在终端编译 Java 程序导致日志错误

Question

I am trying to compile a Java program in the terminal:

Long version containing all the imports:

javac -classpath bin:$OSPL_HOME/jar/dcpssaj5.jar:$OSPL_HOME/jar/dcpssaj5-sources.jar:$OSPL_HOME/jar/dcpssaj-osgi-bundle.jar:$OSPL_HOME/jar/dcpssaj-sources.jar:$OSPL_HOME/jar/dcpssaj.jar:$OSPL_HOME/jar/osplconf.jar:$OSPL_HOME/jar/tooling_common.jar:$OSPL_HOME/jar/dcpsprotobuf.jar:$OSPL_HOME/jar/cmdataadapter.jar:$OSPL_HOME/jar/cmapi.jar:$OSPL_HOME/jar/ddsface.jar:Libraries/httpclient-4.5.12.jar:Libraries/jersey-client-1.19.4.jar:Libraries/jersey-client-1.19.jar:Libraries/jersey-core-1.19.4.jar:Libraries/json-simple-1.1.1.jar:Libraries/json-simple-3.1.0.jar:Libraries/jsr311-api-1.1.1.jar:Libraries/mqtt-client-0.0.6.jar:Libraries/paho-mqtt-client-1.13.0.jar -sourcepath src/ src/afarcloud/Main/afarcloud_main.java

Without all the imports:

javac -classpath bin:(jar_files) -sourcepath src/ src/afarcloud/Main/afarcloud_main.java

I have added what I thought would be all the necessaries jars, however I get the following error related to a logger when I try to run the code on my Ubuntu computer:

src/afarcloud/Log/UtilLog.java:3: error: package org.apache.log4j does not exist
import org.apache.log4j.Logger;
                       ^
src/afarcloud/Log/UtilLog.java:7: error: cannot find symbol
    private static Logger log = Logger.getLogger(UtilLog.class);
                   ^
  symbol:   class Logger
  location: class UtilLog
src/afarcloud/Log/UtilLog.java:7: error: cannot find symbol
    private static Logger log = Logger.getLogger(UtilLog.class);
                                ^
  symbol:   variable Logger
  location: class UtilLog
src/afarcloud/Log/UtilLog.java:10: error: cannot find symbol
        log = Logger.getLogger(clase);
              ^
  symbol:   variable Logger
  location: class UtilLog
4 errors

What confuses me is that there is no folder called "Log" under src/afarcloud, so I am pretty confused about how to proceed... Any help is highly appreciated, thank you.

Answer 1

You're missing JAR dependency on org.apache.log4j.

Of course, this JAR can have further dependencies. This can be endless game. Perhaps you can use Maven and mavenized project, which will take care of dependency tree for you.

Answer 2

Looks that you're missing import statement. As a conclusion, all Logger Objects cannot be find and any new instances cant be created.

Try to use import org.apache.log4j.Logger; .

Or import via CLI. https://logging.apache.org/log4j/2.x/download.html

Answer 3

Instead of mentioning the jar files of a directory individually, you should use wildcard character * to specify all jars of the directory eg

javac -d bin -cp .:$OSPL_HOME/jar/*:Libraries/*:lib/* -sourcepath src src/afarcloud/Main/afarcloud_main.java

where

1. -d bin specifies the directory where the compiled class will be put.
2. . with -cp or -classpath includes the current directory in the classpath.
3. : specifies the separator to use multiple locations in the classpath.
4. $OSPL_HOME/jar/* specifies all the files in the directory, $OSPL_HOME/jar . Alternatively, you can use $OSPL_HOME/jar/*.jar to specify just jar files.

Note: Make sure you also specify the location of the apache-logging-log4j.jar in your command because the error shows that you have missed to include this jar.