Convert json string to string array in java

3 ways to convert String to JSON object in Java? Examples

It’s very common nowadays to receive JSON String from a Java web service instead of XML, but unfortunately, JDK doesn’t yet support conversion between JSON String to JSON object. Keeping JSON as String always is not a good option because you cannot operate on it easily, you need to convert it into a JSON object before you do anything else e.g. retrieve any field or set different values. Fortunately, there are many open-source libraries which allows you to create JSON object from JSON formatted String like Gson from Google, Jackson, and json-simple. In this tutorial, you will learn how to use these 3 main libraries to do this conversion with step-by-step examples.

Even though you can use a simple or complex JSON String with lots of attributes and JSON arrays, I’ll use the following JSON String for example purpose:

jsonString = < "name" : "Ronaldo", "sport" : "soccer", "age" : 25, "id" : 121, "lastScores" : [ 2, 1, 3, 5, 0, 0, 1, 1 ] >

It’s simple, has 5 attributes, two of which are String and the other two are numeric. One attribute, lastScore is a JSON array.

1. String to JSON Object using Gson

The Gson is an open-source library to deal with JSON in Java programs. It comes from none other than Google, which is also behind Guava, a common purpose library for Java programmers. You can convert JSON String to Java object in just 2 lines by using Gson as shown below :

Gson g = new Gson(); Player p = g.fromJson(jsonString, Player.class)

You can also convert a Java object to JSON by using the toJson() method as shown below

The good thing about Gson is that it’s feature-rich and comes from Google, which is known for performance.

2. JSON String to Java object using JSON-Simple

The JSON-Simple is another open-source library that supports JSON parsing and formatting. The good thing about this library is its small size, which is perfect for memory constraint environments like J2ME and Android.

JSONParser parser = new JSONParser(); JSONObject json = (JSONObject) parser.parse(stringToParse);

The good thing about json-simple is that it is also JDK 1.2 compatible, which means you can use it on a legacy project which is not yet in Java 5.

3. String to JSON — Jackson Example

Jackson is I guess the most popular JSON parsing library in the Java world. It’s fast, feature-rich, and supports streaming which is great for parsing large JSON output from web services. Following one-liner convert JSON string representing a soccer player into a Java class representing player:

Player ronaldo = new ObjectMapper().readValue(jsonString, Player.class);

One of the drawbacks of Jackson is that it requires JDK 1.5 so if you are stuck in an earlier Java version then it may not fit there. Also, Jackson doesn’t support J2ME, but one of the main advantages of using Jackson is that it supports streaming which can be used to parse huge JSON responses without loading it fully in memory.

Jackson is a very popular and efficient Java library to map Java objects to JSON and vice-versa. If you want to learn the basics of the Jackson library and how to use them, I suggest you take a look at the Jackson documentation.

That’s all about how to convert String to JSON objects in Java. You can use any of the json-simple, Gson, or Jackson for parsing JSON messages received from web services, each of them has its own advantage. Json-simple has a small memory footprint means it’s quite suitable for J2ME and Android clients, while Jackson is feature-rich so better supported for a large project. Gson is in between them and my favorite general-purpose JSON parser in Java programs.

• 5 JSON libraries Java JEE Programmer should know (list)
• How to parse JSON to/from Java Object using Jackson? (tutorial)
• How to use Google Protocol Buffer (protobuf) in Java? (tutorial)
• Top 10 RESTful Web Service Interview Questions (see here)
• What is the purpose of different HTTP methods in REST? (see here)
• How to convert JSON to HashMap in Java? (guide)
• 10 Things Java developers should learn? (article)
• How to ignore unknown properties while parsing JSON in Java? (tutorial)
• How to parse JSON with date fields in Java? (example)
• 5 Courses to learn RESTful API and Web services in Java? (courses)
• 10 free courses to learn Java in-depth (resource)
• How to convert JSON array to String array in Java using Gson? (tutorial)
• How to parse a large JSON file using Jackson Streaming API? (example)

Thanks for reading this article so far. If you like these 3 ways to convert String to JSON object in Java, then please share with your friends and colleagues. If you have any questions or feedback, then please drop a note.

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JSONObject.toString() – How to Convert JSON to a String in Java

Shittu Olumide

In the world of web applications and services, JSON (JavaScript Object Notation) has become a widely used data format for data exchange between different systems.

