Jersey - Serializing a POJO with json - nested objects will be ignored

Question

HiAll,

i have the following problem in development branch: If i use the jersey REST service to serialize the POJO containig a list of the nested other POJO, then this nested POJO will be NOT serialized. This problem is reproducible only in branch.

If i prototype using POJO structur liked in branch, i have no problem.

The Details:

    The POJO (Domain): 
    public class Article {

     private int id;

    private int name;
     // getter & setter

    }

The POJO ( DTO)

    public class DTO {

    private List<Article> articles;

    private String message;

    public DTO {
     articles= new ArrayList<>();
    }

     getArticles() {
     return articles;
    }

     getArticlesCount() {
     return articles.size();
    }

     public void getMessage() {
     return message;
    }

    public String getMessage() {
     return message;
    }
....
   }

It will be created the 1 article with id = 1 and name "firstArticle" the The results of serialization after service call to find all articles:

in branch

*{"message":"1 article found","articlesCount":1
}*

in prototype

{
{"message":"1 article found","articlesCount":1[{"id":1,"name":"firstArticle"]}
}

i have no idia what's happened. I checked out all settings (web.xml, jersey version, etc.)

Answer 1

If you use Jackson JSON library , your POJO will be automatically handled by Jackson JSON lib to convert between JSON and POJO. You also need to add the following lines in your web.xml:

<init-param>
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
</init-param>

Then in your Jersey resource class, use @Produces and @Consumes annotation to indicate the data format is JSON:

@Path("/myResource")
@Produces("application/json")
public class SomeResource {
    @GET
    public String doGetAsJson() {
        ...
    }
}

Answer 2

Follow the above answer to set up Jersey POJO mappping, and then try the following nested POJO example.

Article class:

public class Article {
    private int id;
    private String name;

    public Article(int id, String name) {
        this.id = id;
        this.name = name;
    }

    //getter and setter ...
}

The Book class that contains the Article class:

public class Book {
    private List<Article> articles;
    private String message;
    private int articleCount;

    public List<Article> getArticles() {
        return articles;
    }

    public void setArticles(List<Article> articles) {
        this.articles = articles;
        setArticleCount(articles.size());
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public int getArticleCount() {
        return articleCount;
    }

    public void setArticleCount(int articleCount) {
        this.articleCount = articleCount;
    }
}

Finally in the Jersey resource class NestedPojoResource:

@Path("/nested-pojo")
public class NestedPojoResource {
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Book getNestedPojo() {
        Book book = new Book();
        List<Article> articles = new ArrayList<Article>();
        articles.add(new Article(1, "firstArticle"));
        articles.add(new Article(2, "secondArticle"));
        book.setArticles(articles);
        book.setMessage(book.getArticleCount() + " articles found");
        return book;
    }
}

When you go to http://example.com/myappname/nested-pojo , you will see the correct JSON output which contains the nested POJO fields:

{"articles":[{"id":1,"name":"firstArticle"},{"id":2,"name":"secondArticle"}],"message":"2 articles found","articleCount":2}