Java MongoDB : Query document

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原文出自：http://www.mkyong.com/mongodb/java-mongodb-query-document/

返回目录：http://ysj5125094.iteye.com/blog/2192754  

 

Java MongoDB : Query document

In this tutorial, we show you few common ways to get or query document from collection.

译：在本教程中，我们向你展示一些常见的从集合获取和查询文档的方式。

Test Data

Insert 5 dummy documents for testing.

译：插入5条虚拟的测试记录（文档）。

 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "mkyong-1"}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "mkyong-2"}
{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "mkyong-3"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "mkyong-4"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "mkyong-5"}

 

1. Find() examples

1.1 Get first matched document only. 

译：获取第一个匹配的文档。

 

	DBObject doc = collection.findOne();
	System.out.println(dbObject);

Output 

 

 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "mkyong-1"}

1.2 Get all matched documents. 

 

译：获取所有匹配的文档。

 

	DBCursor cursor = collection.find();
	while(cursor.hasNext()) {
	    System.out.println(cursor.next());
	}

Output 

 

 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "mkyong-1"}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "mkyong-2"}
{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "mkyong-3"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "mkyong-4"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "mkyong-5"}

1.3 Get single field from matched document. 

 

译：从匹配的文档中获取单个字段。

 

	BasicDBObject allQuery = new BasicDBObject();
	BasicDBObject fields = new BasicDBObject();
	fields.put("name", 1);
 
	DBCursor cursor = collection.find(allQuery, fields);
	while (cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Output 

 

{ "_id" : { "$oid" : "id"} , "name" : "mkyong-1"}
{ "_id" : { "$oid" : "id"} , "name" : "mkyong-2"}
{ "_id" : { "$oid" : "id"} , "name" : "mkyong-3"}
{ "_id" : { "$oid" : "id"} , "name" : "mkyong-4"}
{ "_id" : { "$oid" : "id"} , "name" : "mkyong-5"}

2. Find() and Comparison

2.1 Get all documents where number = 5. 

译：获取所有number=5的文档。

	BasicDBObject whereQuery = new BasicDBObject();
	whereQuery.put("number", 5);
	DBCursor cursor = collection.find(whereQuery);
	while(cursor.hasNext()) {
	    System.out.println(cursor.next());
	}

Output 

{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "mkyong-5"}

2.2 $in example – Get documents where number in 2, 4 and 5. 

译：$in例子 ---- 获取 number in (2,3,5) 的文档。

BasicDBObject inQuery = new BasicDBObject();
	List list = new ArrayList();
	list.add(2);
	list.add(4);
	list.add(5);
	inQuery.put("number", new BasicDBObject("$in", list));
	DBCursor cursor = collection.find(inQuery);
	while(cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Output 

{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "mkyong-2"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "mkyong-4"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "mkyong-5"}

2.3 $gt $lt example – Get documents where 5 > number > 2 . 

译：$gt $lt例子 ---- 获取 5 > number > 2 的文档。

	BasicDBObject gtQuery = new BasicDBObject();
	gtQuery.put("number", new BasicDBObject("$gt", 2).append("$lt", 5));
	DBCursor cursor = collection.find(gtQuery);
	while(cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Output 

{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "mkyong-3"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "mkyong-4"}

2.4 $ne example – Get documents where number != 4 . 

译：$ne例子 ---- 获取 number != 4的文档。

	BasicDBObject neQuery = new BasicDBObject();
	neQuery.put("number", new BasicDBObject("$ne", 4));
	DBCursor cursor = collection.find(neQuery);
	while(cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Output 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "mkyong-1"}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "mkyong-2"}
{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "mkyong-3"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "mkyong-5"}

3. find() and Logical

3.1 $and example – get documents where number = 2 and name = 'mkyong-2'. 

译：$and例子 ---- 获取 number = 2 and name = 'mkyong-2' 的文档。

	BasicDBObject andQuery = new BasicDBObject();
	List obj = new ArrayList();
	obj.add(new BasicDBObject("number", 2));
	obj.add(new BasicDBObject("name", "mkyong-2"));
	andQuery.put("$and", obj);
 
	System.out.println(andQuery.toString());
 
	DBCursor cursor = collection.find(andQuery);
	while (cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Output 

{ "$and" : [ { "number" : 2} , { "name" : "mkyong-2"}]}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "mkyong-2"}

4. find() and Regex

Find document with regular expression pattern. 

译：查询与正则表达式匹配的文档。

4.1 $regex example – get documents where name like pattern 'Mky.*-[1-3]', case insensitive.

译：$regex 例子 ---- 获取name like pattern 'Mky.*-[1-3]'的文档，不区分大小写。

	BasicDBObject regexQuery = new BasicDBObject();
	regexQuery.put("name", 
		new BasicDBObject("$regex", "Mky.*-[1-3]")
		.append("$options", "i"));
 
	System.out.println(regexQuery.toString());
 
	DBCursor cursor = collection.find(regexQuery);
	while (cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Output 

{ "name" : { "$regex" : "Mky.*-[1-3]" , "$options" : "i"}}
{ "_id" : { "$oid" : "515ad59e3004c89329c7b259"} , "number" : 1 , "name" : "mkyong-1"}
{ "_id" : { "$oid" : "515ad59e3004c89329c7b25a"} , "number" : 2 , "name" : "mkyong-2"}
{ "_id" : { "$oid" : "515ad59e3004c89329c7b25b"} , "number" : 3 , "name" : "mkyong-3"}

There are more…
Read this MongoDB operator documentation for complete set of query operators supported in MongoDB. 

