变量“接口”可能尚未初始化

Question

我试图建立一个Morphia和Spring应用程序中使用的模板从另一个项目，我收到以下错误Variable 'assetRepository' might not have been initialized这AssetRepository是一个接口package code.nithin.repository;import code.nithin.entity.Asset;import org.mongodb.morphia.Key;public interface AssetRepository {    public Key<Asset> save(Asset asset);}并且AssetController是package code.nithin.controllers;import code.nithin.entity.Asset;import code.nithin.repository.AssetRepository;import org.mongodb.morphia.Key;public class AssetController{    public String saveAsset(String URL){        AssetRepository assetRepository;        Asset test = new Asset(1, System.currentTimeMillis(),"https://example.com");        String returnString = assetRepository.save(test).getId();    }}该实体是package code.nithin.entity;import org.bson.types.ObjectId;import org.mongodb.morphia.annotations.Entity;import org.mongodb.morphia.annotations.Id;import lombok.Data;import lombok.NoArgsConstructor;@Data@Entity("asset")@NoArgsConstructorpublic class Asset {    @Id    public ObjectId _id;    public int version;    public long timestamp;    public String URL;    public Asset(){}    public Asset(int version, long timestamp, String URL) {        this.version = version;        this.timestamp = timestamp;        this.URL = URL;    }    public ObjectId get_id() {        return _id;    }    public void set_id(ObjectId _id) {        this._id = _id;    }    public int getVersion() {        return version;    }    public void setVersion(int version) {        this.version = version;    }    public long getTimestamp() {        return timestamp;    }    public void setTimestamp(long timestamp) {        this.timestamp = timestamp;    }    public String getURL() {        return URL;    }    public void setURL(String URL) {        this.URL = URL;    }}我所指的项目不会引发任何错误。