier)
throws EvaluationException {

TypedValue typedValue = valueSupplier.get();
getValueRef(state).setValue(typedValue.getValue());
return typedValue;
}

@Override
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2019 the original author or authors.
* Copyright 2002-2023 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.
Expand All @@ -21,6 +21,7 @@
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Supplier;

import org.springframework.asm.Label;
import org.springframework.asm.MethodVisitor;
Expand All @@ -46,6 +47,7 @@
* @author Andy Clement
* @author Juergen Hoeller
* @author Clark Duplichien
* @author Sam Brannen
* @since 3.0
*/
public class PropertyOrFieldReference extends SpelNodeImpl {
Expand Down Expand Up @@ -147,8 +149,12 @@ else if (Map.class == resultDescriptor.getType()) {
}

@Override
public void setValue(ExpressionState state, @Nullable Object newValue) throws EvaluationException {
writeProperty(state.getActiveContextObject(), state.getEvaluationContext(), this.name, newValue);
public TypedValue setValueInternal(ExpressionState state, Supplier<TypedValue> valueSupplier)
throws EvaluationException {

TypedValue typedValue = valueSupplier.get();
writeProperty(state.getActiveContextObject(), state.getEvaluationContext(), this.name, typedValue.getValue());
return typedValue;
}

@Override
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright 2002-2019 the original author or authors.
* Copyright 2002-2023 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.
Expand All @@ -19,6 +19,7 @@
import java.lang.reflect.Constructor;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.util.function.Supplier;

import org.springframework.asm.MethodVisitor;
import org.springframework.asm.Opcodes;
Expand All @@ -40,6 +41,7 @@
*
* @author Andy Clement
* @author Juergen Hoeller
* @author Sam Brannen
* @since 3.0
*/
public abstract class SpelNodeImpl implements SpelNode, Opcodes {
Expand All @@ -64,7 +66,7 @@ public abstract class SpelNodeImpl implements SpelNode, Opcodes {
* <p>The descriptor is like the bytecode form but is slightly easier to work with.
* It does not include the trailing semicolon (for non array reference types).
* Some examples: Ljava/lang/String, I, [I
*/
*/
@Nullable
protected volatile String exitTypeDescriptor;

Expand All @@ -83,8 +85,8 @@ public SpelNodeImpl(int startPos, int endPos, SpelNodeImpl... operands) {


/**
* Return {@code true} if the next child is one of the specified classes.
*/
* Return {@code true} if the next child is one of the specified classes.
*/
protected boolean nextChildIs(Class<?>... classes) {
if (this.parent != null) {
SpelNodeImpl[] peers = this.parent.children;
Expand Down Expand Up @@ -125,6 +127,28 @@ public boolean isWritable(ExpressionState expressionState) throws EvaluationExce

@Override
public void setValue(ExpressionState expressionState, @Nullable Object newValue) throws EvaluationException {
setValueInternal(expressionState, () -> new TypedValue(newValue));
}

/**
* Evaluate the expression to a node and then set the new value created by the
* specified {@link Supplier} on that node.
* <p>For example, if the expression evaluates to a property reference, then the
* property will be set to the new value.
* <p>Favor this method over {@link #setValue(ExpressionState, Object)} when
* the value should be lazily computed.
* <p>By default, this method throws a {@link SpelEvaluationException},
* effectively disabling this feature. Subclasses may override this method to
* provide an actual implementation.
* @param expressionState the current expression state (includes the context)
* @param valueSupplier a supplier of the new value
* @throws EvaluationException if any problem occurs evaluating the expression or
* setting the new value
* @since 5.2.24
*/
public TypedValue setValueInternal(ExpressionState expressionState, Supplier<TypedValue> valueSupplier)
throws EvaluationException {

throw new SpelEvaluationException(getStartPosition(), SpelMessage.SETVALUE_NOT_SUPPORTED, getClass());
}

Expand Down
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