我有一个使用jackson库将Json API回调转换为自定义对象的映射问题。
我有我的用户自定义类：
public class User {
protected String id;
protected GregorianCalendar registredAt;
protected String username;
protected Team team;
public User() {
}
public User(String id, GregorianCalendar registredAt, String username, Team team) {
this.id = id;
this.registredAt = registredAt;
this.username = username;
this.team = team;
}
public User(HashMap<String, Object> attributes) {
this.id = (String) attributes.get("id");
this.registredAt = (GregorianCalendar) attributes.get("registredAt");
this.username = (String) attributes.get("username");
this.team = (Team) attributes.get("team");
}
}
这是我的回拨：
{
id: "4feab37c5600bbd56f000132",
registredAt: {
date: "2012-06-27 09:17:15",
timezone_type: 3,
timezone: "Europe/Paris"
},
username: "John Doe",
team: {
id: "4feab37c5600bbd56f000130",
indice: 1,
name: "John Doe's Team",
score: 200
}
}
然后，我尝试初始化一个User对象：
// Code from a doInBackground() method of a custom AsyncTask.
URL completePath = new URL(apiBaseURL + "api/user/4feab37c5600bbd56f000132/show");
APIconnection = (HttpURLConnection) completePath.openConnection();
APIconnection.setDoInput(true);
APIconnection.connect();
callbackParser = jsonFactory.createJsonParser(APIconnection.getInputStream());
response = objectMapper.readValue(callbackParser, User.class);
// Catch a JsonMappingException :
Can not deserialize instance of java.util.Calendar out of START_OBJECT token at [Source: org.apache.harmony.luni.internal.net.www.protocol.http.FixedLengthInputStream@4082c7a0; line: 1, column: 33] (through reference chain: classes.models.User["registredAt"])
我认为问题是回调registredAt对象是一个json_encoded PHP''DateTime实例。。。我应该更改registredAt Java User对象的类型吗？或者我的构造函数中缺少什么？
您应该使用标准的ISO-8601日期和日历字符串表示；或者，如果要使用JSON对象，请为GregorianCalendar类型编写自己的JsonDeserializer。
最后，我做了这样的事情来解决我的问题：
public User(HashMap<String, Object> attributes) {
this.id = (String) attributes.get("id");
HashMap <String, Object> registredAt = (HashMap<String, Object>) attributes.get("registredAt");
IMDateFormatter formatter = new IMDateFormatter();
this.registredAt = formatter.getCalendarFromJson((String) registredAt.get("date"));
[...]
}
和IMDateFormatter以一种简单的方式格式化我的日期：
public class IMDateFormatter extends DateFormat {
public IMDateFormatter() {
}
@Override
public StringBuffer format(Date arg0, StringBuffer arg1, FieldPosition arg2) {
return null;
}
@Override
public Date parse(String dateFromJson, ParsePosition arg1) {
return null;
}
public GregorianCalendar getCalendarFromJson(String dateFromJson) {
GregorianCalendar calendarFromJson = null;
try {
GregorianCalendar tmpCalendar = new GregorianCalendar();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.FRANCE);
tmpCalendar.setTime(df.parse(dateFromJson));
calendarFromJson = tmpCalendar;
}
catch (NullPointerException NPE) {
NPE.printStackTrace();
}
catch (ParseException PE) {
PE.printStackTrace();
}
return calendarFromJson;
}
}