![](/img/trans.png)
[英]Converting a list of json objects to java object using gson, gets null
[英]Converting Json to java objects using Google's Gson
我正在使用Spring Social FqlQuery从facebook获取数据。 这是我从facebook获得的JSON响应。 我得到Json输出的控制器在这里,
fql = "SELECT work FROM user WHERE uid = me()";
facebook.fqlOperations().query(fql, new FqlResultMapper<Object>() {
public Object mapObject(FqlResult result) {
List list = (List) result.getObject("work");
for (Object object : list) {
JsonHelper jsonHelper = new JsonHelper();
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String jsonOutput = gson.toJson(object);
System.out.println(jsonOutput);
gson.fromJson(jsonOutput, JsonHelper.class);
}
System.out.println for for循环输出多个json,如下所示:
{
"employer": {
"id": 129843057436,
"name": "www.metroplots.com"
},
"location": {
"id": 102186159822587,
"name": "Chennai, Tamil Nadu"
},
"position": {
"id": 108480125843293,
"name": "Web Developer"
},
"start_date": "2012-10-01",
"end_date": "2013-05-31"
}
{
"employer": {
"id": 520808381292985,
"name": "Federation of Indian Blood Donor Organizations"
},
"start_date": "0000-00",
"end_date": "0000-00"
}
这是我的助手班:
import java.util.List;
public class JsonHelper {
class Employer{
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
class Location{
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
class Position{
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
//Edited After here
private String start_Date;
private String end_Date;
private Employer employer;
private Location location;
private Position position;
public String getStart_Date() {
return start_Date;
}
public void setStart_Date(String start_Date) {
this.start_Date = start_Date;
}
public String getEnd_Date() {
return end_Date;
}
public void setEnd_Date(String end_Date) {
this.end_Date = end_Date;
}
public Employer getEmployer() {
return employer;
}
public void setEmployer(Employer employer) {
this.employer = employer;
}
public Location getLocation() {
return location;
}
public void setLocation(Location location) {
this.location = location;
}
public Position getPosition() {
return position;
}
public void setPosition(Position position) {
this.position = position;
}
}
当我尝试将json对象转换为java对象时,如上所述,我得到了这个异常。
HTTP Status 500 - Request processing failed; nested exception is com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 6 column 16
任何人都可以帮助我,我错了。 请帮我转换json到java对象。 希望我的问题很明确。 提前致谢。
编辑为控制器:
facebook.fqlOperations().query(fql, new FqlResultMapper<Object>() {
public Object mapObject(FqlResult result) {
List<JsonHelper> json = new ArrayList<JsonHelper>();
List list = (List) result.getObject("work");
for (Object object : list) {
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String jsonOutput = gson.toJson(object);
System.out.println(jsonOutput);
JsonHelper jsonHelper = gson.fromJson(jsonOutput, JsonHelper.class);
json.add(jsonHelper);
System.out.println(jsonHelper.getStart_Date());
}
for (JsonHelper jsonHelper : json) {
System.out.println(jsonHelper.getStart_Date());
}
return list;
}
});
由于我没有实际的api访问权限,所以我在示例中尝试使用静态值。 首先,在你的JsonHelper
类,全部更换int
由long
,如JSON提到的值类型的long
和String
。 然后尝试如下所述:
String str = "{\n"
+ " \"employer\": {\n"
+ " \"id\": 129843057436,\n"
+ " \"name\": \"www.metroplots.com\"\n"
+ " },\n"
+ " \"location\": {\n"
+ " \"id\": 102186159822587,\n"
+ " \"name\": \"Chennai, Tamil Nadu\"\n"
+ " },\n"
+ " \"position\": {\n"
+ " \"id\": 108480125843293,\n"
+ " \"name\": \"Web Developer\"\n"
+ " },\n"
+ " \"start_date\": \"2012-10-01\",\n"
+ " \"end_date\": \"2013-05-31\"\n"
+ "}";
List<JsonHelper> json = new ArrayList<JsonHelper>();
Gson gson = new Gson();
JsonHelper users = gson.fromJson(str, JsonHelper.class);
json.add(users);
for (JsonHelper js_obj : json) {
System.out.println(js_obj.getEmployer().getId());
System.out.println(js_obj.getEmployer().getName());
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.