Empty metadata while reading data from shape file or geojson file

[XiaWuSharve]

I want to load data from a shape file, the "metadata" column of the result dataframe contains all empty metadata like this:

+-----+--------+--------------------+--------+-----+
|point|polyline|             polygon|metadata|valid|
+-----+--------+--------------------+--------+-----+
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
| null|    null|magellan.Polygon@...|   Map()| true|
+-----+--------+--------------------+--------+-----+

The shapefile: http://www.arcgis.com/home/item.html?id=b07a9393ecbd430795a6f6218443dccc

My code:

val conf: SparkConf = new SparkConf().setMaster("local[*]").setAppName("SpatialQuery")
val spark: SparkSession = SparkSession.builder().config(conf).getOrCreate()

val path: String = "spatial-core/datas/"
val df: DataFrame = spark.read.format("magellan").load(path)
df.show()

Here is my project pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.atguigu.spatial</groupId>
    <artifactId>spatial-core</artifactId>
    <version>1.0</version>

    <repositories>
        <!-- list of other repositories -->
        <repository>
            <id>SparkPackagesRepo</id>
            <url>https://repos.spark-packages.org/</url>
        </repository>
    </repositories>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.11</artifactId>
            <version>2.2.0</version>
        </dependency>
        <!-- list of dependencies -->
        <dependency>
            <groupId>harsha2010</groupId>
            <artifactId>magellan</artifactId>
            <version>1.0.5-s_2.11</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-sql_2.11</artifactId>
            <version>2.2.0</version>
        </dependency>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>2.11.8</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.2.2</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>3.1.0</version>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Is there any ways to load the metadata into dataframes? Thanks a lot.