Fix JSP EL support with Tomcat

Fix TomcatEmbeddedServletContainerFactory to set a MERGED_WEB_XML
attribute when JSPs are used. This is required for EL support with
JSPs since Jasper checks the version number in the web.xml. Without
any web.xml Jasper default to disabling EL.

Issue: #55752948

spring-boot-samples/spring-boot-sample-web-jsp/src/main/java/org/springframework/boot/sample/jsp/SampleWebJspApplication.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2013 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.sample.jsp;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.view.InternalResourceViewResolver;
+
+@Configuration
+@EnableAutoConfiguration
+@ComponentScan
+public class SampleWebJspApplication {
+
+	@Bean
+	public InternalResourceViewResolver defaultViewResolver() {
+		InternalResourceViewResolver resolver = new InternalResourceViewResolver();
+		resolver.setPrefix("/WEB-INF/jsp/");
+		resolver.setSuffix(".jsp");
+		return resolver;
+	}
+
+	public static void main(String[] args) throws Exception {
+		SpringApplication.run(SampleWebJspApplication.class, args);
+	}
+
+}

spring-boot-samples/spring-boot-sample-web-jsp/src/main/java/org/springframework/boot/sample/jsp/WelcomeController.java

@@ -0,0 +1,14 @@
+package org.springframework.boot.sample.jsp;
+
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+@Controller
+public class WelcomeController {
+
+	@RequestMapping("/")
+	public String welcome() {
+		return "welcome";
+	}
+
+}