/*
* Copyright 2002-2016 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.ast;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.asm.MethodVisitor;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.ExpressionInvocationTargetException;
import org.springframework.expression.MethodExecutor;
import org.springframework.expression.MethodResolver;
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.expression.spel.SpelMessage;
import org.springframework.expression.spel.support.ReflectiveMethodExecutor;
import org.springframework.expression.spel.support.ReflectiveMethodResolver;
/**
* Expression language AST node that represents a method reference.
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public class MethodReference extends SpelNodeImpl {
private final String name;
private final boolean nullSafe;
private volatile CachedMethodExecutor cachedExecutor;
public MethodReference(boolean nullSafe, String methodName, int pos, SpelNodeImpl... arguments) {
super(pos, arguments);
this.name = methodName;
this.nullSafe = nullSafe;
}
public final String getName() {
return this.name;
}
@Override
protected ValueRef getValueRef(ExpressionState state) throws EvaluationException {
Object[] arguments = getArguments(state);
if (state.getActiveContextObject().getValue() == null) {
throwIfNotNullSafe(getArgumentTypes(arguments));
return ValueRef.NullValueRef.INSTANCE;
}
return new MethodValueRef(state, arguments);
}
@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
EvaluationContext evaluationContext = state.getEvaluationContext();
Object value = state.getActiveContextObject().getValue();
TypeDescriptor targetType = state.getActiveContextObject().getTypeDescriptor();
Object[] arguments = getArguments(state);
TypedValue result = getValueInternal(evaluationContext, value, targetType, arguments);
updateExitTypeDescriptor();
return result;
}
private TypedValue getValueInternal(EvaluationContext evaluationContext,
Object value, TypeDescriptor targetType, Object[] arguments) {
List<TypeDescriptor> argumentTypes = getArgumentTypes(arguments);
if (value == null) {
throwIfNotNullSafe(argumentTypes);
return TypedValue.NULL;
}
MethodExecutor executorToUse = getCachedExecutor(evaluationContext, value, targetType, argumentTypes);
if (executorToUse != null) {
try {
return executorToUse.execute(evaluationContext, value, arguments);
}
catch (AccessException ex) {
// 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 the situation, 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(value, ex);
// 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;
}
}
// either there was no accessor or it no longer existed
executorToUse = findAccessorForMethod(this.name, argumentTypes, value, evaluationContext);
this.cachedExecutor = new CachedMethodExecutor(
executorToUse, (value instanceof Class ? (Class<?>) value : null), targetType, argumentTypes);
try {
return executorToUse.execute(evaluationContext, value, arguments);
}
catch (AccessException ex) {
// Same unwrapping exception handling as above in above catch block
throwSimpleExceptionIfPossible(value, ex);
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.EXCEPTION_DURING_METHOD_INVOCATION, this.name,
value.getClass().getName(), ex.getMessage());
}
}
private void throwIfNotNullSafe(List<TypeDescriptor> argumentTypes) {
if (!this.nullSafe) {
throw new SpelEvaluationException(getStartPosition(),
SpelMessage.METHOD_CALL_ON_NULL_OBJECT_NOT_ALLOWED,
FormatHelper.formatMethodForMessage(this.name, argumentTypes));
}
}
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.getScopeRootContextObject());
arguments[i] = this.children[i].getValueInternal(state).getValue();
}
finally {
state.popActiveContextObject();
}
}
return arguments;
}
private List<TypeDescriptor> getArgumentTypes(Object... arguments) {
List<TypeDescriptor> descriptors = new ArrayList<>(arguments.length);
for (Object argument : arguments) {
descriptors.add(TypeDescriptor.forObject(argument));
}
return Collections.unmodifiableList(descriptors);
}
private MethodExecutor getCachedExecutor(EvaluationContext evaluationContext, Object value,
TypeDescriptor target, List<TypeDescriptor> argumentTypes) {
List<MethodResolver> methodResolvers = evaluationContext.getMethodResolvers();
if (methodResolvers == null || methodResolvers.size() != 1 ||
!(methodResolvers.get(0) instanceof ReflectiveMethodResolver)) {
// Not a default ReflectiveMethodResolver - don't know whether caching is valid
return null;
}
CachedMethodExecutor executorToCheck = this.cachedExecutor;
if (executorToCheck != null && executorToCheck.isSuitable(value, target, argumentTypes)) {
return executorToCheck.get();
}
this.cachedExecutor = null;
return null;
}
private MethodExecutor findAccessorForMethod(String name, List<TypeDescriptor> argumentTypes,
Object targetObject, EvaluationContext evaluationContext) throws SpelEvaluationException {
List<MethodResolver> methodResolvers = evaluationContext.getMethodResolvers();
if (methodResolvers != null) {
for (MethodResolver methodResolver : methodResolvers) {
try {
MethodExecutor methodExecutor = methodResolver.resolve(
evaluationContext, targetObject, name, argumentTypes);
if (methodExecutor != null) {
return methodExecutor;
}
}
catch (AccessException ex) {
throw new SpelEvaluationException(getStartPosition(), ex,
SpelMessage.PROBLEM_LOCATING_METHOD, name, targetObject.getClass());
}
}
}
throw new SpelEvaluationException(getStartPosition(), SpelMessage.METHOD_NOT_FOUND,
FormatHelper.formatMethodForMessage(name, argumentTypes),
FormatHelper.formatClassNameForMessage(
targetObject instanceof Class ? ((Class<?>) targetObject) : targetObject.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 ex) {
if (ex.getCause() instanceof InvocationTargetException) {
Throwable rootCause = ex.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);
}
}
private void updateExitTypeDescriptor() {
CachedMethodExecutor executorToCheck = this.cachedExecutor;
if (executorToCheck != null && executorToCheck.get() instanceof ReflectiveMethodExecutor) {
Method method = ((ReflectiveMethodExecutor) executorToCheck.get()).getMethod();
this.exitTypeDescriptor = CodeFlow.toDescriptor(method.getReturnType());
}
}
@Override
public String toStringAST() {
StringBuilder sb = new StringBuilder(this.name);
sb.append("(");
for (int i = 0; i < getChildCount(); i++) {
if (i > 0) {
sb.append(",");
}
sb.append(getChild(i).toStringAST());
}
sb.append(")");
return sb.toString();
}
/**
* A method reference is compilable if it has been resolved to a reflectively accessible method
* and the child nodes (arguments to the method) are also compilable.