In Java, it’s common to work with JSON data, and an operation you’ll frequently perform is converting a JSON object to a string representation.

The JSONObject.toString() method is a powerful tool that Java developers can use to convert JSON objects to strings.

In this article, we will explore how to use JSONObject.toString() method to convert JSON objects to strings in Java. We will also discuss the benefits of using this method, and provide examples of how to use it in practical applications.

What is the JSONObject.toString() Method?

JSON (JavaScript Object Notation) is a lightweight data interchange format that is widely used in web applications. It is easy to read and write, and it can be used to represent complex data structures in a simple and compact format.

In Java, the JSONObject class provided by the org.json package is commonly used to create and manipulate JSON objects. The JSONObject.toString() method is a useful method provided by this class that converts a JSON object to a string representation.

The JSONObject.toString() method takes no arguments and returns a string representation of the JSON object. This string representation is formatted according to the JSON syntax and can be used to transmit the JSON object over a network, store it in a file, or display it on a web page.

Here is the syntax for the JSONObject.toString() method:

To use the JSONObject.toString() method, you first need to create a JSON object using the JSONObject constructor or by parsing a JSON string using the JSONObject static method JSONObject.parse() .

Here is an example that demonstrates how to use the JSONObject.toString() method:

import org.json.JSONObject; public class JSONToStringExample < public static void main(String[] args) < JSONObject jsonObject = new JSONObject(); jsonObject.put("name", "John"); jsonObject.put("age", 30); jsonObject.put("married", true); String jsonString = jsonObject.toString(); System.out.println(jsonString); >> 

In the above example, we first create a JSONObject instance and add some key-value pairs to it using the put() method. Then, we call the toString() method on the JSONObject instance to get a string representation of the JSON object. Finally, we print the string to the console.

The output of the above code would be:

As you can see, the JSONObject.toString() method has converted the JSON object to a string representation that conforms to the JSON syntax. The string representation includes the key-value pairs and the appropriate punctuation marks (braces, commas, and colons) to represent the structure of the JSON object.

Benefits of using the JSONObject.toString() method

1. Easy Serialization: Using the JSONObject.toString() method makes it easy to serialize a JSONObject to a JSON-formatted string, which can then be transmitted over a network or stored in a file. This string representation can also be easily deserialized back into a JSONObject or other JSON-compatible object in the future.
2. Debugging: When debugging an application that uses JSON data, it can be helpful to log the JSON string representation of the JSONObject instance. This can help to diagnose issues related to JSON data processing.
3. Readability: The JSON format is a lightweight and easy-to-read format for storing and exchanging data. By using the JSONObject.toString() method, you can generate a JSON-formatted string that is easy to read and understand by other developers or systems.
4. Cross-platform compatibility: JSON is a widely-used data format that is supported by many programming languages and platforms. By using the JSONObject.toString() method, you can easily generate a JSON-formatted string that can be consumed by other systems or services regardless of the programming language or platform they are using.
5. Flexibility: The JSONObject.toString() method can be used to generate JSON-formatted strings that can represent complex and nested data structures. This flexibility allows you to represent a wide range of data types and structures in a standardized format that can be easily consumed by other systems or services.

Conclusion

The JSONObject.toString() method is a useful method provided by the org.json package in Java that converts a JSON object to a string representation. This method is essential when transmitting JSON data over a network, storing it in a file, or displaying it on a web page.

By following the syntax and examples outlined in this article, you can use the JSONObject.toString() method to easily convert JSON objects to string representations in your Java programs.

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How to Convert String to JSON and Vice Versa

In this tutorial, we will learn about How to Convert String to JSON and Vice Versa. First things first, What is JSON?

JSON is an acronym for JavaScript Object Notation. It is lightweight data transferring format among different web services. Mostly it is used to build an API.

Example of a JSON

This is an example of JSON it stores data in key-value format and values can be the array of another primitive datatype or another JSON.

There are three methods to convert JSON to String and Vice Versa in Java

While running a program where these libraries are included we need to download these jar files and add them inside the project according to IDE otherwise functions from these libraries will not support and cause an error. You can refer following links to download these libraries

Let’s look one by one with the help of examples.

