[英]Jackson: parse json to Map<String, Object> for given Map<String, Class<?>>
[英]Jackson JSON: Unmarshalling a Map<String,Object> of attributes back into its original class
我正在使用第三方庫(確切地說是Elasticsearch 2.3.3 ),該庫已經為我解析了給定的JSON結構成Map<String,Object>
實例,並且我想創建該類的實例。最初編組為JSON的對象:
MarshallableObject
→ marshalled_object.json
marshalled_object.json
→ Map<String,Object>
→ MarshallableObject
) 此外,這是一些示例代碼,說明了邏輯:
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Arrays;
import java.util.Map;
import java.util.stream.Stream;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.transport.InetSocketTransportAddress;
import org.elasticsearch.index.query.QueryBuilders;
import com.fasterxml.jackson.databind.ObjectMapper;
public final class AttrMapUnmarshallingTest {
/**
* This class was directly used in the process for creating JSON documents indexed by Elasticsearch
*/
public static final class MarshallableObject {
public String bar;
public String foo;
}
private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
public static void main(final String[] args) throws UnknownHostException {
try (final TransportClient client = TransportClient.builder().build().addTransportAddress(new InetSocketTransportAddress(InetAddress.getLoopbackAddress(), 9300))) {
final SearchResponse response = client.prepareSearch("news").setTypes("article")
.setQuery(QueryBuilders.matchQuery("text", "advertisement")).execute().actionGet();
final Stream<Map<String, Object>> attrMaps = Arrays.stream(response.getHits().getHits())
.map(hit -> hit.sourceAsMap());
final Stream<MarshallableObject> objs = attrMaps.map(attrMap -> {
// TODO: Find way of converting attr map into original class
// which was marshalled into JSON
// final MarshallableObject obj = OBJECT_MAPPER.read(attrMap);
});
}
}
}
我在SearchHit
類上做了一些閱讀,這是我認為可行的方法:
Stream<MarshallableObject> objs = Arrays.stream(response.getHits().getHits())
.filter(hit->hit.hasSource()) // For some reason source could be null.
.map(hit->
OBJECT_MAPPER.readValue(hit.sourceAsString(),
MarshallableObject.class));
注意:您需要將MarshallableObject
類聲明為static
才能使讀取工作。 顯然,無法從json字符串重構隱藏的ParentClass$this
引用。
祝好運。
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