Maven中的jar文件冲突

Question

Right now I am using a maven project . And this project uses some logging.1.jar . There is a new functionality which we are going to add to this project and is dependent on logging.3.jar .

The compilation is fine, but the application is failing at runtime due to jar file conflict.

Reason is the newly added functionality, it is using logging.1.jar instead of logging.3.jar

I cannot initialize a class which is present is newly added functionality as it dependent on logging.3.jar . How can it be resolved?

Will it be resolved using URLClassLoader ?

Answer 1

Add proper jar dependency into your pom.xml and run mvn clean-install -U command. this command clean your discrepancies and update correctly.

Answer 2

See part Dependency Exclusions on Maven introduction .

So you should have to something like this in your pom:

<dependencies>
    ...
    <dependency>
      <groupId>org.examle</groupId>
      <artifactId>including-jar</artifactId>
      <version>1.0.0</version>
      <exclusions>
        <exclusion>  <!-- declare the exclusion here -->
          <groupId>org.logging</groupId>
          <artifactId>logging</artifactId> (or logging1)
        </exclusion>
      </exclusions> 
    </dependency>
    ...
  </dependencies>

The tricky part is that you must find the artifact(s) ( including-jar(s)) that are dependent on the old version and add this exclusion to all of those artifacts.

On the other hand it is also possible to prevent this older artifact to be actually loaded by setting its scope as provided, like:

<dependencies>
    ...
    <dependency>
      <groupId>org.examle</groupId>
      <artifactId>logging</artifactId> // or logging1
      <version>1.0.0</version>
      <scope>provided</scope>
    </dependency>
    ...
  </dependencies>

However this latter solution might not suit all situations and I personally prefer the first because it does not obfuscate the real purpose (so excluding) and will not cause surprises later.