https://github.com/spring-projects/spring-framework: Spring AOP (Spring IO)
  • Juergen Hoeller 
/*
 * 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.
 * 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;


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 null. 
This class interprets arguments in the following way:

    

  1. If the first parameter of the method is of type JoinPoint or ProceedingJoinPoint, it is assumed to be for passing thisJoinPoint to the advice, and the parameter name will be assigned the value "thisJoinPoint".
    2. 

  2. If the first parameter of the method is of type JoinPoint.StaticPart, it is assumed to be for passing "thisJoinPointStaticPart" to the advice, and the parameter name will be assigned the value "thisJoinPointStaticPart".
    3. 

  3. If a throwingName has been set, and there are no unbound arguments of type Throwable+, then an IllegalArgumentException is raised. If there is more than one unbound argument of type Throwable+, then an AmbiguousBindingException is raised. If there is exactly one unbound argument of type Throwable+, then the corresponding parameter name is assigned the value <throwingName>.
    4. 

  4. If there remain unbound arguments, then the pointcut expression is examined. Let 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 a is zero we proceed to the next stage. If a > 1 then an AmbiguousBindingException is raised. If a == 1, and there are no unbound arguments of type Annotation+, then an IllegalArgumentException is raised. if there is exactly one such argument, then the corresponding parameter name is assigned the value from the pointcut expression.
    5. 

  5. If a returningName has been set, and there are no unbound arguments then an IllegalArgumentException is raised. If there is more than one unbound argument then an AmbiguousBindingException is raised. If there is exactly one unbound argument then the corresponding parameter name is assigned the value <returningName>.
    6. 

  6. If there remain unbound arguments, then the pointcut expression is examined once more for this, target, and 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 args) then an AmbiguousBindingException is raised. If there is exactly one argument of a primitive type, then if exactly one args bound variable was found, we assign the corresponding parameter name the variable name. If there were no args bound variables found an IllegalStateException is raised. If there are multiple args bound variables, an AmbiguousBindingException is raised. At this point, if there remains more than one unbound argument we raise an 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 this, target, or args, it is assigned as the corresponding parameter name. If there are multiple possibilities, an AmbiguousBindingException is raised.
    7. 



The behavior on raising an IllegalArgumentException or 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 getParameterNames(..) method will simply return null. If the raiseExceptions property is set to true, the conditions will be thrown as IllegalArgumentException and AmbiguousBindingException, respectively. 
Was that perfectly clear? ;)

Short version: If an unambiguous binding can be deduced, then it is. If the advice requirements cannot possibly be satisfied, then null is returned. By setting the raiseExceptions property to true, descriptive exceptions will be thrown instead of returning null in the case that the parameter names cannot be discovered. 
Author:Adrian Colyer, Juergen Hoeller
Since:2.0
/**
 * {@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}.
 *
 * <p>This class interprets arguments in the following way:
 * <ol>
 * <li>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"}.</li>
 * <li>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"}.</li>
 * <li>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 &lt;throwingName&gt;.</li>
 * <li>If there remain unbound arguments, then the pointcut expression is
 * examined. Let {@code a} be the number of annotation-based pointcut
 * expressions (&#64;annotation, &#64;this, &#64;target, &#64;args,
 * &#64;within, &#64;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} &gt; 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.</li>
 * <li>If a 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 &lt;returningName&gt;.</li>
 * <li>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.</li>
 * </ol>
 *
 * <p>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 {@code getParameterNames(..)} 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.
 *
 * <p>Was that perfectly clear? ;)
 *
 * <p>Short version: 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.
 *
 * @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<String> singleValuedAnnotationPcds = new HashSet<>();
	private static final Set<String> nonReferencePointcutTokens = new HashSet<>();


	static {
		singleValuedAnnotationPcds.add("@this");
		singleValuedAnnotationPcds.add("@target");
		singleValuedAnnotationPcds.add("@within");
		singleValuedAnnotationPcds.add("@withincode");
		singleValuedAnnotationPcds.add("@annotation");

		Set<PointcutPrimitive> 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. 
/** The pointcut expression associated with the advice, as a simple String. */
	@Nullable
	private String pointcutExpression;

	private boolean raiseExceptions;

	
If the advice is afterReturning, and binds the return value, this is the parameter name used. 
/** 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. 
/** 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.

