How to extract array of json inside an attribute of type List from an object

Question

I am using Flickr API to get the information of images and returns the following JSON:

{"photos":{"page":1,"pages":60,"perpage":100,"total":"5964","photo":[{"id":"21577339501","owner":"85277110@N02","secret":"31e850dfeb","server":"5785","farm":6,"title":"P1390956","ispublic":1,"isfriend":0,"isfamily":0}, {"id":"21577287101","owner":"85277110@N02","secret":"412990658f","server":"611","farm":1,"title":"P1400012","ispublic":1,"isfriend":0,"isfamily":0}]

I use this code in the Spring controller to deserialize the JSON:

Collection<Photos> readValues = objectMapper.readValue(new URL(url), new TypeReference<Collection<Photos>>() { });

And returns the following error:

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

How can I solve this problem? I didn't found solutions.

Photos.class:

public class Photos {

    @JsonProperty("page")
    private Integer page;

    @JsonProperty("pages")
    private Integer pages;

    @JsonProperty("perpage")
    private Integer perpage;

    @JsonProperty("total")
    private Integer total;

    @JsonProperty("photo")
    @JsonDeserialize(contentAs = Photo.class, as = ArrayList.class)
    private List<Photo> photo;

    public Photos() {}

    public Photos(Integer page, Integer pages, Integer perpage, Integer total,
            List<Photo> photo) {
        super();
        this.page = page;
        this.pages = pages;
        this.perpage = perpage;
        this.total = total;
        this.photo = photo;
    }

    public Photos(List<Photo> photo) {
        super();
        this.photo = photo;
    }

    public Integer getPage() {
        return page;
    }
    public void setPage(Integer page) {
        this.page = page;
    }
    public Integer getPages() {
        return pages;
    }
    public void setPages(Integer pages) {
        this.pages = pages;
    }
    public Integer getPerpage() {
        return perpage;
    }
    public void setPerpage(Integer perpage) {
        this.perpage = perpage;
    }
    public Integer getTotal() {
        return total;
    }
    public void setTotal(Integer total) {
        this.total = total;
    }
    public List<Photo> getPhoto() {
        return photo;
    }

    public void setPhoto(List<Photo> photo) {
        this.photo = photo;
    }
}

Photo.class:

public class Photo {

    @JsonProperty("id")
    private Integer id;

    @JsonProperty("owner")
    private String owner;

    @JsonProperty("secret")
    private String secret;

    @JsonProperty("server")
    private Integer server;

    @JsonProperty("farm")
    private Integer farm;

    @JsonProperty("title")
    private String title;

    @JsonProperty("ispublic")
    private Boolean isPublic;

    @JsonProperty("isfriend")
    private Boolean isFriend;

    @JsonProperty("isfamily")
    private Boolean isFamily;

    public Photo() { }

    public Photo(Integer id, String owner, String secret, Integer server,
            Integer farm, String title, Boolean isPublic, Boolean isFriend,
            Boolean isFamily) {
        super();
        this.id = id;
        this.owner = owner;
        this.secret = secret;
        this.server = server;
        this.farm = farm;
        this.title = title;
        this.isPublic = isPublic;
        this.isFriend = isFriend;
        this.isFamily = isFamily;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getOwner() {
        return owner;
    }
    public void setOwner(String owner) {
        this.owner = owner;
    }
    public String getSecret() {
        return secret;
    }
    public void setSecret(String secret) {
        this.secret = secret;
    }
    public Integer getServer() {
        return server;
    }
    public void setServer(Integer server) {
        this.server = server;
    }
    public Integer getFarm() {
        return farm;
    }
    public void setFarm(Integer farm) {
        this.farm = farm;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public Boolean getIsPublic() {
        return isPublic;
    }
    public void setIsPublic(Boolean isPublic) {
        this.isPublic = isPublic;
    }
    public Boolean getIsFriend() {
        return isFriend;
    }
    public void setIsFriend(Boolean isFriend) {
        this.isFriend = isFriend;
    }
    public Boolean getIsFamily() {
        return isFamily;
    }
    public void setIsFamily(Boolean isFamily) {
        this.isFamily = isFamily;
    }

}

Answer 1

The basic problem is that your json is not a Collection<Photos> , but a Map<String, Photos> , which has a single entry "photos" -> Photos instance .

I got your json to successfully deserialize by making the following changes...

A) Change the type being read:

Map<String, Photos> readValues = objectMapper.readValue(json, new TypeReference<Map<String, Photos>>() { });

Note that I read straight from a String (not a URL).

B) Change the type of Photo.id from Integer to Long , because your json has id values well exceeding max int size.

C) I added the missing two closing braces from your sample json to make it valid.

FYI, deserialization works with or without the @JsonDeserialize annotation on the List<Photo> photo field of Photos .

---

Here's some runnable code that works:

String json = "{\"photos\":{\"page\":1,\"pages\":60,\"perpage\":100,\"total\":\"5964\",\"photo\":[{\"id\":\"21577339501\",\"owner\":\"85277110@N02\",\"secret\":\"31e850dfeb\",\"server\":\"5785\",\"farm\":6,\"title\":\"P1390956\",\"ispublic\":1,\"isfriend\":0,\"isfamily\":0}, {\"id\":\"21577287101\",\"owner\":\"85277110@N02\",\"secret\":\"412990658f\",\"server\":\"611\",\"farm\":1,\"title\":\"P1400012\",\"ispublic\":1,\"isfriend\":0,\"isfamily\":0}]}}"; 
Map<String, Photos> readValues = new ObjectMapper().readValue(json, new TypeReference<Map<String, Photos>>() { });