Java mongo find all

Содержание

Find a Document
Example
Note
Tip
Legacy API
How to retrieve all the documents from a MongoDB collection using Java?
Syntax
Example
Using Java program
Example
Output
MongoDB find document examples

Find a Document

You can retrieve a single document in a collection by chaining together the find() and first() methods on a MongoCollection object. You can pass a query filter to the find() method to query for and return documents that match the filter in the collection. If you do not include a filter, MongoDB returns all the documents in the collection. The first() method returns the first matching document.

For more information on querying MongoDB with the Java driver, see our guide on Querying Documents .

You can also chain other methods to the find() method such as sort() which organizes the matched documents in a specified order, and projection() which configures the fields included in the returned documents.

For more information on the sort() method, see our guide on Sorting. For more information on the projection() method, see our guide on Projections

The find() method returns an instance of FindIterable , a class that offers several methods to access, organize, and traverse the results. FindIterable also inherits methods from its parent class, MongoIterable such as first() .

The first() method returns the first document from the retrieved results or null if there are no results.

Example

The following snippet finds a single document from the movies collection. It uses the following objects and methods:

A query filter that is passed to the find() method. The eq filter matches only movies with the title exactly matching the text ‘The Room’ .
A sort that organizes matched documents in descending order by rating, so if our query matches multiple documents the returned document is the one with the highest rating.
A projection that includes the objects in the title and imdb fields and excludes the _id field using the helper method excludeId() .

Note

This example connects to an instance of MongoDB using a connection URI. To learn more about connecting to your MongoDB instance, see the connection guide .

package usage.examples;
 import static com.mongodb.client.model.Filters.eq;
 import org.bson.Document;
import org.bson.conversions.Bson;
 import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Projections;
import com.mongodb.client.model.Sorts;
 public class FindOne 
  public static void main( String[] args ) 
  // Replace the uri string with your MongoDB deployment's connection string
 String uri = "";
  try (MongoClient mongoClient = MongoClients.create(uri)) 
  MongoDatabase database = mongoClient.getDatabase("sample_mflix");
 MongoCollection collection = database.getCollection("movies");
  Bson projectionFields = Projections.fields(
 Projections.include("title", "imdb"),
 Projections.excludeId());
  Document doc = collection.find(eq("title", "The Room"))
 .projection(projectionFields)
 .sort(Sorts.descending("imdb.rating"))
 .first();
  if (doc == null) 
 System.out.println("No results found.");
 > else 
 System.out.println(doc.toJson());
 >
 >
 >
>

Tip

Legacy API

If you are using the legacy API, see our FAQ page to learn what changes you need to make to this code example.

For additional information on the classes and methods mentioned on this page, see the following API Documentation:

Источник

How to retrieve all the documents from a MongoDB collection using Java?

You can retrieve documents from an existing collection in MongoDB using the find() method.

Syntax

db is the database.
coll is the collection (name) in which you want to insert the document

Example

Assume we have a collection named students in the MongoDB database with the following documents −

The following query retrieves all the documents from the collected sample.

> use myDatabase() switched to db myDatabase() > db.createCollection(sample) < "ok" : 1 >> > db.sample.find() < "_id" : ObjectId("5e870492af638d501865015f"), "name" : "Ram", "age" : 26, "city" : "Mumbai" > < "_id" : ObjectId("5e870492af638d5018650160"), "name" : "Roja", "age" : 28, "city" : "Hyderabad" > < "_id" : ObjectId("5e870492af638d5018650161"), "name" : "Ramani", "age" : 35, "city" : "Delhi" >>

Using Java program

In Java, you can retrieve all the documents in the current collection using the find() method of the com.mongodb.client.MongoCollection interface. This method returns an iterable object containing all the documents.

Therefore to create a collection in MongoDB using Java program −

Make sure you have installed MongoDB in your system
Add the following dependency to its pom.xml file of your Java project.

 org.mongodb mongo-java-driver 3.12.2

Create a MongoDB client by instantiating the MongoClient class.
Connect to a database using the getDatabase() method.
Get the object of the collection from which you want to retrieve the documents, using the getCollection() method.
Retrieve the iterable object containing all the documents of the current collection by invoking the find() method.

