Creating POJO from JSON using Manifold System

Many a times we need to create POJO from JSON samples. This is a tedious job as we need to create a class & then add the properties. 

Is there a better way that Java can automatically generate the class parsing the JSON file.

Yes, Manifold System comes to the rescue. (http://manifold.systems/)

Let's see an example:

Pre-requisite: 

1. Java 8

2. Intellij IDE

Steps:

Plugin Install:

Open Intellij IDE

Go to Settings->Plugins -> Marketplace

Find Manifold & install the same.

Dependency Addition in Maven Project 

First add the below dependencies in pom.xml

<properties>
  <maven.compiler.source>8</maven.compiler.source>
  <maven.compiler.target>8</maven.compiler.target>  
  <manifold.version>2022.1.29</manifold.version>

</properties> 

Dependency:

<dependency>
  <groupId>systems.manifold</groupId>
  <artifactId>manifold-json-rt</artifactId>
  <version>${manifold.version}</version>
</dependency>

Build Config:

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.8.0</version>
      <configuration>
        <source>8</source>
        <target>8</target>
        <encoding>UTF-8</encoding>
        <compilerArgs>
          <!-- Configure manifold plugin -->
          <arg>-Xplugin:Manifold</arg>
        </compilerArgs>
        <!-- Add the processor path for the plugin -->
        <annotationProcessorPaths>
          <path>
            <groupId>systems.manifold</groupId>
            <artifactId>manifold-json</artifactId>
            <version>${manifold.version}</version>
          </path>
          <path>
            <groupId>systems.manifold</groupId>
            <artifactId>manifold-strings</artifactId>
            <version>${manifold.version}</version>
          </path>
        </annotationProcessorPaths>
      </configuration>
    </plugin>

    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.22.2</version>
    </plugin>
  </plugins>
</build>

If Lombok is already used in the project then use below configuration:

 <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                    <encoding>UTF-8</encoding>
                    <compilerArgs>
                        <!-- Configure manifold plugin -->
                        <arg>-Xplugin:Manifold</arg>
                    </compilerArgs>
                    <!-- Add the processor path for the plugin -->
                    <annotationProcessorPaths>

                        <processorPath>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                            <version>1.18.24</version>
                        </processorPath>
                        <processorPath>
                            <groupId>systems.manifold</groupId>
                            <artifactId>manifold-json</artifactId>
                            <version>${manifold.version}</version>
                        </processorPath>
                        <processorPath>
                            <groupId>systems.manifold</groupId>
                            <artifactId>manifold-strings</artifactId>
                            <version>${manifold.version}</version>
                        </processorPath>


                    </annotationProcessorPaths>
                </configuration>
            </plugin>

Code:

Create a sample JSON file in src/main/resources folder.

The file should be created with package structure. 

The file name should follow the class name.

E.g.

Create a folder named restapi in src/main/resources/

Create a file named User.json with below content:

{
  "firstName": "Sourav",
  "lastName": "Dalal"
}

A new class User.class will be created dynamically.

The class file will be created under package restapi. You can create any package structure of your choice

You can access the class like below

User testUser = User.create();

testUser.setFirstName("X");
testUser.setLastName("Y");
System.out.println(testUser.write().toJson()
Happy Coding !! :)
Further Reading:
http://manifold.systems/articles/articles.html
https://debugagent.com/revolutionize-json-parsing-in-java-with-manifold