classpath - running a java program from the comman

问题:

My code compiled fine with the following command:

javac -cp "../lib/*" AvroReader.java

(lib is where i put my jar files)

At run time I get a ClassNotFoundException on the following line:

DatumReader<?> dtmrdr = new GenericDatumReader();

It says it can't find org.apache.avro.generic.GenericDatumReader even though I've imported it.

Why this is happening?

Thanks!

回答1:

Importing has nothing to do with loading classes or setting CLASSPATH.

Try this:

java -cp .;../lib/* Generator

Using the dot '.' as the first entry in the CLASSPATH assumes that the Generator.class file exists in the directory from which you're running java, and /lib is one level up from that directory. Adjust as needed if both of these are not correct.

回答2:

You should run the program including again the same cp:

java -cp "lib directory where i put all the jars" MainClassOfYourApplication

After you compiled it with:

javac -cp "lib directory where i put all the jars" AvroReader.java

More applied to your example:

First step(compile all the needed java files): javac -cp "path/to/jars/*" AvroReader.java //here you should include all the java files not yet compiled but which you need to run your app
Second step: java -cp "path/to/jars/*" package.subpackage1.subpackage2.Generator