如何从杰克逊的数组开始反序列化JSON文件？ [英] How to deserialize JSON file starting with an array in Jackson?

问题描述

我有一个类似于这样的Json文件：

I have a Json file that looks like this:

[
    { "field":"val" },
....
]

我有Java对象代表单个对象和它们的集合：

I have Java object representing single object and collection of them:

public class Objects{

    public Collection<List> myObject;
}

我想使用 ObjectMapper反序列化JSON 。

ObjectMapper mapper = new ObjectMapper();
mapper.readValue(in, Objects.class);

但我得到：

11-24 23:19:19.828: W/UpdateService(6084): org.codehaus.jackson.map.JsonMappingException: 
Can not deserialize instance of com.project.my.Objects out of START_ARRAY token

推荐答案

尝试

   mapper.readValue(in, ObjectClass[].class);

其中ObjectClass类似于：

Where ObjectClass is something like:

  public class ObjectClass {
    String field;

    public ObjectClass() { }

    public void setField(String value) {
      this.field = value;
    }
  }

注意：在您发布的<$ c版本中$ c>对象类，您正在声明列表集合（即列表列表），这不是您想要的。你可能想要一个 List< ObjectClass> 。但是，在使用Jackson进行反序列化时，只需执行 YourObject []。class ，然后转换为列表就更简单了。

Note: in your posted version of the Objects class, you're declaring a Collection of Lists (i.e. a list of lists), which is not what you want. You probably wanted a List<ObjectClass>. However, it's much simpler to just do YourObject[].class when deserializing with Jackson, and then converting into a list afterwards.

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