How to convert json to object

Converting JSON data to Java object

In this string every JSON object contains an array of other JSON objects. The intention is to extract a list of IDs where any given object possessing a group property that contains other JSON objects. I looked at Google’s Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

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I looked at Google’s Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

Google Gson supports generics and nested beans. The [] in JSON represents an array and should map to a Java collection such as List or just a plain Java array. The <> in JSON represents an object and should map to a Java Map or just some JavaBean class.

You have a JSON object with several properties of which the groups property represents an array of nested objects of the very same type. This can be parsed with Gson the following way:

See also:

Bewaaaaare of Gson! It’s very cool, very great, but the second you want to do anything other than simple objects, you could easily need to start building your own serializers (which isn’t that hard).

Also, if you have an array of Objects, and you deserialize some json into that array of Objects, the true types are LOST! The full objects won’t even be copied! Use XStream.. Which, if using the jsondriver and setting the proper settings, will encode ugly types into the actual json, so that you don’t loose anything. A small price to pay (ugly json) for true serialization.

Note that Jackson fixes these issues, and is faster than GSON.

Oddly, the only decent JSON processor mentioned so far has been GSON.

Here are more good choices:

One more to consider:

Or with Jackson:

Easy and working java code to convert JSONObject to Java Object

Employee.java

LoadFromJSON.java

If, by any change, you are in an application which already uses http://restfb.com/ then you can do:

If you use any kind of special maps with keys or values also of special maps, you will find it’s not contemplated by the implementation of google.

Depending on the input JSON format(string/file) create a jSONString. Sample Message class object corresponding to JSON can be obtained as below:

What’s wrong with the standard stuff?

Give boon a try:

It is wicked fast:

Don’t take my word for it. check out the gatling benchmark.

(Up to 4x is some cases, and out of the 100s of test. It also has a index overlay mode that is even faster. It is young but already has some users.)

It can parse JSON to Maps and Lists faster than any other lib can parse to a JSON DOM and that is without Index Overlay mode. With Boon Index Overlay mode, it is even faster.

It also has a very fast JSON lax mode and a PLIST parser mode. 🙂 (and has a super low memory, direct from bytes mode with UTF-8 encoding on the fly).

It also has the fastest JSON to JavaBean mode too.

It is new, but if speed and simple API is what you are looking for, I don’t think there is a faster or more minimalist API.

How to Convert JSON to JavaScript Object

JSON (JavaScript Object Notation) has become the de facto serialization format for REST APIs, due to the fact that it’s humanly-readable, simple and small in size.

It uses the same notation used to define JavaScript objects, and naturally, it’s extremely straightforward to convert between a JSON string and JavaScript objects.

We’ll be working with the following JSON string:

Convert JSON String to JavaScript Object

It’s built into the language itself so there’s no need to install or import any dependencies:

This results in:

You might be tempted to eval() a string into an object, but be weary of the practice:

This works just fine:

However, this method is also susceptible to code injection. eval() will evaluate and execute any arbitrary text that you put in, provided it can be run. If our jsonString was changed to:

Then just evaluating it would result in:

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Convert JSON String to JavaScript Array

This results in:

Conclusion

In this short tutorial, we’ve taken a look at how to convert a JSON string into a JavaScript object, and remarked at a bad practice that could introduce vulnerabilities in your code.

Convert a JSON string to object in Java ME?

Is there a way in Java/J2ME to convert a string, such as:

to an internal Object representation of the same, in one line of code?

Because the current method is too tedious:

Maybe a JSON library?

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I used a few of them and my favorite is,

The library is very small so it’s perfect for J2ME.

You can parse JSON into Java object in one line like this,

The simplest option is Jackson:

There are other similarly simple to use libraries (Gson was already mentioned); but some choices are more laborious, like original org.json library, which requires you to create intermediate «JSONObject» even if you have no need for those.

GSON is a good option to convert java object to json object and vise versa.
It is a tool provided by google.

for converting json to java object use: fromJson(jsonObject,javaclassname.class)
for converting java object to json object use: toJson(javaObject)
and rest will be done automatically

You can do this easily with Google GSON.

Let’s say you have a class called User with the fields user, width, and height and you want to convert the following json string to the User object.

You can easily do so, without having to cast (keeping nimcap’s comment in mind 😉 ), with the following code:

Формат JSON, метод toJSON

Допустим, у нас есть сложный объект, и мы хотели бы преобразовать его в строку, чтобы отправить по сети или просто вывести для логирования.

Естественно, такая строка должна включать в себя все важные свойства.

Мы могли бы реализовать преобразование следующим образом:

…Но в процессе разработки добавляются новые свойства, старые свойства переименовываются и удаляются. Обновление такого toString каждый раз может стать проблемой. Мы могли бы попытаться перебрать свойства в нём, но что, если объект сложный, и в его свойствах имеются вложенные объекты? Мы должны были бы осуществить их преобразование тоже.

К счастью, нет необходимости писать код для обработки всего этого. У задачи есть простое решение.

JSON.stringify

JSON (JavaScript Object Notation) – это общий формат для представления значений и объектов. Его описание задокументировано в стандарте RFC 4627. Первоначально он был создан для JavaScript, но многие другие языки также имеют библиотеки, которые могут работать с ним. Таким образом, JSON легко использовать для обмена данными, когда клиент использует JavaScript, а сервер написан на Ruby/PHP/Java или любом другом языке.

JavaScript предоставляет методы:

Например, здесь мы преобразуем через JSON.stringify данные студента:

Метод JSON.stringify(student) берёт объект и преобразует его в строку.

Полученная строка json называется JSON-форматированным или сериализованным объектом. Мы можем отправить его по сети или поместить в обычное хранилище данных.

