Plugin org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6 or one of its dependencies could not be resolved - maven

Question

I'm new to GWT and Maven and I was creating a new Maven project and then customizing it using the steps mentioned in this link: Setting and Customizing your Project.
I followed all the steps given in the Customizing your Project section on that page but while running the project in the SuperDevMode, I got many errors in Command Prompt and I don't understand how to resolve those errors even after searching on the Internet.
Here is my pom.xml file:
<?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/maven-v4_0_0.xsd">
<!-- POM file generated with GWT webAppCreator -->
<modelVersion>4.0.0</modelVersion>
<groupId>org.gwtproject.tutorial</groupId>
<artifactId>TodoList</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>org.gwtproject.tutorial.TodoList</name>
<properties>
<!-- Setting maven.compiler.source to something different to 1.8
needs that you configure the sourceLevel in gwt-maven-plugin since
GWT compiler 2.8 requires 1.8 (see gwt-maven-plugin block below) -->
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<!-- Don't let your Mac use a crazy non-standard encoding -->
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
</properties>
<dependencyManagement>
<dependencies>
<!-- ensure all GWT deps use the same version (unless overridden) -->
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt</artifactId>
<version>2.8.1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt-servlet</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt-user</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.vaadin.polymer</groupId>
<artifactId>vaadin-gwt-polymer-elements</artifactId>
<version>1.7.0.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt-dev</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<!-- Output classes directly into the webapp, so that IDEs and "mvn process-classes" update them in DevMode -->
<outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
<plugins>
<!-- GWT Maven Plugin-->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<version>1.0-rc-6</version>
<executions>
<execution>
<goals>
<goal>import-sources</goal>
<goal>compile</goal>
<goal>import-test-sources</goal>
<goal>test</goal>
</goals>
</execution>
</executions>
<configuration>
<moduleName>org.gwtproject.tutorial.TodoList</moduleName>
<moduleShortName>TodoList</moduleShortName>
<failOnError>true</failOnError>
<jsInteropMode>JS</jsInteropMode>
<!-- GWT compiler 2.8 requires 1.8, hence define sourceLevel here if you use
a different source language for java compilation -->
<sourceLevel>1.8</sourceLevel>
<!-- Compiler configuration -->
<compilerArgs>
<!-- Ask GWT to create the Story of Your Compile (SOYC) (gwt:compile) -->
<arg>-compileReport</arg>
<arg>-XcompilerMetrics</arg>
</compilerArgs>
<!-- DevMode configuration -->
<warDir>${project.build.directory}/${project.build.finalName}</warDir>
<classpathScope>compile+runtime</classpathScope>
<!-- URL(s) that should be opened by DevMode (gwt:devmode). -->
<startupUrls>
<startupUrl>TodoList.html</startupUrl>
</startupUrls>
</configuration>
</plugin>
<!-- Skip normal test execution, we use gwt:test instead -->
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.17</version>
<configuration>
<skip>true</skip>
</configuration>
</plugin>
</plugins>
</build>
</project>
Here's what I got in Command Prompt.
C:\Users\TEST>cd TodoListApp
C:\Users\TEST\TodoListApp>mvn war:exploded
[INFO] Scanning for projects...
Downloading: https://repo.maven.apache.org/maven2/org/codehaus/mojo/gwt-maven-plugin/1.0-rc-6/gwt-maven-plugin-1.0-rc-6.pom
[WARNING] The POM for org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 is missing, no dependency information available
Downloading: https://repo.maven.apache.org/maven2/org/codehaus/mojo/gwt-maven-plugin/1.0-rc-6/gwt-maven-plugin-1.0-rc-6.jar
[WARNING] Failed to retrieve plugin descriptor for org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6: Plugin org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6 or one of its dependencies could not be resolved: Could not find artifact org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 in central (https://repo.maven.apache.org/maven2)
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building org.gwtproject.tutorial.TodoList 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 is missing, no dependency information available
[WARNING] Failed to retrieve plugin descriptor for org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6: Plugin org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6 or one of its dependencies could not be resolved: Failure to find org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 in https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced
[INFO]
[INFO] --- maven-war-plugin:2.2:exploded (default-cli) # TodoList ---
[INFO] Exploding webapp
[INFO] Assembling webapp [TodoList] in [C:\Users\TEST\TodoListApp\target\TodoList-1.0-SNAPSHOT]
[INFO] Processing war project
[INFO] Copying webapp resources [C:\Users\TEST\TodoListApp\src\main\webapp]
[INFO] Webapp assembled in [66 msecs]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.198 s
[INFO] Finished at: 2017-08-29T14:24:43+05:30
[INFO] Final Memory: 14M/133M
[INFO] ------------------------------------------------------------------------
C:\Users\TEST\TodoListApp>mvn gwt:devmode
[INFO] Scanning for projects...
[WARNING] The POM for org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 is missing, no dependency information available
[WARNING] Failed to retrieve plugin descriptor for org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6: Plugin org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6 or one of its dependencies could not be resolved: Failure to find org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 in https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced
[WARNING] The POM for org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 is missing, no dependency information available
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.316 s
[INFO] Finished at: 2017-08-29T14:24:53+05:30
[INFO] Final Memory: 7M/106M
[INFO] ------------------------------------------------------------------------
[ERROR] Plugin org.codehaus.mojo:gwt-maven-plugin:1.0-rc-6 or one of its dependencies could not be resolved: Failure to find org.codehaus.mojo:gwt-maven-plugin:jar:1.0-rc-6 in https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException
I edited the groupId of GWT Maven Plugin as "org.codehaus.mojo" by seeing the one written in that GWT page and I don't remember now what was the groupId initially. Please help me to fix this error.

Answer 1

The version of your plugin is wrong; Please replace it with 2.8.1. Like this:
<dependency>
<groupId>org.codehaus.mojo</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<version>2.8.1</version>
</dependency>