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/*
 * 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.
 * You may obtain a copy of the License at
 *
 *      https://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.aop.aspectj;

import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.weaver.tools.PointcutParser;
import org.aspectj.weaver.tools.PointcutPrimitive;

import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;

/**
 * {@link ParameterNameDiscoverer} implementation that tries to deduce parameter names
 * for an advice method from the pointcut expression, returning, and throwing clauses.
 * If an unambiguous interpretation is not available, it returns {@code null}.
 *
 * 

Algorithm Summary

*

If an unambiguous binding can be deduced, then it is. * If the advice requirements cannot possibly be satisfied, then {@code null} * is returned. By setting the {@link #setRaiseExceptions(boolean) raiseExceptions} * property to {@code true}, descriptive exceptions will be thrown instead of * returning {@code null} in the case that the parameter names cannot be discovered. * *

Algorithm Details

*

This class interprets arguments in the following way: *

    *
  1. If the first parameter of the method is of type {@link JoinPoint} * or {@link ProceedingJoinPoint}, it is assumed to be for passing * {@code thisJoinPoint} to the advice, and the parameter name will * be assigned the value {@code "thisJoinPoint"}.
  2. *
  3. If the first parameter of the method is of type * {@code JoinPoint.StaticPart}, it is assumed to be for passing * {@code "thisJoinPointStaticPart"} to the advice, and the parameter name * will be assigned the value {@code "thisJoinPointStaticPart"}.
  4. *
  5. If a {@link #setThrowingName(String) throwingName} has been set, and * there are no unbound arguments of type {@code Throwable+}, then an * {@link IllegalArgumentException} is raised. If there is more than one * unbound argument of type {@code Throwable+}, then an * {@link AmbiguousBindingException} is raised. If there is exactly one * unbound argument of type {@code Throwable+}, then the corresponding * parameter name is assigned the value <throwingName>.
  6. *
  7. If there remain unbound arguments, then the pointcut expression is * examined. Let {@code a} be the number of annotation-based pointcut * expressions (@annotation, @this, @target, @args, * @within, @withincode) that are used in binding form. Usage in * binding form has itself to be deduced: if the expression inside the * pointcut is a single string literal that meets Java variable name * conventions it is assumed to be a variable name. If {@code a} is * zero we proceed to the next stage. If {@code a} > 1 then an * {@code AmbiguousBindingException} is raised. If {@code a} == 1, * and there are no unbound arguments of type {@code Annotation+}, * then an {@code IllegalArgumentException} is raised. If there is * exactly one such argument, then the corresponding parameter name is * assigned the value from the pointcut expression.
  8. *
  9. If a {@code returningName} has been set, and there are no unbound arguments * then an {@code IllegalArgumentException} is raised. If there is * more than one unbound argument then an * {@code AmbiguousBindingException} is raised. If there is exactly * one unbound argument then the corresponding parameter name is assigned * the value of the {@code returningName}.
  10. *
  11. If there remain unbound arguments, then the pointcut expression is * examined once more for {@code this}, {@code target}, and * {@code args} pointcut expressions used in the binding form (binding * forms are deduced as described for the annotation based pointcuts). If * there remains more than one unbound argument of a primitive type (which * can only be bound in {@code args}) then an * {@code AmbiguousBindingException} is raised. If there is exactly * one argument of a primitive type, then if exactly one {@code args} * bound variable was found, we assign the corresponding parameter name * the variable name. If there were no {@code args} bound variables * found an {@code IllegalStateException} is raised. If there are * multiple {@code args} bound variables, an * {@code AmbiguousBindingException} is raised. At this point, if * there remains more than one unbound argument we raise an * {@code AmbiguousBindingException}. If there are no unbound arguments * remaining, we are done. If there is exactly one unbound argument * remaining, and only one candidate variable name unbound from * {@code this}, {@code target}, or {@code args}, it is * assigned as the corresponding parameter name. If there are multiple * possibilities, an {@code AmbiguousBindingException} is raised.
  12. *
* *

