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java - jackson JsonMappingException : Can not deserialize instance

转载 作者:塔克拉玛干 更新时间:2023-11-02 23:49:39 25 4
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我正在尝试使用 Jackson 将我的 json 数据转换为 POJO 对象。这是 MainActivity 和我的 POJO 类代码。我基本上收到 JsonMappingException 错误。我还附上了整个日志。

主要 Activity .java :

ObjectMapper mapper = new ObjectMapper();
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
try {
List<Entries> results = mapper.readValue(new URL("http://collegewires.com/android/jacksoncw.json"), new TypeReference<List<Entries>>(){});
for(int i=0;i<results.size();++i){
System.out.println(results.get(i).getName());
out = out + " ## " + results.get(i).getName();
txt.setText("1111");
}
} catch (JsonParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();

} catch (JsonMappingException e) {
// TODO Auto-generated catch block
e.printStackTrace();

} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

Entries.java(这是 POJO)

package com.collegewires.jackson;

public class Entries {
public Entries(){
}

private String id, name, email, address, gender;
private Phone phone;

public Phone getPhone() {
return phone;
}

public void setPhone(Phone phone) {
this.phone = phone;
}

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

public String getGender() {
return gender;
}

public void setGender(String gender) {
this.gender = gender;
}

@Override
public String toString() {
return "Entries:{id: " + id + ", name: " + name +
", email: " + email + ", address: " + address + ", gender: " + gender + ", phone: " + phone + "}";
}

public class Phone {
public Phone(){
}
public String mobile, home, office;
public String getMobile() {
return mobile;
}

public void setMobile(String mobile) {
this.mobile = mobile;
}

public String getHome() {
return home;
}

public void setHome(String home) {
this.home = home;
}

public String getOffice() {
return office;
}

public void setOffice(String office) {
this.office = office;
}

@Override
public String toString() {
return "Phone:{mobile: " + mobile + ", home: " + home +
", office: " + office + "}";
}
}


}

现在,我在日志中收到以下错误。因此,我无法继续我的工作。这是日志:

07-12 12:06:13.206: W/System.err(30593): 

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
07-12 12:06:13.206: W/System.err(30593): at [Source: http://collegewires.com/android/jacksoncw.json; line: 1, column: 1]
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:575)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:569)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.handleNonArray(CollectionDeserializer.java:259)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:207)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:23)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888)
07-12 12:06:13.211: W/System.err(30593): at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2018)
07-12 12:06:13.211: W/System.err(30593): at com.collegewires.jackson.MainActivity.onCreate(MainActivity.java:81)
07-12 12:06:13.211: W/System.err(30593): at android.app.Activity.performCreate(Activity.java:5250)
07-12 12:06:13.211: W/System.err(30593): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
07-12 12:06:13.211: W/System.err(30593): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
07-12 12:06:13.211: W/System.err(30593): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2297)
07-12 12:06:13.211: W/System.err(30593): at android.app.ActivityThread.access$700(ActivityThread.java:152)
07-12 12:06:13.211: W/System.err(30593): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1282)
07-12 12:06:13.211: W/System.err(30593): at android.os.Handler.dispatchMessage(Handler.java:99)
07-12 12:06:13.211: W/System.err(30593): at android.os.Looper.loop(Looper.java:137)
07-12 12:06:13.211: W/System.err(30593): at android.app.ActivityThread.main(ActivityThread.java:5328)
07-12 12:06:13.211: W/System.err(30593): at java.lang.reflect.Method.invokeNative(Native Method)
07-12 12:06:13.211: W/System.err(30593): at java.lang.reflect.Method.invoke(Method.java:511)
07-12 12:06:13.211: W/System.err(30593): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
07-12 12:06:13.211: W/System.err(30593): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
07-12 12:06:13.211: W/System.err(30593): at dalvik.system.NativeStart.main(Native Method)
07-12 12:06:13.251: D/libEGL(30593): loaded /vendor/lib/egl/libEGL_POWERVR_SGX544_115.so
07-12 12:06:13.261: D/libEGL(30593): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX544_115.so
07-12 12:06:13.266: D/libEGL(30593): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX544_115.so
07-12 12:06:13.271: I/(30593): !@IMGSRV: DATE: 2013.04.23(11:19:33) | BUILDER: LSI3D | REVISION: e9cd1377d8225457ae40
07-12 12:06:13.346: D/OpenGLRenderer(30593): Enabling debug mode 0
07-12 12:06:31.521: W/IInputConnectionWrapper(30593): setComposingText on inactive InputConnection

最佳答案

无法从 START_OBJECT token 中反序列化 java.util.ArrayList 的实例

这里的关键词是ArrayListSTART_OBJECT token。您不能将单个对象反序列化为对象数组。试着理解这样做的意义,你就会明白为什么。

您只能将 JSON 对象的数组反序列化为 POJO 的数组或集合。请注意,JSON 对象由 { } 大括号分隔,而数组由 [ ] 括号分隔,其中包含一些对象。

关于java - jackson JsonMappingException : Can not deserialize instance,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24709643/

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