CODEWITHSUNDEEP
javamongodb
Harshil Shah
Harshil Shah

Reputation: 359

MongoDB get data into java object

I am quite new to MongoDb. i use a find and get the result in JSON format. 

{"Name": "Harshil", "Age":20}

so what i need is parse this in java and get values in the variables.

String name should contain Harshil
int age should contain 20

is there a way to store these details in JAVA object?

Upvotes: 0

Views: 28485

Answers (9)

arnav
arnav

Reputation: 61

Try Using this function to convert JSON returned by mongodb to your custom java object list.

MongoClient mongodb = new MongoClient("localhost", 27017);
DB db = mongodb.getDB("customData-database");
DBCursor customDataCollection = db.getCollection("customDataList").find();
List<CustomJavaObject>  myCustomDataList = null; // this list will hold your custom data
JSON json = new JSON();
ObjectMapper objectMapper = new ObjectMapper();
try {
  //this is where deserialiazation(conversion) takes place
  myCustomDataList = objectMapper.readValue(json.serialize(customDataCollection),
      new TypeReference<List<Restaurant>>() {
      });
} catch (IOException e) {
  e.printStackTrace();
}

CustomJavaObject:

public class CustomJavaObject{
//your json fields go here
String field1, field2;
int num;
ArrayList<String> attributes;

//....write relevantgetter and setter methods
}

sample json:

 {
"field1": "Hsr Layout",
"field2": "www.google.com",
"num": 20,
"attributes": [
  "Benagaluru",
  "Residential"
]
},
{
"field1": "BTM Layout",
"field2": "www.youtube.com",
"num": 10,
"attributes": [
  "Bangalore",
  "Industrial"
]
}

Upvotes: 0

Akshay Bhardwaj
Akshay Bhardwaj

Reputation: 21

As we don't want to use the deprecated methods so, you can use the following code to do so:

MongoClient mongo = new MongoClient( "localhost" , 27017 );
MongoDatabase database = mongo.getDatabase("your_db_name");

MongoCollection<Document> collection = database.getCollection("your_collection_name");

FindIterable<Document> iterDoc = collection.find();
MongoCursor<Document> dbc = iterDoc.iterator();

while(dbc.hasNext()){
try {
         JsonParser jsonParser = new JsonFactory().createParser(dbc.next().toJson());
         ObjectMapper mapper = new ObjectMapper();

         Person person = mapper.readValue(jsonParser, Person.class);
         String name = person.get("Name");
         String age = person.get("Age");

} catch (Exception e){
    e.printStackTrace();
}

JsonFactory, JsonParser,etc. are being used from Jackson to de-serialize the Document to the related Entity object.

Upvotes: 1

Thomas Rokicki
Thomas Rokicki

Reputation: 654

Newer Way [Since getDB() is Deprecated]

Since the original answer was posted the DBObject and corresponding method client.getDB have been deprecated. For anyone who may be looking for a solution since the new update I have done my best to translate.

MongoClient client = new MongoClient("localhost",27017); //Location by Default
MongoDatabase database = client.getDatabase("YOUR_DATABASE_NAME");
MongoCollection<Document> collection = database.getCollection("YOUR_COLLECTION_NAME");

Once connected to the document there are numerous familiar methods of getting data as a Java Object. Assuming you plan to have multiple documents that contain a persons name and their age I suggest collecting all the documents (which you can visualize as rows containing a name and age) in an ArrayList then you can simply pick through the documents in the ArrayList to convert them to java objects as so:

List<Document> documents = (List<Document>) collection.find().into(new ArrayList<Document>());
for (Document document : documents) {
     Document person = documents.get(document);
     String name = person.get("Name");
     String age = person.get("Age");
}

Honestly the for loop is not a pretty way of doing it but I wanted to help the community struggling with deprecation.

Upvotes: 0

Ashutosh Srivastav
Ashutosh Srivastav

Reputation: 669

I would prefer using the new Mongodb Java API. It's very clean and clear. 

public MyEntity findMyEntityById(long entityId) {

    List<Bson> queryFilters = new ArrayList<>();
    queryFilters.add(Filters.eq("_id", entityId));
    Bson searchFilter = Filters.and(queryFilters);

    List<Bson> returnFilters = new ArrayList<>();
    returnFilters.add(Filters.eq("name", 1));

    Bson returnFilter = Filters.and(returnFilters);

    Document doc = getMongoCollection().find(searchFilter).projection(returnFilter).first();

    JsonParser jsonParser = new JsonFactory().createParser(doc.toJson());
    ObjectMapper mapper = new ObjectMapper();

    MyEntity myEntity = mapper.readValue(jsonParser, MyEntity.class);

    return myEntity;
}

Details at http://ashutosh-srivastav-mongodb.blogspot.in/2017/09/mongodb-fetch-operation-using-java-api.html

Upvotes: 0

Tom
Tom

Reputation: 44881

There are many ways and tools, one of which is gson 

class Person {
    private String name;
    private int age;
    public Person() {
        // no-args constructor
    }
}

Gson gson = new Gson();
Person person = gson.fromJson(json, Person.class);

And I'd feel lax if I didn't add this link too.

Upvotes: 3

myildirim
myildirim

Reputation: 2438

Here is how to connect to the your MongoDB:

MongoClient client = new MongoClient("localhost",27017); //with default server and port adress
DB db = client.getDB( "your_db_name" );
DBCollection collection = db.getCollection("Your_Collection_Name");

After the connecting you can pull your data from the server.Below, i assume that your document has Name and Age field : 

DBObject dbo = collection.findOne();
String name = dbo.get("Name");
int age = dbo.get("Age");

Upvotes: 6

Yann Moisan
Yann Moisan

Reputation: 8281

You can just do it with the Java driver :

DBObject dbo = ...
String s = dbo.getString("Name")
int i = dbo.getInt("Age")

Using another framework on top of the Java driver should be considered I you have multiple objects to manage.

Upvotes: 1

Andrey Chaschev
Andrey Chaschev

Reputation: 16526

Have you considere Morphia?

@Entity
class Person{
   @Property("Name") Date name;
   @Property("Age") Date age;
}

Upvotes: 0

Mustafa Gen&#231;
Mustafa Gen&#231;

Reputation: 2579

Take a look at GSON library. It converts JSON to Java objects and vice-versa.

Upvotes: 4

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