javaBean的各种工具方法

1.listToMap将list集合转换成map集合

	public static <K, V> Map<K, V> listToMap(String keyName, List<V> list) {		Map<K, V> map = Maps.newHashMap();		if (CollectionUtils.isNotEmpty(list)) {			for (V val : list) {				try {					PRopertyDescriptor pd = new PropertyDescriptor(keyName,							val.getClass());					Method getMethod = pd.getReadMethod();// 获得get方法					Object o = getMethod.invoke(val);// 执行get方法返回一个Object					if (o != null) {						map.put((K) o, val);					}				} catch (IllegalaccessException | IllegalArgumentException						| InvocationTargetException | IntrospectionException e) {					e.printStackTrace();				}			}		}		return map;	}2.listToMapList将list集合转换成Map<K, List<V>>
	// listToMap，1个key对应的是1个元素	// listToMapList，1个key对应的是1个list。list中属性id一样的，放到1个小的list中。	// 可以去掉k,v这2个参数	public static <K, V> Map<K, List<V>> listToMapList(String keyName,List<V> list) {		Map<K, List<V>> map = Maps.newHashMap();		if (CollectionUtils.isNotEmpty(list)) {			for (V val : list) {				try {					PropertyDescriptor pd = new PropertyDescriptor(keyName,val.getClass());					Method getMethod = pd.getReadMethod();// 获得get方法					Object o = getMethod.invoke(val);// 执行get方法返回一个Object					if (o != null) {						List<V> valueList = map.get((K) o);						if (valueList == null) {							valueList = Lists.newArrayList();						}						valueList.add(val);						map.put((K) o, valueList);					}				} catch (IllegalAccessException | IllegalArgumentException						| InvocationTargetException | IntrospectionException e) {					e.printStackTrace();				}			}		}		return map;	}3.beanToMap将一个javaBean转换成map集合
	public static Map<String, Object> bean2Map(Object obj) {		if (obj == null) {			return null;		}		Map<String, Object> map = Maps.newHashMap();		try {			BeanInfo beanInfo = Introspector.getBeanInfo(obj.getClass());			PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();			for (PropertyDescriptor property : propertyDescriptors) {				String key = property.getName();				// 过滤class属性				if (!key.equalsIgnoreCase("class")) {					// 得到property对应的getter方法					Method getter = property.getReadMethod();					Object value = getter.invoke(obj);					map.put(key, value);				}			}		} catch (Exception e) {			e.printStackTrace();		}		return map;	}4.map批量过滤key的值
	public static Map<String, Object> MapFilter(Map<String, Object> map,			final List<String> keys) {		return Maps.filterKeys(map, new Predicate<String>() {			@Override			public boolean apply(String input) {				return keys.contains(input) ? false : true;			}		});	}5.提取集合中的对象的一个属性, 组合成List
	public static <T> List<T> extractToList(final Collection<?> collection,			final String propertyName) {		if (CollectionUtils.isEmpty(collection)) {			return null;		}		List<T> list = new ArrayList<T>(collection.size());		CollectionUtils.collect(collection, new BeanToPropertyValueTransformer(propertyName), list);		return list;	}6.将一个字符串按指定规则分割然后类型转换，放入list中
	public static List<Long> stringToLongList(String str,String separator){		List<Long> idList = Lists.newArrayList();		String[] idArray = str.split(separator);		if(idArray != null){			for(String id:idArray){				idList.add(Long.valueOf(id));			}		}		return idList;	}