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<Integer> list = new ArrayList<Integer>();
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<BasicDBObject> obj = new ArrayList<BasicDBObject>();
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<DBObject> list = new ArrayList<DBObject>();
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<Integer> list = new ArrayList<Integer>();
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("$ne", 4));
DBCursor cursor6 = collection.find(neQuery);
while (cursor6.hasNext()) {
System.out.println(cursor6.next());
}
System.out.println("\n3. Find when number = 2 and name = 'mkyong-2' example");
BasicDBObject andQuery = new BasicDBObject();
List<BasicDBObject> obj = new ArrayList<BasicDBObject>();
obj.add(new BasicDBObject("number", 2));
obj.add(new BasicDBObject("name", "mkyong-2"));
andQuery.put("$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();
}
}
}
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