如何更改Json格式？

Question

I want to change format of displaying Json.

I tried to printg whole Item object and it's printing all attributes(looks normal). I tried to change controller and service to return String and I tried to manipulate String but it is not a good approach to the problem i think. Must be something better.

{  
   "requestedUrl":"https://www.googleapis.com/books/v1/volumes?q=java&maxResults=40",
   "items":[  
      {  
         "id":"-SYM4PW-YAgC",
         "volumeInfo":{  
            "title":"The Religion of Java",
            "authors":[  
               "Clifford Geertz"
            ],
            "industryIdentifiers":[  
               {  
                  "type":"ISBN_10",
                  "identifier":"0226285103"
               },
               {  
                  "type":"ISBN_13",
                  "identifier":"9780226285108"
               }
            ],
            "readingModes":{  
               "text":true,
               "image":true
            },
            "pageCount":392,
            "printType":"BOOK",
            "categories":[  
               "Religion"
            ]
         }
      }
   ]
}

BookController.java

@CrossOrigin
@RestController
@RequestMapping("/")
public class BookController {

    private BookService service;

    public BookController(BookService service) {
        this.service = service;
    }

    @GetMapping("book/{isbn}")
    public Item getBook(@PathVariable String isbn) {
        return service.findBookByISBN(isbn);
    }

}

BookService.java

public class BookService {

    public BookService() throws IOException {
    }


    public Item findBookByISBN(String isbn) {
// listOfItems taking json file from json file and making List<Item> to itarate over 
        for (Item item : listOfItems) {
            if (item.getVolumeInfo().getIndustryIdentifiers().get(0).getIdentifier().equals(isbn)) {
                return item;
            }
        }
        return null;
    }
}

Of Cours I have POJO class...

For findBookByISBN(9780226285108) json answear is

{
            "title":"The Religion of Java",
            "authors":[  
               "Clifford Geertz"
            ],
            "industryIdentifiers":[  
               {  
                  "type":"ISBN_10",
                  "identifier":"0226285103"
               },
               {  
                  "type":"ISBN_13",
                  "identifier":"9780226285108"
               }
            ],
            "readingModes":{  
               "text":true,
               "image":true
            },
            "pageCount":392,
            "printType":"BOOK",
            "categories":[  
               "Religion"
            ]
}

But I want to make my json like this :

{  
   "title":"The Religion of Java",
   "printType":"BOOK",
   "pageCount":392,
   "authors":[  
      "Clifford Geertz"
   ],
   "categories":[  
      "Religion"
   ]
}

Answer 1

You can use a Data Transfer Object(DTO) and send only required information in response.

 {  
   "title":"The Religion of Java", 
   "printType":"BOOK",
   "pageCount":392,
   "authors":[  
     "Clifford Geertz"
    ],
   "categories":[  
    "Religion"
    ]
 } 

In this case you can write a DTO like

 class NameYouWant{
String title;
String printType;
Integer pageCount;
List<String> authors = new ArrayList<>();
List<String> categories = new ArrayList<>();
//generate getters and setters of the above data members.
 }

now when you are sending response set the data in this dto like this:- create the object

 public Item findBookByISBN(String isbn) {
    for (Item item : listOfItems) {
        if (item.getVolumeInfo().getIndustryIdentifiers().get(0).getIdentifier().equals(isbn)) {
           NameYouWant na = new NameYouWant();
           na.setTitle(item.getTitle());
           na.setPrintType(item.getPrintType());
           na.setPageCount(item.getPageCount());
           na.SetAuthors(item.getAuthors());
           na.SetCategories(item.getCategories());
            return na;
        }
    }
    return null;
}

In this way you can send only required data in the forntend.

Answer 2

create an interface with Getters of required fields and cast your original object to new Interface. When you serialize this object it will produce required result. eg

class Body implements BriefBody {
        String content;
        String type;
        // ---Getters/Setters---
    }

interface BriefBody {
    String getContent();
}

BriefBody getBriefBody() {
    Body body = new Body();
    body.setContent("bodyContent");
    body.setType("bodyType");
    return body;
}

Result will have {"content":"bodyContent"}.

Answer 3

Create a new POJO for your expected response and in your BookService class (don't directly return the item) set the property and return.

Alternatively, create a new Item Object and set only the required property and return, assuming you're using Jackson Api for features like @JsonInclude(Include.NON_NULL) and @JsonPropertyOrder.

Answer 4

You can use marshalling your Item class to JSON in certain format. That will give u precisely what you want. You will find out ways to do it in Spring Boot on google.

Answer 5

If you don't wanna create an additional DTO class or have many different views- you can use Jackson @JsonView annotation on class fields. Example :

1)create class :

public class View {
    public static class UI {}
    public static class NotUI {}
    public static class Rest {}
}

// you can create many different Views here;

2) annotate needed fields of your entity;

    class Book{   
    String title;    
    String printType;
@JsonView(View.Rest.class) 
    Integer pageCount;

// pageCount have 'Rest' view and when controller have 'UI' view - pageCount will be missing

3)Annotate the controller method with appropriate context:

@JsonView(View.UI.class)
  @GetMapping("book/{isbn}")
    public Item getBook(@PathVariable String isbn) {
        return service.findBookByISBN(isbn);
    }