Example

import com.mongodb.client.FindIterable; import com.mongodb.client.MongoCollection; import com.mongodb.client.MongoDatabase; import java.util.Iterator; import org.bson.Document; import com.mongodb.MongoClient; public class RetrievingAllDocuments < public static void main( String args[] ) < //Creating a MongoDB client MongoClient mongo = new MongoClient( "localhost" , 27017 ); //Connecting to the database MongoDatabase database = mongo.getDatabase("myDatabase"); //Creating a collection object MongoCollectioncollection = database.getCollection("students"); //Retrieving the documents FindIterable iterDoc = collection.find(); Iterator it = iterDoc.iterator(); while (it.hasNext()) < System.out.println(it.next()); >> >

Output

Document> Document> Document>

Источник

MongoDB find document examples

Learn to find documents in MongoDB. This mongodb find document tutorial covers a number of ways to query a single document or find multiple documents based on same condition as we do in SQL using WHERE CLAUSE.

Table of Contents 1) Select all documents from a collection 2) Select first document from a collection 3) Select single document and limited field(s) from a collection 4) Select all documents with unique id from a collection 5) Document ids IN clause example 6) Document ids less than or greater than clause example 7) Document ids NOT IN clause example 8) Documents matching multiple fields example 9) Documents matching field value to some REGEX example

MongoDB find document – test data preparation

For building and running examples used in this tutorial, I have populated 20 employee documents in database with employeeId from 1 to 20, and employeeName from TestEmployee_1 to TestEmployee_10.

private static void setUpTestData(DBCollection collection) < for (int i=1; i >

Now run our examples and fetch the data on different scenarios.

1. MongoDB find() – Select all documents from a collection

private static void selectAllRecordsFromACollection(DBCollection collection) < DBCursor cursor = collection.find(); while(cursor.hasNext()) < System.out.println(cursor.next()); >>

 < "_id" : < "$oid" : "538782753641d31b0cad0142">, "employeeId" : 1 , "employeeName" : "TestEmployee_1"> < "_id" : < "$oid" : "538782753641d31b0cad0143">, "employeeId" : 2 , "employeeName" : "TestEmployee_2"> < "_id" : < "$oid" : "538782753641d31b0cad0144">, "employeeId" : 3 , "employeeName" : "TestEmployee_3"> < "_id" : < "$oid" : "538782753641d31b0cad0145">, "employeeId" : 4 , "employeeName" : "TestEmployee_4"> < "_id" : < "$oid" : "538782753641d31b0cad0146">, "employeeId" : 5 , "employeeName" : "TestEmployee_5"> < "_id" : < "$oid" : "538782753641d31b0cad0147">, "employeeId" : 6 , "employeeName" : "TestEmployee_6"> < "_id" : < "$oid" : "538782753641d31b0cad0148">, "employeeId" : 7 , "employeeName" : "TestEmployee_7"> < "_id" : < "$oid" : "538782753641d31b0cad0149">, "employeeId" : 8 , "employeeName" : "TestEmployee_8"> < "_id" : < "$oid" : "538782753641d31b0cad014a">, "employeeId" : 9 , "employeeName" : "TestEmployee_9"> < "_id" : < "$oid" : "538782753641d31b0cad014b">, "employeeId" : 10 , "employeeName" : "TestEmployee_10">

2. MongoDB findOne() – Select first document from a collection

private static void selectFirstRecordInCollection(DBCollection collection)

 < "_id" : < "$oid" : "538782a53641ed9125df86c0">, "employeeId" : 1 , "employeeName" : "TestEmployee_1">

3. MongoDB where clause – Select single document and limited field(s) from a collection

private static void selectSingleRecordAndFieldByRecordNumber(DBCollection collection) < BasicDBObject whereQuery = new BasicDBObject(); whereQuery.put("employeeId", 5); BasicDBObject fields = new BasicDBObject(); fields.put("employeeId", 1); DBCursor cursor = collection.find(whereQuery, fields); while (cursor.hasNext()) < System.out.println(cursor.next()); >>

4. MongoDB find by document id

private static void selectAllRecordByRecordNumber(DBCollection collection) < BasicDBObject whereQuery = new BasicDBObject(); whereQuery.put("employeeId", 5); DBCursor cursor = collection.find(whereQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >>

