MongoDB is a very popular NoSQL database today. This article introduces how to use MongoDB's Java driver to operate MongoDB.
If the Java project that needs to operate MongoDB is a Maven project, you can add the following configuration to the dependencies.
<dependencies> <dependency> <groupId>org.mongodb</groupId> <artifactId>mongo-java-driver</artifactId> <version>2.13.2</version> </dependency> </dependencies>
Or use it by directly downloading the jar package, download address: mongo-java-driver-2.13.2.jar.
For detailed information on how to introduce the MongoDB jar package, please refer to the official documentation.
You can use MongoClient
to connect to MongoDB. The usage of MongoClient
is as follows:
MongoClient mongoClient = new MongoClient("localhost", 27017); DB db = mongoClient.getDB("mydb");
above The code connects to the MongoDB service on localhost:27017 and specifies to use the mydb database. After connecting, you can perform further operations on this database.
It should be pointed out that MongoClient
is thread safe and can share the same MongoClient
in a multi-process environment. Generally speaking, in an application, you only need to generate a global MongoClient
instance, and then use this instance in other places in the program.
You can use multiple methods to authenticate connections. Two methods are introduced below.
method of the MongoCredentialMongoCredential
class can specify the authentication user name, password, and database used, and Returns a MongoCredential
object. The method is declared as follows:
static MongoCredential createCredential(String userName, String database, char[] password)
For example,
MongoCredential credential = MongoCredential.createCredential("user", "mydb", "password".toCharArray();
The above creates a MongoCredential
object with the user name user, password password, and database mydb.
The generated MongoCredential
object will be used as the parameter of the
MongoClient constructor function. Since the MongoClient
constructor is of <a href="http://www.php.cn/wiki/1059.html" target="_blank">List</a>c8197b9f60b4d3b2d4d80193ff32d39a
type, it needs to be constructed into a List first and then passed. A complete authentication example is as follows:
MongoCredential credential = MongoCredential.createCredential("user", "mydb", "password".toCharArray()); ServerAddress serverAddress = new ServerAddress("localhost", 27017); MongoClient mongoClient = new MongoClient(serverAddress, Arrays.asList(credential)); DB db = mongoClient.getDB("mydb");
You can also use MongoClientURI
to complete MongoDB authentication, which represents a URI object. The constructor of MongoClientURI
accepts a string of type String. The format of this string is as follows:
mongodb://[username:password@]host1[:port1][,host2[:port2],…[,hostN[:portN]]][/[database][?options]]
The generated MongoClientURI
object is used as MongoClient
The parameters of the constructor, the complete authentication example is as follows:
String sURI = String.format("mongodb://%s:%s@%s:%d/%s", "user", "password", "localhost", 27017, "mydb"); MongoClientURI uri = new MongoClientURI(sURI); MongoClient mongoClient = new MongoClient(uri); DB db = mongoClient.getDB("mydb");
DBCollection coll = db.getCollection("mycol");
Then you can operate on the specified collection, for example, insert, Delete , search, update documents, etc.
For example, a document is represented by Json as follows,
{ “name”: “mongo”, “info”: { “ver”: “3.0” } }
now needs to be inserted into the collection mycol. To insert into a collection, a document can be constructed using BasicDB<a href="http://www.php.cn/wiki/60.html" target="_blank">Object</a>
.
BasicDBObject doc = new BasicDBObject("name", "mongo").append("info", new BasicDBObject("ver", "3.0")); coll.insert(doc);
You can find a document that meets the conditions through findOne
. For example, for the mycol collection above, executing the following command:
DBObject myDoc = coll.findOne(); System.out.println(myDoc);
will output the first document in the mycol collection. You can also find a document that meets the search conditions by specifying the search parameters of findOne
.
find
is used to find documents that meet the conditions. It returns a DBCursor
object, through Traverse the DBCursor
object to obtain all documents that meet the search conditions.
For explanation and testing, we first insert a batch of documents in the following format
{ “i”: value }
for (int i=0; i < 100; i++) { coll.insert(new BasicDBObject("i", i)); }
find
Usage examples are as follows:
DBCursor cursor = coll.find(); try { while(cursor.hasNext()) { System.out.println(cursor.next()); } } finally { cursor.close(); }
will Output all documents in the mycol collection.
You can also specify the search conditions, for example:
BasicDBObject query = new BasicDBObject("i", 71); DBCursor cursor = coll.find(query); try { while(cursor.hasNext()) { System.out.println(cursor.next()); } } finally { cursor.close(); }
For the case where the search conditions include $operator, for example, the following mongo shell command:
db.coll.find({i: {$gte: 50}});
You can use DBObject
to generate search conditions,
// find all where i >= 50 BasicDBObject query = new BasicDBObject("i", new BasicDBObject("$gte", 50)); DBCursor cursor = coll.find(query); try { while (cursor.hasNext()) { System.out.println(cursor.next()); } } finally { cursor.close(); }
BasicDBObject query = new BasicDBObject("i", 70); BasicDBObject up = new BasicDBObject("$set", new BasicDBObject("i", 100)); coll.update(query, up);
The above statement updates the document with i=70 to the value of i equal to 100.
与我们常用的更新文档的mongo语句一样,DBCollection
还包含了save
,findAndModify
等更新文档的方法,其使用方法在此不再赘述,可以参考API说明文档即可。
可以通过生成一个DBObject
对象来删除指定的文档,例如:
BasicDBObject query = new BasicDBObject("i", 71); coll.remove(query);
上面的语句删除i为71的文档。
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