jackson错误：没有合适的构造函数

我正在使用Jackson将json数组反序列化为某些对象。 这是我的class级：

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); } } } 

而错误：

 W/System.err(26911): org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class org.me.pojos.OfferContainer$Business]: can not instantiate from JSON object (need to add/enable type information?) W/System.err(26911): at [Source: java.io.StringReader@405fec40; line: 1, column: 382] (through reference chain: org.me.pojos.OfferContainer["offer"]->org.me.pojos.Offer["business"]) W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObjectUsingNonDefault(BeanDeserializer.java:740) W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:683) W/System.err(26911): at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580) W/System.err(26911): at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:299) W/System.err(26911): at org.codehaus.jackson.map.deser.SettableBeanProperty$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) 

我一直在使用GSON，但由于性能问题需要放弃它。 当我切换到Jackson时，我只是为所有类添加了默认构造函数，这可能是不必要的，因为没有定义其他构造函数…

编辑：哦，JSON看起来像这样：

  [ { "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" : "[phone]" }, "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" } } ] 

Answer 1

我没有和jackson合作，但我猜测问题是Business类是一个成员类而不是静态的。

jackson需要做的是

 new OfferContainer.Business() 

它不能这样做，因为它是一个成员类。 尝试使类静态。

 public static class Business{ .... } 

Answer 2

我想接受之前发布的答案，因为它让我朝着正确的方向前进。 我使每个成员类都是静态的（后来必须将@JsonIgnoreProperties（ignoreUnknown = true）添加到其中一个）并且它可以工作。