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https://github.com/firebase/geofire-java

GeoFire for Java - Realtime location queries with Firebase
https://github.com/firebase/geofire-java

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GeoFire for Java - Realtime location queries with Firebase

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# GeoFire for Java — Realtime location queries with Firebase



[![Build Status](https://travis-ci.org/firebase/geofire-java.svg?branch=master)](https://travis-ci.org/firebase/geofire-java?branch=master)



**Note** This library is only for _server side_ Java development. If you want to use GeoFire

in your Android application, see [`geofire-android`](https://github.com/firebase/geofire-android).



GeoFire is an open-source library for Java that allows you to store and query a

set of keys based on their geographic location.



At its heart, GeoFire simply stores locations with string keys. Its main

benefit however, is the possibility of querying keys within a given geographic

area - all in realtime.



GeoFire uses the [Firebase Realtime Database](https://firebase.google.com/products/realtime-database/) database for

data storage, allowing query results to be updated in realtime as they change.

GeoFire *selectively loads only the data near certain locations, keeping your

applications light and responsive*, even with extremely large datasets.



GeoFire clients are also available for other languages:



  * [Android](https://github.com/firebase/geofire-android)

  * [Objective-C (iOS)](https://github.com/firebase/geofire-objc)

  * [JavaScript (Web)](https://github.com/firebase/geofire-js)



### Integrating GeoFire with your data



GeoFire is designed as a lightweight add-on to the Firebase Realtime Database. However, to keep things

simple, GeoFire stores data in its own format and its own location within

your Firebase database. This allows your existing data format and security rules to

remain unchanged and for you to add GeoFire as an easy solution for geo queries

without modifying your existing data.



### Example Usage



Assume you are building an app to rate bars and you store all information for a

bar, e.g. name, business hours and price range, at `/bars/`. Later, you

want to add the possibility for users to search for bars in their vicinity. This

is where GeoFire comes in. You can store the location for each bar using

GeoFire, using the bar IDs as GeoFire keys. GeoFire then allows you to easily

query which bar IDs (the keys) are nearby. To display any additional information

about the bars, you can load the information for each bar returned by the query

at `/bars/`.



## Upgrading GeoFire



### Upgrading from GeoFire 1.x to 2.x



GeoFire 2.x is based on the new 3.x release of [Firebase](https://firebase.google.com).



### Upgrading from GeoFire 1.0.x to 1.1.x



With the release of GeoFire for Android/Java 1.1.0, this library now uses [the new query

functionality found in Firebase 2.0.0](https://www.firebase.com/blog/2014-11-04-firebase-realtime-queries.html).

As a result, you will need to upgrade to Firebase 2.x.x and add a new `.indexOn` rule to your

Security and Firebase Rules to get the best performance. You can view [the updated rules

here](https://github.com/firebase/geofire-js/blob/master/examples/securityRules/rules.json)

and [read our docs for more information about indexing your data](https://www.firebase.com/docs/security/guide/indexing-data.html).



## Including GeoFire in your Java project



In order to use GeoFire in your project, you need to [add the Firebase Admin

SDK](https://firebase.google.com/docs/admin/setup). After that you can include GeoFire with one of the choices below.



### Gradle



Add a dependency for GeoFire to your `build.gradle` file:



```groovy

dependencies {

    implementation 'com.firebase:geofire-java:3.0.0'

}



```



### Maven



Add a dependency for GeoFire to your `pom.xml` file:



```xml



  com.firebase

  geofire-java

  3.0.0



```



## Usage



### GeoFire



A `GeoFire` object is used to read and write geo location data to your Firebase

database and to create queries. To create a new `GeoFire` instance you need to attach it to a Firebase database

reference.



```java

DatabaseReference ref = FirebaseDatabase.getInstance().getReference("path/to/geofire");

GeoFire geoFire = new GeoFire(ref);

```



Note that you can point your reference to anywhere in your Firebase database, but don't

forget to [setup security rules for

GeoFire](https://github.com/firebase/geofire-js/blob/master/examples/securityRules).



#### Setting location data



In GeoFire you can set and query locations by string keys. To set a location for

a key simply call the `setLocation` method. The method is passed a key

as a string and the location as a `GeoLocation` object containing the location's latitude and longitude:



```java

geoFire.setLocation("firebase-hq", new GeoLocation(37.7853889, -122.4056973));

```



To check if a write was successfully saved on the server, you can add a

`GeoFire.CompletionListener` to the `setLocation` call:



```java

geoFire.setLocation("firebase-hq", new GeoLocation(37.7853889, -122.4056973), new GeoFire.CompletionListener() {

    @Override

    public void onComplete(String key, FirebaseError error) {

        if (error != null) {

            System.err.println("There was an error saving the location to GeoFire: " + error);

        } else {

            System.out.println("Location saved on server successfully!");

        }

    }

});

```



To remove a location and delete it from the database simply pass the location's key to `removeLocation`:



```java

geoFire.removeLocation("firebase-hq");

