BAEL-5357: Retrieve a Value from MongoDB by Its Key Name (#12005)

persistence-modules/java-mongodb-2/src/main/java/com/baeldung/mongo/RetrieveValue.java

@@ -0,0 +1,118 @@
+package com.baeldung.mongo;
+
+import static com.mongodb.client.model.Aggregates.project;
+import static com.mongodb.client.model.Projections.fields;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import org.bson.Document;
+import org.bson.conversions.Bson;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DB;
+import com.mongodb.DBCollection;
+import com.mongodb.DBCursor;
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.Projections;
+
+public class RetrieveValue {
+
+    private static MongoClient mongoClient;
+    private static MongoDatabase database;
+    private static String testCollectionName;
+    private static String databaseName;
+
+    public static void setUp() {
+        if (mongoClient == null) {
+            mongoClient = new MongoClient("localhost", 27017);
+        }
+
+        databaseName = "baeldung";
+        testCollectionName = "travel";
+
+    }
+
+    public static void retrieveValueUsingFind() {
+
+        DB database = mongoClient.getDB(databaseName);
+        DBCollection collection = database.getCollection(testCollectionName);
+
+        BasicDBObject queryFilter = new BasicDBObject();
+
+        BasicDBObject projection = new BasicDBObject();
+        projection.put("passengerId", 1);
+        projection.put("_id", 0);
+
+        DBCursor dbCursor = collection.find(queryFilter, projection);
+        while (dbCursor.hasNext()) {
+            System.out.println(dbCursor.next());
+        }
+
+    }
+
+    public static void retrieveValueUsingAggregation() {
+
+        ArrayList<Document> response = new ArrayList<>();
+
+        ArrayList<Bson> pipeline = new ArrayList<>(Arrays.asList(
+
+            project(fields(Projections.exclude("_id"), Projections.include("passengerId")))));
+
+        database = mongoClient.getDatabase(databaseName);
+
+        database.getCollection(testCollectionName)
+            .aggregate(pipeline)
+            .allowDiskUse(true)
+            .into(response);
+
+        System.out.println("response:- " + response);
+
+    }
+
+    public static void retrieveValueAggregationUsingDocument() {
+
+        ArrayList<Document> response = new ArrayList<>();
+
+        ArrayList<Document> pipeline = new ArrayList<>(Arrays.asList(new Document("$project", new Document("passengerId", 1L))));
+
+        database = mongoClient.getDatabase(databaseName);
+
+        database.getCollection(testCollectionName)
+            .aggregate(pipeline)
+            .allowDiskUse(true)
+            .into(response);
+
+        System.out.println("response:- " + response);
+
+    }
+
+    public static void main(String args[]) {
+
+        //
+        // Connect to cluster (default is localhost:27017)
+        //
+        setUp();
+
+        //
+        // Fetch the data using find query with projected fields
+        //
+
+        retrieveValueUsingFind();
+
+        //
+        // Fetch the data using aggregate pipeline query with projected fields
+        //
+
+        retrieveValueUsingAggregation();
+
+        //
+        // Fetch the data using aggregate pipeline document query with projected fields
+        //
+
+        retrieveValueAggregationUsingDocument();
+
+    }
+}
+

persistence-modules/java-mongodb-2/src/test/java/com/baeldung/mongo/RetrieveValueLiveTest.java

