大きなJSONファイルを解析するためのJavaメソッドの作成方法

Question

JSON file text.jsonの内容をJacksonライブラリを使用して解析しようとしています。

私が望むのは、すべてのキーと値を取得するためのJavaメソッドを作成することですが、これまでのコードでは、JSONファイルの最初のキーと最初の値だけを取得しています。

私は自分のJavaクラスには、次のされていることを確認するためにガイダンスとして使用されるコードスニペット：

public void parse(String json) { 
    JsonFactory factory = new JsonFactory(); 

    ObjectMapper mapper = new ObjectMapper(factory); 
    JsonNode rootNode = mapper.readTree(json); 

    Iterator<Map.Entry<String,JsonNode>> fieldsIterator = rootNode.fields(); 
    while (fieldsIterator.hasNext()) { 

     Map.Entry<String,JsonNode> field = fieldsIterator.next(); 
     System.out.println("Key: " + field.getKey() + "\tValue:" + field.getValue()); 
    } 
} 

そして、私が作成した私のJavaクラスを以下に示します。

import java.io.File; 
import java.io.IOException; 
import java.util.Iterator; 
import java.util.Map; 

import org.codehaus.jackson.JsonFactory; 
import org.codehaus.jackson.JsonGenerationException; 
import org.codehaus.jackson.JsonNode; 
import org.codehaus.jackson.JsonParser; 
import org.codehaus.jackson.map.JsonMappingException; 
import org.codehaus.jackson.map.ObjectMapper; 

public class JacksonStreamExample { 
    public static void main(String[] args) { 
     try { 
      //Create a JsonFactory instance 
      JsonFactory factory = new JsonFactory(); 

      //Create a JsonParser instance to read from file c:\\text.json 
      JsonParser jParser = factory.createJsonParser(new File("c:\\text.json")); 

      /*Create an ObjectMapper instance to provide a pointer 
      * to root node of the tree after reading the JSON 
      */ 
      ObjectMapper mapper = new ObjectMapper(factory); 

      //Create tree from JSON 
      JsonNode rootNode = mapper.readTree(jParser); 

      Iterator<Map.Entry<String,JsonNode>> fieldsIterator = rootNode.getFields(); 
      while (fieldsIterator.hasNext()) { 
       Map.Entry<String,JsonNode> field = fieldsIterator.next(); 
       System.out.println("Key: " + field.getKey() + "\tValue:" + field.getValue()); 
      } 

      jParser.close(); 

     } catch (JsonGenerationException e) { 
      e.printStackTrace(); 
     } catch (JsonMappingException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
    } 
} 

私のEclipseの出力がある

1組（キー値）しか作成しない次の例は、

Key: cells Value:[{"type":"basic.Circle","size":{"width":90,"height":54},"position":{"x":-80,"y":200},"angle":0,"id":"cae4c219-c2cd-4a4b-b50c-0f269963ca24","embeds":"","z":1,"wi_name":"START","wi_displayName":"START","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"circle":{"fill":"#000000","width":50,"height":30,"stroke-width":1,"stroke-dasharray":"0"},"text":{"font-size":10,"text":"START","fill":"#ffffff","font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"basic.Circle","size":{"width":90,"height":54},"position":{"x":210,"y":200},"angle":0,"id":"d23133e0-e516-4f72-8127-292545d3d479","embeds":"","z":2,"wi_name":"END","wi_displayName":"END","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"circle":{"fill":"#000000","width":50,"height":30,"stroke-width":1,"stroke-dasharray":"0"},"text":{"font-size":10,"text":"END","fill":"#ffffff","font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"basic.Rect","position":{"x":-80,"y":370},"size":{"width":90,"height":54},"angle":0,"id":"a53898a5-c018-45c4-bd3f-4ea4d69f58ed","embeds":"","z":3,"wi_name":"ACTIVITY_1","wi_displayName":"ACTIVITY 1","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"rect":{"width":50,"height":30,"rx":2,"ry":2,"stroke-width":1,"stroke-dasharray":"0"},"text":{"text":"Activity","font-size":10,"font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"basic.Rect","position":{"x":220,"y":370},"size":{"width":90,"height":54},"angle":0,"id":"e2bd21f2-508d-44b9-9f68-e374d4fa87ea","embeds":"","z":4,"wi_name":"ACTIVITY_2","wi_displayName":"ACTIVITY 2","wi_description":"","wi_join":"<None>","wi_split":"<None>","wi_performingRole":"<None>","wi_expected_activity_time":null,"wi_expected_user_time":null,"wi_maximum_activity_time":null,"wi_initial_delay":null,"wi_time_unit":"Seconds","wi_required_transitions_for_AND_JOIN":null,"wi_custom_page":"","attrs":{"rect":{"width":50,"height":30,"rx":2,"ry":2,"stroke-width":1,"stroke-dasharray":"0"},"text":{"text":"Workitem","font-size":10,"font-family":"Arial","stroke":"#000000","stroke-width":0,"font-weight":400}}},{"type":"link","source":{"id":"cae4c219-c2cd-4a4b-b50c-0f269963ca24"},"target":{"id":"d23133e0-e516-4f72-8127-292545d3d479"},"router":{"name":"manhattan"},"labels":[{"position":0.5,"attrs":{"text":{"text":"Name"}}}],"id":"60ee7ff7-3a3b-487d-b581-49027e7bebe4","embeds":"","z":5,"attrs":{".marker-source":{"d":"M 10 0 L 0 5 L 10 10 z","transform":"scale(0.001)"},".marker-target":{"d":"M 10 0 L 0 5 L 10 10 z"},".connection":{"stroke":"black"}}},{"type":"link","source":{"id":"a53898a5-c018-45c4-bd3f-4ea4d69f58ed"},"target":{"id":"e2bd21f2-508d-44b9-9f68-e374d4fa87ea"},"router":{"name":"manhattan"},"labels":[{"position":0.5,"attrs":{"text":{"text":"Name"}}}],"id":"cea0d1c2-2c18-4bd7-ba35-d94918c6fc9b","embeds":"","z":6,"attrs":{".marker-source":{"d":"M 10 0 L 0 5 L 10 10 z","transform":"scale(0.001)"},".marker-target":{"d":"M 10 0 L 0 5 L 10 10 z"},".connection":{"stroke":"black"}}}] 

