我们必须使用 getConfiguration() 方法从作业对象获取配置。创建作业对象时使用的配置对象无法执行此操作。

我也有同样的问题，你应该用：

HCatInputFormat.setInput(job, dbName, inputTableName);
    HCatSchema inputschema = HCatBaseInputFormat.getTableSchema(job.getConfiguration());

不

HCatInputFormat.setInput(job, dbName, inputTableName);
    HCatSchema inputschema = HCatBaseInputFormat.getTableSchema(getConf());

因为，当你使用 Job.getInstance(conf) ，它将复制conf，您不能使用原始conf。下面是代码：

/**
 * A new configuration with the same settings cloned from another.
 * 
 * @param other the configuration from which to clone settings.
 */
@SuppressWarnings("unchecked")
public Configuration(Configuration other) {
  this.resources = (ArrayList<Resource>) other.resources.clone();
  synchronized(other) {
 if (other.properties != null) {
   this.properties = (Properties)other.properties.clone();
 }

 if (other.overlay!=null) {
   this.overlay = (Properties)other.overlay.clone();
 }

 this.updatingResource = new ConcurrentHashMap<String, String[]>(
     other.updatingResource);
 this.finalParameters = Collections.newSetFromMap(
     new ConcurrentHashMap<String, Boolean>());
 this.finalParameters.addAll(other.finalParameters);
}

 synchronized(Configuration.class) {
  REGISTRY.put(this, null);
}
this.classLoader = other.classLoader;
this.loadDefaults = other.loadDefaults;
setQuietMode(other.getQuietMode());
}