AWS使用JAVA从s3对象创建新文件获取错误

我有一个形状文件,我需要从我的java代码中读取形状文件.我使用下面的代码来读取形状文件.

public class App {
    public static void main(String[] args) {
        File file = new File("C:\\Test\\sample.shp");
        Map<String, Object> map = new HashMap<>();//
        try {
            map.put("url", URLs.fileToUrl(file));
            DataStore dataStore = DataStoreFinder.getDataStore(map);
            String typeName = dataStore.getTypeNames()[0];
            SimpleFeatureSource source = dataStore.getFeatureSource(typeName);
            SimpleFeatureCollection collection = source.getFeatures();

            try (FeatureIterator<SimpleFeature> features = collection.features()) {
                while (features.hasNext()) {
                    SimpleFeature feature = features.next();
                    SimpleFeatureType schema = feature.getFeatureType();
                    Class<?> geomType = schema.getGeometryDescriptor().getType().getBinding();

                    String type = "";
                    if (Polygon.class.isAssignableFrom(geomType) || MultiPolygon.class.isAssignableFrom(geomType)) {

                        MultiPolygon geom = (MultiPolygon) feature.getDefaultGeometry();
                        type = "Polygon";
                        if (geom.getNumGeometries() > 1) {
                            type = "MultiPolygon";
                        }
                    } else if (LineString.class.isAssignableFrom(geomType)
                            || MultiLineString.class.isAssignableFrom(geomType)) {
                    } else {

                    }
                    System.out.println(feature.getDefaultGeometryProperty().getValue().toString());

                }
            }
        } catch (Exception e) {
            // TODO: handle exception
        }

    }
}

我得到了所需的输出.但我的要求是写一个aws lambda函数来读取shape文件.为了这
1.我创建了一个s3事件的Lambda java项目.我在handleRequest中编写了相同的代码.我将java lambda项目作为lanbda函数上传并添加了一个触发器.当我将.shp文件上传到s3时,lmbda函数会自动调用.但我收到如下错误

java.lang.RuntimeException: java.io.FileNotFoundException: /sample.shp (No such file or directory)

我的s3存储桶里面有sample.shp文件.我通过以下链接.
How to write an S3 object to a file?

我得到了同样的错误.我试着改变我的代码,如下所示

  S3Object object = s3.getObject(new GetObjectRequest(bucket, key)); 
  InputStream objectData = object.getObjectContent();
  map.put("url", objectData );

代替

File file = new File("C:\\Test\\sample.shp"); 
 map.put("url", URLs.fileToUrl(file));

:-(现在我收到如下错误

java.lang.NullPointerException

我也试过下面的代码

DataStore dataStore = DataStoreFinder.getDataStore(objectData);

代替

DataStore dataStore = DataStoreFinder.getDataStore(map);

错误如下

java.lang.ClassCastException:
com.amazonaws.services.s3.model.S3ObjectInputStream cannot be cast to
java.util.Map

此外,我尝试将键直接添加到地图,也作为DataStore对象.一切都错了..:-(

有没有人可以帮助我?
如果有人能为我做这件事会非常有帮助…

最佳答案
geotools中的DataStoreFinder.getDataStore方法要求您提供包含键/值对的映射,其中键为“url”.与“url”键关联的值必须是文件URL,如“file://host/path/my.shp”.

您正在尝试将Java输入流插入到地图中.这不起作用,因为它不是文件URL.

geotools库不接受http / https URL(请参阅geotools代码herehere),因此您需要file:// URL.这意味着您需要将文件从S3下载到本地Lambda文件系统,然后提供指向该本地文件的file:// URL.要做到这一点,这里的Java代码应该工作:

// get the shape file from S3 to local filesystem
File localshp = new File("/tmp/download.shp");
s3.getObject(new GetObjectRequest(bucket, key), localshp);

// now store file:// URL in the map
map.put("url", localshp.getURI().getURL().toString());

如果geotools库已接受真实URL(不仅仅是file:// URL),那么您可以避免下载,只需为S3对象创建一个有时间限制的预签名URL,并将该URL放入地图中.

这是一个如何做到这一点的例子:

// get current time and add one hour
java.util.Date expiration = new java.util.Date();
long msec = expiration.getTime();
msec += 1000 * 60 * 60;
expiration.setTime(msec);

// request pre-signed URL that will allow bearer to GET the object
GeneratePresignedUrlRequest gpur = new GeneratePresignedUrlRequest(bucket, key);
gpur.setMethod(HttpMethod.GET);
gpur.setExpiration(expiration);

// get URL that will expire in one hour
URL url = s3.generatePresignedUrl(gpur);

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