java 如何在 JSON 中发送地图

How to send a Map in JSON

提问by

I have an object that I need to upload in JSON

我有一个对象需要以 JSON 格式上传

public class Contribution<T extends MovieRequest> {
    private Set<T> elementsToAdd;
    private Map<Long, T> elementsToUpdate;
    private Set<Long> idsToDelete;
}

I want to send this object in JSON using swagger

我想使用 swagger 以 JSON 格式发送此对象

{
  "elementsToAdd": [
    {
      "country": "USA",
      "title": "string"
    }
  ],
  "elementsToUpdate": {},
  "numbersToDelete": [
    0
  ]
}

I do not know how to put an object in "elementsToUpdate": {},. As a key I want to put Long, and int he value put object.

我不知道如何将对象放入"elementsToUpdate": {},. 作为一个键，我想把 Long，和 int 他值 put 对象。

key (Long), value (object)

键（长），值（对象）

I tried this way

我试过这种方式

    "elementsToUpdate": {
   {
      1 : {
      "country": "USA",
      "title": "string"
      }
   }
  }

but throws the error

但抛出错误

JSON parse error: Unexpected character ('{' (code 123)): was expecting double-quote to start field name

回答by utkarsh31

Below is the complete example where I have converted a class to JSON string and back. You can use the same as reference. The point here is I have used TypeReference classto tell JSON that I have a class Contributionof type MovieRequest. Your code inside the project which reads the JSON has to be like this.

下面是我将一个类转换为 JSON 字符串并返回的完整示例。您可以将其用作参考。这里的重点是我曾经TypeReference class告诉 JSON 我有一个Contributiontype 类MovieRequest。您在项目中读取 JSON 的代码必须是这样的。

The Main Test Class

主要测试类

public class Test1
{
    public static void main(String[] args) throws IOException{
        //Creating object of the contribution class.
       Contribution<MovieRequest> c = new Contribution<>();

        Set<MovieRequest> set = new HashSet<>();
        set.add(getMovieObject());
        set.add(getMovieObject());
        set.add(getMovieObject());

        Map<Long, MovieRequest> map = new HashMap<>();
        map.put(1L, getMovieObject());
        map.put(2L, getMovieObject());
        map.put(3L, getMovieObject());

        Set<Long> set2 = new HashSet<>();
        set2.add(1L);
        set2.add(2L);
        set2.add(3L);

        c.setElementsToAdd(set);
        c.setElementsToUpdate(map);
        c.setIdsToDelete(set2);

        //Using Hymanson for Conversion.
        ObjectMapper mapper = new ObjectMapper();
        String value = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(c);
        //JSON String
        System.out.println(value);

        //Converting JSON string back to Object
        //here I am using TyperReference to tell JSON that this is the type of the class
        Contribution<MovieRequest> c1 =  mapper.readValue(value,  new TypeReference<Contribution<MovieRequest>>() { });
        System.out.println(c1);
    }

    //Just some class to spit out random strings. You can ignore it in ur example. Just add some random strings and return objects.
    private static MovieRequest getMovieObject()
    {
        MovieRequest m1 = new MovieRequest();
        m1.setCountry(randomString());
        m1.setTitle(randomString());
        return m1;
    }


    //This is a random string generator. Ignore this.
    public static String randomString()
    {
        return RandomStringUtils.randomAlphanumeric(17);
    }
}

The Bean classes

Bean 类

class Contribution<T extends MovieRequest>
{
    private Set<T> elementsToAdd;

    private Map<Long, T> elementsToUpdate;

    private Set<Long> idsToDelete;

    /**
     * @return the elementsToAdd
     */
    public Set<T> getElementsToAdd()
    {
        return elementsToAdd;
    }

    /**
     * @param elementsToAdd
     *            the elementsToAdd to set
     */
    public void setElementsToAdd(Set<T> elementsToAdd)
    {
        this.elementsToAdd = elementsToAdd;
    }

    /**
     * @return the elementsToUpdate
     */
    public Map<Long, T> getElementsToUpdate()
    {
        return elementsToUpdate;
    }

