如何将SLF4J与Log4J绑定？

Question

我正试图用slf4j log4j建立一个项目，但这该死的东西就是不起作用。。。我不断得到例外：

Failed to instantiate SLF4J LoggerFactory
Reported exception:
java.lang.NoClassDefFoundError: org/apache/log4j/Level
at org.slf4j.LoggerFactory.bind(LoggerFactory.java:129)
at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:108)
at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:302)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:288)
at TestLog.main(TestLog.java:9)
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Level
at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 6 more
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Level
at org.slf4j.LoggerFactory.bind(LoggerFactory.java:129)
at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:108)
at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:302)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:288)
at TestLog.main(TestLog.java:9)
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Level
at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 6 more

我查了一下，班级org.apache.log4j。级别是在我的项目下"Maven依赖

我已经尝试了以下选项：

1. slf4j api log4j
2. slf4j api slf4j-log4j12
3. slf4j api log4j
4. slf4j api slf4j-log4j12 log4j

这些选项都不起作用：（

这是我的currnet pom。xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.sample</groupId>
  <artifactId>DBUnitSample</artifactId>
  <version>1.0</version>

  <dependencies>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.7</version>
    </dependency>

    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.7</version>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
    </dependency>

  </dependencies>

</project>

此外，我注意到当添加slf4j-log4j12时，它将log4j添加为树中的依赖项，所以我猜测在这里显式添加log4j是多余的，但我还是添加了它。还是没有运气。

我的主要代码非常简单：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class SampleDao {
    private static final Logger log = LoggerFactory.getLogger(SampleDao.class);

    public static void main(String[] args) {
        System.out.println("Hello");
        log.info("Logged");
    }
}

还有我的log4j。特性：

log4j.rootLogger=DEBUG, STDOUT
log4j.logger.deng=INFO
log4j.appender.STDOUT=org.apache.log4j.ConsoleAppender
log4j.appender.STDOUT.layout=org.apache.log4j.PatternLayout
log4j.appender.STDOUT.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

有人能告诉我我做错了什么吗？我已经尝试过在SO上搜索答案，但所有提到的答案都添加了log4j依赖项，我已经添加了。。。所以不确定，出了什么问题。

Answer 1

我和你犯了同样的错误。我根据以下两条建议解决了我的问题。我希望有帮助。

1.修改pom文件：

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>1.7.2</version>
</dependency>
<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.12</version>
</dependency>
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.2</version>
</dependency>

2.将jar添加到启动脚本中

java -cp ./lib/log-producer-1.0.4-SNAPSHOT.jar:./lib/slf4j-log4j12-1.7.2.jar:./lib/slf4j-api-1.7.2.jar:./lib/log4j-1.2.12.jar cn.tiakon.core.Bootstrap

Answer 2

如果从命令行运行mvn编译exec： java-D"exec.mainClass"=Sample道，您仍然会出错吗？运行此命令后，我在命令行上看到以下内容，我的机器上有Maven 3.1.1和您的代码：

Hello
 INFO [SampleDao.main()] (SampleDao.java:9) - Logged

所以，您的POM和代码似乎很好。您试图运行代码的方式似乎有问题。

还请注意，以下简化配置应起作用：

<dependencies>
  <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.7</version>
  </dependency>
</dependencies>

如果POM有其他依赖项将不同版本的Log4j添加到项目中，则必须指定特定版本的Log4j。

Answer 3

尝试这些依赖项

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>1.7.5</version>
</dependency>
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>jcl-over-slf4j</artifactId>
    <version>1.7.5</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.5</version>
    <scope>runtime</scope>
</dependency>