Introduce a validation starter

Previously, the only starter that provided validation was
spring-boot-starter-web which included Hibernate Validator and
Tomcat's EL implementation. This left users writing non-web
applications to figure out the dependencies for themselves. They would
sometimes run into difficulties as Hibernate Validator's need for an
EL implementation would trip them up.

This commit adds a new starter, spring-boot-starter-validation,
which provides both Hibernate Validator and Tomcat's EL
implementation. spring-boot-starter-web has been updated to depend on
this starter rather than depending on Hibernate Validator directly.

Closes gh-2678

spring-boot-dependencies/pom.xml

@@ -393,6 +393,11 @@
 				<artifactId>spring-boot-starter-tomcat</artifactId>
 				<version>1.3.0.BUILD-SNAPSHOT</version>
 			</dependency>
+			<dependency>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-starter-validation</artifactId>
+				<version>1.3.0.BUILD-SNAPSHOT</version>
+			</dependency>
 			<dependency>
 				<groupId>org.springframework.boot</groupId>
 				<artifactId>spring-boot-starter-velocity</artifactId>

spring-boot-starters/pom.xml

@@ -59,6 +59,7 @@
 		<module>spring-boot-starter-thymeleaf</module>
 		<module>spring-boot-starter-tomcat</module>
 		<module>spring-boot-starter-undertow</module>
+		<module>spring-boot-starter-validation</module>
 		<module>spring-boot-starter-velocity</module>
 		<module>spring-boot-starter-web</module>
 		<module>spring-boot-starter-websocket</module>

spring-boot-starters/spring-boot-starter-jersey/pom.xml

@@ -27,12 +27,12 @@
 			<artifactId>spring-boot-starter-tomcat</artifactId>
 		</dependency>
 		<dependency>
-			<groupId>com.fasterxml.jackson.core</groupId>
-			<artifactId>jackson-databind</artifactId>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-validation</artifactId>
 		</dependency>
 		<dependency>
-			<groupId>org.hibernate</groupId>
-			<artifactId>hibernate-validator</artifactId>
+			<groupId>com.fasterxml.jackson.core</groupId>
+			<artifactId>jackson-databind</artifactId>
 		</dependency>
 		<dependency>
 			<groupId>org.springframework</groupId>

spring-boot-starters/spring-boot-starter-validation/pom.xml

+<?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-starters</artifactId>
+		<version>1.3.0.BUILD-SNAPSHOT</version>
+	</parent>
+	<artifactId>spring-boot-starter-validation</artifactId>
+	<name>Spring Boot Validation Starter</name>
+	<description>Spring Boot Validation Starter</description>
+	<url>http://projects.spring.io/spring-boot/</url>
+	<organization>
+		<name>Pivotal Software, Inc.</name>
+		<url>http://www.spring.io</url>
+	</organization>
+	<properties>
+		<main.basedir>${basedir}/../..</main.basedir>
+	</properties>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.tomcat.embed</groupId>
+			<artifactId>tomcat-embed-el</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.hibernate</groupId>
+			<artifactId>hibernate-validator</artifactId>
+		</dependency>
+	</dependencies>
+</project>

spring-boot-starters/spring-boot-starter-validation/src/main/resources/META-INF/spring.provides

+provides: hibernate-validator
\ No newline at end of file

spring-boot-starters/spring-boot-starter-web/pom.xml

@@ -27,12 +27,12 @@
 			<artifactId>spring-boot-starter-tomcat</artifactId>
 		</dependency>
 		<dependency>
-			<groupId>com.fasterxml.jackson.core</groupId>
-			<artifactId>jackson-databind</artifactId>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-validation</artifactId>
 		</dependency>
 		<dependency>
-			<groupId>org.hibernate</groupId>
-			<artifactId>hibernate-validator</artifactId>
+			<groupId>com.fasterxml.jackson.core</groupId>
+			<artifactId>jackson-databind</artifactId>
 		</dependency>
 		<dependency>
 			<groupId>org.springframework</groupId>