我正在尝试查询Firebase数据并将其存储到下面的示例链接中的恐龙类中。将Firebase直接导入Dinosaur Facts类时出现问题。它能够创建Query并输入“onChildAdded”方法。然后它进入恐龙构造函数类，但在此之后崩溃。
DinosaurFacts facts = snapshot.getValue(DinosaurFacts.class); //CRASHES HERE
https://www.firebase.com/docs/android/guide/retrieving-data.html
package jobsme.com.firebasequery;
import android.util.Log;
public class DinosaurFacts {
long height;
double length;
long weight;
public DinosaurFacts() {
Log.i("MyActivity", "FIIIIIIIIIIIIIIIIIINDMEEEE2");
// empty default constructor, necessary for Firebase to be able to deserialize blog posts
}
public long getHeight() {
Log.i("MyActivity", "FIIIIIIIIIIIIIIIIIINDMEEEE3");
return height;
}
public double getLength() {
return length;
}
public long getWeight() {
return weight;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Firebase.setAndroidContext(this);
Firebase ref = new Firebase("https://dinosaur-facts.firebaseio.com/dinosaurs");
Query queryRef = ref.orderByChild("height");
queryRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot snapshot, String previousChild) {
Log.i("MyActivity", "onChildAdded");
DinosaurFacts facts = snapshot.getValue(DinosaurFacts.class);
Log.i("MyActivity", snapshot.getKey() + " was " + facts.getHeight() + " meters tall");
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
// ....
});
Log.i("MyActivity", "FIIIIIIIIIIIIIIIIIINDMEEEE");
}
查询成功但导入崩溃。希望这意味着我正确设置了一切？
12-11 16:48:37.793 5581-5581/jobsme.com.firebasequery E/AndroidRuntime: FATAL EXCEPTION: main
Process: jobsme.com.firebasequery, PID: 5581
com.firebase.client.FirebaseException: Failed to bounce to type
at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:196)
at jobsme.com.firebasequery.MainActivity$2.onChildAdded(MainActivity.java:45)
at com.firebase.client.core.ChildEventRegistration$1.run(ChildEventRegistration.java:50)
at com.firebase.client.core.view.EventRaiser$1.run(EventRaiser.java:37)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "vanished" (class jobsme.com.firebasequery.DinosaurFacts), not marked as ignorable (3 known properties: , "weight", "length", "height"])
at [Source: java.io.StringReader@52851428; line: 1, column: 33] (through reference chain: jobsme.com.firebasequery.DinosaurFacts["vanished"])
at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:555)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:708)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1160)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:315)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:121)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2034)
at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:192)
at jobsme.com.firebasequery.MainActivity$2.onChildAdded(MainActivity.java:45)
at com.firebase.client.core.ChildEventRegistration$1.run(ChildEventRegistration.java:50)
at com.firebase.client.core.view.EventRaiser$1.run(EventRaiser.java:37)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
这是该数据库中恐龙之一的JSON：
"bruhathkayosaurus": {
"appeared": -70000000,
"height": 25,
"length": 44,
"order": "saurischia",
"vanished": -70000000,
"weight": 135000
},
您使用的DinosaurFacts课程只包含以下属性的字段+获取者：height，length，weight。因此，当Firebase尝试将JSON反序列化为DinosaurFacts对象时，它会抱怨未映射的属性。
摆脱错误的最简单方法是告诉Jackson（Firebase在内部使用JSON和Java之间的映射）来忽略它在JSON中遇到的任何未映射的属性：
@JsonIgnoreProperties(ignoreUnknown = true)
public static class DinosaurFacts {
但是要小心这个。如果您现在将<{em} 一个DinosaurFacts对象重新写回数据库，它将只有height，length和weight属性。它不会有：appeared，order或vanished。实际上：即使之前属性存在于数据库中，将该对象写回也将删除它们。
因此，正确的解决方案是将JSON结构中的所有属性映射到Java类：
public static class DinosaurFacts {
long appeared, vanished;
double height, length, weight;
String order;
public long getAppeared() {
return appeared;
}
public long getVanished() {
return vanished;
}
public double getHeight() {
return height;
}
public double getLength() {
return length;
}
public double getWeight() {
return weight;
}
public String getOrder() {
return order;
}
}