如何追溯这个编译错误？

Question

我正在通过从书中复制的示例开始学习使用 mahout。然而，Eclipse 编译器给了我以下消息：

> Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at org.apache.mahout.cf.taste.impl.model.file.FileDataModel.<clinit>(FileDataModel.java:119)
    at mia.recommender.ch02.RecommenderIntro.main(RecommenderIntro.java:18)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    ... 2 more

在我看来，问题来自 FileDataModel.java，它属于这个库本身。如何回溯或者分析这个错误。

示例代码如下，完全是从书上抄来的。造成麻烦的线路是

DataModel model = new FileDataModel(new File("intro.csv")); 


import org.apache.mahout.cf.taste.impl.model.file.*;
import org.apache.mahout.cf.taste.impl.neighborhood.*;
import org.apache.mahout.cf.taste.impl.recommender.*;
import org.apache.mahout.cf.taste.impl.similarity.*;
import org.apache.mahout.cf.taste.model.*;
import org.apache.mahout.cf.taste.neighborhood.*;
import org.apache.mahout.cf.taste.recommender.*;
import org.apache.mahout.cf.taste.similarity.*;
import java.io.*;
import java.util.*;
class RecommenderIntro {
  public static void main(String[] args) throws Exception {


    DataModel model = new FileDataModel(new File("intro.csv")); 
    UserSimilarity similarity = new PearsonCorrelationSimilarity(model);
    UserNeighborhood neighborhood =
      new NearestNUserNeighborhood(2, similarity, model);
    Recommender recommender = new GenericUserBasedRecommender(
        model, neighborhood, similarity); 
    List<RecommendedItem> recommendations =
        recommender.recommend(1, 1); 
    for (RecommendedItem recommendation : recommendations) {
      System.out.println(recommendation);
    }
  }
}

Answer 1

看起来 SLF4J 依赖项未安装/在类路径上： slf4j-api.jar

请参阅： http://www.slf4j .org/