@@ -0,0 +1,114 @@
+package com.baeldung.mongo;
+
+import static com.mongodb.client.model.Aggregates.project;
+import static com.mongodb.client.model.Projections.fields;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import org.bson.Document;
+import org.bson.conversions.Bson;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DB;
+import com.mongodb.DBCollection;
+import com.mongodb.DBCursor;
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.Filters;
+import com.mongodb.client.model.Projections;
+
+public class RetrieveValueLiveTest {
+
+    private static MongoClient mongoClient;
+    private static MongoDatabase database;
+    private static MongoCollection<Document> collection;
+    private static final String DATASET_JSON = "/travel.json";
+    private static DB db;
+    private static DBCollection dbCollection;
+
+    @BeforeClass
+    public static void setup() throws IOException {
+        if (mongoClient == null) {
+            mongoClient = new MongoClient("localhost", 27017);
+            database = mongoClient.getDatabase("baeldung");
+            db = mongoClient.getDB("baeldung");
+            dbCollection = db.getCollection("travel");
+            collection = database.getCollection("travel");
+            collection.drop();
+
+            InputStream is = BulkOperationLiveTest.class.getResourceAsStream(DATASET_JSON);
+            BufferedReader reader = new BufferedReader(new InputStreamReader(is));
+            reader.lines()
+                .forEach(line -> collection.insertOne(Document.parse(line)));
+            reader.close();
+        }
+    }
+
+    @Test
+    public void givenTravelCollection_whenfetchUsingFindOperations_thenCheckingForDocument() {
+
+        BasicDBObject queryFilter = new BasicDBObject();
+
+        BasicDBObject projection = new BasicDBObject();
+        projection.put("passengerId", 1);
+        projection.put("_id", 0);
+
+        DBCursor dbCursor = dbCollection.find(queryFilter, projection);
+        while (dbCursor.hasNext()) {
+            System.out.println(dbCursor.next());
+        }
+
+        Document travelDetail = collection.find(Filters.eq("passengerId", 145))
+            .first();
+        assertNotNull(travelDetail);
+        assertFalse(travelDetail.isEmpty());
+
+    }
+
+    @Test
+    public void givenTravelCollection_whenfetchUsingAggregationOperations_thenCheckingForDocument() {
+
+        ArrayList<Document> response = new ArrayList<>();
+        ArrayList<Bson> pipeline = new ArrayList<>(Arrays.asList(project(fields(Projections.exclude("_id"), Projections.include("passengerId")))));
+        collection.aggregate(pipeline)
+            .allowDiskUse(true)
+            .into(response);
+
+        Document travelDetail = collection.find(Filters.eq("passengerId", 145))
+            .first();
+        assertNotNull(travelDetail);
+        assertFalse(travelDetail.isEmpty());
+    }
+
+    @Test
+    public void givenTravelCollection_whenfetchUsingAggregationUsingDocumentOperations_thenCheckingForDocument() {
+
+        ArrayList<Document> response = new ArrayList<>();
+        ArrayList<Document> pipeline = new ArrayList<>(Arrays.asList(new Document("$project", new Document("passengerId", 1L))));
+        collection.aggregate(pipeline)
+            .allowDiskUse(true)
+            .into(response);
+
+        Document travelDetail = collection.find(Filters.eq("passengerId", 145))
+            .first();
+        assertNotNull(travelDetail);
+        assertFalse(travelDetail.isEmpty());
+    }
+
+    @AfterClass
+    public static void cleanUp() {
+        mongoClient.close();
+    }
+}
+

persistence-modules/java-mongodb-2/src/test/resources/travel.json

@@ -0,0 +1,4 @@
+{  "passengerId":145, "passengerName":"Nathan Green", "passengerAge":25,    "sourceStation":"London","destinationStation":"Birmingham","seatType":"Slepper","emailAddress":"nathongreen12@gmail.com"}
+{ "passengerId":148,"passengerName":"Kevin Joseph","passengerAge":28,"sourceStation":"Manchester","destinationStation":"London","seatType":"Slepper","emailAddress":"kevin13@gmail.com"}
+{"passengerId":154,"passengerName":"Sheldon burns","passengerAge":26,"sourceStation":"Cambridge","destinationStation":"Leeds","seatType":"Slepper","emailAddress":"sheldonnn160@gmail.com"}
+{"passengerId":168,"passengerName":"Jack Ferguson","passengerAge":24,"sourceStation":"Cardiff","destinationStation":"Coventry","seatType":"Slepper","emailAddress":"jackfergusion9890@gmail.com"}