如何查找符合多个条件的文档 [英] How to find documents matching multiple criteria

问题描述

我试图使用操作数AND'd查询一个集合。我已经得到了shell版本的工作：

pre $ db $ $ $ db.widgets.find（{color：'black，shape：'round' ，weight：100}）

我无法找到Java的等价物（使用原生驱动程序）。我已经尝试了各种各样的东西，但这是我最近的尝试：

  //找到所有重量为100 $的黑色圆形小工具b $ b List< BasicDBObject> criteria = new ArrayList< BasicDBObject>（）; 
 criteria.add（new BasicDBObject（color，black））; 
 criteria.add（new BasicDBObject（shape，round））; 
 criteria.add（新的BasicDBObject（weight，100））; 
 
 DBCursor cur = widgets.find（new BasicDBObject（$ and，criteria））; 
 
 //获取所有匹配的小部件并将它们放入列表中
 List< Widget> widgetList = new ArrayList< Widget>（）; 
 DBCursor cur = widgets.find（andQuery）; $（）。
 while（cur.hasNext（））{
 widgetList.add（new Widget（cur.next（）））; 
 
 
 if（widgetList.isEmpty（））
 System.out.println（No results found）; 
  

任何想法有什么不对？

解决方案

  BasicDBObject criteria = BasicDBObject（）; 
 criteria.append（color，black）; 
 criteria.append（shape，round）; 
 criteria.append（weight，100）; 
 
 DBCursor cur = widgets.find（criteria）; 
  

I'm trying to query a collection using operands AND'd together. I've got the shell version working:

db.widgets.find({color: 'black, shape: 'round', weight: 100})

I'm unable to find the Java equivalent (using the native driver). I've tried various things, but here is my latest attempt:

// Find all black, round widgets with weight 100
List<BasicDBObject> criteria = new ArrayList<BasicDBObject>();
criteria.add(new BasicDBObject("color", "black"));
criteria.add(new BasicDBObject("shape", "round"));
criteria.add(new BasicDBObject("weight", 100));

DBCursor cur = widgets.find(new BasicDBObject("$and", criteria));

// Get all matching widgets and put them into a list
List<Widget> widgetList = new ArrayList<Widget>();
DBCursor cur = widgets.find(andQuery);
while (cur.hasNext()) {
  widgetList.add(new Widget(cur.next()));
}

if (widgetList.isEmpty())
  System.out.println("No results found");

Any ideas what is wrong?

解决方案

BasicDBObject criteria = BasicDBObject();
criteria.append("color", "black");
criteria.append("shape", "round");
criteria.append("weight", 100);

DBCursor cur = widgets.find(criteria);

这篇关于如何查找符合多个条件的文档的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！