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/pom.xml

@@ -25,6 +25,7 @@
 		<module>spring-boot-sample-tomcat</module>
 		<module>spring-boot-sample-traditional</module>
 		<module>spring-boot-sample-web-static</module>
+		<module>spring-boot-sample-web-jsp</module>
 		<module>spring-boot-sample-web-ui</module>
 		<module>spring-boot-sample-websocket</module>
 		<module>spring-boot-sample-xml</module>

spring-boot-samples/spring-boot-sample-web-jsp/pom.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>0.5.0.BUILD-SNAPSHOT</version>
+		<relativePath>../../spring-boot-starters/spring-boot-starter-parent</relativePath>
+	</parent>
+	<artifactId>spring-boot-sample-web-jsp</artifactId>
+	<packaging>war</packaging>
+	<properties>
+		<main.basedir>${basedir}/../..</main.basedir>
+	</properties>
+	<dependencies>
+		<dependency>
+			<groupId>${project.groupId}</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.tomcat.embed</groupId>
+			<artifactId>tomcat-embed-jasper</artifactId>
+		</dependency>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<configuration>
+					<useSystemClassLoader>false</useSystemClassLoader>
+				</configuration>
+			</plugin>
+			<plugin>
+				<groupId>${project.groupId}</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+</project>

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";
+	}
+
+}

spring-boot-samples/spring-boot-sample-web-jsp/src/main/webapp/WEB-INF/jsp/welcome.jsp

@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+
+<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
+
+<html lang="en">
+
+<body>
+	<spring:url value="/resources/text.txt" htmlEscape="true" var="springUrl" />
+	${springUrl}
+</body>
+
+</html>

spring-boot-samples/spring-boot-sample-web-jsp/src/test/java/org/springframework/boot/sample/jsp/SampleWebJspApplicationTests.java

@@ -0,0 +1,72 @@
+package org.springframework.boot.sample.jsp;
+
+import java.io.IOException;
+import java.util.concurrent.Callable;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.springframework.boot.SpringApplication;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.http.client.ClientHttpResponse;
+import org.springframework.web.client.DefaultResponseErrorHandler;
+import org.springframework.web.client.RestTemplate;
+
+import static org.junit.Assert.*;
+
+/**
+ * Basic integration tests for JSP application.
+ *
+ * @author Phillip Webb
+ */
+public class SampleWebJspApplicationTests {
+
+	private static ConfigurableApplicationContext context;
+
+	@BeforeClass
+	public static void start() throws Exception {
+		Future<ConfigurableApplicationContext> future = Executors
+				.newSingleThreadExecutor().submit(
+						new Callable<ConfigurableApplicationContext>() {
+							@Override
+							public ConfigurableApplicationContext call() throws Exception {
+								return (ConfigurableApplicationContext) SpringApplication
+										.run(SampleWebJspApplication.class);
+							}
+						});
+		context = future.get(60, TimeUnit.SECONDS);
+	}
+
+	@AfterClass
+	public static void stop() {
+		if (context != null) {
+			context.close();
+		}
+	}
+
+	@Test
+	public void testJspWithEl() throws Exception {
+		ResponseEntity<String> entity = getRestTemplate().getForEntity(
+				"http://localhost:8080", String.class);
+		assertEquals(HttpStatus.OK, entity.getStatusCode());
+		assertTrue("Wrong body:\n" + entity.getBody(), entity
+				.getBody().contains("/resources/text.txt"));
+	}
+
+	private RestTemplate getRestTemplate() {
+		RestTemplate restTemplate = new RestTemplate();
+		restTemplate.setErrorHandler(new DefaultResponseErrorHandler() {
+			@Override
+			public void handleError(ClientHttpResponse response) throws IOException {
+			}
+		});
+		return restTemplate;
+
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainerFactory.java

@@ -18,14 +18,20 @@ package org.springframework.boot.context.embedded.tomcat;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.Method;
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 
+import javax.servlet.ServletContext;
+
 import org.apache.catalina.Context;
 import org.apache.catalina.Host;
+import org.apache.catalina.Lifecycle;
+import org.apache.catalina.LifecycleEvent;
 import org.apache.catalina.LifecycleListener;
 import org.apache.catalina.Valve;
 import org.apache.catalina.Wrapper;
@@ -48,6 +54,7 @@ import org.springframework.core.io.ResourceLoader;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
+import org.springframework.util.StreamUtils;
 
 /**
  * {@link EmbeddedServletContainerFactory} that can be used to create
@@ -161,6 +168,7 @@ public class TomcatEmbeddedServletContainerFactory extends
 				&& ClassUtils.isPresent(getJspServletClassName(), getClass()
 						.getClassLoader())) {
 			addJspServlet(context);
+			context.addLifecycleListener(new StoreMergedWebXmlListener());
 		}
 		ServletContextInitializer[] initializersToUse = mergeInitializers(initializers);
 		configureContext(context, initializersToUse);
@@ -443,4 +451,45 @@ public class TomcatEmbeddedServletContainerFactory extends
 
 	}
 
+	/**
+	 * {@link LifecycleListener} that stores an empty merged web.xml. This is critical for
+	 * Jasper to prevent warnings about missing web.xml files and to enable EL.
+	 */
+	private static class StoreMergedWebXmlListener implements LifecycleListener {
+
+		private String MERGED_WEB_XML = org.apache.tomcat.util.scan.Constants.MERGED_WEB_XML;
+
+		@Override
+		public void lifecycleEvent(LifecycleEvent event) {
+			if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
+				onStart((Context) event.getLifecycle());
+			}
+		}
+
+		private void onStart(Context context) {
+			ServletContext servletContext = context.getServletContext();
+			if (servletContext.getAttribute(this.MERGED_WEB_XML) == null) {
+				servletContext.setAttribute(this.MERGED_WEB_XML, getEmptyWebXml());
+			}
+		}
+
+		private String getEmptyWebXml() {
+			InputStream stream = TomcatEmbeddedServletContainerFactory.class
+					.getResourceAsStream("empty-web.xml");
+			Assert.state(stream != null, "Unable to read empty web.xml");
+			try {
+				try {
+					return StreamUtils.copyToString(stream, Charset.forName("UTF-8"));
+				}
+				finally {
+					stream.close();
+				}
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException(ex);
+			}
+		}
+
+	}
+
 }

spring-boot/src/main/resources/org/springframework/boot/context/embedded/tomcat/empty-web.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
+	http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
+</web-app>