compilation error when referring to a library using maven

Question

I am newbie to maven and i am having some trouble building my project. i have added the log4j dependency to the pom file

    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.16</version>
        <scope>runtime</scope>
    </dependency>

and i am using it in a normal use in one of my classes

import org.apache.log4j.Logger;

public class ConnectionPoolImpl implements Runnable, ConnectionPool {
  static Logger logger = Logger.getLogger(ConnectionPoolImpl.class);

the compilation went well until i have used the mvn clean command. now when i try to build my project using mvn compile i am getting:

[INFO] Compiling 2 source files to C:\Temp\cp\target\classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] \Temp\cp\src\main\java\com\opower\connectionpool\ConnectionPoolImpl.java
:[9,23] package org.apache.log4j does not exist
[ERROR] \Temp\cp\src\main\java\com\opower\connectionpool\ConnectionPoolImpl.java
:[19,9] cannot find symbol
symbol  : class Logger
location: class com.opower.connectionpool.ConnectionPoolImpl
[ERROR] \Temp\cp\src\main\java\com\opower\connectionpool\ConnectionPoolImpl.java
:[19,25] cannot find symbol
symbol  : variable Logger
location: class com.opower.connectionpool.ConnectionPoolImpl
[INFO] 3 errors

any ideas what i am doing wrong?

Answer 1

I am not a Maven specialist, but the log4j scope should be compile instead of runtime. Please correct me if I am wrong.

From maven doc,

runtime - this scope indicates that the dependency is not required for compilation, but is for execution. It is in the runtime and test classpaths, but not the compile classpath.

Answer 2

If you had the scope as runtime, the original intention likely was to use SLF4J or somesuch instead. Very easy to import the wrong namespace for Logger.