Expose record-style accessor methods for instance fields as bean properties

Closes gh-24391

spring-beans/src/main/java/org/springframework/beans/CachedIntrospectionResults.java

@@ -20,7 +20,10 @@ import java.beans.BeanInfo;
 import java.beans.IntrospectionException;
 import java.beans.Introspector;
 import java.beans.PropertyDescriptor;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -92,6 +95,8 @@ public final class CachedIntrospectionResults {
 	 */
 	public static final String IGNORE_BEANINFO_PROPERTY_NAME = "spring.beaninfo.ignore";
 
+	private static final PropertyDescriptor[] EMPTY_PROPERTY_DESCRIPTOR_ARRAY = {};
+
 
 	private static final boolean shouldIntrospectorIgnoreBeaninfoClasses =
 			SpringProperties.getFlag(IGNORE_BEANINFO_PROPERTY_NAME);
@@ -253,7 +258,7 @@ public final class CachedIntrospectionResults {
 	private final BeanInfo beanInfo;
 
 	/** PropertyDescriptor objects keyed by property name String. */
-	private final Map<String, PropertyDescriptor> propertyDescriptorCache;
+	private final Map<String, PropertyDescriptor> propertyDescriptors;
 
 	/** TypeDescriptor objects keyed by PropertyDescriptor. */
 	private final ConcurrentMap<PropertyDescriptor, TypeDescriptor> typeDescriptorCache;
@@ -274,7 +279,9 @@ public final class CachedIntrospectionResults {
 			if (logger.isTraceEnabled()) {
 				logger.trace("Caching PropertyDescriptors for class [" + beanClass.getName() + "]");
 			}
-			this.propertyDescriptorCache = new LinkedHashMap<>();
+			this.propertyDescriptors = new LinkedHashMap<>();
+
+			Set<String> readMethodNames = new HashSet<>();
 
 			// This call is slow so we do it once.
 			PropertyDescriptor[] pds = this.beanInfo.getPropertyDescriptors();
@@ -291,17 +298,26 @@ public final class CachedIntrospectionResults {
 									"; editor [" + pd.getPropertyEditorClass().getName() + "]" : ""));
 				}
 				pd = buildGenericTypeAwarePropertyDescriptor(beanClass, pd);
-				this.propertyDescriptorCache.put(pd.getName(), pd);
+				this.propertyDescriptors.put(pd.getName(), pd);
+				Method readMethod = pd.getReadMethod();
+				if (readMethod != null) {
+					readMethodNames.add(readMethod.getName());
+				}
 			}
 
 			// Explicitly check implemented interfaces for setter/getter methods as well,
 			// in particular for Java 8 default methods...
 			Class<?> currClass = beanClass;
 			while (currClass != null && currClass != Object.class) {
-				introspectInterfaces(beanClass, currClass);
+				introspectInterfaces(beanClass, currClass, readMethodNames);
 				currClass = currClass.getSuperclass();
 			}
 
+			// Check for record-style accessors without prefix: e.g. "lastName()"
+			// - accessor method directly referring to instance field of same name
+			// - same convention for component accessors of Java 15 record classes
+			introspectPlainAccessors(beanClass, readMethodNames);
+
 			this.typeDescriptorCache = new ConcurrentReferenceHashMap<>();
 		}
 		catch (IntrospectionException ex) {
@@ -309,24 +325,58 @@ public final class CachedIntrospectionResults {
 		}
 	}
 
-	private void introspectInterfaces(Class<?> beanClass, Class<?> currClass) throws IntrospectionException {
+	private void introspectInterfaces(Class<?> beanClass, Class<?> currClass, Set<String> readMethodNames)
+			throws IntrospectionException {
+
 		for (Class<?> ifc : currClass.getInterfaces()) {
 			if (!ClassUtils.isJavaLanguageInterface(ifc)) {
 				for (PropertyDescriptor pd : getBeanInfo(ifc).getPropertyDescriptors()) {
-					PropertyDescriptor existingPd = this.propertyDescriptorCache.get(pd.getName());
+					PropertyDescriptor existingPd = this.propertyDescriptors.get(pd.getName());
 					if (existingPd == null ||
 							(existingPd.getReadMethod() == null && pd.getReadMethod() != null)) {
 						// GenericTypeAwarePropertyDescriptor leniently resolves a set* write method
 						// against a declared read method, so we prefer read method descriptors here.
 						pd = buildGenericTypeAwarePropertyDescriptor(beanClass, pd);
-						this.propertyDescriptorCache.put(pd.getName(), pd);
+						this.propertyDescriptors.put(pd.getName(), pd);
+						Method readMethod = pd.getReadMethod();
+						if (readMethod != null) {
+							readMethodNames.add(readMethod.getName());
+						}
 					}
 				}
-				introspectInterfaces(ifc, ifc);
+				introspectInterfaces(ifc, ifc, readMethodNames);
+			}
+		}
+	}
+
+	private void introspectPlainAccessors(Class<?> beanClass, Set<String> readMethodNames)
+			throws IntrospectionException {
+
+		for (Method method : beanClass.getMethods()) {
+			if (!this.propertyDescriptors.containsKey(method.getName()) &&
+					!readMethodNames.contains((method.getName())) && isPlainAccessor(method)) {
+				this.propertyDescriptors.put(method.getName(),
+						new GenericTypeAwarePropertyDescriptor(beanClass, method.getName(), method, null, null));
+				readMethodNames.add(method.getName());
 			}
 		}
 	}
 
