@nullable all the way: null-safety at field level

This commits extends nullability declarations to the field level, formalizing the interaction between methods and their underlying fields and therefore avoiding any nullability mismatch.

Issue: SPR-15720

Author: jhoeller

spring-aop/src/main/java/org/springframework/aop/aspectj/AbstractAspectJAdvice.java

@@ -104,11 +104,11 @@ public static JoinPoint currentJoinPoint() {
 	private final AspectInstanceFactory aspectInstanceFactory;
 
 	/**
-	 * The name of the aspect (ref bean) in which this advice was defined (used
-	 * when determining advice precedence so that we can determine
+	 * The name of the aspect (ref bean) in which this advice was defined
+	 * (used when determining advice precedence so that we can determine
 	 * whether two pieces of advice come from the same aspect).
 	 */
-	private String aspectName;
+	private String aspectName = "";
 
 	/**
 	 * The order of declaration of this advice within the aspect.
@@ -119,13 +119,16 @@ public static JoinPoint currentJoinPoint() {
 	 * This will be non-null if the creator of this advice object knows the argument names
 	 * and sets them explicitly
 	 */
-	private String[] argumentNames = null;
+	@Nullable
+	private String[] argumentNames;
 
 	/** Non-null if after throwing advice binds the thrown value */
-	private String throwingName = null;
+	@Nullable
+	private String throwingName;
 
 	/** Non-null if after returning advice binds the return value */
-	private String returningName = null;
+	@Nullable
+	private String returningName;
 
 	private Class<?> discoveredReturningType = Object.class;
 
@@ -143,10 +146,12 @@ public static JoinPoint currentJoinPoint() {
 	 */
 	private int joinPointStaticPartArgumentIndex = -1;
 
+	@Nullable
 	private Map<String, Integer> argumentBindings;
 
 	private boolean argumentsIntrospected = false;
 
+	@Nullable
 	private Type discoveredReturningGenericType;
 	// Note: Unlike return type, no such generic information is needed for the throwing type,
 	// since Java doesn't allow exception types to be parameterized.
@@ -464,6 +469,7 @@ protected ParameterNameDiscoverer createParameterNameDiscoverer() {
 	}
 
 	private void bindExplicitArguments(int numArgumentsLeftToBind) {
+		Assert.state(this.argumentNames != null, "No argument names available");
 		this.argumentBindings = new HashMap<>();
 
 		int numExpectedArgumentNames = this.aspectJAdviceMethod.getParameterCount();
@@ -504,36 +510,36 @@ private void bindExplicitArguments(int numArgumentsLeftToBind) {
 		}
 
 		// configure the pointcut expression accordingly.
-		configurePointcutParameters(argumentIndexOffset);
+		configurePointcutParameters(this.argumentNames, argumentIndexOffset);
 	}
 
 	/**
 	 * All parameters from argumentIndexOffset onwards are candidates for
 	 * pointcut parameters - but returning and throwing vars are handled differently
 	 * and must be removed from the list if present.
 	 */
-	private void configurePointcutParameters(int argumentIndexOffset) {
+	private void configurePointcutParameters(String[] argumentNames, int argumentIndexOffset) {
 		int numParametersToRemove = argumentIndexOffset;
 		if (this.returningName != null) {
 			numParametersToRemove++;
 		}
 		if (this.throwingName != null) {
 			numParametersToRemove++;
 		}
-		String[] pointcutParameterNames = new String[this.argumentNames.length - numParametersToRemove];
+		String[] pointcutParameterNames = new String[argumentNames.length - numParametersToRemove];
 		Class<?>[] pointcutParameterTypes = new Class<?>[pointcutParameterNames.length];
 		Class<?>[] methodParameterTypes = this.aspectJAdviceMethod.getParameterTypes();
 
 		int index = 0;
-		for (int i = 0; i < this.argumentNames.length; i++) {
+		for (int i = 0; i < argumentNames.length; i++) {
 			if (i < argumentIndexOffset) {
 				continue;
 			}
-			if (this.argumentNames[i].equals(this.returningName) ||
-				this.argumentNames[i].equals(this.throwingName)) {
+			if (argumentNames[i].equals(this.returningName) ||
+				argumentNames[i].equals(this.throwingName)) {
 				continue;
 			}
-			pointcutParameterNames[index] = this.argumentNames[i];
+			pointcutParameterNames[index] = argumentNames[i];
 			pointcutParameterTypes[index] = methodParameterTypes[i];
 			index++;
 		}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAdviceParameterNameDiscoverer.java

@@ -114,6 +114,7 @@
  * 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 {
@@ -155,26 +156,23 @@ public class AspectJAdviceParameterNameDiscoverer implements ParameterNameDiscov
 	}
 
