Jsonobject java get string

Jsonobject java get string

Class JSONObject

public class JSONObject extends Object

A JSONObject is an unordered collection of name/value pairs. Its external form is a string wrapped in curly braces with colons between the names and values, and commas between the values and names. The internal form is an object having get and opt methods for accessing the values by name, and put methods for adding or replacing values by name. The values can be any of these types: Boolean , JSONArray , JSONObject , Number , String , or the JSONObject.NULL object. A JSONObject constructor can be used to convert an external form JSON text into an internal form whose values can be retrieved with the get and opt methods, or to convert values into a JSON text using the put and toString methods. A get method returns a value if one can be found, and throws an exception if one cannot be found. An opt method returns a default value instead of throwing an exception, and so is useful for obtaining optional values. The generic get() and opt() methods return an object, which you can cast or query for type. There are also typed get and opt methods that do type checking and type coercion for you. The opt methods differ from the get methods in that they do not throw. Instead, they return a specified value, such as null. The put methods add or replace values in an object. For example,

myString = new JSONObject().put("JSON", "Hello, World!").toString();

• An extra , (comma) may appear just before the closing brace.
• Strings may be quoted with ‘ (single quote).
• Strings do not need to be quoted at all if they do not begin with a quote or single quote, and if they do not contain leading or trailing spaces, and if they do not contain any of these characters: < >[ ] / \ : , = ; # and if they do not look like numbers and if they are not the reserved words true , false , or null .
• Keys can be followed by = or => as well as by : .
• Values can be followed by ; (semicolon) as well as by , (comma).
• Numbers may have the 0x- (hex) prefix.

Field Summary

It is sometimes more convenient and less ambiguous to have a NULL object than to use Java’s null value.

Constructor Summary

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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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Jsonobject java get string

JsonObject class represents an immutable JSON object value (an unordered collection of zero or more name/value pairs). It also provides unmodifiable map view to the JSON object name/value mappings. A JsonObject instance can be created from an input source using JsonReader.readObject() . For example:

 JsonReader jsonReader = Json.createReader(. ); JsonObject object = jsonReader.readObject(); jsonReader.close(); 

It can also be built from scratch using a JsonObjectBuilder . For example 1: An empty JSON object can be built as follows:

 JsonObject object = Json.createObjectBuilder().build(); 

 JsonObject value = Json.createObjectBuilder() .add("firstName", "John") .add("lastName", "Smith") .add("age", 25) .add("address", Json.createObjectBuilder() .add("streetAddress", "21 2nd Street") .add("city", "New York") .add("state", "NY") .add("postalCode", "10021")) .add("phoneNumber", Json.createArrayBuilder() .add(Json.createObjectBuilder() .add("type", "home") .add("number", "212 555-1234")) .add(Json.createObjectBuilder() .add("type", "fax") .add("number", "646 555-4567"))) .build(); 

 JsonWriter writer = . JsonObject obj = . ; writer.writeObject(obj); 

JsonObject values can be JsonObject , JsonArray , JsonString , JsonNumber , JsonValue.TRUE , JsonValue.FALSE , JsonValue.NULL . These values can be accessed using various accessor methods. In the above example 2, «John» can be got using

 String firstName = object.getString("firstName"); 

This map object provides read-only access to the JSON object data, and attempts to modify the map, whether direct or via its collection views, result in an UnsupportedOperationException . The map object’s iteration ordering is based on the order in which name/value pairs are added to the corresponding builder or the order in which name/value pairs appear in the corresponding stream.

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Java JSONObject Example

On this page we will learn using org.json.JSONObject class. The org.json API handles the JSON operation in Java application.
1. The JSONObject is an unordered collection of name/value pairs.
2. The JSONObject produces output as JSON string.
3. In JSONObject , we put values using put method that accepts key/value parameters. Key is string but value can be any datatype, for example, boolean , Collection , Map , int etc.
4. The toString() method makes a JSON text of this JSONObject .
5. Instantiate JSONObject as following.

JSONObject jsonOb = new JSONObject();

Contents

1. Putting values to JSONObject

The put method accepts key/value pair. Key is string and value can be any datatype for example boolean , Collection , double , float , int , long , Map and Object .
Find the methods to put values.

JSONObject put(String key, boolean value) JSONObject put(String key, Collection value) JSONObject put(String key, double value) JSONObject put(String key, Map value)

JSONObject jsonOb = new JSONObject(); jsonOb.put("101", "Mahesh"); jsonOb.put("102", "Nilesh"); jsonOb.put("103", "Jugesh"); System.out.println(jsonOb);

JSONObject jsonOb = new JSONObject(); jsonOb.put("2", 4); jsonOb.put("3", 9); jsonOb.put("4", 16); System.out.println(jsonOb);

Map map1 = new HashMap<>(); map1.put(101, "Mohit"); map1.put(102, "Suresh"); map1.put(103, "Anand"); Map map2 = new HashMap<>(); map2.put(101, 25); map2.put(102, 20); map2.put(103, 30); JSONObject jsonOb = new JSONObject(); jsonOb.put("name", map1); jsonOb.put("age", map2); System.out.println(jsonOb);

2. Getting Values from JSONObject

The JSONObject has more methods to get the values, for example,
getInt(String key) returns int value.
getBoolean(String key) returns boolean value.
getDouble(String key) returns double value.
getString(String key) returns String value.

JSONObject jsonOb = new JSONObject(); jsonOb.put("101", "Mahesh"); jsonOb.put("102", "Nilesh"); jsonOb.put("103", "Jugesh"); String name = jsonOb.getString("102"); // Nilesh System.out.println(name);

3. toString() Method

String toString(int indentFactor)

Make a pretty-printed JSON text. The indentFactor is the number of spaces to add to each level of indentation.

JSONObject jsonOb = new JSONObject(); jsonOb.put("101", "Mahesh"); jsonOb.put("102", "Nilesh"); String jsonOutput = jsonOb.toString(2); System.out.println(jsonOutput);

4. accumulate() Method

JSONObject accumulate(String key, Object value)

The accumulate() method accumulates values under a key. It is similar to put() method but the difference is that, for accumulate() method, when the key is already present, the values are stored as JSONArray .

JSONObject jsonOb = new JSONObject(); jsonOb.put("101", "Mahesh"); jsonOb.accumulate("102", "Nilesh"); jsonOb.accumulate("102", "Jugesh"); System.out.println(jsonOb);

5. append() Method

JSONObject append(String key, Object value)

The append method appends values to the array under a key.
If key is not available, then key is put in JSONObject with its value being JSONArray .
If key is available with value as JSONArray , then given value is appended to this array.

JSONObject jsonOb = new JSONObject(); jsonOb.put("101", "Mahesh"); jsonOb.append("102", "Nilesh"); System.out.println(jsonOb); jsonOb.append("102", "Jugesh"); System.out.println(jsonOb);

6. getNames() Method

static String[] getNames(Object object)

public class JSONDemo < public static void main(String. args) < String[] ob = JSONObject.getNames(new Student()); for(String n: ob) < System.out.println(n); >> > class Student

7. opt() Method

The opt method gets an optional value associated with a key. It returns an object which is the value, or null if there is no value.

JSONObject jsonOb = new JSONObject(); jsonOb.put("101", "Mahesh"); jsonOb.put("102", "Nilesh"); String data = (String)jsonOb.opt("102"); System.out.println(data); // Nilesh data = (String)jsonOb.opt("103"); System.out.println(data); // null

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