Analyse JSON en Java POJO en utilisant GSON

Question

J'ai un problème très simple ici. J'ai besoin de prendre JSON provenant de l'API et de le convertir en objets que j'ai créés pour eux.

loin, il les désérialiser dans ma liste, mais chaque objet métrique a des valeurs nulles

JSON ENTRÉE EN

{ 
"metrics": [ 
    { 
     "metric": { 
      "type": 1, 
      "name": "slide-11-start", 
      "value": "1287249598295", 
      "sessionID": "" 
     } 
    }, 
    { 
     "metric": { 
      "type": 1, 
      "name": "slide-21-start", 
      "value": "1287249601368", 
      "sessionID": "" 
     } 
    }, 
    { 
     "metric": { 
      "type": 7, 
      "name": "resolution", 
      "value": "1680x1050", 
      "sessionID": "" 
     } 
    }, 
    { 
     "metric": { 
      "type": 6, 
      "name": "OS", 
      "value": "Linux", 
      "sessionID": "" 
     } 
    }, 
    { 
     "metric": { 
      "type": 5, 
      "name": "browser", 
      "value": "Netscape", 
      "sessionID": "" 
     } 
    } 
] 

}

objet métrique

public class Metric { 

    private int type; 
    private String name; 
    private String value; 
    private String sessionID; 

    /** 
    * @return the type 
    */ 
    public int getType() { 
     return type; 
    } 

    /** 
    * @param type the type to set 
    */ 
    public void setType(int type) { 
     this.type = type; 
    } 

    /** 
    * @return the name 
    */ 
    public String getName() { 
     return name; 
    } 

    /** 
    * @param name the name to set 
    */ 
    public void setName(String name) { 
     this.name = name; 
    } 

    /** 
    * @return the value 
    */ 
    public String getValue() { 
     return value; 
    } 

    /** 
    * @param value the value to set 
    */ 
    public void setValue(String value) { 
     this.value = value; 
    } 

    /** 
    * @return the sessionID 
    */ 
    public String getSessionID() { 
     return sessionID; 
    } 

    /** 
    * @param sessionID the sessionID to set 
    */ 
    public void setSessionID(String sessionID) { 
     this.sessionID = sessionID; 
    } 

} 

Container Ojbect

import java.util.List; 

/** 
* 
* @author joshua 
*/ 
public class MetricSet { 

    private List<Metric> metrics; 

    /** 
    * @return the metrics 
    */ 
    public List<Metric> getMetrics() { 
     return metrics; 
    } 

    /** 
    * @param metrics the metrics to set 
    */ 
    public void setMetrics(List<Metric> metrics) { 
     this.metrics = metrics; 
    } 
} 

CODE TRANSFORMER LE JSON

String json = ""; 
    if(request.getParameter("data") != null) { 
     json = request.getParameter("data"); 
    } 

    MetricSet metrics = new MetricSet(); 

    try { 
     Gson gson = new Gson(); 
     Type listType = new TypeToken<MetricSet>() {}.getType(); 
     metrics = gson.fromJson(json, MetricSet.class); 
    } 
    catch(Exception ex) { 
     String msg = ex.toString(); 
    } 

Answer 1

(Il ne fait que 7,5 mois.)

Le problème est que la structure de classe que vous essayez désérialiser ne correspond pas à la structure JSON.

Voici un exemple simple qui fonctionne pour désérialiser le JSON fourni. La sortie est

[Metrics: [ 
[MetricContainer: [Metric: type=1, name=slide-11-start, value=1287249598295, sessionID=]], 
[MetricContainer: [Metric: type=1, name=slide-21-start, value=1287249601368, sessionID=]], 
[MetricContainer: [Metric: type=7, name=resolution, value=1680x1050, sessionID=]], 
[MetricContainer: [Metric: type=6, name=OS, value=Linux, sessionID=]], 
[MetricContainer: [Metric: type=5, name=browser, value=Netscape, sessionID=]]]]