The behavior on raising an {@code IllegalArgumentException} or * {@code AmbiguousBindingException} is configurable to allow this discoverer * to be used as part of a chain-of-responsibility. By default the condition will * be logged and the {@link #getParameterNames(Method)} method will simply return * {@code null}. If the {@link #setRaiseExceptions(boolean) raiseExceptions} * property is set to {@code true}, the conditions will be thrown as * {@code IllegalArgumentException} and {@code AmbiguousBindingException}, * respectively. * * @author Adrian Colyer * @author Juergen Hoeller * @since 2.0 */ public class AspectJAdviceParameterNameDiscoverer implements ParameterNameDiscoverer { private static final String THIS_JOIN_POINT = "thisJoinPoint"; private static final String THIS_JOIN_POINT_STATIC_PART = "thisJoinPointStaticPart"; // Steps in the binding algorithm... private static final int STEP_JOIN_POINT_BINDING = 1; private static final int STEP_THROWING_BINDING = 2; private static final int STEP_ANNOTATION_BINDING = 3; private static final int STEP_RETURNING_BINDING = 4; private static final int STEP_PRIMITIVE_ARGS_BINDING = 5; private static final int STEP_THIS_TARGET_ARGS_BINDING = 6; private static final int STEP_REFERENCE_PCUT_BINDING = 7; private static final int STEP_FINISHED = 8; private static final Set singleValuedAnnotationPcds = Set.of( "@this", "@target", "@within", "@withincode", "@annotation"); private static final Set nonReferencePointcutTokens = new HashSet<>(); static { Set pointcutPrimitives = PointcutParser.getAllSupportedPointcutPrimitives(); for (PointcutPrimitive primitive : pointcutPrimitives) { nonReferencePointcutTokens.add(primitive.getName()); } nonReferencePointcutTokens.add("&&"); nonReferencePointcutTokens.add("!"); nonReferencePointcutTokens.add("||"); nonReferencePointcutTokens.add("and"); nonReferencePointcutTokens.add("or"); nonReferencePointcutTokens.add("not"); } /** The pointcut expression associated with the advice, as a simple String. */ @Nullable private final String pointcutExpression; private boolean raiseExceptions; /** If the advice is afterReturning, and binds the return value, this is the parameter name used. */ @Nullable private String returningName; /** If the advice is afterThrowing, and binds the thrown value, this is the parameter name used. */ @Nullable private String throwingName; private Class[] argumentTypes = new Class[0]; private String[] parameterNameBindings = new String[0]; private int numberOfRemainingUnboundArguments; /** * Create a new discoverer that attempts to discover parameter names. * from the given pointcut expression. */ public AspectJAdviceParameterNameDiscoverer(@Nullable String pointcutExpression) { this.pointcutExpression = pointcutExpression; } /** * Indicate whether {@link IllegalArgumentException} and {@link AmbiguousBindingException} * must be thrown as appropriate in the case of failing to deduce advice parameter names. * @param raiseExceptions {@code true} if exceptions are to be thrown */ public void setRaiseExceptions(boolean raiseExceptions) { this.raiseExceptions = raiseExceptions; } /** * If {@code afterReturning} advice binds the return value, the * {@code returning} variable name must be specified. * @param returningName the name of the returning variable */ public void setReturningName(@Nullable String returningName) { this.returningName = returningName; } /** * If {@code afterThrowing} advice binds the thrown value, the * {@code throwing} variable name must be specified. * @param throwingName the name of the throwing variable */ public void setThrowingName(@Nullable String throwingName) { this.throwingName = throwingName; } /** * Deduce the parameter names for an advice method. *

