JSON as Data (Java)
There are a lot of competing Java JSON libraries around. I've used org.json which is available at:
- URL: https://github.com/stleary/JSON-java
- Maven: org.json:json
When searching for tutorials and documentation, be careful to search for "parsing" JSON. You will find a lot of Java tools that refer to serialising/deserialsing objects, or that make reference to pojo (plain-old-java-objects). For simple parsing of data received from a web api, these will be more complex than your needs.
Refererences:
- JavaDocs: https://stleary.github.io/JSON-java/
- https://www.baeldung.com/java-org-json
- https://www.codevoila.com/post/65/java-json-tutorial-and-example-json-java-orgjson
- https://github.com/stleary/JSON-java
- http://theoryapp.com/parse-json-in-java/
Sample code
package com.pbaumgarten.beyondbasics;
import org.json.*; // JSON parsing
class JSONDemo {
public boolean saveData(String filename) {
// Convert the ArrayList of Person objects into a JSONArray of JSONObjects
JSONArray ja = new JSONArray();
for (Person p : people) {
JSONObject jo = new JSONObject(p);
ja.put(jo);
}
// Save the JSONArray to a text file
try {
FileWriter fw = new FileWriter(filename);
PrintWriter output = new PrintWriter(fw);
output.println( ja.toString() );
output.close();
fw.close();
return true;
} catch(Exception e) {
System.out.println("[saveData] error saving "+filename);
return false;
}
}
public ArrayList<Person> loadData(String filename) {
StringBuilder sb = new StringBuilder();
ArrayList<Person> results = new ArrayList<Person>();
try {
// Load the JSON file as String data
File f = new File(filename);
Scanner reader = new Scanner(f);
while (reader.hasNextLine()) {
sb.append(reader.nextLine());
}
reader.close();
// Create a JSONArray from the String
JSONArray ja = new JSONArray(sb.toString());
// Iterate over the JSONObjects within the JSONArray
for (int i=0; i< ja.length(); i++) {
JSONObject o = ja.getJSONObject(i);
// Use each JSONObject to create a Person object
Person p = new Person(
o.getString("name"),
o.getString("email"),
o.getString("phoneNumber"),
o.getString("dateOfBirthString")
);
// Add the Person object to the ArrayList of people
results.add(p);
}
return results;
} catch(Exception e) {
System.out.println("[loadData] error loading "+filename);
return null;
}
}
public static void main(String[] args) {
// TO DO
}
}