Java MongoDB 查询

本文介绍如何从集合中查询文档的通用方法。

测试数据

插入5条测试文档

{ "_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()

1.1 获取第一条文档

Document document = collection.find().first();System.out.println(document);

输出：

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

1.2 获取所有文档

FindIterable<Document> documents = collection.find();MongoCursor<Document> mongoCursor = documents.iterator();while (mongoCursor.hasNext()) {    System.out.println(mongoCursor.next());}

输出：

{ "_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 获取文档的单一字段

Document fields = new Document();fields.put("name", 1);FindIterable<Document> projection = collection.find().projection(fields);MongoCursor<Document> iterator = projection.iterator();while (iterator.hasNext()) {    System.out.println(iterator.next());}

输出：

{ "_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. 使用find()对比查询

2.1 获取所有number = 5的文档

Document whereQuery = new Document();whereQuery.put("number", 5);FindIterable<Document> whereDocuments = collection.find(whereQuery);MongoCursor<Document> whereIterator = whereDocuments.iterator();while (whereIterator.hasNext()) {    System.out.println(whereIterator.next());}

输出：

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

2.2 $in - 获取number在2、4、5中的文档

Document inQuery = new Document();List<Integer> list = new ArrayList<Integer>();list.add(2);list.add(4);list.add(5);inQuery.put("number", new Document("$in", list));FindIterable<Document> listDocuments = collection.find(inQuery);MongoCursor<Document> listIterator = listDocuments.iterator();while (listIterator.hasNext()) {    System.out.println(listIterator.next());}

输出：

{ "_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 - 获取5 > number > 2的文档

Document gtQuery = new Document();gtQuery.put("number", new Document("$gt", 2).append("$lt", 5));FindIterable<Document> gtDocuments = collection.find(gtQuery);MongoCursor<Document> gtIterator = gtDocuments.iterator();while (gtIterator.hasNext()) {    System.out.println(gtIterator.next());}

输出：

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

2.4 $ne - 获取number != 4的文档

Document neQuery = new Document();neQuery.put("number", new Document("$ne", 4));FindIterable<Document> neDocuments = collection.find(neQuery);MongoCursor<Document> neIterator = neDocuments.iterator();while (neIterator.hasNext()) {    System.out.println(neIterator.next());}

输出：

{ "_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. 使用find()进行逻辑查询

3.1 $and - 获取number = 2 and name = 'mkyong-2'的文档

Document andQuery = new Document();List<Document> obj = new ArrayList<Document>();obj.add(new Document("number", 2));obj.add(new Document("name", "mkyong-2"));andQuery.put("$and", obj);System.out.println(andQuery.toString());FindIterable<Document> andDocuments = collection.find(andQuery);MongoCursor<Document> andIterator = andDocuments.iterator();while (andIterator.hasNext()) {    System.out.println(andIterator.next());}

输出：

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

4. 使用find()通过正则表达式查询

4.1 $regex

Document regexQuery = new Document();regexQuery.put("name",        new Document("$regex", "Mky.*-[1-3]")                .append("$options", "i"));System.out.println(regexQuery.toString());FindIterable<Document> regexDocuments = collection.find(regexQuery);MongoCursor<Document> regexIterator = regexDocuments.iterator();while (regexIterator.hasNext()) {    System.out.println(regexIterator.next());}

输出：

{ "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"}

5. 完整实例

import com.mongodb.MongoClient;import com.mongodb.MongoException;import com.mongodb.client.FindIterable;import com.mongodb.client.MongoCollection;import com.mongodb.client.MongoCursor;import com.mongodb.client.MongoDatabase;import org.bson.Document;import java.util.ArrayList;import java.util.Calendar;import java.util.List;public class FindDocument {    public static void insertDummyDocuments(MongoCollection<Document> collection) {        List<Document> list = new ArrayList<Document>();        Calendar cal = Calendar.getInstance();        for (int i = 1; i <= 5; i++) {            Document data = new Document();            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.insertMany(list);    }    public static void main(String[] args) {        try {            MongoClient mongoClient = new MongoClient("localhost", 27017);            MongoDatabase database = mongoClient.getDatabase("test");            // get a single collection            MongoCollection<Document> collection = database.getCollection("dummyColl");            insertDummyDocuments(collection);            System.out.println("1. Find first matched document");            Document document = collection.find().first();            System.out.println(document);            System.out.println("\n1. Find all matched documents");            FindIterable<Document> documents = collection.find();            MongoCursor<Document> mongoCursor = documents.iterator();            while (mongoCursor.hasNext()) {                System.out.println(mongoCursor.next());            }            System.out.println("\n1. Get 'name' field only");//            Document allQuery = new Document();            Document fields = new Document();            fields.put("name", 1);            FindIterable<Document> projection = collection.find().projection(fields);            MongoCursor<Document> iterator = projection.iterator();            while (iterator.hasNext()) {                System.out.println(iterator.next());            }            System.out.println("\n2. Find where number = 5");            Document whereQuery = new Document();            whereQuery.put("number", 5);            FindIterable<Document> whereDocuments = collection.find(whereQuery);            MongoCursor<Document> whereIterator = whereDocuments.iterator();            while (whereIterator.hasNext()) {                System.out.println(whereIterator.next());            }            System.out.println("\n2. Find where number in 2,4 and 5");            Document inQuery = new Document();            List<Integer> list = new ArrayList<Integer>();            list.add(2);            list.add(4);            list.add(5);            inQuery.put("number", new Document("$in", list));            FindIterable<Document> listDocuments = collection.find(inQuery);            MongoCursor<Document> listIterator = listDocuments.iterator();            while (listIterator.hasNext()) {                System.out.println(listIterator.next());            }            System.out.println("\n2. Find where 5 > number > 2");            Document gtQuery = new Document();            gtQuery.put("number", new Document("$gt", 2).append("$lt", 5));            FindIterable<Document> gtDocuments = collection.find(gtQuery);            MongoCursor<Document> gtIterator = gtDocuments.iterator();            while (gtIterator.hasNext()) {                System.out.println(gtIterator.next());            }            System.out.println("\n2. Find where number != 4");            Document neQuery = new Document();            neQuery.put("number", new Document("$ne", 4));            FindIterable<Document> neDocuments = collection.find(neQuery);            MongoCursor<Document> neIterator = neDocuments.iterator();            while (neIterator.hasNext()) {                System.out.println(neIterator.next());            }            System.out.println("\n3. Find when number = 2 and name = 'mkyong-2' example");            Document andQuery = new Document();            List<Document> obj = new ArrayList<Document>();            obj.add(new Document("number", 2));            obj.add(new Document("name", "mkyong-2"));            andQuery.put("$and", obj);            System.out.println(andQuery.toString());            FindIterable<Document> andDocuments = collection.find(andQuery);            MongoCursor<Document> andIterator = andDocuments.iterator();            while (andIterator.hasNext()) {                System.out.println(andIterator.next());            }            System.out.println("\n4. Find where name = 'Mky.*-[1-3]', case sensitive example");            Document regexQuery = new Document();            regexQuery.put("name",                    new Document("$regex", "Mky.*-[1-3]")                            .append("$options", "i"));            System.out.println(regexQuery.toString());            FindIterable<Document> regexDocuments = collection.find(regexQuery);            MongoCursor<Document> regexIterator = regexDocuments.iterator();            while (regexIterator.hasNext()) {                System.out.println(regexIterator.next());            }            collection.drop();            System.out.println("Done");        } catch (MongoException e) {            e.printStackTrace();        }    }}