See the {@link AspectJAdviceParameterNameDiscoverer class-level javadoc} * for this class for details on the algorithm used. * @param method the target {@link Method} * @return the parameter names */ @Override @Nullable public String[] getParameterNames(Method method) { this.argumentTypes = method.getParameterTypes(); this.numberOfRemainingUnboundArguments = this.argumentTypes.length; this.parameterNameBindings = new String[this.numberOfRemainingUnboundArguments]; int minimumNumberUnboundArgs = 0; if (this.returningName != null) { minimumNumberUnboundArgs++; } if (this.throwingName != null) { minimumNumberUnboundArgs++; } if (this.numberOfRemainingUnboundArguments < minimumNumberUnboundArgs) { throw new IllegalStateException( "Not enough arguments in method to satisfy binding of returning and throwing variables"); } try { int algorithmicStep = STEP_JOIN_POINT_BINDING; while ((this.numberOfRemainingUnboundArguments > 0) && algorithmicStep < STEP_FINISHED) { switch (algorithmicStep++) { case STEP_JOIN_POINT_BINDING -> { if (!maybeBindThisJoinPoint()) { maybeBindThisJoinPointStaticPart(); } } case STEP_THROWING_BINDING -> maybeBindThrowingVariable(); case STEP_ANNOTATION_BINDING -> maybeBindAnnotationsFromPointcutExpression(); case STEP_RETURNING_BINDING -> maybeBindReturningVariable(); case STEP_PRIMITIVE_ARGS_BINDING -> maybeBindPrimitiveArgsFromPointcutExpression(); case STEP_THIS_TARGET_ARGS_BINDING -> maybeBindThisOrTargetOrArgsFromPointcutExpression(); case STEP_REFERENCE_PCUT_BINDING -> maybeBindReferencePointcutParameter(); default -> throw new IllegalStateException("Unknown algorithmic step: " + (algorithmicStep - 1)); } } } catch (AmbiguousBindingException | IllegalArgumentException ex) { if (this.raiseExceptions) { throw ex; } else { return null; } } if (this.numberOfRemainingUnboundArguments == 0) { return this.parameterNameBindings; } else { if (this.raiseExceptions) { throw new IllegalStateException("Failed to bind all argument names: " + this.numberOfRemainingUnboundArguments + " argument(s) could not be bound"); } else { // convention for failing is to return null, allowing participation in a chain of responsibility return null; } } } /** * An advice method can never be a constructor in Spring. * @return {@code null} * @throws UnsupportedOperationException if * {@link #setRaiseExceptions(boolean) raiseExceptions} has been set to {@code true} */ @Override @Nullable public String[] getParameterNames(Constructor ctor) { if (this.raiseExceptions) { throw new UnsupportedOperationException("An advice method can never be a constructor"); } else { // we return null rather than throw an exception so that we behave well // in a chain-of-responsibility. return null; } } private void bindParameterName(int index, @Nullable String name) { this.parameterNameBindings[index] = name; this.numberOfRemainingUnboundArguments--; } /** * If the first parameter is of type JoinPoint or ProceedingJoinPoint, bind "thisJoinPoint" as * parameter name and return true, else return false. */ private boolean maybeBindThisJoinPoint() { if ((this.argumentTypes[0] == JoinPoint.class) || (this.argumentTypes[0] == ProceedingJoinPoint.class)) { bindParameterName(0, THIS_JOIN_POINT); return true; } else { return false; } } private void maybeBindThisJoinPointStaticPart() { if (this.argumentTypes[0] == JoinPoint.StaticPart.class) { bindParameterName(0, THIS_JOIN_POINT_STATIC_PART); } } /** * If a throwing name was specified and there is exactly one choice remaining * (argument that is a subtype of Throwable) then bind it. */ private void maybeBindThrowingVariable() { if (this.throwingName == null) { return; } // So there is binding work to do... int throwableIndex = -1; for (int i = 0; i < this.argumentTypes.length; i++) { if (isUnbound(i) && isSubtypeOf(Throwable.class, i)) { if (throwableIndex == -1) { throwableIndex = i; } else { // Second candidate we've found - ambiguous binding throw new AmbiguousBindingException("Binding of throwing parameter '" + this.throwingName + "' is ambiguous: could be bound to argument " + throwableIndex + " or " + i); } } } if (throwableIndex == -1) { throw new IllegalStateException("Binding of throwing parameter '" + this.throwingName + "' could not be completed as no available arguments are a subtype of Throwable"); } else { bindParameterName(throwableIndex, this.throwingName); } } /** * If a returning variable was specified and there is only one choice remaining, bind it. */ private void maybeBindReturningVariable() { if (this.numberOfRemainingUnboundArguments == 0) { throw new IllegalStateException( "Algorithm assumes that there must be at least one unbound parameter on entry to this method"); } if (this.returningName != null) { if (this.numberOfRemainingUnboundArguments > 1) { throw new AmbiguousBindingException("Binding of returning parameter '" + this.returningName + "' is ambiguous: there are " + this.numberOfRemainingUnboundArguments + " candidates."); } // We're all set... find the unbound parameter, and bind it. for (int i = 0; i < this.parameterNameBindings.length; i++) { if (this.parameterNameBindings[i] == null) { bindParameterName(i, this.returningName); break; } } } } /** * Parse the string pointcut expression looking for: * @this, @target, @args, @within, @withincode, @annotation. * If we find one of these pointcut expressions, try and extract a candidate variable * name (or variable names, in the case of args). *

