Spring Web Flow validation not working in IDE - spring-boot

Question

As a follow up to my last question about Web Flow not finding my validator class, I ran into another problem concerning the validation.
When I run my project via mvn spring-boot:run the validation works without problems. However, when I run it in Eclipse, STS or IntelliJ via executing the main class as Spring Boot application, validation is not working anymore.
I don't know where to look for hints on this problem. For starters these are my pom files. I based them on the JHipster pom.xml because I liked their dev and prod profile implementations.
Parent pom
<?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>
<groupId>twofa</groupId>
<artifactId>2fa-parent</artifactId>
<version>1.0.0</version>
<packaging>pom</packaging>
<modules>
<module>../2fa-portal</module>
</modules>
<properties>
<java.version>1.7</java.version>
<maven-enforcer-plugin.version>1.4.1</maven-enforcer-plugin.version>
<maven-war-plugin.version>2.6</maven-war-plugin.version>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<sortpom-maven-plugin.version>2.5.0</sortpom-maven-plugin.version>
<spring.boot.version>1.4.1.RELEASE</spring.boot.version>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>${spring.boot.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<repositories>
<repository>
<id>com.springsource.repository.bundles.release</id>
<name>SpringSource Enterprise Bundle Repository - SpringSource Bundle Releases</name>
<url>http://repository.springsource.com/maven/bundles/release</url>
</repository>
<repository>
<id>com.springsource.repository.bundles.external</id>
<name>SpringSource Enterprise Bundle Repository - External Bundle Releases</name>
<url>http://repository.springsource.com/maven/bundles/external</url>
</repository>
</repositories>
<build>
<defaultGoal>spring-boot:run</defaultGoal>
<plugins>
<plugin>
<groupId>com.github.ekryd.sortpom</groupId>
<artifactId>sortpom-maven-plugin</artifactId>
<version>${sortpom-maven-plugin.version}</version>
<executions>
<execution>
<phase>verify</phase>
<goals>
<goal>sort</goal>
</goals>
</execution>
</executions>
<configuration>
<sortProperties>true</sortProperties>
<nrOfIndentSpace>4</nrOfIndentSpace>
<sortDependencies>groupId,artifactId</sortDependencies>
<sortPlugins>groupId,artifactId</sortPlugins>
<keepBlankLines>true</keepBlankLines>
<expandEmptyElements>false</expandEmptyElements>
</configuration>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.0</version>
<configuration>
<source>${maven.compiler.source}</source>
<target>${maven.compiler.target}</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>${maven-enforcer-plugin.version}</version>
<executions>
<execution>
<id>enforce-versions</id>
<goals>
<goal>enforce</goal>
</goals>
</execution>
</executions>
<configuration>
<rules>
<requireMavenVersion>
<message>You are running an older version of Maven. Application requires at least Maven 3.0</message>
<version>[3.0.0,)</version>
</requireMavenVersion>
<requireJavaVersion>
<message>You are running an older version of Java. Application requires at least JDK ${java.version}</message>
<version>[${java.version}.0,)</version>
</requireJavaVersion>
</rules>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.18.1</version>
<configuration>
<!-- Force alphabetical order to have a reproducible build -->
<runOrder>alphabetical</runOrder>
<includes>
<include>**/*Tests.java</include>
<include>**/*Test.java</include>
<include>**/Test*.java</include>
</includes>
<excludes>
<exclude>**/Abstract*.java</exclude>
</excludes>
</configuration>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring.boot.version}</version>
<configuration>
<executable>true</executable>
<fork>true</fork>
</configuration>
</plugin>
</plugins>
</build>
</project>
Portal pom
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<artifactId>2fa-parent</artifactId>
<groupId>twofa</groupId>
<version>1.0.0</version>
<relativePath>../2fa-parent/pom.xml</relativePath>
</parent>
<artifactId>2fa-portal</artifactId>
<packaging>war</packaging>
<name>2fa-portal</name>
<prerequisites>
<maven>3.0.0</maven>
</prerequisites>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-velocity</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-webflow</artifactId>
<version>2.4.4.RELEASE</version>
</dependency>
</dependencies>
<build>
<!-- creates 2fa-portal.war file -->
<!-- Resource filtering to fill in placeholders "#...#" in properties -->
<resources>
<resource>
<filtering>true</filtering>
<directory>${basedir}/src/main/resources</directory>
<includes>
<include>**/application*.properties</include>
</includes>
</resource>
<resource>
<directory>${basedir}/src/main/resources</directory>
<excludes>
<exclude>**/application*.properties</exclude>
</excludes>
</resource>
</resources>
<finalName>2fa-portal</finalName>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>2.7</version>
<dependencies>
<dependency>
<groupId>org.apache.maven.shared</groupId>
<artifactId>maven-filtering</artifactId>
<version>1.3</version>
</dependency>
</dependencies>
<configuration>
<delimiters>
<delimiter>#</delimiter>
<!-- delimiter that doesn't clash with Spring ${} placeholders -->
</delimiters>
<useDefaultDelimiters>false</useDefaultDelimiters>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
<archive>
<manifest>
<addDefaultImplementationEntries>true</addDefaultImplementationEntries>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
<profiles>
<profile>
<id>dev</id>
<activation>
<activeByDefault>true</activeByDefault>
</activation>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>${maven-war-plugin.version}</version>
</plugin>
</plugins>
</build>
<properties>
<!-- log configuration -->
<logback.loglevel>DEBUG</logback.loglevel>
<!-- default Spring profile -->
<spring.profiles.active>dev</spring.profiles.active>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>
</dependencies>
</profile>
<profile>
<id>test</id>
<build>
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>2.5</version>
<configuration>
<filesets>
<fileset>
<directory>target/</directory>
</fileset>
</filesets>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
</configuration>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>build-info</goal>
</goals>
</execution>
</executions>
<configuration>
<executable>false</executable>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<spring.profiles.active>test</spring.profiles.active>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
</dependencies>
</profile>
<profile>
<id>prod</id>
<build>
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>2.5</version>
<configuration>
<filesets>
<fileset>
<directory>target/</directory>
</fileset>
</filesets>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
</configuration>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>build-info</goal>
</goals>
</execution>
</executions>
<configuration>
<executable>false</executable>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<spring.profiles.active>prod</spring.profiles.active>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
</dependencies>
</profile>
</profiles>
</project>

Answer 1

It turned out to be a problem with Spring Devtools together with Spring Web Flow. Further information and the workaround can be found at this Spring Boot issue.
Quoting the workaround:
I think the problem is due to the separation of restart and base class loaders and is easily solved by adding the following spring-devtools.properties entry
restart.include.spring=/spring-.*\.jar