Jacksonデータバインディングドキュメント は、Jacksonが "すべてのサポートされている型の配列"の逆シリアル化をサポートしていることを示していますが、正確な構文はわかりません。
単一のオブジェクトの場合、これを行います。
//json input
{
"id" : "junk",
"stuff" : "things"
}
//Java
MyClass instance = objectMapper.readValue(json, MyClass.class);
今、私はこれをしたい配列のために:
//json input
[{
"id" : "junk",
"stuff" : "things"
},
{
"id" : "spam",
"stuff" : "eggs"
}]
//Java
List<MyClass> entries = ?
誰もが魔法の行方不明のコマンドがあるかどうか知っていますか?もしそうでなければ、解決策は何ですか?
まずマッパーを作成します。
import com.fasterxml.jackson.databind.ObjectMapper;// in play 2.3
ObjectMapper mapper = new ObjectMapper();
配列として:
MyClass[] myObjects = mapper.readValue(json, MyClass[].class);
リストとして:
List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>(){});
リストタイプを指定する別の方法:
List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));
出身地 - Eugene Tskhovrebov
List<MyClass> myObjects = Arrays.asList(mapper.readValue(json, MyClass[].class))
この解決策は私には最良のようです
一般的な実装の場合
public static <T> List<T> parseJsonArray(String json,
Class<T> classOnWhichArrayIsDefined)
throws IOException, ClassNotFoundException {
ObjectMapper mapper = new ObjectMapper();
Class<T[]> arrayClass = (Class<T[]>) Class.forName("[L" + classOnWhichArrayIsDefined.getName() + ";");
T[] objects = mapper.readValue(json, arrayClass);
return Arrays.asList(objects);
}
最初にスレッドセーフなObjectReaderのインスタンスを作成します。
ObjectMapper objectMapper = new ObjectMapper();
ObjectReader objectReader = objectMapper.reader().forType(new TypeReference<List<MyClass>>(){});
それを使ってください。
List<MyClass> result = objectReader.readValue(inputStream);
try {
ObjectMapper mapper = new ObjectMapper();
JsonFactory f = new JsonFactory();
List<User> lstUser = null;
JsonParser jp = f.createJsonParser(new File("C:\\maven\\user.json"));
TypeReference<List<User>> tRef = new TypeReference<List<User>>() {};
lstUser = mapper.readValue(jp, tRef);
for (User user : lstUser) {
System.out.println(user.toString());
}
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
これはあなたのpojo(エンティティT)がなんであれ、json2objectまたはObject2jsonを変換するためのユーティリティです。
import Java.io.IOException;
import Java.io.StringWriter;
import Java.util.List;
import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
/**
*
* @author TIAGO.MEDICI
*
*/
public class JsonUtils {
public static boolean isJSONValid(String jsonInString) {
try {
final ObjectMapper mapper = new ObjectMapper();
mapper.readTree(jsonInString);
return true;
} catch (IOException e) {
return false;
}
}
public static String serializeAsJsonString(Object object) throws JsonGenerationException, JsonMappingException, IOException {
ObjectMapper objMapper = new ObjectMapper();
objMapper.enable(SerializationFeature.INDENT_OUTPUT);
objMapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
StringWriter sw = new StringWriter();
objMapper.writeValue(sw, object);
return sw.toString();
}
public static String serializeAsJsonString(Object object, boolean indent) throws JsonGenerationException, JsonMappingException, IOException {
ObjectMapper objMapper = new ObjectMapper();
if (indent == true) {
objMapper.enable(SerializationFeature.INDENT_OUTPUT);
objMapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
}
StringWriter stringWriter = new StringWriter();
objMapper.writeValue(stringWriter, object);
return stringWriter.toString();
}
public static <T> T jsonStringToObject(String content, Class<T> clazz) throws JsonParseException, JsonMappingException, IOException {
T obj = null;
ObjectMapper objMapper = new ObjectMapper();
obj = objMapper.readValue(content, clazz);
return obj;
}
@SuppressWarnings("rawtypes")
public static <T> T jsonStringToObjectArray(String content) throws JsonParseException, JsonMappingException, IOException {
T obj = null;
ObjectMapper mapper = new ObjectMapper();
obj = mapper.readValue(content, new TypeReference<List>() {
});
return obj;
}
public static <T> T jsonStringToObjectArray(String content, Class<T> clazz) throws JsonParseException, JsonMappingException, IOException {
T obj = null;
ObjectMapper mapper = new ObjectMapper();
mapper = new ObjectMapper().configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
obj = mapper.readValue(content, mapper.getTypeFactory().constructCollectionType(List.class, clazz));
return obj;
}