译：阅读 MongoDB操作文档，了解更多。

5. Full Example

package com.mkyong.core;
 
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
 
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
 
/**
 * Java MongoDB : Query document
 * 
 * @author mkyong
 * 
 */
public class QueryApp {
 
	public static void insertDummyDocuments(DBCollection collection) {
 
		List list = new ArrayList();
 
		Calendar cal = Calendar.getInstance();
 
		for (int i = 1; i <= 5; i++) {
 
			BasicDBObject data = new BasicDBObject();
			data.append("number", i);
			data.append("name", "mkyong-" + i);
			// data.append("date", cal.getTime());
 
			// +1 day
			cal.add(Calendar.DATE, 1);
 
			list.add(data);
 
		}
 
		collection.insert(list);
 
	}
 
	public static void main(String[] args) {
 
	try {
 
	  Mongo mongo = new Mongo("localhost", 27017);
	  DB db = mongo.getDB("yourdb");
 
	  // get a single collection
	  DBCollection collection = db.getCollection("dummyColl");
 
	  insertDummyDocuments(collection);
 
	  System.out.println("1. Find first matched document");
	  DBObject dbObject = collection.findOne();
	  System.out.println(dbObject);
 
	  System.out.println("\n1. Find all matched documents");
	  DBCursor cursor = collection.find();
	  while (cursor.hasNext()) {
		System.out.println(cursor.next());
	  }
 
	  System.out.println("\n1. Get 'name' field only");
	  BasicDBObject allQuery = new BasicDBObject();
	  BasicDBObject fields = new BasicDBObject();
	  fields.put("name", 1);
 
	  DBCursor cursor2 = collection.find(allQuery, fields);
	  while (cursor2.hasNext()) {
		System.out.println(cursor2.next());
	  }
 
	  System.out.println("\n2. Find where number = 5");
	  BasicDBObject whereQuery = new BasicDBObject();
	  whereQuery.put("number", 5);
	  DBCursor cursor3 = collection.find(whereQuery);
	  while (cursor3.hasNext()) {
		System.out.println(cursor3.next());
	  }
 
	  System.out.println("\n2. Find where number in 2,4 and 5");
	  BasicDBObject inQuery = new BasicDBObject();
	  List list = new ArrayList();
	  list.add(2);
	  list.add(4);
	  list.add(5);
	  inQuery.put("number", new BasicDBObject("$in", list));
	  DBCursor cursor4 = collection.find(inQuery);
	  while (cursor4.hasNext()) {
		System.out.println(cursor4.next());
	  }
 
	  System.out.println("\n2. Find where 5 > number > 2");
	  BasicDBObject gtQuery = new BasicDBObject();
	  gtQuery.put("number", new BasicDBObject("$gt", 2).append("$lt", 5));
	  DBCursor cursor5 = collection.find(gtQuery);
	  while (cursor5.hasNext()) {
		System.out.println(cursor5.next());
	  }
 
	  System.out.println("\n2. Find where number != 4");
	  BasicDBObject neQuery = new BasicDBObject();
	  neQuery.put("number", new BasicDBObject("$ne", 4));
	  DBCursor cursor6 = collection.find(neQuery);
	  while (cursor6.hasNext()) {
		System.out.println(cursor6.next());
	  }
 
	  System.out.println("\n3. Find when number = 2 and name = 'mkyong-2' example");
	  BasicDBObject andQuery = new BasicDBObject();
 
	  List obj = new ArrayList();
	  obj.add(new BasicDBObject("number", 2));
	  obj.add(new BasicDBObject("name", "mkyong-2"));
	  andQuery.put("$and", obj);
 
	  System.out.println(andQuery.toString());
 
	  DBCursor cursor7 = collection.find(andQuery);
	  while (cursor7.hasNext()) {
		System.out.println(cursor7.next());
	  }
 
	  System.out.println("\n4. Find where name = 'Mky.*-[1-3]', case sensitive example");
	  BasicDBObject regexQuery = new BasicDBObject();
	  regexQuery.put("name",
		new BasicDBObject("$regex", "Mky.*-[1-3]")
                    .append("$options", "i"));
 
	  System.out.println(regexQuery.toString());
 
	  DBCursor cursor8 = collection.find(regexQuery);
	  while (cursor8.hasNext()) {
		System.out.println(cursor8.next());
	  }
 
	  collection.drop();
 
	  System.out.println("Done");
 
	 } catch (UnknownHostException e) {
		e.printStackTrace();
	 } catch (MongoException e) {
		e.printStackTrace();
	 }
 
	}
}

 

 

References

1. Query, Update, and Projection Operators Quick Reference