Suddenly got it all working. Perhaps I fixed a boo-boo on my end, but actually I believe some Maven or Vaadin repositories got updated. Thanks for all the help in posts above.
As of 2018-11-15, for Vaadin 12.0.0.beta2, take a working project such as one created from “Project Base” on the Vaadin pago of starter-packs, and make the following changes.
(1)
Refresh your local cache for Maven.
In IntelliJ 2018, choose Preferences/Settings > Build, Execution, Deployment > Build Tools > Maven > Repositories > Update (button). See attached screenshot.
(2)
Change this:
<vaadin.version>11.0.2</vaadin.version>
… to this:
<vaadin.version>12.0.0.beta2</vaadin.version>
(3)
Inside the repositories element, add this:
<repository>
<id>vaadin-prereleases</id>
<url>https://maven.vaadin.com/vaadin-prereleases</url>
</repository>
(4)
Below the repositories element, add this:
<pluginRepositories>
<!-- Repository needed for prerelease versions of Vaadin -->
<pluginRepository>
<id>vaadin-prereleases</id>
<url>https://maven.vaadin.com/vaadin-prereleases</url>
</pluginRepository>
</pluginRepositories>
(5)
Perform a Maven clean and install.
Verify that your POM reports no errors.
Here is a complete working 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>com.basilbourque.acme</groupId>
<artifactId>acme</artifactId>
<name>Acme</name>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<properties>
<maven.compiler.source>10</maven.compiler.source>
<maven.compiler.target>10</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<failOnMissingWebXml>false</failOnMissingWebXml>
<!--<vaadin.version>11.0.2</vaadin.version>-->
<!--Change above line to line below for alphas-betas-->
<vaadin.version>12.0.0.beta2</vaadin.version>
</properties>
<repositories>
<!-- Repository used by many Vaadin add-ons -->
<repository>
<id>Vaadin Directory</id>
<url>http://maven.vaadin.com/vaadin-addons</url>
</repository>
<!--Add this for alphas-betas-->
<repository>
<id>vaadin-prereleases</id>
<url>https://maven.vaadin.com/vaadin-prereleases</url>
</repository>
</repositories>
<!--Add this for alphas-betas-->
<pluginRepositories>
<!-- Repository needed for prerelease versions of Vaadin -->
<pluginRepository>
<id>vaadin-prereleases</id>
<url>https://maven.vaadin.com/vaadin-prereleases</url>
</pluginRepository>
</pluginRepositories>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.vaadin</groupId>
<artifactId>vaadin-bom</artifactId>
<type>pom</type>
<scope>import</scope>
<version>${vaadin.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>com.vaadin</groupId>
<artifactId>vaadin-core</artifactId>
</dependency>
<!-- Added to provide logging output as Flow uses -->
<!-- the unbound SLF4J no-operation (NOP) logger implementation -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<!-- Jetty plugin for easy testing without a server -->
<plugin>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>9.4.11.v20180605</version>
<configuration>
<scanIntervalSeconds>1</scanIntervalSeconds>
</configuration>
</plugin>
</plugins>
</build>
<profiles>
<profile>
<!-- Production mode can be activated with either property or profile -->
<id>production-mode</id>
<activation>
<property>
<name>vaadin.productionMode</name>
</property>
</activation>
<properties>
<vaadin.productionMode>true</vaadin.productionMode>
</properties>
<dependencies>
<dependency>
<groupId>com.vaadin</groupId>
<artifactId>flow-server-production-mode</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>com.vaadin</groupId>
<artifactId>vaadin-maven-plugin</artifactId>
<version>${vaadin.version}</version>
<executions>
<execution>
<goals>
<goal>copy-production-files</goal>
<goal>package-for-production</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</profile>
</profiles>
</project>