Some more support from AspectJ in doing this exercise would be nice... :) */ private void maybeBindAnnotationsFromPointcutExpression() { List varNames = new ArrayList<>(); String[] tokens = StringUtils.tokenizeToStringArray(this.pointcutExpression, " "); for (int i = 0; i < tokens.length; i++) { String toMatch = tokens[i]; int firstParenIndex = toMatch.indexOf('('); if (firstParenIndex != -1) { toMatch = toMatch.substring(0, firstParenIndex); } if (singleValuedAnnotationPcds.contains(toMatch)) { PointcutBody body = getPointcutBody(tokens, i); i += body.numTokensConsumed; String varName = maybeExtractVariableName(body.text); if (varName != null) { varNames.add(varName); } } else if (tokens[i].startsWith("@args(") || tokens[i].equals("@args")) { PointcutBody body = getPointcutBody(tokens, i); i += body.numTokensConsumed; maybeExtractVariableNamesFromArgs(body.text, varNames); } } bindAnnotationsFromVarNames(varNames); } /** * Match the given list of extracted variable names to argument slots. */ private void bindAnnotationsFromVarNames(List varNames) { if (!varNames.isEmpty()) { // we have work to do... int numAnnotationSlots = countNumberOfUnboundAnnotationArguments(); if (numAnnotationSlots > 1) { throw new AmbiguousBindingException("Found " + varNames.size() + " potential annotation variable(s) and " + numAnnotationSlots + " potential argument slots"); } else if (numAnnotationSlots == 1) { if (varNames.size() == 1) { // it's a match findAndBind(Annotation.class, varNames.get(0)); } else { // multiple candidate vars, but only one slot throw new IllegalArgumentException("Found " + varNames.size() + " candidate annotation binding variables" + " but only one potential argument binding slot"); } } else { // no slots so presume those candidate vars were actually type names } } } /** * If the token starts meets Java identifier conventions, it's in. */ @Nullable private String maybeExtractVariableName(@Nullable String candidateToken) { if (AspectJProxyUtils.isVariableName(candidateToken)) { return candidateToken; } return null; } /** * Given an args pointcut body (could be {@code args} or {@code at_args}), * add any candidate variable names to the given list. */ private void maybeExtractVariableNamesFromArgs(@Nullable String argsSpec, List varNames) { if (argsSpec == null) { return; } String[] tokens = StringUtils.tokenizeToStringArray(argsSpec, ","); for (int i = 0; i < tokens.length; i++) { tokens[i] = tokens[i].strip(); String varName = maybeExtractVariableName(tokens[i]); if (varName != null) { varNames.add(varName); } } } /** * Parse the string pointcut expression looking for this(), target() and args() expressions. * If we find one, try and extract a candidate variable name and bind it. */ private void maybeBindThisOrTargetOrArgsFromPointcutExpression() { if (this.numberOfRemainingUnboundArguments > 1) { throw new AmbiguousBindingException("Still " + this.numberOfRemainingUnboundArguments + " unbound args at this()/target()/args() binding stage, with no way to determine between them"); } List varNames = new ArrayList<>(); String[] tokens = StringUtils.tokenizeToStringArray(this.pointcutExpression, " "); for (int i = 0; i < tokens.length; i++) { if (tokens[i].equals("this") || tokens[i].startsWith("this(") || tokens[i].equals("target") || tokens[i].startsWith("target(")) { PointcutBody body = getPointcutBody(tokens, i); i += body.numTokensConsumed; String varName = maybeExtractVariableName(body.text); if (varName != null) { varNames.add(varName); } } else if (tokens[i].equals("args") || tokens[i].startsWith("args(")) { PointcutBody