public class Foo 
{ 
    static String jsonInput = 
    "{" + 
     "\"metrics\":" + 
     "[" + 
     "{" + 
      "\"metric\":" + 
      "{" + 
      "\"type\":1," + 
      "\"name\":\"slide-11-start\"," + 
      "\"value\":\"1287249598295\"," + 
      "\"sessionID\":\"\"" + 
      "}" + 
     "}," + 
     "{" + 
      "\"metric\":" + 
      "{" + 
      "\"type\":1," + 
      "\"name\":\"slide-21-start\"," + 
      "\"value\":\"1287249601368\"," + 
      "\"sessionID\":\"\"" + 
      "}" + 
     "}," + 
     "{" + 
      "\"metric\":" + 
      "{" + 
      "\"type\":7," + 
      "\"name\":\"resolution\"," + 
      "\"value\":\"1680x1050\"," + 
      "\"sessionID\":\"\"" + 
      "}" + 
     "}," + 
     "{" + 
      "\"metric\":" + 
      "{" + 
      "\"type\":6," + 
      "\"name\":\"OS\"," + 
      "\"value\":\"Linux\"," + 
      "\"sessionID\":\"\"" + 
      "}" + 
     "}," + 
     "{" + 
      "\"metric\":" + 
      "{" + 
      "\"type\":5," + 
      "\"name\":\"browser\"," + 
      "\"value\":\"Netscape\"," + 
      "\"sessionID\":\"\"" + 
      "}" + 
     "}" + 
     "]" + 
    "}"; 

    public static void main(String[] args) 
    { 
    GsonBuilder gsonBuilder = new GsonBuilder(); 
    Gson gson = gsonBuilder.create(); 
    Metrics metrics = gson.fromJson(jsonInput, Metrics.class); 
    System.out.println(metrics); 
    } 
} 

class Metrics 
{ 
    private List<MetricContainer> metrics; 

    @Override 
    public String toString() 
    { 
    return String.format(
     "[Metrics: %1$s]", 
     metrics); 
    } 
} 

class MetricContainer 
{ 
    private Metric metric; 

    @Override 
    public String toString() 
    { 
    return String.format(
     "[MetricContainer: %1$s]", 
     metric); 
    } 
} 

class Metric 
{ 
    private int type; 
    private String name; 
    private String value; 
    private String sessionID; 

    @Override 
    public String toString() 
    { 
    return String.format(
     "[Metric: type=%1$d, name=%2$s, value=%3$s, sessionID=%4$s]", 
     type, name, value, sessionID); 
    } 
} 

Answer 2

Vous pouvez créer des classes correspondant java pour les objets JSON. Les valeurs integer, string peuvent être mappées en l'état. JSON peut être analysé comme ceci:

Gson gson = new GsonBuilder().create(); 
Response r = gson.fromJson(jsonString, Response.class); 

Voici un exemple: http://rowsandcolumns.blogspot.com/2013/02/url-encode-http-get-solr-request-and.html

Answer 3

Vous pouvez jeter un oeil à Gson Guide.

JSON à l'aide liée au traitement de Java POJO GSON:

public class Response { 

private List<MetricsBean> metrics; 

public List<MetricsBean> getMetrics() { 
    return metrics; 
} 

public void setMetrics(List<MetricsBean> metrics) { 
    this.metrics = metrics; 
} 

public static class MetricsBean { 
    /** 
    * metric : {"type":1,"name":"slide-11-start","value":"1287249598295","sessionID":""} 
    */ 

    private MetricBean metric; 

    public MetricBean getMetric() { 
     return metric; 
    } 

    public void setMetric(MetricBean metric) { 
     this.metric = metric; 
    } 

    public static class MetricBean { 
     /** 
     * type : 1 
     * name : slide-11-start 
     * value : 1287249598295 
     * sessionID : 
     */ 

     private int type; 
     private String name; 
     private String value; 
     private String sessionID; 

     public int getType() { 
      return type; 
     } 

     public void setType(int type) { 
      this.type = type; 
     } 

     public String getName() { 
      return name; 
     } 

     public void setName(String name) { 
      this.name = name; 
     } 

     public String getValue() { 
      return value; 
     } 

     public void setValue(String value) { 
      this.value = value; 
     } 

     public String getSessionID() { 
      return sessionID; 
     } 

     public void setSessionID(String sessionID) { 
      this.sessionID = sessionID; 
     } 
    } 
    } 
}