将JSON字符串中的值转换为对象。

huangapple
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英文:

Convert values from json string to object

问题

I have a JSON payload of the format, with each value a list with a single map element:

  1. {
  2.   "redundant_str_1": [
  3.     {
  4.       "attr_1": "val1",
  5.       "attr_2": "val2"
  6.     }
  7.   ],
  8.   "rendundant_str_2": [
  9.     {
  10.       "attr_1": "val4",
  11.       "attr_2": "val3"
  12.     }
  13.   ]
  14. }

Model is:

  1. public class MyObj {
  2.      private String attr_1;
  3.      private String attr_2;
  4. }

How can I map the above response to List<MyObj> by neglecting the keys and taking only elements from lists?

英文:

I have a JSON payload of the format, with each value a list with single map element:

  1. {
  2.   &quot;redundant_str_1&quot;: [
  3.     {
  4.       &quot;attr_1&quot;: &quot;val1&quot;,
  5.       &quot;attr_2&quot;: &quot;val2&quot;
  6.     }
  7.   ],
  8.   &quot;rendundant_str_2&quot;: [
  9.     {
  10.       &quot;attr_1&quot;: &quot;val4&quot;,
  11.       &quot;attr_2&quot;: &quot;val3&quot;
  12.     }
  13.   ]
  14. }

Model is:

  1. public class MyObj {
  3.      private String attr_1;
  4.      private String attr_2;
  5. }

How can I map above response to List&lt;MyObj&gt; by neglecting the keys and taking only element from lists?

答案1

得分: 1

以下是代码的翻译部分：

  1. String json = "{\"redundant_str_1\": [{\"attr_1\": \"val1\", \"attr_2\": \"val2\"}], \"rendundant_str_2\": [{\"attr_1\": \"val4\", \"attr_2\": \"val3\"}]}";
  2. ObjectMapper objectMapper = new ObjectMapper();
  3. List<MyObj> myObjList = new ArrayList<>();
  5. ObjectNode objectNode = (ObjectNode) objectMapper.readTree(json);
  6. for (Iterator<JsonNode> it = objectNode.elements(); it.hasNext(); ) {
  7.     ArrayNode arrayNode = (ArrayNode) it.next();
  8.     MyObj myObj = objectMapper.treeToValue(arrayNode.get(0), MyObj.class);
  9.     myObjList.add(myObj);
  10. }
  11. System.out.println("List : " + myObjList);

输出：

  1. List : [MyObj{attr_1='val1', attr_2='val2'}, MyObj{attr_1='val4', attr_2='val3'}]

希望这有助于您的需要！

英文: 
  1. String json = &quot;{\&quot;redundant_str_1\&quot;: [{\&quot;attr_1\&quot;: \&quot;val1\&quot;, \&quot;attr_2\&quot;: \&quot;val2\&quot;}], \&quot;rendundant_str_2\&quot;: [{\&quot;attr_1\&quot;: \&quot;val4\&quot;, \&quot;attr_2\&quot;: \&quot;val3\&quot;}]}&quot;;
  2. ObjectMapper objectMapper = new ObjectMapper();
  3. List&lt;MyObj&gt; myObjList = new ArrayList&lt;&gt;();
  5. ObjectNode objectNode = (ObjectNode) objectMapper.readTree(json);
  6.     for (Iterator&lt;JsonNode&gt; it = objectNode.elements(); it.hasNext(); ) {
  7.         ArrayNode arrayNode = (ArrayNode) it.next();
  8.         MyObj myObj = objectMapper.treeToValue(arrayNode.get(0),MyObj.class);
  9.         myObjList.add(myObj);
  10.     }
  11. System.out.println(&quot;List : &quot; + myObjList);

Output :

  1.    List : [MyObj{attr_1=&#39;val1&#39;, attr_2=&#39;val2&#39;}, MyObj{attr_1=&#39;val4&#39;,attr_2=&#39;val3&#39;}]

答案2

得分: 0

你可以使用Jackson（添加jackson-core和jackson-databind的依赖项）：

  1. String json = "["
  2.                 + "{\"attr_1\": \"val1\", \"attr_2\": \"val2\"}, "
  3.                 + "{\"attr_1\": \"val4\", \"attr_2\": \"val3\"}"
  4.                 + "]";
  5.     
  6. ObjectMapper mapper = new ObjectMapper();
  7. mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
  8. List<MyObj> list = Arrays.asList(mapper.readValue(json, MyObj[].class));

