Make max length of SpEL expressions in an ApplicationContext configurable

This commit introduces support for a Spring property named
`spring.context.expression.maxLength`. When set, the value of that
property is used internally in StandardBeanExpressionResolver to
configure the SpelParserConfiguration used when evaluating String
values in bean definitions, @⁠Value, etc.

Closes gh-31952

spring-context/src/main/java/org/springframework/context/expression/StandardBeanExpressionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -23,6 +23,7 @@ import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanExpressionException;
 import org.springframework.beans.factory.config.BeanExpressionContext;
 import org.springframework.beans.factory.config.BeanExpressionResolver;
+import org.springframework.core.SpringProperties;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.expression.Expression;
@@ -47,6 +48,7 @@ import org.springframework.util.StringUtils;
  * beans such as "environment", "systemProperties" and "systemEnvironment".
  *
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 3.0
  * @see BeanExpressionContext#getBeanFactory()
  * @see org.springframework.expression.ExpressionParser
@@ -55,6 +57,14 @@ import org.springframework.util.StringUtils;
  */
 public class StandardBeanExpressionResolver implements BeanExpressionResolver {
 
+	/**
+	 * System property to configure the maximum length for SpEL expressions: {@value}.
+	 * <p>Can also be configured via the {@link SpringProperties} mechanism.
+	 * @since 6.1.3
+	 * @see SpelParserConfiguration#getMaximumExpressionLength()
+	 */
+	public static final String MAX_SPEL_EXPRESSION_LENGTH_PROPERTY_NAME = "spring.context.expression.maxLength";
+
 	/** Default expression prefix: "#{". */
 	public static final String DEFAULT_EXPRESSION_PREFIX = "#{";
 
@@ -90,18 +100,24 @@ public class StandardBeanExpressionResolver implements BeanExpressionResolver {
 
 	/**
 	 * Create a new {@code StandardBeanExpressionResolver} with default settings.
+	 * <p>As of Spring Framework 6.1.3, the maximum SpEL expression length can be
+	 * configured via the {@link #MAX_SPEL_EXPRESSION_LENGTH_PROPERTY_NAME} property.
 	 */
 	public StandardBeanExpressionResolver() {
-		this.expressionParser = new SpelExpressionParser();
+		this(null);
 	}
 
 	/**
 	 * Create a new {@code StandardBeanExpressionResolver} with the given bean class loader,
 	 * using it as the basis for expression compilation.
+	 * <p>As of Spring Framework 6.1.3, the maximum SpEL expression length can be
+	 * configured via the {@link #MAX_SPEL_EXPRESSION_LENGTH_PROPERTY_NAME} property.
 	 * @param beanClassLoader the factory's bean class loader
 	 */
 	public StandardBeanExpressionResolver(@Nullable ClassLoader beanClassLoader) {
-		this.expressionParser = new SpelExpressionParser(new SpelParserConfiguration(null, beanClassLoader));
+		SpelParserConfiguration parserConfig = new SpelParserConfiguration(
+				null, beanClassLoader, false, false, Integer.MAX_VALUE, retrieveMaxExpressionLength());
+		this.expressionParser = new SpelExpressionParser(parserConfig);
 	}
 
 
@@ -178,4 +194,22 @@ public class StandardBeanExpressionResolver implements BeanExpressionResolver {
 	protected void customizeEvaluationContext(StandardEvaluationContext evalContext) {
 	}
 
+	private static int retrieveMaxExpressionLength() {
+		String value = SpringProperties.getProperty(MAX_SPEL_EXPRESSION_LENGTH_PROPERTY_NAME);
+		if (!StringUtils.hasText(value)) {
+			return SpelParserConfiguration.DEFAULT_MAX_EXPRESSION_LENGTH;
+		}
+
+		try {
+			int maxLength = Integer.parseInt(value.trim());
+			Assert.isTrue(maxLength > 0, () -> "Value [" + maxLength + "] for system property ["
+					+ MAX_SPEL_EXPRESSION_LENGTH_PROPERTY_NAME + "] must be positive");
+			return maxLength;
+		}
+		catch (NumberFormatException ex) {
+			throw new IllegalArgumentException("Failed to parse value for system property [" +
+					MAX_SPEL_EXPRESSION_LENGTH_PROPERTY_NAME + "]: " + ex.getMessage(), ex);
+		}
+	}
+
 }