 < "_id" : < "$oid" : "538783623641e9b2da299fa7">, "employeeId" : 5 , "employeeName" : "TestEmployee_5">

5. MongoDB IN clause example

private static void in_Example(DBCollection collection) < BasicDBObject inQuery = new BasicDBObject(); Listlist = new ArrayList(); list.add(2); list.add(4); list.add(5); inQuery.put("employeeId", new BasicDBObject("$in", list)); DBCursor cursor = collection.find(inQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >>

 < "_id" : < "$oid" : "5387838d3641024de174c795">, "employeeId" : 2 , "employeeName" : "TestEmployee_2"> < "_id" : < "$oid" : "5387838d3641024de174c797">, "employeeId" : 4 , "employeeName" : "TestEmployee_4"> < "_id" : < "$oid" : "5387838d3641024de174c798">, "employeeId" : 5 , "employeeName" : "TestEmployee_5">

6. MongoDB – Less than or greater than clause example

private static void lessThan_GreaterThan_Example(DBCollection collection) < BasicDBObject getQuery = new BasicDBObject(); getQuery.put("employeeId", new BasicDBObject("$gt", 2).append("$lt", 5)); DBCursor cursor = collection.find(getQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >>

 < "_id" : < "$oid" : "538783b63641720cd34f98c8">, "employeeId" : 3 , "employeeName" : "TestEmployee_3"> < "_id" : < "$oid" : "538783b63641720cd34f98c9">, "employeeId" : 4 , "employeeName" : "TestEmployee_4">

7. MongoDb NOT IN clause example

private static void negation_Example(DBCollection collection) < BasicDBObject neQuery = new BasicDBObject(); neQuery.put("employeeId", new BasicDBObject("$ne", 4)); DBCursor cursor = collection.find(neQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >>

 < "_id" : < "$oid" : "538783db3641d3ca9d400510">, "employeeId" : 1 , "employeeName" : "TestEmployee_1"> < "_id" : < "$oid" : "538783db3641d3ca9d400511">, "employeeId" : 2 , "employeeName" : "TestEmployee_2"> < "_id" : < "$oid" : "538783db3641d3ca9d400512">, "employeeId" : 3 , "employeeName" : "TestEmployee_3"> < "_id" : < "$oid" : "538783db3641d3ca9d400514">, "employeeId" : 5 , "employeeName" : "TestEmployee_5"> //4 is missing < "_id" : < "$oid" : "538783db3641d3ca9d400515">, "employeeId" : 6 , "employeeName" : "TestEmployee_6"> < "_id" : < "$oid" : "538783db3641d3ca9d400516">, "employeeId" : 7 , "employeeName" : "TestEmployee_7"> < "_id" : < "$oid" : "538783db3641d3ca9d400517">, "employeeId" : 8 , "employeeName" : "TestEmployee_8"> < "_id" : < "$oid" : "538783db3641d3ca9d400518">, "employeeId" : 9 , "employeeName" : "TestEmployee_9"> < "_id" : < "$oid" : "538783db3641d3ca9d400519">, "employeeId" : 10 , "employeeName" : "TestEmployee_10">

8. MongoDb find documents matching multiple fields example

private static void andLogicalComparison_Example(DBCollection collection) < BasicDBObject andQuery = new BasicDBObject(); Listobj = new ArrayList(); obj.add(new BasicDBObject("employeeId", 2)); obj.add(new BasicDBObject("employeeName", "TestEmployee_2")); andQuery.put("$and", obj); System.out.println(andQuery.toString()); DBCursor cursor = collection.find(andQuery); while (cursor.hasNext()) < System.out.println(cursor.next()); >>

 < "$and" : [ < "employeeId" : 2>, < "employeeName" : "TestEmployee_2">]> < "_id" : < "$oid" : "5387840336418a41167caaa4">, "employeeId" : 2 , "employeeName" : "TestEmployee_2">

9. MongoDb find documents matching REGEX example

private static void regex_Example(DBCollection collection) < BasicDBObject regexQuery = new BasicDBObject(); regexQuery.put("employeeName", new BasicDBObject("$regex", "TestEmployee_[3]") .append("$options", "i")); System.out.println(regexQuery.toString()); DBCursor cursor = collection.find(regexQuery); while (cursor.hasNext()) < System.out.println(cursor.next()); >>

