Fix placeholder resolution in PropertySourcesPlaceholderConfigurer

Currently, the placeholder resolution algorithm in
PropertySourcesPlaceholderConfigurer fails in several scenarios, and
the root cause for this category of failures has actually existed since
PropertySourcesPlaceholderConfigurer was introduced in Spring Framework
3.1.

Specifically, PropertySourcesPlaceholderConfigurer creates its own
PropertySourcesPropertyResolver that indirectly delegates to another
"nested" PropertySourcesPropertyResolver to interact with
PropertySources from the Environment, which results in double
placeholder parsing and resolution attempts, and that behavior leads to
a whole category of bugs.

For example, #27947 was addressed in Spring Framework 5.3.16, and due
to #34315 and #34326 we have recently realized that additional bugs
exist with placeholder resolution: nested placeholder resolution can
fail when escape characters are used, and it is currently impossible
to disable the escape character support for nested resolution.

To address this category of bugs, we no longer indirectly use or
directly create a "nested" PropertySourcesPropertyResolver in
PropertySourcesPlaceholderConfigurer. Instead, properties from property
sources from the Environment are now accessed directly without
duplicate/nested placeholder resolution.

See gh-27947
See gh-34326
See gh-34862
Closes gh-34861

spring-context/src/main/java/org/springframework/context/support/PropertySourcesPlaceholderConfigurer.java

@@ -24,12 +24,12 @@ import org.springframework.beans.factory.BeanInitializationException;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.config.PlaceholderConfigurerSupport;
 import org.springframework.context.EnvironmentAware;
+import org.springframework.core.env.CompositePropertySource;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.ConfigurablePropertyResolver;
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertiesPropertySource;
-import org.springframework.core.env.PropertyResolver;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.PropertySources;
 import org.springframework.core.env.PropertySourcesPropertyResolver;
@@ -133,28 +133,24 @@ public class PropertySourcesPlaceholderConfigurer extends PlaceholderConfigurerS
 		if (this.propertySources == null) {
 			this.propertySources = new MutablePropertySources();
 			if (this.environment != null) {
-				PropertyResolver propertyResolver = this.environment;
-				// If the ignoreUnresolvablePlaceholders flag is set to true, we have to create a
-				// local PropertyResolver to enforce that setting, since the Environment is most
-				// likely not configured with ignoreUnresolvablePlaceholders set to true.
-				// See https://github.com/spring-projects/spring-framework/issues/27947
-				if (this.ignoreUnresolvablePlaceholders &&
-						(this.environment instanceof ConfigurableEnvironment configurableEnvironment)) {
-					PropertySourcesPropertyResolver resolver =
-							new PropertySourcesPropertyResolver(configurableEnvironment.getPropertySources());
-					resolver.setIgnoreUnresolvableNestedPlaceholders(true);
-					propertyResolver = resolver;
+				PropertySource<?> environmentPropertySource;
+				if (this.environment instanceof ConfigurableEnvironment configurableEnvironment) {
+					environmentPropertySource = new CompositePropertySource(ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME,
+							configurableEnvironment.getPropertySources());
 				}
-				PropertyResolver propertyResolverToUse = propertyResolver;
-				this.propertySources.addLast(
-					new PropertySource<>(ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME, this.environment) {
-						@Override
-						@Nullable
-						public String getProperty(String key) {
-							return propertyResolverToUse.getProperty(key);
-						}
-					}
-				);
+				else {
+					// Fallback code path that should never apply in a regular scenario, since the
+					// Environment in the ApplicationContext should always be a ConfigurableEnvironment.
+					environmentPropertySource =
+						new PropertySource<>(ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME, this.environment) {
+							@Override
+							@Nullable
+							public Object getProperty(String key) {
+								return super.source.getProperty(key);
+							}
+						};
+				}
+				this.propertySources.addLast(environmentPropertySource);
 			}
 			try {
 				PropertySource<?> localPropertySource =

spring-context/src/test/java/org/springframework/context/support/PropertySourcesPlaceholderConfigurerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -19,11 +19,13 @@ package org.springframework.context.support;
 import java.util.Optional;
 import java.util.Properties;
 
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.testfixture.beans.TestBean;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
@@ -432,6 +434,150 @@ class PropertySourcesPlaceholderConfigurerTests {
 	}
 
