Problem:
How to connect to MongoDB 3 from Java? In this post we’ll show how to use MongoDB Java Driver to create Mongo Clients with different options.
MongoDB 3 Java Driver comes with very intuitive API, which we’ll explore in next few posts. In this one we’ll show how to setup Java project, ReplicaSet, and create MongoClient and get a database.
Solution:
Add MongoDB Java Driver as project dependency:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.farenda.java</groupId>
<artifactId>mongodb</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.mongodb</groupId>
<artifactId>mongodb-driver</artifactId>
<version>3.2.2</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.2</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
In the following code we create three instances of MongoClient with different options:
- MongoClient with default connection settings.
- MongoClient connecting using SSL and setting WriteConcern.JOURNALED to confirm writing data.
- MongoClient that will connect to a local replica set.
To setup local ReplicaSet you can use the following script:
mkdir -p /tmp/data/rs1 /tmp/data/rs2 mongod --replSet farenda --logpath "1.log" --dbpath /tmp/data/rs1 --port 7017 --oplogSize 64 --smallfiles --fork mongod --replSet farenda --logpath "2.log" --dbpath /tmp/data/rs2 --port 7018 --oplogSize 64 --smallfiles --fork
And configure nodes from the mongo shell:
config = { _id: "farenda",
members: [
{ _id : 0, host : "localhost:7017"},
{ _id : 1, host : "localhost:7018"}
]
};
rs.initiate(config);
rs.status();
It’s not needed for one-node Mongo instance, which are usually used for programming. :-)
package com.farenda.mongodb;
import com.mongodb.MongoClient;
import com.mongodb.MongoClientOptions;
import com.mongodb.ServerAddress;
import com.mongodb.WriteConcern;
import com.mongodb.client.MongoDatabase;
import java.util.LinkedList;
import java.util.List;
import static java.util.Arrays.asList;
public class MongoConnectionExample {
public static void main(String[] args) {
defaultConnection();
withSslAndWriteConcern();
connectToReplicaSet();
}
private static void defaultConnection() {
System.out.println("Creating database with default options.");
try (MongoClient client = new MongoClient("localhost")) {
List<String> databases = client
.listDatabaseNames()
.into(new LinkedList<>());
System.out.println("Databases: " + databases);
MongoDatabase db = client.getDatabase("test");
displayOptions(db);
}
}
private static void withSslAndWriteConcern() {
System.out.println("Creating client with SSL.");
MongoClientOptions.Builder builder = MongoClientOptions.builder()
.sslEnabled(true)
.sslInvalidHostNameAllowed(true)
.writeConcern(WriteConcern.JOURNALED);
try (MongoClient client = new MongoClient("localhost", builder.build())) {
MongoDatabase db = client.getDatabase("test");
displayOptions(db);
}
}
private static void connectToReplicaSet() {
System.out.println("Connecting client to replica set.");
// Setup nodes first!
try (MongoClient client = new MongoClient(
asList(new ServerAddress("localhost", 7017),
new ServerAddress("localhost", 7018)))) {
MongoDatabase db = client.getDatabase("test");
displayOptions(db);
}
}
private static void displayOptions(MongoDatabase db) {
System.out.printf("Database read concern: %s, write concern: %s%n%n",
db.getReadConcern(), db.getWriteConcern());
}
}
The code in straightforward. One thing to note is List<String> list = client.listX().into(new LinkedList<>()), which returns collection of elements from Mongo Driver in given object – here LinkedList. The into(target collection type) is a pattern that you will see a lot in Mongo API.
In the following output you can see that it has successfully connected to databases using different clients:
Creating database with default options.
mar 29, 2016 4:33:42 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Cluster created with settings {hosts=[localhost:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
mar 29, 2016 4:33:42 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: No server chosen by ReadPreferenceServerSelector{readPreference=primary} from cluster description ClusterDescription{type=UNKNOWN, connectionMode=SINGLE, all=[ServerDescription{address=localhost:27017, type=UNKNOWN, state=CONNECTING}]}. Waiting for 30000 ms before timing out
mar 29, 2016 4:33:42 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Opened connection [connectionId{localValue:1, serverValue:250}] to localhost:27017
mar 29, 2016 4:33:42 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Monitor thread successfully connected to server with description ServerDescription{address=localhost:27017, type=STANDALONE, state=CONNECTED, ok=true, version=ServerVersion{versionList=[3, 2, 4]}, minWireVersion=0, maxWireVersion=4, maxDocumentSize=16777216, roundTripTimeNanos=6952108}
mar 29, 2016 4:33:42 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Opened connection [connectionId{localValue:2, serverValue:251}] to localhost:27017
Databases: [m101, students, school, blog, quartz_mongodb_test, local, test]
Database read concern: com.mongodb.ReadConcern@0, write concern: WriteConcern{w=null, wTimeout=null ms, fsync=null, journal=null
mar 29, 2016 4:33:42 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Closed connection [connectionId{localValue:2, serverValue:251}] to localhost:27017 because the pool has been closed.
Creating client with SSL.
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Cluster created with settings {hosts=[localhost:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
Database read concern: com.mongodb.ReadConcern@0, write concern: WriteConcern{w=null, wTimeout=null ms, fsync=null, journal=true
Connecting client to replica set.
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Cluster created with settings {hosts=[localhost:7017, localhost:7018], mode=MULTIPLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Adding discovered server localhost:7017 to client view of cluster
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Adding discovered server localhost:7018 to client view of cluster
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Opened connection [connectionId{localValue:4, serverValue:9}] to localhost:7017
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Monitor thread successfully connected to server with description ServerDescription{address=localhost:7017, type=REPLICA_SET_PRIMARY, state=CONNECTED, ok=true, version=ServerVersion{versionList=[3, 2, 4]}, minWireVersion=0, maxWireVersion=4, maxDocumentSize=16777216, roundTripTimeNanos=4506819, setName='farenda', canonicalAddress=localhost:7017, hosts=[localhost:7017, localhost:7018], passives=[], arbiters=[], primary='localhost:7017', tagSet=TagSet{[]}, electionId=7fffffff0000000000000001, setVersion=1}
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Discovered cluster type of REPLICA_SET
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Setting max election id to 7fffffff0000000000000001 from replica set primary localhost:7017
Database read concern: com.mongodb.ReadConcern@0, write concern: WriteConcern{w=null, wTimeout=null ms, fsync=null, journal=null
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Setting max set version to 1 from replica set primary localhost:7017
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Opened connection [connectionId{localValue:5, serverValue:5}] to localhost:7018
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Discovered replica set primary localhost:7017
mar 29, 2016 4:33:44 PM com.mongodb.diagnostics.logging.JULLogger log
INFO: Monitor thread successfully connected to server with description ServerDescription{address=localhost:7018, type=REPLICA_SET_SECONDARY, state=CONNECTED, ok=true, version=ServerVersion{versionList=[3, 2, 4]}, minWireVersion=0, maxWireVersion=4, maxDocumentSize=16777216, roundTripTimeNanos=2308274, setName='farenda', canonicalAddress=localhost:7018, hosts=[localhost:7017, localhost:7018], passives=[], arbiters=[], primary='localhost:7017', tagSet=TagSet{[]}, electionId=null, setVersion=1}
In the next post we’ll explore MongoDB 3 API.