body = getPointcutBody(tokens, i); i += body.numTokensConsumed; List candidateVarNames = new ArrayList<>(); maybeExtractVariableNamesFromArgs(body.text, candidateVarNames); // we may have found some var names that were bound in previous primitive args binding step, // filter them out... for (String varName : candidateVarNames) { if (!alreadyBound(varName)) { varNames.add(varName); } } } } if (varNames.size() > 1) { throw new AmbiguousBindingException("Found " + varNames.size() + " candidate this(), target(), or args() variables but only one unbound argument slot"); } else if (varNames.size() == 1) { for (int j = 0; j < this.parameterNameBindings.length; j++) { if (isUnbound(j)) { bindParameterName(j, varNames.get(0)); break; } } } // else varNames.size must be 0 and we have nothing to bind. } private void maybeBindReferencePointcutParameter() { if (this.numberOfRemainingUnboundArguments > 1) { throw new AmbiguousBindingException("Still " + this.numberOfRemainingUnboundArguments + " unbound args at reference pointcut binding stage, with no way to determine between them"); } List varNames = new ArrayList<>(); String[] tokens = StringUtils.tokenizeToStringArray(this.pointcutExpression, " "); for (int i = 0; i < tokens.length; i++) { String toMatch = tokens[i]; if (toMatch.startsWith("!")) { toMatch = toMatch.substring(1); } int firstParenIndex = toMatch.indexOf('('); if (firstParenIndex != -1) { toMatch = toMatch.substring(0, firstParenIndex); } else { if (tokens.length < i + 2) { // no "(" and nothing following continue; } else { String nextToken = tokens[i + 1]; if (nextToken.charAt(0) != '(') { // next token is not "(" either, can't be a pc... continue; } } } // eat the body PointcutBody body = getPointcutBody(tokens, i); i += body.numTokensConsumed; if (!nonReferencePointcutTokens.contains(toMatch)) { // then it could be a reference pointcut String varName = maybeExtractVariableName(body.text); if (varName != null) { varNames.add(varName); } } } if (varNames.size() > 1) { throw new AmbiguousBindingException("Found " + varNames.size() + " candidate reference pointcut variables but only one unbound argument slot"); } else if (varNames.size() == 1) { for (int j = 0; j < this.parameterNameBindings.length; j++) { if (isUnbound(j)) { bindParameterName(j, varNames.get(0)); break; } } } // else varNames.size must be 0 and we have nothing to bind. } /** * We've found the start of a binding pointcut at the given index into the * token array. Now we need to extract the pointcut body and return it. */ private PointcutBody getPointcutBody(String[] tokens, int startIndex) { int numTokensConsumed = 0; String currentToken = tokens[startIndex]; int bodyStart = currentToken.indexOf('('); if (currentToken.charAt(currentToken.length() - 1) == ')') { // It's an all in one... get the text between the first (and the last) return new PointcutBody(0, currentToken.substring(bodyStart + 1, currentToken.length() - 1)); } else { StringBuilder sb = new StringBuilder(); if (bodyStart >= 0 && bodyStart != (currentToken.length() - 1)) { sb.append(currentToken.substring(bodyStart + 1)); sb.append(' '); } numTokensConsumed++; int currentIndex = startIndex + numTokensConsumed; while (currentIndex < tokens.length) { if (tokens[currentIndex].equals("(")) { currentIndex++; continue; } if (tokens[currentIndex].endsWith(")")) { sb.append(tokens[currentIndex], 0, tokens[currentIndex].length() - 1); return new PointcutBody(numTokensConsumed, sb.toString().trim()); } String toAppend = tokens[currentIndex]; if (toAppend.startsWith("(")) { toAppend = toAppend.substring(1); } sb.append(toAppend); sb.append(' '); currentIndex++; numTokensConsumed++; } } // We looked and failed... return new PointcutBody(numTokensConsumed, null); } /** * Match up args against unbound arguments of primitive types. */ private void maybeBindPrimitiveArgsFromPointcutExpression() { int numUnboundPrimitives = countNumberOfUnboundPrimitiveArguments(); if (numUnboundPrimitives > 1) { throw new AmbiguousBindingException("Found " + numUnboundPrimitives + " unbound primitive arguments with no way to distinguish between them."); } if (numUnboundPrimitives == 1) { // Look for arg variable and bind it if we find exactly one... List varNames = new ArrayList<>(); String[] tokens = StringUtils.tokenizeToStringArray(this.pointcutExpression, " "); for (int i = 0; i < tokens.length; i++) { if (tokens[i].equals("args") || tokens[i].startsWith("args(")) { PointcutBody body = getPointcutBody(tokens, i); i += body.numTokensConsumed; maybeExtractVariableNamesFromArgs(body.text, varNames); } } if (varNames.size() > 1) { throw new AmbiguousBindingException("Found " + varNames.size() + " candidate variable names but only one candidate binding slot when matching primitive args"); } else if (varNames.size() == 1) { // 1 primitive arg, and one candidate... for (int i = 0; i < this.argumentTypes.length; i++) { if (isUnbound(i) && this.argumentTypes[i].isPrimitive()) { bindParameterName(i, varNames.get(0)); break; } } } } } /* * Return true if the parameter name binding for the given parameter * index has not yet been assigned. */ private boolean isUnbound(int i) { return this.parameterNameBindings[i] == null; } private boolean alreadyBound(String varName) { for (int i = 0; i < this.parameterNameBindings.length; i++) { if (!isUnbound(i) && varName.equals(this.parameterNameBindings[i])) { return true; } } return false; } /** * Return {@code true} if the given argument type is a subclass * of the given supertype. */ private boolean isSubtypeOf(Class supertype, int argumentNumber) { return supertype.isAssignableFrom(this.argumentTypes[argumentNumber]); } private int countNumberOfUnboundAnnotationArguments() { int count = 0; for (int i = 0; i < this.argumentTypes.length; i++) { if (isUnbound(i) && isSubtypeOf(Annotation.class, i)) { count++; } } return count; } private int countNumberOfUnboundPrimitiveArguments() { int count = 0; for (int i = 0; i < this.argumentTypes.length; i++) { if (isUnbound(i) && this.argumentTypes[i].isPrimitive()) { count++; } } return count; } /** * Find the argument index with the given type, and bind the given * {@code varName} in that position. */ private void findAndBind(Class argumentType, String varName) { for (int i = 0; i < this.argumentTypes.length; i++) { if (isUnbound(i) && isSubtypeOf(argumentType, i)) { bindParameterName(i, varName); return; } } throw new IllegalStateException("Expected to find an unbound argument of type '" + argumentType.getName() + "'"); } /** * Simple record to hold the extracted text from a pointcut body, together * with the number of tokens consumed in extracting it. */ private record PointcutBody(int numTokensConsumed, @Nullable String text) {} /** * Thrown in response to an ambiguous binding being detected when * trying to resolve a method's parameter names. */ @SuppressWarnings("serial") public static class AmbiguousBindingException extends RuntimeException { /** * Construct a new AmbiguousBindingException with the specified message. * @param msg the detail message */ public AmbiguousBindingException(String msg) { super(msg); } } }





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