 
+	/**
+	 * Tests that use the escape character (or disable it) with nested placeholder
+	 * resolution.
+	 */
+	@Nested
+	class EscapedNestedPlaceholdersTests {
+
+		@Test  // gh-34861
+		void singleEscapeWithDefaultEscapeCharacter() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "admin")
+					.withProperty("my.property", "\\DOMAIN\\${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			ppc.postProcessBeanFactory(bf);
+
+			// \DOMAIN\${user.home} resolves to \DOMAIN${user.home} instead of \DOMAIN\admin
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("\\DOMAIN${user.home}");
+		}
+
+		@Test  // gh-34861
+		void singleEscapeWithCustomEscapeCharacter() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "admin\\~${nested}")
+					.withProperty("my.property", "DOMAIN\\${user.home}\\~${enigma}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			// Set custom escape character.
+			ppc.setEscapeCharacter('~');
+			ppc.postProcessBeanFactory(bf);
+
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("DOMAIN\\admin\\${nested}\\${enigma}");
+		}
+
+		@Test  // gh-34861
+		void singleEscapeWithEscapeCharacterDisabled() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "admin\\")
+					.withProperty("my.property", "\\DOMAIN\\${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			// Disable escape character.
+			ppc.setEscapeCharacter(null);
+			ppc.postProcessBeanFactory(bf);
+
+			// \DOMAIN\${user.home} resolves to \DOMAIN\admin
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("\\DOMAIN\\admin\\");
+		}
+
+		@Test  // gh-34861
+		void tripleEscapeWithDefaultEscapeCharacter() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "admin\\\\\\")
+					.withProperty("my.property", "DOMAIN\\\\\\${user.home}#${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			ppc.postProcessBeanFactory(bf);
+
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("DOMAIN\\\\${user.home}#admin\\\\\\");
+		}
+
+		@Test  // gh-34861
+		void tripleEscapeWithCustomEscapeCharacter() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "admin\\~${enigma}")
+					.withProperty("my.property", "DOMAIN~~~${user.home}#${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			// Set custom escape character.
+			ppc.setEscapeCharacter('~');
+			ppc.postProcessBeanFactory(bf);
+
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("DOMAIN~~${user.home}#admin\\${enigma}");
+		}
+
+		@Test  // gh-34861
+		void singleEscapeWithDefaultEscapeCharacterAndIgnoreUnresolvablePlaceholders() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "${enigma}")
+					.withProperty("my.property", "\\${DOMAIN}${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			ppc.setIgnoreUnresolvablePlaceholders(true);
+			ppc.postProcessBeanFactory(bf);
+
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("${DOMAIN}${enigma}");
+		}
+
+		@Test  // gh-34861
+		void singleEscapeWithCustomEscapeCharacterAndIgnoreUnresolvablePlaceholders() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "${enigma}")
+					.withProperty("my.property", "~${DOMAIN}\\${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			// Set custom escape character.
+			ppc.setEscapeCharacter('~');
+			ppc.setIgnoreUnresolvablePlaceholders(true);
+			ppc.postProcessBeanFactory(bf);
+
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("${DOMAIN}\\${enigma}");
+		}
+
+		@Test  // gh-34861
+		void tripleEscapeWithDefaultEscapeCharacterAndIgnoreUnresolvablePlaceholders() {
+			MockEnvironment env = new MockEnvironment()
+					.withProperty("user.home", "${enigma}")
+					.withProperty("my.property", "X:\\\\\\${DOMAIN}${user.home}");
+
+			DefaultListableBeanFactory bf = createBeanFactory();
+			PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+			ppc.setEnvironment(env);
+			ppc.setIgnoreUnresolvablePlaceholders(true);
+			ppc.postProcessBeanFactory(bf);
+
+			assertThat(bf.getBean(TestBean.class).getName()).isEqualTo("X:\\\\${DOMAIN}${enigma}");
+		}
+
+		private static DefaultListableBeanFactory createBeanFactory() {
+			BeanDefinition beanDefinition = genericBeanDefinition(TestBean.class)
+					.addPropertyValue("name", "${my.property}")
+					.getBeanDefinition();
+			DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+			bf.registerBeanDefinition("testBean",beanDefinition);
+			return bf;
+		}
+
+	}
+
+
 	private static class OptionalTestBean {
 
 		private Optional<String> name;