In this example we are going to use the JSON-Java (org.json) library to read or parse JSON file. First we start by getting the InputStream of the JSON file to be read using getResourceAsStream() method. Next we construct a JSONTokener from the input stream and create an instance of JSONObject to read the JSON entries.
We can use method like getString(), getInt(), getLong(), etc. to read a key-value from the JSON file. The getJSONArray() method allow us to read a list of values returned in JSONArray object, which can be iterated to get each values represented by the key. Let’s see the detail code snippet below.
package org.kodejava.json;
import org.json.JSONArray;
import org.json.JSONObject;
import org.json.JSONTokener;
import java.io.InputStream;
public class ReadJSONString {
public static void main(String[] args) {
// info.json
// {
// "id": "1",
// "name": "Alice",
// "age": "20",
// "courses": [
// "Engineering",
// "Finance",
// "Chemistry"
// ]
// }
String resourceName = "/info.json";
InputStream is = ReadJSONString.class.getResourceAsStream(resourceName);
if (is == null) {
throw new NullPointerException("Cannot find resource file " + resourceName);
}
JSONTokener tokener = new JSONTokener(is);
JSONObject object = new JSONObject(tokener);
System.out.println("Id : " + object.getLong("id"));
System.out.println("Name: " + object.getString("name"));
System.out.println("Age : " + object.getInt("age"));
System.out.println("Courses: ");
JSONArray courses = object.getJSONArray("courses");
for (int i = 0; i < courses.length(); i++) {
System.out.println(" - " + courses.get(i));
}
}
}
The result of the code snippet above is:
Id : 1
Name: Alice
Age : 20
Courses:
- Engineering
- Finance
- Chemistry
Maven Dependencies
<dependencies>
<!-- https://search.maven.org/remotecontent?filepath=org/json/json/20220924/json-20220924.jar -->
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20220924</version>
<type>bundle</type>
</dependency>
</dependencies>
Founder at Kode Java Org
A programmer, runner, recreational diver, live in the island of Bali, Indonesia. Programming in Java, Spring, Hibernate / JPA. You can support me working on this project, buy me a cup of coffee ☕, every little bit helps, thank you 🙏
Latest posts by Wayan (see all)
- How do I build simple search page using ZK and Spring Boot? - March 8, 2023
- How do I calculate days between two dates excluding weekends and holidays? - January 12, 2023
- How do I discover the quarter of a given date? - January 11, 2023
Hi, I am trying the example you have given but getting an error at the line:
JSONTokener tokener = new JSONTokener(is);And the error is below:
The constructor JSONTokener(InputStream) is undefined.
Can you please check and know which library you using?
Regards
Rohit
Hi Rohit,
I’m using the library as shown in the maven dependency section in the post above.
I had the same error but add the line below, it will work:
There is no such thing as ‘ReadJSONString’. Netbeans throws the fits.
ReadJSONString is the clas sname used in the example, you have to use your class name
Hi Wayan, Where do you place the file:
info.json? I try relative path and absolute path and couldn’t find it.Hi Chao, I am placing the
info.jsonfile under theresourcesdirectory (in a maven project structure). If you want to use absolute path you can do it like: