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Fixed getCachedExecutor race condition in MethodReference 

This commit includes a full backport of the changes in SPR-10657, instead of just the initial commit which the original backport request referred to.

Issue: SPR-10884
Issue: SPR-10657
This commit is contained in:
Juergen Hoeller 2013-09-02 15:33:15 +02:00
parent 9317d8f43e
commit 0c30618ae8
2 changed files with 150 additions and 176 deletions
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298
spring-expression/src/main/java/org/springframework/expression/spel/ast/MethodReference.java
View File

@ -62,116 +62,98 @@ public class MethodReference extends SpelNodeImpl {
@Override @Override
protected ValueRef getValueRef(ExpressionState state) throws EvaluationException { protected ValueRef getValueRef(ExpressionState state) throws EvaluationException {
TypedValue currentContext = state.getActiveContextObject(); Object[] arguments = getArguments(state);
Object[] arguments = new Object[getChildCount()]; if (state.getActiveContextObject().getValue() == null) {
for (int i = 0; i < arguments.length; i++) { throwIfNotNullSafe(getArgumentTypes(arguments));
// Make the root object the active context again for evaluating the parameter
// expressions
try {
state.pushActiveContextObject(state.getRootContextObject());
arguments[i] = this.children[i].getValueInternal(state).getValue();
}
finally {
state.popActiveContextObject();
}
}
if (currentContext.getValue() == null) {
if (this.nullSafe) {
return ValueRef.NullValueRef.instance; return ValueRef.NullValueRef.instance;
} }
else { return new MethodValueRef(state);
throw new SpelEvaluationException(getStartPosition(), SpelMessage.METHOD_CALL_ON_NULL_OBJECT_NOT_ALLOWED,
FormatHelper.formatMethodForMessage(this.name, getTypes(arguments)));
}
}
return new MethodValueRef(state,state.getEvaluationContext(),state.getActiveContextObject().getValue(),arguments);
} }
@Override @Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException { public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
TypedValue currentContext = state.getActiveContextObject(); EvaluationContext evaluationContext = state.getEvaluationContext();
Object[] arguments = new Object[getChildCount()]; Object value = state.getActiveContextObject().getValue();
for (int i = 0; i < arguments.length; i++) { TypeDescriptor targetType = state.getActiveContextObject().getTypeDescriptor();
// Make the root object the active context again for evaluating the parameter Object[] arguments = getArguments(state);
// expressions return getValueInternal(evaluationContext, value, arguments, targetType);
try {
state.pushActiveContextObject(state.getRootContextObject());
arguments[i] = this.children[i].getValueInternal(state).getValue();
}
finally {
state.popActiveContextObject();
}
}
List<TypeDescriptor> argumentTypes = getTypes(arguments);
if (currentContext.getValue() == null) {
if (this.nullSafe) {
return TypedValue.NULL;
}
else {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.METHOD_CALL_ON_NULL_OBJECT_NOT_ALLOWED,
FormatHelper.formatMethodForMessage(this.name, argumentTypes));
}
} }
MethodExecutor executorToUse = getCachedExecutor(argumentTypes); private TypedValue getValueInternal(EvaluationContext evaluationContext,
Object value, Object[] arguments, TypeDescriptor targetType) {
List<TypeDescriptor> argumentTypes = getArgumentTypes(arguments);
if (value == null) {
throwIfNotNullSafe(argumentTypes);
return TypedValue.NULL;
}
MethodExecutor executorToUse = getCachedExecutor(targetType, argumentTypes);
if (executorToUse != null) { if (executorToUse != null) {
try { try {
return executorToUse.execute(state.getEvaluationContext(), return executorToUse.execute(evaluationContext, value, arguments);
state.getActiveContextObject().getValue(), arguments);
} }
catch (AccessException ae) { catch (AccessException ae) {
// Two reasons this can occur: // Two reasons this can occur:
// 1. the method invoked actually threw a real exception // 1. the method invoked actually threw a real exception
// 2. the method invoked was not passed the arguments it expected and has become 'stale' // 2. the method invoked was not passed the arguments it expected and
// has become 'stale'
// In the first case we should not retry, in the second case we should see if there is a // In the first case we should not retry, in the second case we should see
// better suited method. // if there is a better suited method.
// To determine which situation it is, the AccessException will contain a cause. // To determine the situation, the AccessException will contain a cause.
// If the cause is an InvocationTargetException, a user exception was thrown inside the method. // If the cause is an InvocationTargetException, a user exception was
// thrown inside the method.
// Otherwise the method could not be invoked. // Otherwise the method could not be invoked.
throwSimpleExceptionIfPossible(state, ae); throwSimpleExceptionIfPossible(value, ae);
// at this point we know it wasn't a user problem so worth a retry if a better candidate can be found // at this point we know it wasn't a user problem so worth a retry if a
// better candidate can be found
this.cachedExecutor = null; this.cachedExecutor = null;
} }
} }
// either there was no accessor or it no longer existed // either there was no accessor or it no longer existed
executorToUse = findAccessorForMethod(this.name, argumentTypes, state); executorToUse = findAccessorForMethod(this.name, argumentTypes, value, evaluationContext);
this.cachedExecutor = new CachedMethodExecutor(executorToUse, argumentTypes); this.cachedExecutor = new CachedMethodExecutor(executorToUse, targetType, argumentTypes);
try { try {
return executorToUse.execute( return executorToUse.execute(evaluationContext, value, arguments);
state.getEvaluationContext(), state.getActiveContextObject().getValue(), arguments);
} }
catch (AccessException ae) { catch (AccessException ex) {
// Same unwrapping exception handling as above in above catch block // Same unwrapping exception handling as above in above catch block
throwSimpleExceptionIfPossible(state, ae); throwSimpleExceptionIfPossible(value, ex);
throw new SpelEvaluationException( getStartPosition(), ae, SpelMessage.EXCEPTION_DURING_METHOD_INVOCATION, throw new SpelEvaluationException(getStartPosition(), ex,
this.name, state.getActiveContextObject().getValue().getClass().getName(), ae.getMessage()); SpelMessage.EXCEPTION_DURING_METHOD_INVOCATION, this.name,
value.getClass().getName(), ex.getMessage());
} }
} }
/** private void throwIfNotNullSafe(List<TypeDescriptor> argumentTypes) {
* Decode the AccessException, throwing a lightweight evaluation exception or, if the cause was a RuntimeException, if (!this.nullSafe) {
* throw the RuntimeException directly. throw new SpelEvaluationException(getStartPosition(),
*/ SpelMessage.METHOD_CALL_ON_NULL_OBJECT_NOT_ALLOWED,
private void throwSimpleExceptionIfPossible(ExpressionState state, AccessException ae) { FormatHelper.formatMethodForMessage(this.name, argumentTypes));
if (ae.getCause() instanceof InvocationTargetException) {
Throwable rootCause = ae.getCause().getCause();
if (rootCause instanceof RuntimeException) {
throw (RuntimeException) rootCause;
}
else {
throw new ExpressionInvocationTargetException(getStartPosition(),
"A problem occurred when trying to execute method '" + this.name +
"' on object of type '" + state.getActiveContextObject().getValue().getClass().getName() + "'",
rootCause);
}
} }
} }
private List<TypeDescriptor> getTypes(Object... arguments) { private Object[] getArguments(ExpressionState state) {
Object[] arguments = new Object[getChildCount()];
for (int i = 0; i < arguments.length; i++) {
// Make the root object the active context again for evaluating the parameter
// expressions
try {
state.pushActiveContextObject(state.getRootContextObject());
arguments[i] = this.children[i].getValueInternal(state).getValue();
}
finally {
state.popActiveContextObject();
}
}
return arguments;
}
private List<TypeDescriptor> getArgumentTypes(Object... arguments) {
List<TypeDescriptor> descriptors = new ArrayList<TypeDescriptor>(arguments.length); List<TypeDescriptor> descriptors = new ArrayList<TypeDescriptor>(arguments.length);
for (Object argument : arguments) { for (Object argument : arguments) {
descriptors.add(TypeDescriptor.forObject(argument)); descriptors.add(TypeDescriptor.forObject(argument));
@ -179,6 +161,60 @@ public class MethodReference extends SpelNodeImpl {
return Collections.unmodifiableList(descriptors); return Collections.unmodifiableList(descriptors);
} }
private MethodExecutor getCachedExecutor(TypeDescriptor target, List<TypeDescriptor> argumentTypes) {
CachedMethodExecutor executorToCheck = this.cachedExecutor;
if (executorToCheck != null && executorToCheck.isSuitable(target, argumentTypes)) {
return executorToCheck.get();
}
this.cachedExecutor = null;
return null;
}
private MethodExecutor findAccessorForMethod(String name,
List<TypeDescriptor> argumentTypes, Object contextObject,
EvaluationContext evaluationContext) throws SpelEvaluationException {
List<MethodResolver> methodResolvers = evaluationContext.getMethodResolvers();
if (methodResolvers != null) {
for (MethodResolver methodResolver : methodResolvers) {
try {
MethodExecutor methodExecutor = methodResolver.resolve(
evaluationContext, contextObject, name, argumentTypes);
if (methodExecutor != null) {
return methodExecutor;
}
}
catch (AccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.PROBLEM_LOCATING_METHOD, name, contextObject.getClass());
}
}
}
throw new SpelEvaluationException(getStartPosition(), SpelMessage.METHOD_NOT_FOUND,
FormatHelper.formatMethodForMessage(name, argumentTypes),
FormatHelper.formatClassNameForMessage(
contextObject instanceof Class ? ((Class<?>) contextObject) : contextObject.getClass()));
}
/**
* Decode the AccessException, throwing a lightweight evaluation exception or, if the
* cause was a RuntimeException, throw the RuntimeException directly.