+	private boolean isPlainAccessor(Method method) {
+		if (method.getParameterCount() > 0 || method.getReturnType() == void.class ||
+				method.getDeclaringClass() == Object.class || Modifier.isStatic(method.getModifiers())) {
+			return false;
+		}
+		try {
+			// Accessor method referring to instance field of same name?
+			method.getDeclaringClass().getDeclaredField(method.getName());
+			return true;
+		}
+		catch (Exception ex) {
+			return false;
+		}
+	}
+
 
 	BeanInfo getBeanInfo() {
 		return this.beanInfo;
@@ -338,27 +388,19 @@ public final class CachedIntrospectionResults {
 
 	@Nullable
 	PropertyDescriptor getPropertyDescriptor(String name) {
-		PropertyDescriptor pd = this.propertyDescriptorCache.get(name);
+		PropertyDescriptor pd = this.propertyDescriptors.get(name);
 		if (pd == null && StringUtils.hasLength(name)) {
 			// Same lenient fallback checking as in Property...
-			pd = this.propertyDescriptorCache.get(StringUtils.uncapitalize(name));
+			pd = this.propertyDescriptors.get(StringUtils.uncapitalize(name));
 			if (pd == null) {
-				pd = this.propertyDescriptorCache.get(StringUtils.capitalize(name));
+				pd = this.propertyDescriptors.get(StringUtils.capitalize(name));
 			}
 		}
-		return (pd == null || pd instanceof GenericTypeAwarePropertyDescriptor ? pd :
-				buildGenericTypeAwarePropertyDescriptor(getBeanClass(), pd));
+		return pd;
 	}
 
 	PropertyDescriptor[] getPropertyDescriptors() {
-		PropertyDescriptor[] pds = new PropertyDescriptor[this.propertyDescriptorCache.size()];
-		int i = 0;
-		for (PropertyDescriptor pd : this.propertyDescriptorCache.values()) {
-			pds[i] = (pd instanceof GenericTypeAwarePropertyDescriptor ? pd :
-					buildGenericTypeAwarePropertyDescriptor(getBeanClass(), pd));
-			i++;
-		}
-		return pds;
+		return this.propertyDescriptors.values().toArray(EMPTY_PROPERTY_DESCRIPTOR_ARRAY);
 	}
 
 	private PropertyDescriptor buildGenericTypeAwarePropertyDescriptor(Class<?> beanClass, PropertyDescriptor pd) {

spring-beans/src/main/java/org/springframework/beans/GenericTypeAwarePropertyDescriptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * 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.
@@ -60,12 +60,13 @@ final class GenericTypeAwarePropertyDescriptor extends PropertyDescriptor {
 	@Nullable
 	private Class<?> propertyType;
 
+	@Nullable
 	private final Class<?> propertyEditorClass;
 
 
 	public GenericTypeAwarePropertyDescriptor(Class<?> beanClass, String propertyName,
-			@Nullable Method readMethod, @Nullable Method writeMethod, Class<?> propertyEditorClass)
-			throws IntrospectionException {
+			@Nullable Method readMethod, @Nullable Method writeMethod,
+			@Nullable Class<?> propertyEditorClass) throws IntrospectionException {
 
 		super(propertyName, null, null);
 		this.beanClass = beanClass;
@@ -156,6 +157,7 @@ final class GenericTypeAwarePropertyDescriptor extends PropertyDescriptor {
 	}
 
 	@Override
+	@Nullable
 	public Class<?> getPropertyEditorClass() {
 		return this.propertyEditorClass;
 	}

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ServletAnnotationControllerHandlerMethodTests.java

@@ -3834,11 +3834,11 @@ public class ServletAnnotationControllerHandlerMethodTests extends AbstractServl
 	public static class DataClass {
 
 		@NotNull
-		public final String param1;
+		private final String param1;
 
-		public final boolean param2;
+		private final boolean param2;
 
-		public int param3;
+		private int param3;
 
 		@ConstructorProperties({"param1", "param2", "optionalParam"})
 		public DataClass(String param1, boolean p2, Optional<Integer> optionalParam) {
@@ -3848,9 +3848,21 @@ public class ServletAnnotationControllerHandlerMethodTests extends AbstractServl
 			optionalParam.ifPresent(integer -> this.param3 = integer);
 		}
 
+		public String param1() {
+			return param1;
+		}
+
+		public boolean param2() {
+			return param2;
+		}
+
 		public void setParam3(int param3) {
 			this.param3 = param3;
 		}
+
+		public int getParam3() {
+			return param3;
+		}
 	}
 
 	@RestController
@@ -3876,7 +3888,6 @@ public class ServletAnnotationControllerHandlerMethodTests extends AbstractServl
 
 		@InitBinder
 		public void initBinder(WebDataBinder binder) {
-			binder.initDirectFieldAccess();
 			binder.setConversionService(new DefaultFormattingConversionService());
 			LocalValidatorFactoryBean vf = new LocalValidatorFactoryBean();
 			vf.afterPropertiesSet();