运行RAM数据采集Jar包时出现Could not find or load main class错误的求助

Let's break down the issues you're facing step by step—there are a few overlapping problems here that are causing your errors:

1. Jar File Name & Path Mismatch #

First, look at the error when you tried using -jar:

Error: Unable to access jarfile /home/ubuntu/RAMDataGenerator/target/RAMDataGenerator-1.0.0-SNAPSHOT-jar-with-dependencies.jar

But your pom.xml clearly defines:

• <artifactId>RAMGenerator</artifactId>
• <version>0.0.1-SNAPSHOT</version>

This means Maven should generate a jar named RAMGenerator-0.0.1-SNAPSHOT-jar-with-dependencies.jar (not RAMDataGenerator-1.0.0-...). You’re either:

• Running the wrong jar file (verify the actual filename in your target folder with ls ~/RAMDataGenerator/target/), or
• You modified the artifactId/version in your pom but didn’t re-run mvn package to rebuild the jar with the correct name.

This mismatch is also likely why your -cp command failed earlier—if the jar path you specified doesn’t exist, Java can’t find the data.App class inside it.

2. Conflicting Java Command Arguments #

You tried combining -jar and -cp, which doesn’t work:

java -jar -cp ~/...jar data.App

The -jar flag tells Java to use the manifest file inside the jar to handle the classpath and main class, so it completely ignores any -cp or -classpath arguments you provide. You have two valid options to run your app:

Option A: Use -jar (Recommended) #

Since your maven-assembly-plugin already configures <mainClass>data.App</mainClass> in the jar’s manifest, just run the correct jar file:

java -jar ~/RAMDataGenerator/target/RAMGenerator-0.0.1-SNAPSHOT-jar-with-dependencies.jar

Java will automatically locate and run the main class defined in the manifest.

Option B: Use -cp Without -jar #

If you want to explicitly specify the main class, use -cp and omit -jar:

java -cp ~/RAMDataGenerator/target/RAMGenerator-0.0.1-SNAPSHOT-jar-with-dependencies.jar data.App

Just make sure the jar file exists with the exact name you’re referencing.

3. Inconsistent Java Version Configuration #

Your pom has conflicting Java version settings:

• The maven-compiler-plugin is set to <source>7</source> and <target>7</target>
• But the properties section uses <maven.compiler.source>1.8</maven.compiler.source> and <maven.compiler.target>1.8</maven.compiler.target>

This could lead to unexpected compilation issues down the line. Pick one version (preferably Java 8 or higher, since Lombok 1.18.12 works best with Java 8+) and align both settings. For example:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
        <source>${maven.compiler.source}</source>
        <target>${maven.compiler.target}</target>
    </configuration>
</plugin>

Step-by-Step Fix #

1. Verify the jar filename in your target directory:

   ls ~/RAMDataGenerator/target/
   

2. If the filename doesn’t match your pom’s configuration, run mvn clean package to rebuild the jar with the correct name.
3. Use either the -jar or -cp command as shown above, using the exact jar filename from step 1.
4. Fix the Java version mismatch in your pom to avoid future compilation problems.

I suspect the jar filename mismatch is the root cause here—once you use the correct Maven-generated jar name, the main class should load without issues, especially since you confirmed data/App.class exists in the jar.

内容的提问来源于stack exchange，提问作者PiotrKulesza