How can I import data to Mongodb from Json file using java

Question

I am struggling with importing data into Mongodb from a Json file.
I can do the same in command line by using mongoimport command.

Answer 1

Had a similar "problem" myself and ended up using Jackson with POJO databinding, and Morphia.

While this sound a bit like cracking a nut with a sledgehammer, it is actually very easy to use, robust and quite performant and easy to maintain code wise.

Small caveat: You need to map your test_id field to MongoDB's _id if you want to reuse it.

Step 1: Create an annotated bean

You need to hint Jackson how to map the data from a JSON file to a POJO. I shortened the class a bit for the sake of readability:

@JsonRootName(value="person")
@Entity
public class Person {

  @JsonProperty(value="test_id")
  @Id
  Integer id;

  String name;

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

}

As for the embedded document Job, please have a look at the POJO data binding examples linked.

Step 2: Map the POJO and create a datastore

Somewhere during your application initialization, you need to map the annotated POJO. Since you already should have a MongoClient, I am going to reuse that ;)

Morphia morphia = new Morphia();
morphia.map(Person.class);

/* You can reuse this datastore */
Datastore datastore = morphia.createDatastore(mongoClient, "myDatabase");

/* 
 * Jackson's ObjectMapper, which is reusable, too,
 * does all the magic.
 */
ObjectMapper mapper = new ObjectMapper();

Do the actual importing

Now importing a given JSON file becomes as easy as

public Boolean importJson(Datastore ds, ObjectMapper mapper, String filename) {

    try {           
        JsonParser parser = new JsonFactory().createParser(new FileReader(filename));
        Iterator<Person> it = mapper.readValues(parser, Person.class);

        while(it.hasNext()) {
            ds.save(it.next());
        }

        return Boolean.TRUE;

    } catch (JsonParseException e) {
        /* Json was invalid, deal with it here */
    } catch (JsonMappingException e) {
        /* Jackson was not able to map
         * the JSON values to the bean properties,
         * possibly because of
         * insufficient mapping information.
         */
    } catch (IOException e) {
        /* Most likely, the file was not readable
         * Should be rather thrown, but was
         * cought for the sake of showing what can happen
         */
    }

    return Boolean.FALSE;
}

With a bit of refatcoring, this can be converted in a generic importer for Jackson annotated beans. Obviously, I left out some special cases, but this would out of the scope of this answer.