*/
private void throwSimpleExceptionIfPossible(Object value, AccessException ae) {
if (ae.getCause() instanceof InvocationTargetException) {
Throwable rootCause = ae.getCause().getCause();
if (rootCause instanceof RuntimeException) {
throw (RuntimeException) rootCause;
}
throw new ExpressionInvocationTargetException(getStartPosition(),
"A problem occurred when trying to execute method '" + this.name +
"' on object of type '" +
value.getClass().getName() + "'",
rootCause);
}
}
@Override @Override
public String toStringAST() { public String toStringAST() {
StringBuilder sb = new StringBuilder(); StringBuilder sb = new StringBuilder();
@ -193,105 +229,27 @@ public class MethodReference extends SpelNodeImpl {
return sb.toString(); return sb.toString();
} }
private MethodExecutor findAccessorForMethod(String name, List<TypeDescriptor> argumentTypes, ExpressionState state)
throws SpelEvaluationException {
return findAccessorForMethod(name, argumentTypes,
state.getActiveContextObject().getValue(), state.getEvaluationContext());
}
private MethodExecutor findAccessorForMethod(String name,
List<TypeDescriptor> argumentTypes, Object contextObject, EvaluationContext eContext)
throws SpelEvaluationException {
List<MethodResolver> methodResolvers = eContext.getMethodResolvers();
if (methodResolvers != null) {
for (MethodResolver methodResolver : methodResolvers) {
try {
MethodExecutor methodExecutor = methodResolver.resolve(eContext,
contextObject, name, argumentTypes);
if (methodExecutor != null) {
return methodExecutor;
}
}
catch (AccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex, SpelMessage.PROBLEM_LOCATING_METHOD, name,
contextObject.getClass());
}
}
}
throw new SpelEvaluationException(getStartPosition(), SpelMessage.METHOD_NOT_FOUND,
FormatHelper.formatMethodForMessage(name, argumentTypes),
FormatHelper.formatClassNameForMessage(contextObject instanceof Class ? ((Class<?>) contextObject) : contextObject.getClass()));
}
private MethodExecutor getCachedExecutor(List<TypeDescriptor> argumentTypes) {
if (this.cachedExecutor == null || !this.cachedExecutor.isSuitable(argumentTypes)) {
this.cachedExecutor = null;
return null;
}
return this.cachedExecutor.get();
}
private class MethodValueRef implements ValueRef { private class MethodValueRef implements ValueRef {
private final ExpressionState state;
private final EvaluationContext evaluationContext; private final EvaluationContext evaluationContext;
private final Object target; private final Object value;
private final TypeDescriptor targetType;
private final Object[] arguments; private final Object[] arguments;
private final List<TypeDescriptor> argumentTypes; public MethodValueRef(ExpressionState state) {
this.evaluationContext = state.getEvaluationContext();
MethodValueRef(ExpressionState state, EvaluationContext evaluationContext, Object object, Object[] arguments) { this.value = state.getActiveContextObject().getValue();
this.state = state; this.targetType = state.getActiveContextObject().getTypeDescriptor();
this.evaluationContext = evaluationContext; this.arguments = getArguments(state);
this.target = object;
this.arguments = arguments;
this.argumentTypes = getTypes(this.arguments);
} }
@Override @Override
public TypedValue getValue() { public TypedValue getValue() {
MethodExecutor executorToUse = getCachedExecutor(this.argumentTypes); return getValueInternal(this.evaluationContext, this.value, this.arguments, this.targetType);
if (executorToUse != null) {
try {
return executorToUse.execute(this.evaluationContext, this.target, this.arguments);
}
catch (AccessException ae) {
// Two reasons this can occur:
// 1. the method invoked actually threw a real exception
// 2. the method invoked was not passed the arguments it expected and has become 'stale'
// In the first case we should not retry, in the second case we should see if there is a
// better suited method.
// To determine which situation it is, the AccessException will contain a cause.
// If the cause is an InvocationTargetException, a user exception was thrown inside the method.
