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Tôi đang sử dụng Jackson để khử mảng json thành một số đối tượng. Đây là lớp học của tôi:Lỗi Jackson: không có hàm tạo thích hợp
public class OfferContainer extends ActiveRecordBase{
public Offer offer;
public OfferContainer(){}
public OfferContainer(Database db) {
super(db);
}
@Override
public String toString()
{
return this.getID() + offer.toString();
}
public String getDescription() {
return offer.description;
}
public String getBusinessName() {
return offer.business.name;
}
public class Offer
{
public Category category;
public String description;
public String discount;
public Date expiration;
public Date published;
public String rescinded_at;
public String title;
public String hook;
public Date valid_from;
public Date valid_to;
public String id;
public Business business;
public Location location;
public String image_270x155;
public Offer() {
}
@Override
public String toString()
{
return String.format(
"[Offer: category=%1$s, description=%2$s, discount=%3$s, expiration=%4$s, published=%5$s, rescinded_at=%6$s, title=%7$s, valid_from=%8$s, valid_to=%9$s, id=%10$s, business=%11$s, location=%12$s]",
category, description, discount, expiration, published, rescinded_at, title, valid_from, valid_to, id,
business, location);
}
}
public enum Category
{
Salon, Spa, Restaurant, Other
}
// public class Category {
// public String category;
//
// public String toString() {
// return String.format("[Category: category=%1$s]", category);
// }
// }
public class Business
{
public String name;
public String phone;
public Address address;
public Business(){}
@Override
public String toString()
{
return String.format(
"[Business: name=%1$s, phone=%2$s, address=%3$s]",
name, phone, address);
}
}
public class Address
{
public String address_1;
public String address_2;
public String city;
public String cross_streets;
public String state;
public String zip;
public Address() {
}
@Override
public String toString()
{
return String.format(
"[Address: address_1=%1$s, address_2=%2$s, city=%3$s, cross_streets=%4$s, state=%5$s, zip=%6$s]",
address_1, address_2, city, cross_streets, state, zip);
}
}
public class Location {
public double latitude;
public double longitude;
public Location() {
}
public String toString() {
return String.format("[Location: longitude=%1$s, latitude=%2$s]", longitude, latitude);
}
}
}
Và các lỗi:
W/System.err(26911): org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class org.me.pojos.OfferContainer$Business]: can not instantiate from JSON object (need to add/enable type information?)
W/System.err(26911): at [Source: [email protected]; line: 1, column: 382] (through reference chain: org.me.pojos.OfferContainer["offer"]->org.me.pojos.Offer["business"])
W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObjectUsingNonDefault(BeanDeserializer.java:740)
W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:683)
W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)
W/System.err(26911): at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:299)
W/System.err(26911): at org.codehaus.jackson.map.deser.SettableBeanProperty$FieldProperty.deserializeAndSet(SettableBeanProperty.java:579)
W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:635)
W/System.err(26911): at org.codehaus.jackson.map.deser.SettableBeanProperty$InnerClassProperty.deserializeAndSet(SettableBeanProperty.java:780)
W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:697)
W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)
W/System.err(26911): at org.codehaus.jackson.map.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:104)
W/System.err(26911): at org.codehaus.jackson.map.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:18)
W/System.err(26911): at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2723)
W/System.err(26911): at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1854)
W/System.err(26911): at org.me.OffersUpdater.updateOffersIfNeeded(OffersUpdater.java:107)
W/System.err(26911): at com.activities.Main$UpdateOffersTask.doInBackground(Main.java:265)
W/System.err(26911): at com.activities.Main$UpdateOffersTask.doInBackground(Main.java:239)
W/System.err(26911): at android.os.AsyncTask$2.call(AsyncTask.java:185)
W/System.err(26911): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
W/System.err(26911): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
W/System.err(26911): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
W/System.err(26911): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
W/System.err(26911): at java.lang.Thread.run(Thread.java:1019)
tôi đã sử dụng GSON nhưng cần phải từ bỏ nó trên tài khoản của các vấn đề hiệu suất. Khi tôi chuyển sang Jackson, tôi chỉ cần thêm constructor mặc định cho tất cả các lớp, mà có lẽ là không cần thiết vì không có nhà xây dựng khác theo quy định ...