 
+	/** 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;
 
-	/**
-	 * The pointcut expression associated with the advice, as a simple String.
-	 */
-	private String pointcutExpression;
-
-	private Class<?>[] argumentTypes;
+	private Class<?>[] argumentTypes = new Class<?>[0];
 
-	private String[] parameterNameBindings;
+	private String[] parameterNameBindings = new String[0];
 
 	private int numberOfRemainingUnboundArguments;
 
@@ -202,7 +200,7 @@ public void setRaiseExceptions(boolean raiseExceptions) {
 	 * returning variable name must be specified.
 	 * @param returningName the name of the returning variable
 	 */
-	public void setReturningName(String returningName) {
+	public void setReturningName(@Nullable String returningName) {
 		this.returningName = returningName;
 	}
 
@@ -211,7 +209,7 @@ public void setReturningName(String returningName) {
 	 * throwing variable name must be specified.
 	 * @param throwingName the name of the throwing variable
 	 */
-	public void setThrowingName(String throwingName) {
+	public void setThrowingName(@Nullable String throwingName) {
 		this.throwingName = throwingName;
 	}
 
@@ -781,6 +779,7 @@ private static class PointcutBody {
 
 		private int numTokensConsumed;
 
+		@Nullable
 		private String text;
 
 		public PointcutBody(int tokens, @Nullable String text) {

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJExpressionPointcut.java

@@ -102,16 +102,20 @@ public class AspectJExpressionPointcut extends AbstractExpressionPointcut
 
 	private static final Log logger = LogFactory.getLog(AspectJExpressionPointcut.class);
 
+	@Nullable
 	private Class<?> pointcutDeclarationScope;
 
 	private String[] pointcutParameterNames = new String[0];
 
 	private Class<?>[] pointcutParameterTypes = new Class<?>[0];
 
+	@Nullable
 	private BeanFactory beanFactory;
 
+	@Nullable
 	private transient ClassLoader pointcutClassLoader;
 
+	@Nullable
 	private transient PointcutExpression pointcutExpression;
 
 	private transient Map<Method, ShadowMatch> shadowMatchCache = new ConcurrentHashMap<>(32);
@@ -169,13 +173,13 @@ public void setBeanFactory(BeanFactory beanFactory) {
 
 	@Override
 	public ClassFilter getClassFilter() {
-		checkReadyToMatch();
+		obtainPointcutExpression();
 		return this;
 	}
 
 	@Override
 	public MethodMatcher getMethodMatcher() {
-		checkReadyToMatch();
+		obtainPointcutExpression();
 		return this;
 	}
 
@@ -184,14 +188,15 @@ public MethodMatcher getMethodMatcher() {
 	 * Check whether this pointcut is ready to match,
 	 * lazily building the underlying AspectJ pointcut expression.
 	 */
-	private void checkReadyToMatch() {
+	private PointcutExpression obtainPointcutExpression() {
 		if (getExpression() == null) {
 			throw new IllegalStateException("Must set property 'expression' before attempting to match");
 		}
 		if (this.pointcutExpression == null) {
 			this.pointcutClassLoader = determinePointcutClassLoader();
 			this.pointcutExpression = buildPointcutExpression(this.pointcutClassLoader);
 		}
+		return this.pointcutExpression;
 	}
 
 	/**
@@ -258,16 +263,15 @@ private String replaceBooleanOperators(String pcExpr) {
 	 * Return the underlying AspectJ pointcut expression.
 	 */
 	public PointcutExpression getPointcutExpression() {
-		checkReadyToMatch();
-		return this.pointcutExpression;
+		return obtainPointcutExpression();
 	}
 
 	@Override
 	public boolean matches(Class<?> targetClass) {
-		checkReadyToMatch();
+		PointcutExpression pointcutExpression = obtainPointcutExpression();
 		try {
 			try {
-				return this.pointcutExpression.couldMatchJoinPointsInType(targetClass);
+				return pointcutExpression.couldMatchJoinPointsInType(targetClass);
 			}
 			catch (ReflectionWorldException ex) {
 				logger.debug("PointcutExpression matching rejected target class - trying fallback expression", ex);
@@ -286,7 +290,7 @@ public boolean matches(Class<?> targetClass) {
 
 	@Override
 	public boolean matches(Method method, @Nullable Class<?> targetClass, boolean beanHasIntroductions) {
-		checkReadyToMatch();
+		obtainPointcutExpression();
 		Method targetMethod = AopUtils.getMostSpecificMethod(method, targetClass);
 		ShadowMatch shadowMatch = getShadowMatch(targetMethod, method);
 
@@ -321,13 +325,12 @@ public boolean matches(Method method, @Nullable Class<?> targetClass) {
 