< "employeeName" : < "$regex" : "TestEmployee_[3]" , "$options" : "i">> < "_id" : < "$oid" : "538784213641917ce7068c57">, "employeeId" : 3 , "employeeName" : "TestEmployee_3">

10. All mondodb find query examples

package examples.mongodb.crud; import java.net.UnknownHostException; import java.util.ArrayList; 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.MongoClient; import com.mongodb.WriteResult; public class MongoDBSelectExample < private static void setUpTestData(DBCollection collection)< for (int i=1; i > public static void main(String[] args) throws UnknownHostException < MongoClient mongo = new MongoClient("localhost", 27017); DB db = mongo.getDB("howtodoinjava"); DBCollection collection = db.getCollection("users"); //Delete All documents before running example again WriteResult result = collection.remove(new BasicDBObject()); System.out.println(result.toString()); //Set up test data setUpTestData(collection); //Select all document from a collection selectAllRecordsFromACollection(collection); //Select first document in collection selectFirstRecordInCollection(collection); //Select single document and single field based on record number selectSingleRecordAndFieldByRecordNumber(collection); //Select all documents where record number = n selectAllRecordByRecordNumber(collection); //In example in_Example(collection); //Less than OR greater than example lessThan_GreaterThan_Example(collection); //Select document where record number != n negation_Example(collection); //And logical comparison query example andLogicalComparison_Example(collection); //Select documents based on regex match LIKE example regex_Example(collection); >private static void selectFirstRecordInCollection(DBCollection collection) < DBObject dbObject = collection.findOne(); System.out.println(dbObject); >private static void selectAllRecordsFromACollection(DBCollection collection) < DBCursor cursor = collection.find(); while(cursor.hasNext()) < System.out.println(cursor.next()); >> private static void selectSingleRecordAndFieldByRecordNumber(DBCollection collection) < BasicDBObject whereQuery = new BasicDBObject(); whereQuery.put("employeeId", 5); BasicDBObject fields = new BasicDBObject(); fields.put("employeeId", 1); DBCursor cursor = collection.find(whereQuery, fields); while (cursor.hasNext()) < System.out.println(cursor.next()); >> private static void selectAllRecordByRecordNumber(DBCollection collection) < BasicDBObject whereQuery = new BasicDBObject(); whereQuery.put("employeeId", 5); DBCursor cursor = collection.find(whereQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >> private static void in_Example(DBCollection collection) < BasicDBObject inQuery = new BasicDBObject(); Listlist = new ArrayList(); list.add(2); list.add(4); list.add(5); inQuery.put("employeeId", new BasicDBObject("$in", list)); DBCursor cursor = collection.find(inQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >> private static void lessThan_GreaterThan_Example( DBCollection collection) < BasicDBObject gtQuery = new BasicDBObject(); gtQuery.put("employeeId", new BasicDBObject("$gt", 2).append("$lt", 5)); DBCursor cursor = collection.find(gtQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >> private static void negation_Example(DBCollection collection) < BasicDBObject neQuery = new BasicDBObject(); neQuery.put("employeeId", new BasicDBObject("$ne", 4)); DBCursor cursor = collection.find(neQuery); while(cursor.hasNext()) < System.out.println(cursor.next()); >> private static void andLogicalComparison_Example(DBCollection collection) < BasicDBObject andQuery = new BasicDBObject(); Listobj = new ArrayList(); obj.add(new BasicDBObject("employeeId", 2)); obj.add(new BasicDBObject("employeeName", "TestEmployee_2")); andQuery.put("$and", obj); System.out.println(andQuery.toString()); DBCursor cursor = collection.find(andQuery); while (cursor.hasNext()) < System.out.println(cursor.next()); >> private static void regex_Example(DBCollection collection) < BasicDBObject regexQuery = new BasicDBObject(); regexQuery.put("employeeName", new BasicDBObject("$regex", "TestEmployee_[3]") .append("$options", "i")); System.out.println(regexQuery.toString()); DBCursor cursor = collection.find(regexQuery); while (cursor.hasNext()) < System.out.println(cursor.next()); >> >

That’s all for different techniques to fetch ducument from MongoDB.

Источник