/**
	 * 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 IllegalArgumentException and AmbiguousBindingException must be thrown as appropriate in the case of failing to deduce advice parameter names. 
Params:
  • raiseExceptions – true if exceptions are to be thrown
/**
	 * 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 afterReturning advice binds the return value, the returning variable name must be specified. 
Params:
  • returningName – the name of the returning variable
/**
	 * If {@code afterReturning} advice binds the return value, the
	 * returning variable name must be specified.
	 * @param returningName the name of the returning variable
	 */
	public void setReturningName(@Nullable String returningName) {
		this.returningName = returningName;
	}

	
If afterThrowing advice binds the thrown value, the throwing variable name must be specified. 
Params:
  • throwingName – the name of the throwing variable
/**
	 * If {@code afterThrowing} advice binds the thrown value, the
	 * 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 class level javadoc for this class for details of the algorithm used. 
Params:
Returns:the parameter names
/**
	 * Deduce the parameter names for an advice method.
	 * <p>See the {@link AspectJAdviceParameterNameDiscoverer class level javadoc}
	 * for this class for details of 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();
						}
						break;
					case STEP_THROWING_BINDING:
						maybeBindThrowingVariable();
						break;
					case STEP_ANNOTATION_BINDING:
						maybeBindAnnotationsFromPointcutExpression();
						break;
					case STEP_RETURNING_BINDING:
						maybeBindReturningVariable();
						break;
					case STEP_PRIMITIVE_ARGS_BINDING:
						maybeBindPrimitiveArgsFromPointcutExpression();
						break;
					case STEP_THIS_TARGET_ARGS_BINDING:
						maybeBindThisOrTargetOrArgsFromPointcutExpression();
						break;
					case STEP_REFERENCE_PCUT_BINDING:
						maybeBindReferencePointcutParameter();
						break;
					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.

Throws:
Returns: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, 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.

/**
	 * 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.

/**
	 * 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 argument " + 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.

/**
	 * 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... :)

/**
	 * Parse the string pointcut expression looking for:
	 * &#64;this, &#64;target, &#64;args, &#64;within, &#64;withincode, &#64;annotation.
	 * If we find one of these pointcut expressions, try and extract a candidate variable
	 * name (or variable names, in the case of args).
	 * <p>Some more support from AspectJ in doing this exercise would be nice... :)
	 */
	private void maybeBindAnnotationsFromPointcutExpression() {
		List<String> 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.

/**
	 * Match the given list of extracted variable names to argument slots.
	 */
	private void bindAnnotationsFromVarNames(List<String> 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 args or at_args), add any candidate variable names to the given list. 
/**
	 * 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<String> varNames) {
		if (argsSpec == null) {
			return;
		}
		String[] tokens = StringUtils.tokenizeToStringArray(argsSpec, ",");
		for (int i = 0; i < tokens.length; i++) {
			tokens[i] = StringUtils.trimWhitespace(tokens[i]);
			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.

/**
	 * 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<String> 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<String> 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<String> 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.

/**
	 * 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<String> 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 struct to hold the extracted text from a pointcut body, together
with the number of tokens consumed in extracting it.

/**
	 * Simple struct to hold the extracted text from a pointcut body, together
	 * with the number of tokens consumed in extracting it.
	 */
	private static class PointcutBody {

		private int numTokensConsumed;

		@Nullable
		private String text;

		public PointcutBody(int tokens, @Nullable String text) {
			this.numTokensConsumed = tokens;
			this.text = text;
		}
	}


	
Thrown in response to an ambiguous binding being detected when
trying to resolve a method's parameter names.

/**
	 * 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.

Params:
  • msg – the detail message
/**
		 * Construct a new AmbiguousBindingException with the specified message.
		 * @param msg the detail message
		 */
		public AmbiguousBindingException(String msg) {
			super(msg);
		}
	}

}