Deprecate support for theme

As seen in gh-28868, the support for Themes is now deprecated as of
Spring Framework 6.0 and will be removed in a future release.

Closes gh-29114

spring-web/src/main/java/org/springframework/web/context/support/AbstractRefreshableWebApplicationContext.java

@@ -57,6 +57,7 @@ import org.springframework.web.context.ServletContextAware;
  * {@link org.springframework.context.support.AbstractApplicationContext},
  * this class detects a bean of type {@link org.springframework.ui.context.ThemeSource}
  * in the context, under the special bean name "themeSource".
+ * Theme support is deprecated as of 6.0
  *
  * <p><b>This is the web context to be subclassed for a different bean definition format.</b>
  * Such a context implementation can be specified as "contextClass" context-param
@@ -75,9 +76,9 @@ import org.springframework.web.context.ServletContextAware;
  * @since 1.1.3
  * @see #loadBeanDefinitions
  * @see org.springframework.web.context.ConfigurableWebApplicationContext#setConfigLocations
- * @see org.springframework.ui.context.ThemeSource
  * @see XmlWebApplicationContext
  */
+@SuppressWarnings("deprecation")
 public abstract class AbstractRefreshableWebApplicationContext extends AbstractRefreshableConfigApplicationContext
 		implements ConfigurableWebApplicationContext, ThemeSource {
 
@@ -95,6 +96,7 @@ public abstract class AbstractRefreshableWebApplicationContext extends AbstractR
 
 	/** the ThemeSource for this ApplicationContext. */
 	@Nullable
+	@Deprecated
 	private ThemeSource themeSource;
 
 
@@ -197,6 +199,7 @@ public abstract class AbstractRefreshableWebApplicationContext extends AbstractR
 	 * Initialize the theme capability.
 	 */
 	@Override
+	@Deprecated
 	protected void onRefresh() {
 		this.themeSource = UiApplicationContextUtils.initThemeSource(this);
 	}
@@ -215,6 +218,7 @@ public abstract class AbstractRefreshableWebApplicationContext extends AbstractR
 
 	@Override
 	@Nullable
+	@Deprecated
 	public Theme getTheme(String themeName) {
 		Assert.state(this.themeSource != null, "No ThemeSource available");
 		return this.themeSource.getTheme(themeName);

spring-web/src/main/java/org/springframework/web/context/support/GenericWebApplicationContext.java

@@ -52,6 +52,7 @@ import org.springframework.web.context.ServletContextAware;
  * <p>In addition to the special beans detected by
  * {@link org.springframework.context.support.AbstractApplicationContext AbstractApplicationContext},
  * this class detects a {@link ThemeSource} bean in the context, with the name "themeSource".
+ * Theme support is deprecated as of 6.0
  *
  * <p>If you wish to register annotated <em>component classes</em> with a
  * {@code GenericWebApplicationContext}, you can use an
@@ -77,6 +78,7 @@ import org.springframework.web.context.ServletContextAware;
  * @author Sam Brannen
  * @since 1.2
  */
+@SuppressWarnings("deprecation")
 public class GenericWebApplicationContext extends GenericApplicationContext
 		implements ConfigurableWebApplicationContext, ThemeSource {
 
@@ -84,6 +86,7 @@ public class GenericWebApplicationContext extends GenericApplicationContext
 	private ServletContext servletContext;
 
 	@Nullable
+	@Deprecated
 	private ThemeSource themeSource;
 
 
@@ -195,6 +198,7 @@ public class GenericWebApplicationContext extends GenericApplicationContext
 	 * Initialize the theme capability.
 	 */
 	@Override
+	@Deprecated
 	protected void onRefresh() {
 		this.themeSource = UiApplicationContextUtils.initThemeSource(this);
 	}
@@ -213,6 +217,7 @@ public class GenericWebApplicationContext extends GenericApplicationContext
 
 	@Override
 	@Nullable
+	@Deprecated
 	public Theme getTheme(String themeName) {
 		Assert.state(this.themeSource != null, "No ThemeSource available");
 		return this.themeSource.getTheme(themeName);

spring-web/src/main/java/org/springframework/web/context/support/StaticWebApplicationContext.java

@@ -50,11 +50,13 @@ import org.springframework.web.context.ServletContextAware;
  * {@link org.springframework.context.support.AbstractApplicationContext},
  * this class detects a bean of type {@link org.springframework.ui.context.ThemeSource}
  * in the context, under the special bean name "themeSource".
+ * Theme support is deprecated as of 6.0
  *
  * @author Rod Johnson
  * @author Juergen Hoeller
  * @see org.springframework.ui.context.ThemeSource
  */
+@SuppressWarnings("deprecation")
 public class StaticWebApplicationContext extends StaticApplicationContext
 		implements ConfigurableWebApplicationContext, ThemeSource {
 
@@ -68,6 +70,7 @@ public class StaticWebApplicationContext extends StaticApplicationContext
 	private String namespace;
 
 	@Nullable
+	@Deprecated
 	private ThemeSource themeSource;
 
 
@@ -186,6 +189,7 @@ public class StaticWebApplicationContext extends StaticApplicationContext
 	 * Initialize the theme capability.
 	 */
 	@Override
+	@Deprecated
 	protected void onRefresh() {
 		this.themeSource = UiApplicationContextUtils.initThemeSource(this);
 	}
@@ -198,6 +202,7 @@ public class StaticWebApplicationContext extends StaticApplicationContext
 
 	@Override
 	@Nullable
+	@Deprecated
 	public Theme getTheme(String themeName) {
 		Assert.state(this.themeSource != null, "No ThemeSource available");
 		return this.themeSource.getTheme(themeName);