Book Image

Jakarta EE Cookbook - Second Edition

By : Elder Moraes
Book Image

Jakarta EE Cookbook - Second Edition

By: Elder Moraes

Overview of this book

Jakarta EE is widely used around the world for developing enterprise applications for a variety of domains. With this book, Java professionals will be able to enhance their skills to deliver powerful enterprise solutions using practical recipes. This second edition of the Jakarta EE Cookbook takes you through the improvements introduced in its latest version and helps you get hands-on with its significant APIs and features used for server-side development. You'll use Jakarta EE for creating RESTful web services and web applications with the JAX-RS, JSON-P, and JSON-B APIs and learn how you can improve the security of your enterprise solutions. Not only will you learn how to use the most important servers on the market, but you'll also learn to make the best of what they have to offer for your project. From an architectural point of view, this Jakarta book covers microservices, cloud computing, and containers. It allows you to explore all the tools for building reactive applications using Jakarta EE and core Java features such as lambdas. Finally, you'll discover how professionals can improve their projects by engaging with and contributing to the community. By the end of this book, you'll have become proficient in developing and deploying enterprise applications using Jakarta EE.
Table of Contents (14 chapters)

Running your first JSON-P 1.1 code

Jakarta JSON Processing is the API for JSON processing. By processing, we mean generating, transforming, parsing, and querying JSON strings and/or objects.

In this recipe, you will learn how to use a JSON Pointer to get a specific value from a JSON message very easily.

Getting ready

Let's get our dependency:

<dependencies>
<dependency>
<groupId>org.eclipse</groupId>
<artifactId>yasson</artifactId>
<version>1.0.3</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.1.4</version>
</dependency>
<dependency>
<groupId>jakarta.platform</groupId>
<artifactId>jakarta.jakartaee-api</artifactId>
<version>8.0.0</version>
<scope>runtime</runtime>
</dependency>
</dependencies>

How to do it...

You need to perform the following steps to try this recipe:

  1. First, we define a JSON message to represent the User object:
{
"user": {
"email": "[email protected]",
"name": "Elder",
"profile": [
{
"id": 1
},
{
"id": 2
},
{
"id": 3
}
]
}
}
  1. Now, we create a method to read it and print the values we want:
public class JPointer {

public static void main(String[] args) throws IOException{
try (InputStream is =
JPointer.class.getClassLoader().getResourceAsStream("user.json");
JsonReader jr = Json.createReader(is)) {

JsonStructure js = jr.read();
JsonPointer jp = Json.createPointer("/user/profile");
JsonValue jv = jp.getValue(js);
System.out.println("profile: " + jv);
}
}
}
  1. The execution of this code prints the following:
profile: [{"id":1},{"id":2},{"id":3}]

How it works...

The JSON Pointer is a standard defined by the Internet Engineering Task Force (IETF) under Request for Comments (RFC) 6901. The standard basically says that a JSON Pointer is a string that identifies a specific value in a JSON document.

Without a JSON Pointer, you would need to parse the whole message and iterate through it until you find the desired value—probably lots of if and else instances and things like that.

So, a JSON Pointer helps you to decrease the written code dramatically by doing this kind of operation very elegantly.

See also

  • You can stay tuned with everything related to JSON-P at https://javaee.github.io/jsonp/.
  • The source code of this recipe is at https://github.com/eldermoraes/javaee8-cookbook/tree/master/chapter01/ch01-jsonp.