2. Your First Serializer

With juneau-marshall on the classpath (the project from the previous page has it), the Json marshaller turns a bean into JSON and back in one call.

Create the bean, src/main/java/com/example/demo/Pet.java. The REST pages reuse it:

package com.example.demo;

public class Pet {
    public int id;
    public String name;

    public Pet() {}
    public Pet(int id, String name) { this.id = id; this.name = name; }
}

Then create src/main/java/com/example/demo/Main.java:

package com.example.demo;

import org.apache.juneau.marshall.json.JsonSerializer;
import org.apache.juneau.marshall.marshaller.Json;
import org.apache.juneau.marshall.marshaller.Json5;

public class Main {
    public static void main(String[] args) throws Exception {
        String json = Json.of(new Pet(1, "Fido"));           // {"id":1,"name":"Fido"}
        System.out.println(json);

        Pet pet = Json.to(json, Pet.class);                  // back to a bean
        System.out.println(pet.name);                        // Fido

        System.out.println(Json5.of(new Pet(1, "Fido")));    // {id:1,name:'Fido'}

        JsonSerializer serializer = JsonSerializer.create().sq().build();
        System.out.println(serializer.write(new Pet(1, "Fido")));   // {'id':1,'name':'Fido'}
    }
}

Run it from the project directory:

mvn compile exec:java -Dexec.mainClass=com.example.demo.Main

Expected output:

{"id":1,"name":"Fido"}
Fido
{id:1,name:'Fido'}
{'id':1,'name':'Fido'}

Import the marshaller classes by name, as above. A wildcard import of both org.apache.juneau.marshall.json.* and org.apache.juneau.marshall.marshaller.* makes Json ambiguous, because both packages have a class of that name.

Other formats

Each format has a marshaller with the same of(...) / to(...) methods. Json5 (used in Main above) writes the relaxed, quote-free JSON dialect, which is handy for logs and tests.

For XML, HTML, YAML, CSV, MessagePack, and the rest, see juneau-marshall.

Configuring a serializer

The marshaller uses a default serializer and parser. When you need different settings, build your own and reuse it (serializers are thread-safe and cache their class metadata). Main builds one that uses single quotes:

JsonSerializer serializer = JsonSerializer.create().sq().build();
String json = serializer.write(new Pet(1, "Fido"));   // {'id':1,'name':'Fido'}

See Serializers and Parsers for the full set of options.

Next

Your first REST app