Non-resolvable import POM Failure to find

Question

I experimented with spring boot like module in parent pom and now I get error

[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[ERROR] Non-resolvable import POM: Failure to find org.springframework.boot:spring-boot-dependencies:pom:2.0.0.M6 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 @ line 30, column 19
 @ 
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR]   
[ERROR]   The project mydomain.project:main-project:1.0-SNAPSHOT (D:\gitProjects\main-server\sources\pom.xml) has 1 error
[ERROR]     Non-resolvable import POM: Failure to find org.springframework.boot:spring-boot-dependencies:pom:2.0.0.M6 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 @ line 30, column 19 -> [Help 2]
[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/ProjectBuildingException
[ERROR] [Help 2] http://cwiki.apache.org/confluence/display/MAVEN/UnresolvableModelException

I tried delete myproject in .m2 local repo

I have maven project with 2 modules(simple java and spring boot). I extract parent from spring boot to main pom like dependensyManagment and set paren to spring boot - main project. After that I get this error

I revert changes and all works fine. The step by step I faunt point when all crush

1. I add this to main pom

<dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-dependencies</artifactId>
        <version>2.0.0.M6</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>   </dependencyManagement>

2. in spring boot I change this

<parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.0.0.M6</version>
      <relativePath/> <!-- lookup parent from repository -->
  </parent>

to this:

<parent>
        <artifactId>main-project</artifactId>
        <groupId>main.project</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>

Answer 1

The version 2.0.0.M6 isn't located in the repo http://repo.maven.apache.org/maven2. If you wan't to use this version you have to use the maven repo http://repo.spring.io/milestone. So add it to your POM file:

<repositories>
    <repository>
        <id>spring-milestone-repo</id>
        <url>http://repo.spring.io/milestone/</url>
    </repository>
</repositories>

I would recommend you to use the latest release version of spring-boot (1.5.8.RELEASE), not a milestone version. I don't know how your POM looks like, but you can define spring boot in your POM in different ways:

1. Using the Spring Boot parent POM

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.8.RELEASE</version>
</parent>

Then you can add the dependencies you wish to use e.g.:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
</dependencies>

See: https://spring.io/guides/gs/spring-boot/

2. Declare Spring-Boot in Dependency-Management

If you already using an own parent POM, you could also import the spring boot dependency management in your POM:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.5.8.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

Same as in variant #1 you can declare afterwards the dependencies of spring boot you wish to use.