GSON example – Read and write JSON

In this post,we will see how can we read and write JSON using GSON.

Java JSON Tutorial Content:

reading and writing JSON using json-simple.We will use another way(i.e. GSON) of reading JSON.
Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.
There are various goals or advantages of using GSON(taken from GSON offcial page)

  • Provide simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa
  • Allow pre-existing unmodifiable objects to be converted to and from JSON
  • Extensive support of Java Generics
  • Allow custom representations for objects
  • Support arbitrarily complex objects (with deep inheritance hierarchies and extensive use of generic types)

Reading and writing JSON using GSON is very easy.You can use these two methods:
toJSON() : It will convert simple pojo object to JSON string.
FromJSON() : It will convert JSON string to pojo object.
In this post,we will read and write JSON using GSON.
Download gson-2.2.4 jar from here.
Create a java project named “GSONExample”
Create a folder jars and paste downloaded jar gson-2.2.4.jar.
right click on project->Property->java build path->Add jars and then go to src->jars->gson-2.2.4.jar.

Click on ok.
Then you will see json-simple-1.1 jar added to your libraries and then click on ok

First create a pojo named “Country.java”

Write JSON to file:

Create a new class named “GSONWritingToFileExample.java” in src->org.arpit.java2blog

Run above program and content of file CountryGSON.json will be as below :

Read JSON to file:

Here we will read above created JSON file.
Create a new class named “JSONSimpleReadingFromFileExample.java” in src->org.arpit.java2blog

Run above program and you will get following output:

Project Structure:

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Comments

  1. Is there an example w/simple json where you update records within a json object.

    For example w/structure below how to add a key/value pair to each element?
    {
    “data”: [
    {
    “Atomic Symbol”: “H”,
    “Atomic Number”: “1”,
    },
    {
    “Atomic Symbol”: “He”,
    “Atomic Number”: “2”,
    }

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