 	@Override
 	public boolean isRuntime() {
-		checkReadyToMatch();
-		return this.pointcutExpression.mayNeedDynamicTest();
+		return obtainPointcutExpression().mayNeedDynamicTest();
 	}
 
 	@Override
 	public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
-		checkReadyToMatch();
+		obtainPointcutExpression();
 		ShadowMatch shadowMatch = getShadowMatch(AopUtils.getMostSpecificMethod(method, targetClass), method);
 		ShadowMatch originalShadowMatch = getShadowMatch(method, method);
 
@@ -436,7 +439,7 @@ private ShadowMatch getShadowMatch(Method targetMethod, Method originalMethod) {
 				if (shadowMatch == null) {
 					try {
 						try {
-							shadowMatch = this.pointcutExpression.matchesMethodExecution(methodToMatch);
+							shadowMatch = obtainPointcutExpression().matchesMethodExecution(methodToMatch);
 						}
 						catch (ReflectionWorldException ex) {
 							// Failed to introspect target method, probably because it has been loaded
@@ -454,7 +457,7 @@ private ShadowMatch getShadowMatch(Method targetMethod, Method originalMethod) {
 						if (shadowMatch == null && targetMethod != originalMethod) {
 							methodToMatch = originalMethod;
 							try {
-								shadowMatch = this.pointcutExpression.matchesMethodExecution(methodToMatch);
+								shadowMatch = obtainPointcutExpression().matchesMethodExecution(methodToMatch);
 							}
 							catch (ReflectionWorldException ex3) {
 								// Could neither introspect the target class nor the proxy class ->
@@ -519,18 +522,16 @@ public int hashCode() {
 	public String toString() {
 		StringBuilder sb = new StringBuilder();
 		sb.append("AspectJExpressionPointcut: ");
-		if (this.pointcutParameterNames != null && this.pointcutParameterTypes != null) {
-			sb.append("(");
-			for (int i = 0; i < this.pointcutParameterTypes.length; i++) {
-				sb.append(this.pointcutParameterTypes[i].getName());
-				sb.append(" ");
-				sb.append(this.pointcutParameterNames[i]);
-				if ((i+1) < this.pointcutParameterTypes.length) {
-					sb.append(", ");
-				}
+		sb.append("(");
+		for (int i = 0; i < this.pointcutParameterTypes.length; i++) {
+			sb.append(this.pointcutParameterTypes[i].getName());
+			sb.append(" ");
+			sb.append(this.pointcutParameterNames[i]);
+			if ((i+1) < this.pointcutParameterTypes.length) {
+				sb.append(", ");
 			}
-			sb.append(")");
 		}
+		sb.append(")");
 		sb.append(" ");
 		if (getExpression() != null) {
 			sb.append(getExpression());

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJPointcutAdvisor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -21,6 +21,7 @@
 import org.springframework.aop.Pointcut;
 import org.springframework.aop.PointcutAdvisor;
 import org.springframework.core.Ordered;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -38,6 +39,7 @@ public class AspectJPointcutAdvisor implements PointcutAdvisor, Ordered {
 
 	private final Pointcut pointcut;
 
+	@Nullable
 	private Integer order;
 
 

spring-aop/src/main/java/org/springframework/aop/aspectj/MethodInvocationProceedingJoinPoint.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -57,12 +57,15 @@ public class MethodInvocationProceedingJoinPoint implements ProceedingJoinPoint,
 
 	private final ProxyMethodInvocation methodInvocation;
 
+	@Nullable
 	private Object[] defensiveCopyOfArgs;
 
 	/** Lazily initialized signature object */
+	@Nullable
 	private Signature signature;
 
 	/** Lazily initialized source location object */
+	@Nullable
 	private SourceLocation sourceLocation;
 
 
@@ -178,6 +181,7 @@ public String toString() {
 	 */
 	private class MethodSignatureImpl implements MethodSignature {
 
+		@Nullable
 		private volatile String[] parameterNames;
 
 		@Override
@@ -216,6 +220,7 @@ public Class<?>[] getParameterTypes() {
 		}
 
 		@Override
+		@Nullable
 		public String[] getParameterNames() {
 			if (this.parameterNames == null) {
 				this.parameterNames = parameterNameDiscoverer.getParameterNames(getMethod());

spring-aop/src/main/java/org/springframework/aop/aspectj/RuntimeTestWalker.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -37,6 +37,7 @@
 import org.aspectj.weaver.reflect.ShadowMatchImpl;
 import org.aspectj.weaver.tools.ShadowMatch;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 
@@ -78,6 +79,7 @@ class RuntimeTestWalker {
 	}
 
 
+	@Nullable
 	private final Test runtimeTest;