如何使M2E（Eclipse的Maven集成）知道在哪里找到依赖项？

Question

When work in STS (springsource tool suite), open pom.xml file and check dependencies in "dependencies tab", add/select maven dependency will give 0 result found. We need edit pom.xml to add dependency by hand. Is there a way to let M2E know where to check repository to search dependency?

Answer 1

By default , all pom.xml will automatically extend the Super POM , which is located in the maven_installation_folder/lib/maven-xxx-uber.jar ==> package org.apache.maven.project ==> pom-4.0.0.xml . All the configuration specified in the Super POM is inherited by the POMs you created for your projects.

If you open pom-4.0.0.xml , you will find that the maven central repository http://repo1.maven.org/maven2/ is defined here . That means if you specify a <dependency> in your pom.xml , maven will try to download this dependency in the following orders:

1. Maven local repository (ie your local hard disk)
2. Maven central repository specifed in the Super POM (ie http://repo1.maven.org/maven2/ )
3. Maven remote repository (Defined in the <repository> section of your pom.xml )

Normally , I will use some maven repository search engines , such as this , to find out the <dependency> of the libraries /frameworks /tools that I want to use and then paste them in the pom.xml

If the dependency exists in the Maven central repository , everything will be fine and it will be download to your local repository . However , if some of the <dependency> (eg Hibernate) cannot be found and downloaded from the Maven central repository , you can try to visit its official site to find out its repository link and paste them in the <repository> section of your pom.xml .For example , Hibernate require to define the jboss repository in the pom.xml like this:

<repositories>
        <repository>
            <id>repository.jboss.org</id>
            <name>JBoss Repository</name>
            <url>http://repository.jboss.org/nexus/content/groups/public-jboss</url>
           <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>     
        </repository>        
 </repositories>

You can refer to this for the use of <repository>

Answer 2

M2e by default searches maven central repository for artifacts. It downloads an index file which has artifact details. You can configure additional repositories to be searched by specifying the same in repository section of your settings.xml file. Do note that some repositories do not have this index file.