    /**
     * @param elementsToUpdate
     *            the elementsToUpdate to set
     */
    public void setElementsToUpdate(Map<Long, T> elementsToUpdate)
    {
        this.elementsToUpdate = elementsToUpdate;
    }

    /**
     * @return the idsToDelete
     */
    public Set<Long> getIdsToDelete()
    {
        return idsToDelete;
    }

    /**
     * @param idsToDelete
     *            the idsToDelete to set
     */
    public void setIdsToDelete(Set<Long> idsToDelete)
    {
        this.idsToDelete = idsToDelete;
    }

    /**
     * @inheritDoc
     */
    @JsonIgnore
    @Override
    public String toString()
    {
        return "Contribution [elementsToAdd=" + elementsToAdd + ", elementsToUpdate="
                + elementsToUpdate + ", idsToDelete=" + idsToDelete + "]";
    }

}

class MovieRequest
{
    private String country;

    private String title;

    /**
     * @return the country
     */
    public String getCountry()
    {
        return country;
    }

    /**
     * @param country
     *            the country to set
     */
    public void setCountry(String country)
    {
        this.country = country;
    }

    /**
     * @return the title
     */
    public String getTitle()
    {
        return title;
    }

    /**
     * @param title
     *            the title to set
     */
    public void setTitle(String title)
    {
        this.title = title;
    }

    /**
     * @inheritDoc
     */
    @JsonIgnore
    @Override
    public String toString()
    {
        return "MovieRequest [country=" + country + ", title=" + title + "]";
    }

}

Output

输出

{
  "elementsToAdd" : [ {
    "country" : "08Pv3v048kXbz9gRg",
    "title" : "ljuih0hctsTRC2FfY"
  }, {
    "country" : "847JRWP65Fum3Ttm5",
    "title" : "Z7kS3YGbyjKOVTX6p"
  }, {
    "country" : "JmkjGDW81BMDyyPgj",
    "title" : "X3c5J0xurKsbXNgCY"
  } ],
  "elementsToUpdate" : {
    "1" : {
      "country" : "ItZF8GgzFMAs8WRk5",
      "title" : "tMnb1z1ooSUOuqEMS"
    },
    "2" : {
      "country" : "HOhk142Q6brYmOMWC",
      "title" : "7FQv9TVj6nOjxU2Ri"
    },
    "3" : {
      "country" : "hJYbY33KOsMbJN2o6",
      "title" : "uW5zEkoosux9QsC44"
    }
  },
  "idsToDelete" : [ 1, 2, 3 ]
}
Contribution [elementsToAdd=[MovieRequest [country=08Pv3v048kXbz9gRg, title=ljuih0hctsTRC2FfY], MovieRequest [country=847JRWP65Fum3Ttm5, title=Z7kS3YGbyjKOVTX6p], MovieRequest [country=JmkjGDW81BMDyyPgj, title=X3c5J0xurKsbXNgCY]], elementsToUpdate={1=MovieRequest [country=ItZF8GgzFMAs8WRk5, title=tMnb1z1ooSUOuqEMS], 2=MovieRequest [country=HOhk142Q6brYmOMWC, title=7FQv9TVj6nOjxU2Ri], 3=MovieRequest [country=hJYbY33KOsMbJN2o6, title=uW5zEkoosux9QsC44]}, idsToDelete=[1, 2, 3]]

回答by saffron

1. Key is always should be string.
2. Why it still doesn't work ? because the error comes from redundant brace inside of "elementsToUpdate", below is sample:

1. 键始终应该是字符串。
2. 为什么它仍然不起作用？因为错误来自“elementsToUpdate”内部的冗余大括号，下面是示例：

"elementsToUpdate": {
  {  // redundant
    "1": {
      "country": "USA",
      "title": "string"
    }
  }  // redundant
}

correct one : 
"elementsToUpdate": {
    "1": {
      "country": "USA",
      "title": "string"
    }
}

"elementsToUpdate": {
  {  // redundant
    "1": {
      "country": "USA",
      "title": "string"
    }
  }  // redundant
}

correct one : 
"elementsToUpdate": {
    "1": {
      "country": "USA",
      "title": "string"
    }
}