WICKET-6899 Add setExceptionMapperProvider() to Application
diff --git a/wicket-core/src/main/java/org/apache/wicket/Application.java b/wicket-core/src/main/java/org/apache/wicket/Application.java
index fa4ce29..a450fad 100644
--- a/wicket-core/src/main/java/org/apache/wicket/Application.java
+++ b/wicket-core/src/main/java/org/apache/wicket/Application.java
@@ -651,8 +651,8 @@
 
 		pageFactory = newPageFactory();
 
-		requestCycleProvider = (context) -> new RequestCycle(context);
-		exceptionMapperProvider = () -> new DefaultExceptionMapper();
+		requestCycleProvider = RequestCycle::new;
+		exceptionMapperProvider = DefaultExceptionMapper::new;
 
 		// add a request cycle listener that logs each request for the requestlogger.
 		getRequestCycleListeners().add(new RequestLoggerRequestCycleListener());
@@ -671,6 +671,10 @@
 		return exceptionMapperProvider;
 	}
 
+	public void setExceptionMapperProvider(Supplier<IExceptionMapper> exceptionMapperProvider) {
+		this.exceptionMapperProvider = Args.notNull(exceptionMapperProvider, "exceptionMapperProvider");
+	}
+
 	/**
 	 * 
 	 * @return Session state provider