Example JSON Library

In the code given below, we have a JSON data stored in the form of String. Converting a string JSON is very much convenient to perform multiple actions. JSONObject is a class of org.json package that converts a string to an JSON object.

import org.json.JSONException; import org.json.JSONObject; public class StudyTonight < public static void main(String[] args) < String myJSON =""; try < JSONObject jsonObject = new JSONObject(myJSON); System.out.println("JSON Object: "+jsonObject); >catch (JSONException e) < System.out.println("Error "+e.toString()); >> >

Example JSON Library : JSON to String

In the above code, we learned how to convert a string to a JSON object and now we can go for JSON object to a string we will learn creating an object from scratch also. Firstly we will create a JSON object and add values this class has JSONObject.put() method which accepts two parameter key and value.

import org.json.JSONObject; public class StudyTonight < public static void main(String[] args) < //Creating a JSON Object JSONObject jsonObject = new JSONObject(); jsonObject.put("name", "studytonight"); jsonObject.put("address", "Noida"); //Converting JSON Object using toString() method String myJSONString = jsonObject.toString(); System.out.println("JSON String: "+myJSONString); >>

Example GSON Library

Whatever the two things we did in the above code block we will do the same stuff using the Gson library. This library is developed by Google and widely used in the industry. JsonParser is a class that is responsible to parse a string and parse() is a method that accepts a string. Finally, we use getAsJsonObject() to get all the above conversion in JsonObject format.

import com.google.gson.JsonObject; import com.google.gson.JsonParser; public class StudyTonight < public static void main(String[] args) < //JSON String String myJSON =""; //JSON Parser from Gson Library JsonParser parser = new JsonParser(); //Creating JSONObject from String using parser JsonObject JSONObject = parser.parse(myJSON).getAsJsonObject(); System.out.println("Object: "+JSONObject); > >

Example GSON Library : JSON to String

To create JSON object inside the com.google.gson we use the JsonObject class and method addPropety() . addProperty() which will accept two parameters i.e. key and value which will be added to a JSON object.

import com.google.gson.JsonObject; public class StudyTonight < public static void main(String[] args) < //Creating Json Object JsonObject JSONObject = new JsonObject(); JSONObject.addProperty("name", "studytonight"); JSONObject.addProperty("address", "Noida"); //Converting Json Object to String String myJSON = JSONObject.toString(); System.out.println("String: "+myJSON); >>

Example Jackson Library

Jackson is a library that provides a lot of flexibility while working with JSON. We need to create a mapper from ObjectMapper class then we create a JsonFactory class object from a mapper and call that mapper to create a parser and finally this parse will create actually JSON object for us using readTree() method. readTree() will accept the parser object and trace the hierarchy of JSON.

import org.codehaus.jackson.JsonFactory; import org.codehaus.jackson.JsonNode; import org.codehaus.jackson.JsonParser; import org.codehaus.jackson.map.ObjectMapper; public class StudyTonight < public static void main(String[] args) < //JSON String String myJSON =""; ObjectMapper mapper = new ObjectMapper(); JsonFactory factory = mapper.getJsonFactory(); try < JsonParser parser = factory.createJsonParser(myJSON); JsonNode actualObj = mapper.readTree(parser); System.out.println("Object: "+actualObj); >catch(Exception e) < System.out.println("Error: "+e.toString()); >> >

Example Jackson Library : JSON to String

To create String from Json object Jackson library provides writeValueAsString() method in ObjectMapper class. This value accepts JSON objects and returns the string.

import org.codehaus.jackson.map.ObjectMapper; import org.codehaus.jackson.node.ObjectNode; public class StudyTonight < public static void main(String[] args) < ObjectMapper mapper = new ObjectMapper(); // create a JSON object ObjectNode JSONObject = mapper.createObjectNode(); JSONObject.put("name", "studytonight"); JSONObject.put("address", "Noida"); try < //Json object to String String JSONString = mapper.writeValueAsString(JSONObject); System.out.println("String: "+JSONString); >catch(Exception e) < System.out.println("Error "+e); >> >

Conclusion:

JSON is JavaScript Object Notation and it is very popular for building web services like RESTful APIs. We used json , gson , and Jackson libraries to convert JSON to String and String to JSON.

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