*/
@Override
public boolean isCompilable() {
CachedMethodExecutor executorToCheck = this.cachedExecutor;
if (executorToCheck == null || !(executorToCheck.get() instanceof ReflectiveMethodExecutor)) {
return false;
}
for (SpelNodeImpl child : this.children) {
if (!child.isCompilable()) {
return false;
}
}
ReflectiveMethodExecutor executor = (ReflectiveMethodExecutor) executorToCheck.get();
if (executor.didArgumentConversionOccur()) {
return false;
}
Method method = executor.getMethod();
Class<?> clazz = method.getDeclaringClass();
if (!Modifier.isPublic(clazz.getModifiers()) && executor.getPublicDeclaringClass() == null) {
return false;
}
return true;
}
@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
CachedMethodExecutor executorToCheck = this.cachedExecutor;
if (executorToCheck == null || !(executorToCheck.get() instanceof ReflectiveMethodExecutor)) {
throw new IllegalStateException("No applicable cached executor found: " + executorToCheck);
}
ReflectiveMethodExecutor methodExecutor = (ReflectiveMethodExecutor) executorToCheck.get();
Method method = methodExecutor.getMethod();
boolean isStaticMethod = Modifier.isStatic(method.getModifiers());
String descriptor = cf.lastDescriptor();
if (descriptor == null) {
if (!isStaticMethod) {
// Nothing on the stack but something is needed
cf.loadTarget(mv);
}
}
else {
if (isStaticMethod) {
// Something on the stack when nothing is needed
mv.visitInsn(POP);
}
}
if (CodeFlow.isPrimitive(descriptor)) {
CodeFlow.insertBoxIfNecessary(mv, descriptor.charAt(0));
}
String classDesc = (Modifier.isPublic(method.getDeclaringClass().getModifiers()) ?
method.getDeclaringClass().getName().replace('.', '/') :
methodExecutor.getPublicDeclaringClass().getName().replace('.', '/'));
if (!isStaticMethod) {
if (descriptor == null || !descriptor.substring(1).equals(classDesc)) {
CodeFlow.insertCheckCast(mv, "L" + classDesc);
}
}
generateCodeForArguments(mv, cf, method, this.children);
mv.visitMethodInsn((isStaticMethod ? INVOKESTATIC : INVOKEVIRTUAL), classDesc, method.getName(),
CodeFlow.createSignatureDescriptor(method), method.getDeclaringClass().isInterface());
cf.pushDescriptor(this.exitTypeDescriptor);
}
private class MethodValueRef implements ValueRef {
private final EvaluationContext evaluationContext;
private final Object value;
private final TypeDescriptor targetType;
private final Object[] arguments;
public MethodValueRef(ExpressionState state, Object[] arguments) {
this.evaluationContext = state.getEvaluationContext();
this.value = state.getActiveContextObject().getValue();
this.targetType = state.getActiveContextObject().getTypeDescriptor();
this.arguments = arguments;
}
@Override
public TypedValue getValue() {
TypedValue result = MethodReference.this.getValueInternal(
this.evaluationContext, this.value, this.targetType, this.arguments);
updateExitTypeDescriptor();
return result;
}
@Override
public void setValue(Object newValue) {
throw new IllegalAccessError();
}
@Override
public boolean isWritable() {
return false;
}
}
private static class CachedMethodExecutor {
private final MethodExecutor methodExecutor;
private final Class<?> staticClass;
private final TypeDescriptor target;
private final List<TypeDescriptor> argumentTypes;
public CachedMethodExecutor(MethodExecutor methodExecutor, Class<?> staticClass,
TypeDescriptor target, List<TypeDescriptor> argumentTypes) {
this.methodExecutor = methodExecutor;
this.staticClass = staticClass;
this.target = target;
this.argumentTypes = argumentTypes;
}
public boolean isSuitable(Object value, TypeDescriptor target, List<TypeDescriptor> argumentTypes) {
return ((this.staticClass == null || this.staticClass == value) &&
this.target.equals(target) && this.argumentTypes.equals(argumentTypes));
}
public MethodExecutor get() {
return this.methodExecutor;
}
}
}