Jackson deserialize json string but bean missing json string's property/key

Question

When I used Jackson to deserialize the json string ,i often don't want to create all the bean class's properties, and also I just need some json string's field ,other field i don't need. So i often just write some properties in my java class bean which i needed . but when Jackson parsed it it will return as null for the bean field.

1.The java bean class is: GistObject is:

public class GistObject {
   private String id;
}

2. The jackson Main class code is:

     String json = " {\\n" + " \\"url\\": \\"https://api.github.com/gists/e69fd9f9ef85eb3f30a3b93d2cc9b9b3\\",\\n" + " \\"forks_url\\": \\"https://api.github.com/gists/e69fd9f9ef85eb3f30a3b93d2cc9b9b3/forks\\",\\n" + " \\"commits_url\\": \\"https://api.github.com/gists/e69fd9f9ef85eb3f30a3b93d2cc9b9b3/commits\\",\\n" + " \\"id\\": \\"e69fd9f9ef85eb3f30a3b93d2cc9b9b3\\",\\n" + " \\"git_pull_url\\": \\"https://gist.github.com/e69fd9f9ef85eb3f30a3b93d2cc9b9b3.git\\",\\n" + " \\"git_push_url\\": \\"https://gist.github.com/e69fd9f9ef85eb3f30a3b93d2cc9b9b3.git\\",\\n" + " \\"html_url\\": \\"https://gist.github.com/e69fd9f9ef85eb3f30a3b93d2cc9b9b3\\",\\n" + " \\"files\\": {\\n" + " \\"sample template\\": {\\n" + " \\"filename\\": \\"sample template\\",\\n" + " \\"type\\": \\"text/plain\\",\\n" + " \\"language\\": null,\\n" + " \\"raw_url\\": \\"https://gist.githubusercontent.com/becauseqa-walter/e69fd9f9ef85eb3f30a3b93d2cc9b9b3/raw/a85b555ce30da1f13aa3b7db3a2756bd64462278/sample%20template\\",\\n" + " \\"size\\": 877\\n" + " }\\n" + " },\\n" + " \\"public\\": false,\\n" + " \\"created_at\\": \\"2017-05-16T13:28:44Z\\",\\n" + " \\"updated_at\\": \\"2017-05-16T13:28:44Z\\",\\n" + " \\"description\\": \\"\\",\\n" + " \\"comments\\": 0,\\n" + " \\"user\\": null,\\n" + " \\"comments_url\\": \\"https://api.github.com/gists/e69fd9f9ef85eb3f30a3b93d2cc9b9b3/comments\\",\\n" + " \\"owner\\": {\\n" + " \\"login\\": \\"becauseqa-walter\\",\\n" + " \\"id\\": 5029046,\\n" + " \\"avatar_url\\": \\"https://avatars1.githubusercontent.com/u/5029046?v=3\\",\\n" + " \\"gravatar_id\\": \\"\\",\\n" + " \\"url\\": \\"https://api.github.com/users/becauseqa-walter\\",\\n" + " \\"html_url\\": \\"https://github.com/becauseqa-walter\\",\\n" + " \\"followers_url\\": \\"https://api.github.com/users/becauseqa-walter/followers\\",\\n" + " \\"following_url\\": \\"https://api.github.com/users/becauseqa-walter/following{/other_user}\\",\\n" + " \\"gists_url\\": \\"https://api.github.com/users/becauseqa-walter/gists{/gist_id}\\",\\n" + " \\"starred_url\\": \\"https://api.github.com/users/becauseqa-walter/starred{/owner}{/repo}\\",\\n" + " \\"subscriptions_url\\": \\"https://api.github.com/users/becauseqa-walter/subscriptions\\",\\n" + " \\"organizations_url\\": \\"https://api.github.com/users/becauseqa-walter/orgs\\",\\n" + " \\"repos_url\\": \\"https://api.github.com/users/becauseqa-walter/repos\\",\\n" + " \\"events_url\\": \\"https://api.github.com/users/becauseqa-walter/events{/privacy}\\",\\n" + " \\"received_events_url\\": \\"https://api.github.com/users/becauseqa-walter/received_events\\",\\n" + " \\"type\\": \\"User\\",\\n" + " \\"site_admin\\": false\\n" + " },\\n" + " \\"truncated\\": false\\n" + " }"; ObjectMapper mapper= new ObjectMapper(); mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL); mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); GistObject gistObject =mapper.readValue(json, GistObject.class); 

Then the returned GistObject with field id is null , not expected e69fd9f9ef85eb3f30a3b93d2cc9b9b3 . So SOmeone know how to deserialize the json string to java bean without writing all the json string's fields in my java bean class. thanks for your response!

Answer 1

You need to add a setter for your property id into your data class like that:

public static class GistObject {
    private String id;

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

Or you can use the JsonProperty annotation:

public static class GistObject {
    @JsonProperty
    private String id;
}