Converting a BufferedReader to a JSONObject

1. Overview

In this quick tutorial, we're going to show how to convert a BufferedReader to a JSONObject using two different approaches.

2. Dependency

Before we get started, we need to add the org.json dependency into our pom.xml:

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20200518</version>
</dependency>

3. JSONTokener

The latest version of the org.json library comes with a JSONTokener constructor. It directly accepts a Reader as a parameter.

So, let's convert a BufferedReader to a JSONObject using that:

@Test
public void givenValidJson_whenUsingBufferedReader_thenJSONTokenerConverts() {
    byte[] b = "{ \"name\" : \"John\", \"age\" : 18 }".getBytes(StandardCharsets.UTF_8);
    InputStream is = new ByteArrayInputStream(b);
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
    JSONTokener tokener = new JSONTokener(bufferedReader);
    JSONObject json = new JSONObject(tokener);

    assertNotNull(json);
    assertEquals("John", json.get("name"));
    assertEquals(18, json.get("age"));
}

4. First Convert to String

Now, let's look at another approach to obtain the JSONObject by first converting a BufferedReader to a String.

This approach can be used when working in an older version of org.json:

@Test
public void givenValidJson_whenUsingString_thenJSONObjectConverts()
  throws IOException {
    // ... retrieve BufferedReader<br />
    StringBuilder sb = new StringBuilder();
    String line;
    while ((line = bufferedReader.readLine()) != null) {
        sb.append(line);
    }
    JSONObject json = new JSONObject(sb.toString());

    // ... same checks as before
}

Here, we're converting a BufferedReader to a String and then we're using the JSONObject constructor to convert a String to a JSONObject.

5. Conclusion

In this article, we've seen two different ways of converting a BufferedReader to a JSONObject with simple examples. Undoubtedly, the latest version of org.json provides a neat and clean way of converting a BufferedReader to a JSONObject with fewer lines of code.

As always, the full source code of the example is available over on GitHub.