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Thread-safe compiled expression evaluation in SpelExpression
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Closes gh-24265
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@jhoeller
jhoeller committed Jan 8, 2020
1 parent 9d6e40f commit 259ffe9
Showing 1 changed file with 63 additions and 45 deletions.
108 changes: 63 additions & 45 deletions ...expression/src/main/java/org/springframework/expression/spel/standard/SpelExpression.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2019 the original author or authors.
* Copyright 2002-2020 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 @@ -67,15 +67,15 @@ public class SpelExpression implements Expression {

// Holds the compiled form of the expression (if it has been compiled)
@Nullable
private CompiledExpression compiledAst;
private volatile CompiledExpression compiledAst;

// Count of many times as the expression been interpreted - can trigger compilation
// when certain limit reached
private final AtomicInteger interpretedCount = new AtomicInteger(0);

// The number of times compilation was attempted and failed - enables us to eventually
// give up trying to compile it when it just doesn't seem to be possible.
private volatile int failedAttempts = 0;
private final AtomicInteger failedAttempts = new AtomicInteger(0);


/**
Expand Down Expand Up @@ -118,16 +118,17 @@ public String getExpressionString() {
@Override
@Nullable
public Object getValue() throws EvaluationException {
if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
EvaluationContext context = getEvaluationContext();
return this.compiledAst.getValue(context.getRootObject().getValue(), context);
return compiledAst.getValue(context.getRootObject().getValue(), context);
}
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -146,10 +147,11 @@ public Object getValue() throws EvaluationException {
@Override
@Nullable
public <T> T getValue(@Nullable Class<T> expectedResultType) throws EvaluationException {
if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
EvaluationContext context = getEvaluationContext();
Object result = this.compiledAst.getValue(context.getRootObject().getValue(), context);
Object result = compiledAst.getValue(context.getRootObject().getValue(), context);
if (expectedResultType == null) {
return (T) result;
}
Expand All @@ -161,8 +163,8 @@ public <T> T getValue(@Nullable Class<T> expectedResultType) throws EvaluationEx
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -181,15 +183,16 @@ public <T> T getValue(@Nullable Class<T> expectedResultType) throws EvaluationEx
@Override
@Nullable
public Object getValue(@Nullable Object rootObject) throws EvaluationException {
if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
return this.compiledAst.getValue(rootObject, getEvaluationContext());
return compiledAst.getValue(rootObject, getEvaluationContext());
}
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -209,9 +212,10 @@ public Object getValue(@Nullable Object rootObject) throws EvaluationException {
@Override
@Nullable
public <T> T getValue(@Nullable Object rootObject, @Nullable Class<T> expectedResultType) throws EvaluationException {
if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
Object result = this.compiledAst.getValue(rootObject, getEvaluationContext());
Object result = compiledAst.getValue(rootObject, getEvaluationContext());
if (expectedResultType == null) {
return (T)result;
}
Expand All @@ -223,8 +227,8 @@ public <T> T getValue(@Nullable Object rootObject, @Nullable Class<T> expectedRe
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -246,15 +250,16 @@ public <T> T getValue(@Nullable Object rootObject, @Nullable Class<T> expectedRe
public Object getValue(EvaluationContext context) throws EvaluationException {
Assert.notNull(context, "EvaluationContext is required");

if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
return this.compiledAst.getValue(context.getRootObject().getValue(), context);
return compiledAst.getValue(context.getRootObject().getValue(), context);
}
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -275,9 +280,10 @@ public Object getValue(EvaluationContext context) throws EvaluationException {
public <T> T getValue(EvaluationContext context, @Nullable Class<T> expectedResultType) throws EvaluationException {
Assert.notNull(context, "EvaluationContext is required");

if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
Object result = this.compiledAst.getValue(context.getRootObject().getValue(), context);
Object result = compiledAst.getValue(context.getRootObject().getValue(), context);
if (expectedResultType != null) {
return ExpressionUtils.convertTypedValue(context, new TypedValue(result), expectedResultType);
}
Expand All @@ -288,8 +294,8 @@ public <T> T getValue(EvaluationContext context, @Nullable Class<T> expectedResu
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -309,15 +315,16 @@ public <T> T getValue(EvaluationContext context, @Nullable Class<T> expectedResu
public Object getValue(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException {
Assert.notNull(context, "EvaluationContext is required");

if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
return this.compiledAst.getValue(rootObject, context);
return compiledAst.getValue(rootObject, context);
}
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand All @@ -340,9 +347,10 @@ public <T> T getValue(EvaluationContext context, @Nullable Object rootObject, @N

Assert.notNull(context, "EvaluationContext is required");

if (this.compiledAst != null) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
try {
Object result = this.compiledAst.getValue(rootObject, context);
Object result = compiledAst.getValue(rootObject, context);
if (expectedResultType != null) {
return ExpressionUtils.convertTypedValue(context, new TypedValue(result), expectedResultType);
}
Expand All @@ -353,8 +361,8 @@ public <T> T getValue(EvaluationContext context, @Nullable Object rootObject, @N
catch (Throwable ex) {
// If running in mixed mode, revert to interpreted
if (this.configuration.getCompilerMode() == SpelCompilerMode.MIXED) {
this.interpretedCount.set(0);
this.compiledAst = null;
this.interpretedCount.set(0);
}
else {
// Running in SpelCompilerMode.immediate mode - propagate exception to caller
Expand Down Expand Up @@ -492,31 +500,41 @@ private void checkCompile(ExpressionState expressionState) {
}
}


/**
* Perform expression compilation. This will only succeed once exit descriptors for all nodes have
* been determined. If the compilation fails and has failed more than 100 times the expression is
* no longer considered suitable for compilation.
* Perform expression compilation. This will only succeed once exit descriptors for
* all nodes have been determined. If the compilation fails and has failed more than
* 100 times the expression is no longer considered suitable for compilation.
* @return whether this expression has been successfully compiled
*/
public boolean compileExpression() {
if (this.failedAttempts > FAILED_ATTEMPTS_THRESHOLD) {
CompiledExpression compiledAst = this.compiledAst;
if (compiledAst != null) {
// Previously compiled
return true;
}
if (this.failedAttempts.get() > FAILED_ATTEMPTS_THRESHOLD) {
// Don't try again
return false;
}
if (this.compiledAst == null) {
synchronized (this.expression) {
// Possibly compiled by another thread before this thread got into the sync block
if (this.compiledAst != null) {
return true;
}
SpelCompiler compiler = SpelCompiler.getCompiler(this.configuration.getCompilerClassLoader());
this.compiledAst = compiler.compile(this.ast);
if (this.compiledAst == null) {
this.failedAttempts++;
}

synchronized (this) {
if (this.compiledAst != null) {
// Compiled by another thread before this thread got into the sync block
return true;
}
SpelCompiler compiler = SpelCompiler.getCompiler(this.configuration.getCompilerClassLoader());
compiledAst = compiler.compile(this.ast);
if (compiledAst != null) {
// Successfully compiled
this.compiledAst = compiledAst;
return true;
}
else {
// Failed to compile
this.failedAttempts.incrementAndGet();
return false;
}
}
return (this.compiledAst != null);
}

/**
Expand All @@ -527,7 +545,7 @@ public boolean compileExpression() {
public void revertToInterpreted() {
this.compiledAst = null;
this.interpretedCount.set(0);
this.failedAttempts = 0;
this.failedAttempts.set(0);
}

/**
Expand Down

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