java - 从 json 到 json 立即崩溃

Question

以下代码段因 Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING

崩溃

GsonBuilder gsonBuilder = new GsonBuilder();   
Gson gson = gsonBuilder.create();  
String jsonObjString = gson.toJson(customClassInstance, MyCustomClass.class);  
gson.fromJson(jsonObjString, MyCustomClass.class);  // Crashes here

为什么？当我打印 jsonObjString 时，它看起来很好。
并且编码/解码似乎是正确的。问题是什么？

更新:

public class MyCustomClass {

    @SerializedName(“customer_city”)
    private String customerCity;

    @SerializedName(“customer_id”)
    private String customerId;

    private LocalDate entry;

    @SerializedName(“customer_income”)
    private double customerIncome;

    private String[] cards;


    @SerializedName(“customer_name")
    private String customerName;

}

Answer 1

您的 LocalDate 需要一种确定的序列化和反序列化方式。为此，您必须在 Gson 实例中注册自定义类型适配器。

   public class LocalDateAdapter extends TypeAdapter<LocalDate> {
     public LocalDate read(JsonReader reader) throws IOException {
       if (reader.peek() == JsonToken.NULL) {
         reader.nextNull();
         return null;
       }
       String xy = reader.nextString();
       return new LocalDate(new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").parse(xy);
     }
     public void write(JsonWriter writer, LocalDate value) throws IOException {
       if (value == null) {
         writer.nullValue();
         return;
       }
       String xy = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(value.getTime());
       writer.value(xy);
     }
   }

你需要这样的东西，虽然我不太确定 LocalDate 的 API。

然后注册到你的Gson实例

Gson gson = new GsonBuilder()
     .registerTypeAdapter(LocalDate.class, new LocalDateAdapter())
     .create();