使用gradle构建框架使用log4j包构建应用程序时出错

Question

I created a simple java project using gradle, starting with "gradle init --type java-application".

Content of main java file - "App.java":

import org.apache.log4j.Logger;
import java.io.*;
import java.sql.SQLException;
import java.util.*;


public class App {

    public static void main(String[] args) {
        System.out.println("Howdy");
    }
}

Content of file "build.gradle":

apply plugin: 'java'
apply plugin: 'application'

repositories {
    jcenter()
}

dependencies {
    compile 'com.google.guava:guava:21.0'
    testCompile 'junit:junit:4.12'

    // Following added by me for log4j
    compile group: 'org.apache.logging.log4j', name: 'log4j-api', version: '2.11.0'
    compile group: 'org.apache.logging.log4j', name: 'log4j-core', version: '2.11.0'

}

mainClassName = 'App'

The log4j jar file seems to have been downloaded successfully by gradle:

/home/ahmed/.gradle/caches/modules-2/files-2.1/org.apache.logging.log4j/log4j-api/2.11.0/bede79a3f150711634a3047985517431bf6499f2/log4j-api-2.11.0.jar
/home/ahmed/.gradle/caches/modules-2/files-2.1/org.apache.logging.log4j/log4j-core/2.11.0/e6b751e02120c08702d98750f6a80bc25343b7f5/log4j-core-2.11.0.jar

There are a bunch of log4j jar/pom files in ~/.gradle directory. When I try to build, I am getting the following build error:

$ gradle build
:compileJava
/home/ahmed/temp/javatut/gradle-demo/src/main/java/App.java:5: error: package org.apache.log4j does not exist
import org.apache.log4j.Logger;
                       ^
1 error
:compileJava FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 0.808 secs

I am new to gradle/java. Any help would be greatly appreciated.

Thank you, Ahmed.

Answer 1

In build.gradle file, you are specify dependencies of log4j2 jars, but, in code, you are using log4j (version 1) class

import org.apache.log4j.Logger;

This statement specifies the Logger class which is present in log4j version 1.

In log4j2 , it is changed to org.apache.logging.log4j.Logger -

import org.apache.logging.log4j.Logger;