Deprecate PropertyPlaceholderConfigurer

This commit deprecates PropertyPlaceholderConfigurer in favor of
PropertySourcesPlaceholderConfigurer.

Closes gh-22181

spring-beans/src/main/java/org/springframework/beans/factory/config/PropertyPlaceholderConfigurer.java

@@ -32,11 +32,6 @@ import org.springframework.util.StringValueResolver;
  * {@link #setLocation local} {@link #setProperties properties} and/or system properties
  * and environment variables.
  *
- * <p>As of Spring 3.1, {@link org.springframework.context.support.PropertySourcesPlaceholderConfigurer
- * PropertySourcesPlaceholderConfigurer} should be used preferentially over this implementation; it is
- * more flexible through taking advantage of the {@link org.springframework.core.env.Environment} and
- * {@link org.springframework.core.env.PropertySource} mechanisms also made available in Spring 3.1.
- *
  * <p>{@link PropertyPlaceholderConfigurer} is still appropriate for use when:
  * <ul>
  * <li>the {@code spring-context} module is not available (i.e., one is using Spring's
@@ -54,8 +49,12 @@ import org.springframework.util.StringValueResolver;
  * @see #setSystemPropertiesModeName
  * @see PlaceholderConfigurerSupport
  * @see PropertyOverrideConfigurer
- * @see org.springframework.context.support.PropertySourcesPlaceholderConfigurer
+
+ * @deprecated use {@code org.springframework.context.support.PropertySourcesPlaceholderConfigurer} instead;
+ * it is more flexible through taking advantage of the {@link org.springframework.core.env.Environment} and
+ * {@link org.springframework.core.env.PropertySource} mechanisms.
  */
+@Deprecated
 public class PropertyPlaceholderConfigurer extends PlaceholderConfigurerSupport {
 
 	/** Never check system properties. */

spring-context/src/main/java/org/springframework/context/config/PropertyPlaceholderBeanDefinitionParser.java

@@ -18,7 +18,6 @@ package org.springframework.context.config;
 
 import org.w3c.dom.Element;
 
-import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.xml.ParserContext;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
@@ -40,6 +39,7 @@ class PropertyPlaceholderBeanDefinitionParser extends AbstractPropertyLoadingBea
 
 
 	@Override
+	@SuppressWarnings("deprecation")
 	protected Class<?> getBeanClass(Element element) {
 		// As of Spring 3.1, the default value of system-properties-mode has changed from
 		// 'FALLBACK' to 'ENVIRONMENT'. This latter value indicates that resolution of
@@ -51,7 +51,7 @@ class PropertyPlaceholderBeanDefinitionParser extends AbstractPropertyLoadingBea
 
 		// The user has explicitly specified a value for system-properties-mode: revert to
 		// PropertyPlaceholderConfigurer to ensure backward compatibility with 3.0 and earlier.
-		return PropertyPlaceholderConfigurer.class;
+		return org.springframework.beans.factory.config.PropertyPlaceholderConfigurer.class;
 	}
 
 	@Override