// Otherwise the method could not be invoked.
throwSimpleExceptionIfPossible(this.state, ae);
// at this point we know it wasn't a user problem so worth a retry if a better candidate can be found
MethodReference.this.cachedExecutor = null;
}
}
// either there was no accessor or it no longer existed
executorToUse = findAccessorForMethod(MethodReference.this.name, argumentTypes, this.target, this.evaluationContext);
MethodReference.this.cachedExecutor = new CachedMethodExecutor(executorToUse, this.argumentTypes);
try {
return executorToUse.execute(this.evaluationContext, this.target, this.arguments);
}
catch (AccessException ex) {
// Same unwrapping exception handling as above in above catch block
throwSimpleExceptionIfPossible(this.state, ex);
throw new SpelEvaluationException(getStartPosition(), ex, SpelMessage.EXCEPTION_DURING_METHOD_INVOCATION,
MethodReference.this.name, this.state.getActiveContextObject().getValue().getClass().getName(),
ex.getMessage());
}
} }
@Override @Override
@ -310,15 +268,19 @@ public class MethodReference extends SpelNodeImpl {
private final MethodExecutor methodExecutor; private final MethodExecutor methodExecutor;
private final TypeDescriptor target;
private final List<TypeDescriptor> argumentTypes; private final List<TypeDescriptor> argumentTypes;
public CachedMethodExecutor(MethodExecutor methodExecutor, List<TypeDescriptor> argumentTypes) { public CachedMethodExecutor(MethodExecutor methodExecutor, TypeDescriptor target, List<TypeDescriptor> argumentTypes) {
this.methodExecutor = methodExecutor; this.methodExecutor = methodExecutor;
this.target = target;
this.argumentTypes = argumentTypes; this.argumentTypes = argumentTypes;
} }
public boolean isSuitable(List<TypeDescriptor> argumentTypes) { public boolean isSuitable(TypeDescriptor target, List<TypeDescriptor> argumentTypes) {
return (this.methodExecutor != null && this.argumentTypes.equals(argumentTypes)); return (this.methodExecutor != null && this.target != null &&
this.target.equals(target) && this.argumentTypes.equals(argumentTypes));
} }
public MethodExecutor get() { public MethodExecutor get() {

26
spring-expression/src/test/java/org/springframework/expression/spel/CachedMethodExecutorTests.java
View File

@ -1,5 +1,5 @@
/* /*
* Copyright 2002-2012 the original author or authors. * Copyright 2002-2013 the original author or authors.
* *
* Licensed under the Apache License, Version 2.0 (the "License"); * Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License. * you may not use this file except in compliance with the License.
@ -18,6 +18,7 @@ package org.springframework.expression.spel;
import org.junit.Before; import org.junit.Before;
import org.junit.Test; import org.junit.Test;
import org.springframework.expression.Expression; import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser; import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.ast.MethodReference; import org.springframework.expression.spel.ast.MethodReference;
@ -45,31 +46,42 @@ public class CachedMethodExecutorTests {
@Test @Test
public void testCachedExecution() throws Exception { public void testCachedExecutionForParameters() throws Exception {
Expression expression = this.parser.parseExpression("echo(#something)"); Expression expression = this.parser.parseExpression("echo(#var)");
assertMethodExecution(expression, 42, "int: 42"); assertMethodExecution(expression, 42, "int: 42");
assertMethodExecution(expression, 42, "int: 42"); assertMethodExecution(expression, 42, "int: 42");
assertMethodExecution(expression, "Deep Thought", "String: Deep Thought"); assertMethodExecution(expression, "Deep Thought", "String: Deep Thought");
assertMethodExecution(expression, 42, "int: 42"); assertMethodExecution(expression, 42, "int: 42");
} }
@Test
public void testCachedExecutionForTarget() throws Exception {
Expression expression = this.parser.parseExpression("#var.echo(42)");
assertMethodExecution(expression, new RootObject(), "int: 42");
assertMethodExecution(expression, new RootObject(), "int: 42");
assertMethodExecution(expression, new BaseObject(), "String: 42");
assertMethodExecution(expression, new RootObject(), "int: 42");
}
private void assertMethodExecution(Expression expression, Object var, String expected) { private void assertMethodExecution(Expression expression, Object var, String expected) {
this.context.setVariable("something", var); this.context.setVariable("var", var);
assertEquals(expected, expression.getValue(this.context)); assertEquals(expected, expression.getValue(this.context));
} }
public static class RootObject { public static class BaseObject {
public String echo(String value) { public String echo(String value) {
return "String: " + value; return "String: " + value;
} }
}
public static class RootObject extends BaseObject {
public String echo(int value) { public String echo(int value) {
return "int: " + value; return "int: " + value;
} }
} }
} }