EDIT: Oh, và JSON trông như thế này:
[ { "offer" : { "business" : { "address" : { "address_1" : "340 9th Avenue",
"address_2" : null,
"city" : "New York",
"cross_streets" : null,
"state" : "NY",
"zip" : "10001"
},
"name" : "Blarney Stone",
"phone" : "2125024656"
},
"category" : "Restaurant",
"claim_link" : "http://m.thinknear.com/offers/BLARNEY__1323954754?app_id=kz4hjo&latitude=40.75042&longitude=-73.99633",
"description" : "$1 off all drinks This discount was authorized by Toni Rossi. ",
"discount" : null,
"distance" : 161.40291744228713,
"draws" : [ "American" ],
"expiration" : "2011-12-15T21:59:59Z",
"hook" : "$1 Off Drinks",
"id" : "BLARNEY__1323954754",
"image_270x155" : "https://s3.amazonaws.com/default_images/restaurant_stock_255x170.jpg",
"location" : { "latitude" : "40.750444",
"longitude" : "-73.99824579999999"
},
"mobile_claim_link" : "http://m.thinknear.com/offers/BLARNEY__1323954754?app_id=kz4hjo&latitude=40.75042&longitude=-73.99633",
"published" : "2011-12-15T13:12:37Z",
"rescinded_at" : null,
"title" : "$1 Off All Drinks",
"valid_from" : "2011-12-15T13:12:34Z",
"valid_to" : "2011-12-15T21:29:59Z"
} },
{ "offer" : { "business" : { "address" : { "address_1" : "252 W 31st St",
"address_2" : null,
"city" : "New York",
"cross_streets" : null,
"state" : "NY",
"zip" : "10019"
},
"name" : "Hush Spa for Men",
"phone" : "2127570508"
},
"category" : "Spa",
"claim_link" : "http://m.thinknear.com/offers/HUSH_SPA_1323962075?app_id=kz4hjo&latitude=40.75042&longitude=-73.99633",
"description" : "Use this offer now to enjoy this great Spa at a 30% discount. Applies to all services except massages. This discount was authorized by Andy Paningua. ",
"discount" : "30",
"distance" : 185.37847063528784,
"draws" : [ "Body Work",
"Facial",
"Hair Removal"
],
"expiration" : "2011-12-16T02:59:59Z",
"hook" : "30% OFF",
"id" : "HUSH_SPA_1323962075",
"image_270x155" : "https://s3.amazonaws.com/ThinkNearMobileImages/hush_255x170.jpg",
"location" : { "latitude" : "40.7499612",
"longitude" : "-73.9942143"
},
"mobile_claim_link" : "http://m.thinknear.com/offers/HUSH_SPA_1323962075?app_id=kz4hjo&latitude=40.75042&longitude=-73.99633",
"published" : "2011-12-15T15:14:36Z",
"rescinded_at" : null,
"title" : "30% off at Hush Spa for Men",
"valid_from" : "2011-12-15T15:14:35Z",
"valid_to" : "2011-12-16T02:29:59Z"
} },
{ "offer" : { "business" : { "address" : { "address_1" : "481 8th Ave",
"address_2" : "Ste 740 ",
"city" : "New York",
"cross_streets" : "34th & 35th (New Yorker Hotel)",
"state" : "NY",
"zip" : "10001"
},
"name" : "Fusion Spa",
"phone" : "+18325329272"
},
"category" : "Spa",
"claim_link" : "http://m.thinknear.com/offers/FUSION_S_1323979416?app_id=kz4hjo&latitude=40.75042&longitude=-73.99633",
"description" : "Use this offer now to enjoy this great Spa at a 20% discount. New customers only. Not valid with other offers. By appointment only. Call ahead for appointment. This discount was authorized by Tiffany Albert. ",
"discount" : "20",
"distance" : 350.0873566571568,
"draws" : [ "Facial" ],
"expiration" : "2011-12-16T01:59:59Z",
"hook" : "20% OFF",
"id" : "FUSION_S_1323979416",
"image_270x155" : "https://s3.amazonaws.com/ThinkNearMobileImages/Fusion%2BSpa+1.jpg",
"location" : { "latitude" : "40.7526135",
"longitude" : "-73.99334859999999"
},
"mobile_claim_link" : "http://m.thinknear.com/offers/FUSION_S_1323979416?app_id=kz4hjo&latitude=40.75042&longitude=-73.99633",
"published" : "2011-12-15T20:03:38Z",
"rescinded_at" : null,
"title" : "20% off at Fusion Spa",
"valid_from" : "2011-12-15T20:03:36Z",
"valid_to" : "2011-12-16T01:29:59Z"
} }
]
Những người khác đã chỉ ra chính xác rằng các lớp bên trong không tĩnh có vấn đề. Tuy nhiên, Jackson 1.9.0 thực sự có một số hỗ trợ cho các lớp như vậy - vì vậy nếu bạn đang sử dụng một phiên bản cũ hơn, nâng cấp cũng có thể có những thứ cố định. Tuy nhiên, thực hành tốt là chỉ sử dụng các lớp bên trong tĩnh nếu có thể (để tránh chi phí vượt qua tham chiếu cha mẹ ngầm xung quanh) – StaxMan