私はちょうどpuすべてのキーと値のペアを取得するには、このコードを使用します。

//Create a JsonFactory instance 
JsonFactory factory = new JsonFactory(); 

//Create a JsonParser instance to read from file c:\\text.json 
JsonParser jParser = factory.createJsonParser(new File("c:\\text.json")); 

/*Create an ObjectMapper instance to provide a pointer 
*to root node of the tree after reading the JSON 
*/ 
ObjectMapper mapper = new ObjectMapper(factory); 

//Create tree from JSON 
JsonNode rootNode = mapper.readTree(jParser); 


Iterator<Map.Entry<String,JsonNode>> fieldsIterator = rootNode.getFields(); 
while (fieldsIterator.hasNext()) { 

    Map.Entry<String,JsonNode> field = fieldsIterator.next(); 
    System.out.println("Key: " + field.getKey() + "\tValue:" + field.getValue()); 
} 

どうすればよいですか？

Answer 1

JSONライブラリを変更して問題を解決しました。

私が働いていた私の最終的なコードは以下の通りですjson-simple-1.1.1

を使用：

package jsontoxml; 

import java.io.*; 

import org.json.simple.parser.JSONParser; 
import org.json.simple.*; 
import java.util.*; 


public class JacksonStreamExample { 

    public static void main(String[] args) { 
     JSONParser parser = new JSONParser(); 
    try { 
     Object obj = parser.parse(new FileReader("text.json")); 
     JSONObject jsonObject = (JSONObject) obj; 

     JSONArray cells = (JSONArray) jsonObject.get("cells"); 
     Iterator<JSONObject> iterator = cells.iterator(); 
     while(iterator.hasNext()){ 
      System.out.println(iterator.next()); 
     } 

    } catch (Exception e) { 

     e.printStackTrace(); 

    } 

    } 

} 

Answer 2

Jackson1の代わりにJackson2を使用する必要があります。エラーメッセージが示すように、Jackson1のJsonNodeはfields()メソッドを実際には持ちません。Jackson2's version doesです。 Jackson1で

、あなたはこのような何かしなければならないでしょう：

public static void main(String[] args) { 
    try { 
     Map source = (new ObjectMapper()).readValue(new File(
       "C:\\json.txt"), Map.class); 

     Map<String, Object> result = new LinkedHashMap<>(); 
     buildFlattenedMap(result, source, null); 
     for (String s : result.keySet()) { 
      System.out.println(s); 
     } 

    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
} 

private static void buildFlattenedMap(Map<String, Object> result, 
     Map<String, Object> source, String path) { 
    for (Map.Entry<String, Object> entry : source.entrySet()) { 
     String key = entry.getKey(); 
     if (hasText(path)) { 
      if (key.charAt(0) == '[') { 
       key = StringUtils.join(path, key); 
      } else { 
       key = StringUtils.join(path, '.', key); 
      } 
     } 
     Object value = entry.getValue(); 
     if (value instanceof String) { 
      result.put(key, value); 
     } else if (value instanceof Map) { 
      // Need a compound key 
      @SuppressWarnings("unchecked") 
      Map<String, Object> map = (Map<String, Object>) value; 
      buildFlattenedMap(result, map, key); 
     } else if (value instanceof Collection) { 
      // Need a compound key 
      @SuppressWarnings("unchecked") 
      Collection<Object> collection = (Collection<Object>) value; 
      int count = 0; 
      for (Object object : collection) { 
       buildFlattenedMap(result, Collections.singletonMap("[" 
         + (count++) + "]", object), key); 
      } 
     } else { 
      result.put(key, value == null ? StringUtils.EMPTY : value); 
     } 
    } 
} 

private static boolean hasText(CharSequence str) { 
    if (StringUtils.isEmpty(str)) { 
     return false; 
    } 
    int strLen = str.length(); 
    for (int i = 0; i < strLen; i++) { 
     if (!Character.isWhitespace(str.charAt(i))) { 
      return true; 
     } 
    } 
    return false; 
} 

：

Iterator<String> fieldNameIterator = rootNode.getFieldNames(); 

while (fieldNameIterator.hasNext()) { 
    String fieldName = fieldNameIterator.next(); 
    JsonNode fieldValue = rootNode.getFieldValue(fieldName); 

    System.out.println("Key: " + fieldName + "\tValue:" + fieldValue); 
} 

Answer 3

を今、あなたは、質問とJSONを変更したことを、ここにあなたが探しているソリューションです参考までに、buildFlattenedMapメソッドは、実際に似たようなものを処理するために私が最近使った春のフレームワークです。 https://github.com/spring-projects/spring-framework/blob/master/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java