```



#### Retrieving a location



Retrieving a location for a single key in GeoFire happens with callbacks:



```java

geoFire.getLocation("firebase-hq", new LocationCallback() {

    @Override

    public void onLocationResult(String key, GeoLocation location) {

        if (location != null) {

            System.out.println(String.format("The location for key %s is [%f,%f]", key, location.latitude, location.longitude));

        } else {

            System.out.println(String.format("There is no location for key %s in GeoFire", key));

        }

    }



    @Override

    public void onCancelled(DatabaseError databaseError) {

        System.err.println("There was an error getting the GeoFire location: " + databaseError);

    }

});

```



### Geo Queries



GeoFire allows you to query all keys within a geographic area using `GeoQuery`

objects. As the locations for keys change, the query is updated in realtime and fires events

letting you know if any relevant keys have moved. `GeoQuery` parameters can be updated

later to change the size and center of the queried area.



```java

// creates a new query around [37.7832, -122.4056] with a radius of 0.6 kilometers

GeoQuery geoQuery = geoFire.queryAtLocation(new GeoLocation(37.7832, -122.4056), 0.6);

```



#### Receiving events for geo queries



##### Key Events



There are five kinds of "key" events that can occur with a geo query:



1. **Key Entered**: The location of a key now matches the query criteria.

2. **Key Exited**: The location of a key no longer matches the query criteria.

3. **Key Moved**: The location of a key changed but the location still matches the query criteria.

4. **Query Ready**: All current data has been loaded from the server and all

   initial events have been fired.

5. **Query Error**: There was an error while performing this query, e.g. a

   violation of security rules.



Key entered events will be fired for all keys initially matching the query as well as any time

afterwards that a key enters the query. Key moved and key exited events are guaranteed to be

preceded by a key entered event.



Sometimes you want to know when the data for all the initial keys has been

loaded from the server and the corresponding events for those keys have been

fired. For example, you may want to hide a loading animation after your data has

fully loaded. This is what the "ready" event is used for.



Note that locations might change while initially loading the data and key moved and key

exited events might therefore still occur before the ready event is fired.



When the query criteria is updated, the existing locations are re-queried and the

ready event is fired again once all events for the updated query have been

fired. This includes key exited events for keys that no longer match the query.



To listen for events you must add a `GeoQueryEventListener` to the `GeoQuery`:



```java

geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {

    @Override

    public void onKeyEntered(String key, GeoLocation location) {

        System.out.println(String.format("Key %s entered the search area at [%f,%f]", key, location.latitude, location.longitude));

    }



    @Override

    public void onKeyExited(String key) {

        System.out.println(String.format("Key %s is no longer in the search area", key));

    }



    @Override

    public void onKeyMoved(String key, GeoLocation location) {

        System.out.println(String.format("Key %s moved within the search area to [%f,%f]", key, location.latitude, location.longitude));

    }



    @Override

    public void onGeoQueryReady() {

        System.out.println("All initial data has been loaded and events have been fired!");

    }



    @Override

    public void onGeoQueryError(DatabaseError error) {

        System.err.println("There was an error with this query: " + error);

    }

});

```



You can call either `removeGeoQueryEventListener` to remove a

single event listener or `removeAllListeners` to remove all event listeners

for a `GeoQuery`.



##### Data Events



If you are storing model data and geo data in the same database location, you may

want access to the `DataSnapshot` as part of geo events. In this case, use a

`GeoQueryDataEventListener` rather than a key listener.



These "data event" listeners have all of the same events as the key listeners with

one additional event type:



  6. **Data Changed**: the underlying `DataSnapshot` has changed. Every "data moved"

     event is followed by a data changed event but you can also get change events without

     a move if the data changed does not affect the location.



Adding a data event listener is similar to adding a key event listener:



```java

geoQuery.addGeoQueryDataEventListener(new GeoQueryDataEventListener() {



  @Override

  public void onDataEntered(DataSnapshot dataSnapshot, GeoLocation location) {

    // ...

  }



  @Override

  public void onDataExited(DataSnapshot dataSnapshot) {

    // ...

  }



  @Override

  public void onDataMoved(DataSnapshot dataSnapshot, GeoLocation location) {

    // ...

  }



  @Override

  public void onDataChanged(DataSnapshot dataSnapshot, GeoLocation location) {

    // ...

  }



  @Override

  public void onGeoQueryReady() {

    // ...

  }



  @Override

  public void onGeoQueryError(DatabaseError error) {

    // ...

  }



});



```



#### Updating the query criteria



The `GeoQuery` search area can be changed with `setCenter` and `setRadius`. Key

exited and key entered events will be fired for keys moving in and out of

the old and new search area, respectively. No key moved events will be

fired; however, key moved events might occur independently.



Updating the search area can be helpful in cases such as when you need to update

the query to the new visible map area after a user scrolls.



## Deployment



- In your local environment set `$BINTRAY_USER` and `$BINTRAY_KEY` to your

  Bintray.com username and API key.

- Checkout and update the master branch.

- Run `./release.sh` to build and deploy.

- On bintray.com, publish the draft artifacts.

```