或者，如果在MyObj上添加字段的setter方法或使它们成为public，那么不需要以下行：

  1. mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
英文:

You can use Jackson (add dependencies to jackson-core and jackson-databind):

  1.   String json = &quot;[&quot; +
  2.                 &quot;{\&quot;attr_1\&quot;: \&quot;val1\&quot;, \&quot;attr_2\&quot;: \&quot;val2\&quot;}, &quot; +
  3.                 &quot;{\&quot;attr_1\&quot;: \&quot;val4\&quot;, \&quot;attr_2\&quot;: \&quot;val3\&quot;}&quot;
  4.                 + &quot;]&quot;;
  6.   ObjectMapper mapper = new ObjectMapper();
  7.   mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
  8.   List&lt;MyObj&gt; list = Arrays.asList(mapper.readValue(json, MyObj[].class));

Or, if you add to MyObj setters on fields or make them public there will be no needed the row:

  1. mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);

答案3

得分: 0

你的回应是 Map<String, List<MyObj>> 的格式。你可以将其反序列化为给定类型，然后将其转换为 List<MyObj>。

  1. import com.fasterxml.jackson.core.type.TypeReference;
  2. import com.fasterxml.jackson.databind.ObjectMapper;
  3. import com.fasterxml.jackson.databind.json.JsonMapper;
  4. import lombok.Data;
  5. import lombok.ToString;
  7. import java.io.File;
  8. import java.io.IOException;
  9. import java.util.Collection;
  10. import java.util.List;
  11. import java.util.Map;
  12. import java.util.stream.Collectors;
  14. public class MyObjApp {
  15.     public static void main(String[] args) throws IOException {
  16.         File jsonFile = new File("./resource/test.json").getAbsoluteFile();
  18.         ObjectMapper mapper = JsonMapper.builder().build();
  19.         TypeReference<Map<String, List<MyObj>>> respType = new TypeReference<Map<String, List<MyObj>>>() {};
  20.         Map<String, List<MyObj>> response = mapper.readValue(jsonFile, respType);
  22.         List<MyObj> myObjs = response.values().stream().flatMap(Collection::stream).collect(Collectors.toList());
  23.         System.out.println(myObjs);
  24.     }
  25. }
  27. @Data
  28. @ToString
  29. class MyObj {
  31.     private String attr_1;
  32.     private String attr_2;
  33. }

以上代码会打印出：

  1. [MyObj(attr_1=val1, attr_2=val2), MyObj(attr_1=val4, attr_2=val3)]
英文:

Your response is of form Map&lt;String, List&lt;MyObj&gt;&gt;. You can deserialise it to given type and after this convert to a List&lt;MyObj&gt;.

  1. import com.fasterxml.jackson.core.type.TypeReference;
  2. import com.fasterxml.jackson.databind.ObjectMapper;
  3. import com.fasterxml.jackson.databind.json.JsonMapper;
  4. import lombok.Data;
  5. import lombok.ToString;
  7. import java.io.File;
  8. import java.io.IOException;
  9. import java.util.Collection;
  10. import java.util.List;
  11. import java.util.Map;
  12. import java.util.stream.Collectors;
  14. public class MyObjApp {
  15. 	public static void main(String[] args) throws IOException {
  16. 		File jsonFile = new File(&quot;./resource/test.json&quot;).getAbsoluteFile();
  18. 		ObjectMapper mapper = JsonMapper.builder().build();
  19. 		TypeReference&lt;Map&lt;String, List&lt;MyObj&gt;&gt;&gt; respType = new TypeReference&lt;Map&lt;String, List&lt;MyObj&gt;&gt;&gt;() {};
  20. 		Map&lt;String, List&lt;MyObj&gt;&gt; response = mapper.readValue(jsonFile, respType);
  22. 		List&lt;MyObj&gt; myObjs = response.values().stream().flatMap(Collection::stream).collect(Collectors.toList());
  23. 		System.out.println(myObjs);
  24. 	}
  25. }
  27. @Data
  28. @ToString
  29. class MyObj {
  31. 	private String attr_1;
  32. 	private String attr_2;
  33. }

Above code prints:

  1. [MyObj(attr_1=val1, attr_2=val2), MyObj(attr_1=val4, attr_2=val3)]

huangapple
  • 本文由 发表于 2020年7月28日 19:42:26
  • 转载请务必保留本文链接：https://go.coder-hub.com/63133322.html
  • deserialization
  • jackson
  • java
  • json
  • json-deserialization
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