CODEWITHSUNDEEP
javamavenbuilddependenciespackage
nz_21
nz_21

Reputation: 7383

Basic maven question: Does maven transitively install dependencies?

I've looked here https://blog.packagecloud.io/eng/2017/03/09/how-does-a-maven-repository-work/ and that does seem to be the case.

However, I tried to experiment with mvn install and I'm not sure if it's worked as expected. Here's what I did

(1) I created a lib.

(2) Ran mvn install from the command line

(3) Copied the path of my newly created jar

(4) Opened a new maven project, stuck the path into my pom.xml

I'm able to reuse my library methods, BUT: one of my library methods returns a TransportClient which is part of the elasticsearch api. Using intellij inside my new project, it seems like I don't have elasticsearch even though I'm referencing the jar.

Is this expected? I was expecting it to have transitively installed elasticsearch when it referenced my jar.

I'd love a pointer or two in the right direction, I'm completely new to this. :)

My pom.xml for the lib that uses elasticsearch as dependency. 

<?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>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <groupId>estutorial</groupId>
    <artifactId>estutorial</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.2</version>
            <scope>provided</scope>
        </dependency>


        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>6.4.2</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>transport</artifactId>
            <version>6.4.2</version>
        </dependency>


        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.11.1</version>
        </dependency>

    </dependencies>

</project>

My pom.xml for the new maven project that tries to reference the lib for the above pom.xml:

<?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>
    <properties>
        <maven.compiler.target>1.8</maven.compiler.target>
        <maven.compiler.source>1.8</maven.compiler.source>
    </properties>


    <groupId>sth</groupId>
    <artifactId>sth</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.4</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>estutorial</groupId>
            <artifactId>estutorial</artifactId>
            <version>1.0</version>
            <scope>system</scope>
            <systemPath>/home/dell/.m2/repository/estutorial/estutorial/1.0-SNAPSHOT/estutorial-1.0-SNAPSHOT.jar
            </systemPath>
        </dependency>
    </dependencies>

</project>

Upvotes: 0

Views: 72

Answers (2)

bmargulies
bmargulies

Reputation: 100153

No. mvn install is a nearly useless command. It stuffs a jar file into your local repository, for subsequent use by other maven builds. You use the term 'path'. If you run mvn install:install-file to put a jar into your local repo under some coordinates, you can reference those coordinates from another pom; but it will generally lead to future problems as compare to deploying the jar into a proper repository manager.

Upvotes: 1

EdH
EdH

Reputation: 5003

So, if I understand your steps, your dependency declaration in your referencing application uses a direct classpath to the jar file in your local repository? If so, this is unusual. You shouldn't need to know direct file locations for any of your dependencies of a Maven project. What you should be doing.

In the referenced project (that which requires the Elasticsearch library), it's pom.xml file would defined the elasticsearch dependency itself. This should follow maven standards for dependency declaration (groupId, artifactId and artifactVerion). If you don't have the elasticsearch artifact, maven will attempt to find it and store it in your local repository. You shouldn't have to have any path in your pom.xml file.

When you install the referenced project, it will install into your local repostory both the JAR file and the pom.xml.

In the referencing project, you should define the dependency to your referenced artifact in it's pom file. Same format: groupId, artifactId and artifactVersion. You shouldn't need to provide a specific path. What maven will do is find your referenced jar, but also use the installed POM.xml file for the referenced jar to find the transitive dependencies and include them in your classpath.

From what you've described, your dependency declarations aren't correct. If you can provide your POM file more details can be provided. Otherwise, review the maven intro to dependencies.

Upvotes: 1

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