無法使用GSON將複雜的json序列化爲對象？

Question

下面是我通過從服務API調用回來的JSON字符串。爲了理解目的，我只用了三個reportRecords來縮短它。一般情況下，它可能有5〜50 reportRecords

{ 
    "aggRecords": { 
     "reportRecords": [ 
     { 
      "min": 0, 
      "max": 12, 
      "avg": 0.3699187, 
      "count": 246, 
      "sumSq": 571, 
      "stddev": 1.4779372, 
      "median": 0, 
      "percentileMap": { 
       "95": 4 
      }, 
      "metricName": "TransactionDuration", 
      "dimensions": { 
       "env": "dev", 
       "pool": "titan", 
       "Name": "PostProcessing", 
       "Type": "PostProcessing" 
      }, 
      "value": 91 
     }, 
     { 
      "min": 0, 
      "max": 23, 
      "avg": 2.3991289E-4, 
      "count": 1463031, 
      "sumSq": 3071, 
      "stddev": 0.045814946, 
      "median": 0, 
      "percentileMap": { 
       "95": 0 
      }, 
      "metricName": "TransactionDuration", 
      "dimensions": { 
       "env": "dev", 
       "pool": "titan", 
       "Name": "ResourceContext", 
       "Type": "ResourceContext" 
      }, 
      "value": 351 
     }, 
     { 
      "min": 0, 
      "max": 1209, 
      "avg": 1.9203402, 
      "count": 7344636, 
      "sumSq": 71832774, 
      "stddev": 2.4683187, 
      "median": 2, 
      "percentileMap": { 
       "95": 4 
      }, 
      "metricName": "TransactionDuration", 
      "dimensions": { 
       "env": "dev", 
       "pool": "titan", 
       "Name": "Client::Sync", 
       "Type": "Client::Sync" 
      }, 
      "value": 14104200 
     } 
     ] 
    }, 
    "minRecordsMap": {} 
} 

現在從上面的JSON響應，我需要提取reportRecords其Name是Client::Sync。意思是，我只需要從上面的JSON響應中提取低於reportRecords。

  { 
      "min": 0, 
      "max": 1209, 
      "avg": 1.9203402, 
      "count": 7344636, 
      "sumSq": 71832774, 
      "stddev": 2.4683187, 
      "median": 2, 
      "percentileMap": { 
       "95": 4 
      }, 
      "metricName": "TransactionDuration", 
      "dimensions": { 
       "env": "dev", 
       "pool": "titan", 
       "Name": "Client::Sync", 
       "Type": "Client::Sync" 
      }, 
      "value": 14104200 
     } 

現在我需要爲Client::Sync上述reportRecords解析以下對象 -

public class DataMetrics { 

    private String pool; 
    private String name; 
    private String type; 
    private String env; 
    private String metricName; 
    private String percentile; 
    private String median; 
    private String stdDev; 
    private String sumSq; 
    private String count; 
    private String avg; 
    private String max; 
    private String min; 

    // getters and setters here 
} 

所以經過序列化，上述目的應該是這樣的 -

pool is titan 
name is Client::Sync 
type is Client::Sync 
env is dev 
metricNname is TransactionDuration 
95th percentile is 4 
median is 2 
stdDev is 2.4683187 
sumSq is 71832774 
count is 7344636 
avg is 1.9203402 
max is 1209 
min is 0 

我使用這裏和下面的GSON庫是我迄今試過的 -

private static RestTemplate restTemplate = new RestTemplate(); 

public static void main(String[] args) { 

    String jsonLine = restTemplate.getForObject("some_url", String.class); 
    System.out.println(jsonLine); // here jsonLine will give me above big JSON String 

    JsonElement jelement = new JsonParser().parse(jsonLine); 
    JsonObject jobject = jelement.getAsJsonObject(); 
    jobject = jobject.getAsJsonObject("aggRecords"); 
    JsonArray jarray = jobject.getAsJsonArray("reportRecords"); 

    Type type = new TypeToken<List<DataMetrics>>() {}.getType(); 
    List<DataMetrics> records = gson.fromJson(jsonArrayThatYouHave, type);  

    List<DataMetrics> result = new LinkedList<>(); 

    for(DataMetrics record : records){ 
     if(record.name.equals("Client::Sync")){ 
      result.add(record); 
     } 
    }  
} 

但由於某些原因，DataMetrics中的某些字段會向我顯示數據，但某些字段會變空，以至於使我認爲上述代碼中存在某些錯誤，或者我的DataMetrics類不正確？

Answer 1

一般來說，像dimensions嵌套的對象，你會宣佈另一個POJO它

class DataMetrics{ 
    private String min; 
    private String max; 
    private String avg; 
    /*Insert other members*/ 

    private Dimensions dimensions; 

    public boolean isClientSync(){ 
    return "Client::Sync".equals(dimensions.Name); 
    } 
    private class Dimensions{ 
    private String env; 
    private String pool; 
    private String Name; 
    } 
} 

測試：

public void test() { 

String json = "[{\"min\": 0,\"max\": 1209,\"avg\": 1.9203402,\"count\": 7344636,\"sumSq\": 71832774, \"stddev\": 2.4683187, \"median\": 2,\"percentileMap\": {\"95\": 4},\"metricName\": \"TransactionDuration\",\"dimensions\": {\"env\": \"dev\",\"pool\": \"titan\",\"Name\": \"Client::Sync\", \"Type\": \"Client::Sync\"},\"value\": 14104200}]"; 

final Gson gson = new Gson(); 
final Type type = new TypeToken<List<DataMetrics>>() {}.getType(); 
final List<DataMetrics> records = gson.fromJson(json, type); 

Assert.assertTrue(records.get(0).isClientSync()); 
} 

爲percentileMap，你會希望有一個實際的地圖

private Map<String, Integer> percentileMap; 

另請注意，成員變量名稱應與JSON示例匹配RTY名稱完全

• stdDev =>stddev
• name =>Name
• percentile =>percentileMap