Geometry from json (#770)

* Update java level to 1.8

* [geojson] Add static method to load Geometry form json string

Author: ivovandongen

build.gradle

@@ -49,8 +49,8 @@ subprojects {
     }
   }
 
-  sourceCompatibility = "1.7"
-  targetCompatibility = "1.7"
+  sourceCompatibility = "1.8"
+  targetCompatibility = "1.8"
 
   dependencies {
 

services-geojson/src/main/java/com/mapbox/geojson/Geometry.java

@@ -1,5 +1,12 @@
 package com.mapbox.geojson;
 
+import android.support.annotation.NonNull;
+
+import com.google.gson.GsonBuilder;
+import com.mapbox.geojson.gson.GeoJsonAdapterFactory;
+import com.mapbox.geojson.gson.GeometryDeserializer;
+import com.mapbox.geojson.gson.PointDeserializer;
+
 /**
  * Each of the six geometries and {@link GeometryCollection}
  * which make up GeoJson implement this interface.
@@ -8,4 +15,20 @@
  */
 public interface Geometry extends GeoJson {
 
+  /**
+   * Create a new instance of this class by passing in a formatted valid JSON String.
+   *
+   * @param json a formatted valid JSON string defining a GeoJson Geometry
+   * @return a new instance of this class defined by the values passed inside this static factory
+   *   method
+   * @since 3.0.0
+   */
+  static Geometry fromJson(@NonNull String json) {
+    GsonBuilder gson = new GsonBuilder();
+    gson.registerTypeAdapterFactory(GeoJsonAdapterFactory.create());
+    gson.registerTypeAdapter(Point.class, new PointDeserializer());
+    gson.registerTypeAdapter(Geometry.class, new GeometryDeserializer());
+    return gson.create().fromJson(json, Geometry.class);
+  }
+
 }

services-geojson/src/test/java/com/mapbox/geojson/GeometryTest.java

@@ -0,0 +1,21 @@
+package com.mapbox.geojson;
+
+import com.mapbox.core.TestUtils;
+
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static org.junit.Assert.assertEquals;
+
+public class GeometryTest extends TestUtils {
+
+  private static final String SAMPLE_GEOMETRY_COLLECTION = "sample-geometrycollection.json";
+
+  @Test
+  public void fromJson() throws IOException {
+    final String json = loadJsonFixture(SAMPLE_GEOMETRY_COLLECTION);
+    Geometry geo = Geometry.fromJson(json);
+    assertEquals(geo.type(), "GeometryCollection");
+  }
+}