Обратите внимание, что объект в формате JSON имеет несколько важных отличий от объектного литерала:

JSON.stringify может быть применён и к примитивам.

JSON поддерживает следующие типы данных:

JSON является независимой от языка спецификацией для данных, поэтому JSON.stringify пропускает некоторые специфические свойства объектов JavaScript.

Обычно это нормально. Если это не то, чего мы хотим, то скоро мы увидим, как можно настроить этот процесс.

Самое замечательное, что вложенные объекты поддерживаются и конвертируются автоматически.

Важное ограничение: не должно быть циклических ссылок.

Исключаем и преобразуем: replacer

Полный синтаксис JSON.stringify :

Если мы передадим ему массив свойств, будут закодированы только эти свойства.

Здесь мы, наверное, слишком строги. Список свойств применяется ко всей структуре объекта. Так что внутри participants – пустые объекты, потому что name нет в списке.

К счастью, в качестве replacer мы можем использовать функцию, а не массив.

Обратите внимание, что функция replacer получает каждую пару ключ/значение, включая вложенные объекты и элементы массива. И она применяется рекурсивно. Значение this внутри replacer – это объект, который содержит текущее свойство.

Идея состоит в том, чтобы дать как можно больше возможностей replacer – у него есть возможность проанализировать и заменить/пропустить даже весь объект целиком, если это необходимо.

Форматирование: space

Третий аргумент в JSON.stringify(value, replacer, space) – это количество пробелов, используемых для удобного форматирования.

Ранее все JSON-форматированные объекты не имели отступов и лишних пробелов. Это нормально, если мы хотим отправить объект по сети. Аргумент space используется исключительно для вывода в удобочитаемом виде.

Ниже space = 2 указывает JavaScript отображать вложенные объекты в несколько строк с отступом в 2 пробела внутри объекта:

Третьим аргументом также может быть строка. В этом случае строка будет использоваться для отступа вместо ряда пробелов.

Параметр space применяется исключительно для логирования и красивого вывода.

Пользовательский «toJSON»

Как и toString для преобразования строк, объект может предоставлять метод toJSON для преобразования в JSON. JSON.stringify автоматически вызывает его, если он есть.

Теперь давайте добавим собственную реализацию метода toJSON в наш объект room (2) :

Easiest way to convert json data into objects with methods attached?

What’s the quickest and easiest way to convert my json, containing the data of the objects, into actual objects with methods attached?

By way of example, I get data for a fruitbowl with an array of fruit objects which in turn contain an array of seeds thus:

That’s all nice and good but down on the client we do stuff with this fruit, like eat it and plant trees.

My ajax’s success routine currently is currently looping over the thing and constructing each object in turn and it doesn’t handle the seeds yet, because before I go looping over seed constructors I’m thinking

Is there not a better way?

I haven’t explored looping over the objects as they are and attaching all the methods. Would that work?

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Yes, it would work, but it’s not desirable. Apart from appearing slightly hacky IMO, you’re attaching methods to each instance of your fruit and seeds, where you should instead be using the prototype chain. If you’re going to be using instanceof in the future, this method won’t work anyway.

If you’re feeling adventurous, you can use JSONP instead of AJAX, with the JSONP response looking something like:

Which will save you having to do all your object looping, and you’ll get your Fruit and Seeds how you want (and instanceof support); however I would still stick to what you’re doing already.

Best of look growing your bananas.

Pass the data to the object constructor then use jquery’s «extend» to combine the data and methods:

You still have loops involved; and must manually code loops for the nested objects (like seeds), but still a very simple way to get past the problem.

You could modify the JSON structure to store the type information. If you have a lot of objects to serialize and deserialize back and forth, this would save time writing custom code for each object.

Also note, this modifies the JSON structure and adds a __type__ property to each custom object. I think this is a cleaner approach than keeping separate configuration files. So without further ado, this is how it basically works:

call serialize on the object to get a JSON representation

call deserialize on the JSON encoded string to reconstruct the objects

now you can access properties and call methods on the objects:

It works for any levels of deeply nested objects, although it might be a little buggy for now. Also it is most likely not cross-browser (only tested on Chrome). Since the deserializer is not familiar with an object’s constructor function, it basically creates each custom object without passing any parameters. I’ve setup a working demo on jsfiddle at http://jsfiddle.net/kSATj/1/.

The constructor function had to be modified to account for the two ways it’s objects could be created

All constructors would need to accommodate creation from both ends, so each property needs to be assigned a default fallback value incase nothing was passed.

For reference, the modified JSON looks like:

This is just a helper function to identify simple types:

Serializes an object into JSON (with type info preserved):

Deserialize (with custom objects reconstructed):

Simply define your objects statically then use Object.create to extend them.

It’s as simple as Object.create(Bowl, transform(data));

You will need to define the transform function and more importantly tell it the object type of nested arrays of data.

Using D Crockford’s «json2» library, you can supply a «reviver» function to the parsing process. The reviver function is passed each key and each value, and should return the actual effective value to be used in the parsed result.

There’s a corresponding optional parameter in the «stringify» method.

This actually took me a while to figure out, I’m really surprised there are not more pages on this.

Reviver is part of ECMA 5 and is supported in Firefox, WebKit (Opera/Chrome), and JSON2.js.

Here is a code example based on the JSON doc. You can see we are setting a type property on Dog and then using a reviver function that recognizes that type property.

I have a couple concerns about their example. The first is that it depends on the constructor being global (on window). The second is a security concern in that rogue JSON can get us to call any constructor by adding a type property to their JSON.

I’ve chosen to have an explicit list of types and their constructors. This ensures only constructors I know are safe will be called and also allows me to use a custom type mapping approach if I like (rather than depending on the constructor name and it being in the global space). I also verify the JSON object has a type (some may not and they will be treated normally).