/*
* 实现一个map按值的排序算法
*/
@SuppressWarnings("unchecked")
public static Map sortByValue(Map map, final boolean reverse) {
List list = new LinkedList(map.entrySet());
Collections.sort(list, new Comparator() {
public int compare(Object o1, Object o2) {
if (reverse) {
return -((Comparable) ((Map.Entry) o1).getValue()).compareTo(((Map.Entry) o2).getValue());
}
return ((Comparable) ((Map.Entry) o1).getValue()).compareTo(((Map.Entry) o2).getValue());
}
});
Map result = new LinkedHashMap();
for (Iterator it = list.iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
result.put(entry.getKey(), entry.getValue());
}
return result;
}
}
}
还需要自定义一个UDTF，安装分隔符将字符串切分，将字符串转化为多行的列表输出：
public class ExplodeMap extends GenericUDTF {
@Override
public void close() throws HiveException {
}
@Override
public StructObjectInspector initialize(ObjectInspector[] args) throws UDFArgumentException {
if (args.length != 1) {
throw new UDFArgumentLengthException("ExplodeMap takes only one argument");
}
if (args[0].getCategory() != ObjectInspector.Category.PRIMITIVE) {
throw new UDFArgumentException("ExplodeMap takes string as a parameter");
}
ArrayList<String> fieldNames = new ArrayList<String>();
ArrayList<ObjectInspector> fieldOIs = new ArrayList<ObjectInspector>();
fieldNames.add("col1");
fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
fieldNames.add("col2");
fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
fieldNames.add("col3");
fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
return ObjectInspectorFactory.getStandardStructObjectInspector(fieldNames, fieldOIs);
}