polymorpic对象和Parcelable列表

polymorpic对象和Parcelable列表

本文介绍了JsonSubTypes,polymorpic对象和Parcelable列表的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我的JSON结构:

  {
     ...
     类型:后,//类型可以改变
     项目:[] //项目的数组,每个产品的typeof(类型)
     ...
}

我如何反序列化,妥善我的包裹里的POJO 项目清单:

 公共类ItemsEnvelope {
    私人字符串类型;    @JsonTypeInfo(
            使用= JsonTypeInfo.Id.NAME,
            包括= JsonTypeInfo.As.EXTERNAL_PROPERTY,
            财产=类型,
            可见=真)
    @JsonSubTypes({
            @ JsonSubTypes.Type(值=的A.class,NAME =A),
            @ JsonSubTypes.Type(值= B.class,NAME =B),
            @ JsonSubTypes.Type(值= C.class,NAME =C)
    })
    私人列表<项目>项目;    接口扩展项目Parcelable {}    A类项目实现{
        // getter / setter方法​​和Parcelable方法串/构造
    }    B类项目实现{
        // getter / setter方法​​和Parcelable方法串/构造
    }    C类实现项目{
        // getter / setter方法​​和Parcelable方法串/构造
    }    // getter / setter方法​​和Parcelable方法串/构造
}

要包裹类型列表应提供 CREATOR 对象,该对象的接口,很明显,不能有。
我应该用一个抽象类,而不是接口的?


解决方案

好吧,既然杰克逊预计,键入每个列表元素的信息,我不想写一个自定义解串器FOT这个POJO - 我解决了它的另一种方式

首先,我做了一个界面,我所有的亚型的项目必须实现。

  @JsonTypeInfo(
        使用= JsonTypeInfo.Id.NAME,
        包括= JsonTypeInfo.As.EXTERNAL_PROPERTY,
        财产=类型,
        可见=真)
@JsonSubTypes({
        @ JsonSubTypes.Type(值= PostFeedItem.class,名称= BaseFeedItem.TYPE_POST)
        @ JsonSubTypes.Type(值= PhotoFeedItem.class,名称= BaseFeedItem.TYPE_PHOTO)
        @ JsonSubTypes.Type(值= AudioFeedItem.class,名称= BaseFeedItem.TYPE_AUDIO)
        @ JsonSubTypes.Type(值= VideoFeedItem.class,名称= BaseFeedItem.TYPE_VIDEO)
        @ JsonSubTypes.Type(值= FriendFeedItem.class,名称= BaseFeedItem.TYPE_FRIEND)
})
公共接口FeedItem扩展Parcelable {
    // ...
    @ BaseFeedItem.Type
    串的getType();
    // ...
}

然后我做了一个基类,这我所有的亚型项目不得不延长。

 公共抽象类BaseFeedItem实现FeedItem {
    公共静态最后弦乐TYPE_POST =邮报;
    公共静态最后弦乐TYPE_COMMUNITY_POST =group_post;
    公共静态最后弦乐TYPE_PHOTO =照片;
    公共静态最后弦乐TYPE_AUDIO =音频;
    公共静态最后弦乐TYPE_VIDEO =视频;
    公共静态最后弦乐TYPE_FRIEND =朋友;    @Retention(RetentionPolicy.SOURCE)
    @StringDef({TYPE_POST,TYPE_COMMUNITY_POST,TYPE_PHOTO,TYPE_AUDIO,TYPE_VIDEO,TYPE_FRIEND})
    公共@interface类型{}
    私人字符串类型;    @类型
    公共字符串的getType(){
        返回类型;
    }
    // ...
}

最后,我的POJO类:

 公共类NewsFeedEnvelope {
    // ...
    @JsonProperty(行)
    私人列表< FeedItem>项目;
    // ...
}

现在POJO成功自动杰克逊没有任何自定义解串器反序列化。

My JSON structure:

{
     ...
     "type":"post", // Type could vary
     "items":[]     // Array of items, each item is typeOf("type")
     ...
}

How can i deserialize and properly parcel items list inside my POJO:

public class ItemsEnvelope {
    private String type;

    @JsonTypeInfo(
            use = JsonTypeInfo.Id.NAME,
            include = JsonTypeInfo.As.EXTERNAL_PROPERTY,
            property = "type",
            visible = true)
    @JsonSubTypes({
            @JsonSubTypes.Type(value = A.class, name = "A"),
            @JsonSubTypes.Type(value = B.class, name = "B"),
            @JsonSubTypes.Type(value = C.class, name = "C")
    })
    private List<Item> items;

    interface Item extends Parcelable {}

    class A implements Item {
        // Bunch of getters/setters and Parcelable methods/constructor
    }

    class B implements Item {
        // Bunch of getters/setters and Parcelable methods/constructor
    }

    class C implements Item {
        // Bunch of getters/setters and Parcelable methods/constructor
    }

    // Bunch of getters/setters and Parcelable methods/constructor
}

To parcel typed list a CREATOR object should be provided, which an interface, obviously, can't have.Should i use an abstract class instead of interface?

解决方案

Well, since Jackson expects type information on each list element and i didn't want to write a custom deserializer fot this POJO - i solved it another way.

First of all i did an interface which all my subtype items had to implement.

@JsonTypeInfo(
        use = JsonTypeInfo.Id.NAME,
        include = JsonTypeInfo.As.EXTERNAL_PROPERTY,
        property = "type",
        visible = true)
@JsonSubTypes({
        @JsonSubTypes.Type(value = PostFeedItem.class, name = BaseFeedItem.TYPE_POST),
        @JsonSubTypes.Type(value = PhotoFeedItem.class, name = BaseFeedItem.TYPE_PHOTO),
        @JsonSubTypes.Type(value = AudioFeedItem.class, name = BaseFeedItem.TYPE_AUDIO),
        @JsonSubTypes.Type(value = VideoFeedItem.class, name = BaseFeedItem.TYPE_VIDEO),
        @JsonSubTypes.Type(value = FriendFeedItem.class, name = BaseFeedItem.TYPE_FRIEND)
})
public interface FeedItem extends Parcelable {
    // ...
    @BaseFeedItem.Type
    String getType();
    // ...
}

Then i've made a base class, which all my subtype items had to extend.

public abstract class BaseFeedItem implements FeedItem {
    public static final String TYPE_POST = "post";
    public static final String TYPE_COMMUNITY_POST = "group_post";
    public static final String TYPE_PHOTO = "photo";
    public static final String TYPE_AUDIO = "audio";
    public static final String TYPE_VIDEO = "video";
    public static final String TYPE_FRIEND = "friend";

    @Retention(RetentionPolicy.SOURCE)
    @StringDef({TYPE_POST, TYPE_COMMUNITY_POST, TYPE_PHOTO, TYPE_AUDIO, TYPE_VIDEO, TYPE_FRIEND})
    public @interface Type {}
    private String type;

    @Type
    public String getType() {
        return type;
    }
    // ...
}

Finally, my POJO class:

public class NewsFeedEnvelope {
    // ...
    @JsonProperty("rows")
    private List<FeedItem> items;
    // ...
}

Now POJO is successfully automatically deserialized by Jackson without any custom deserializers.

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08-06 22:55