Serialize JSON object với JsonWriter dùng Object Model (javax.json)

javax.json.JsonWriter ghi JSON object/array ra output source (Writer, OutputStream). Tạo qua Json.createWriter() hoặc JsonWriterFactory.

Cú pháp

public static JsonWriter createWriter(Writer writer)

Ví dụ: Build JsonObject bằng JsonObjectBuilder rồi write

import javax.json.*;
import java.io.StringWriter;

public class JsonWriterTest {
    public static void main(String[] args) {
        // Build JsonObject dùng Object Model API (Builder pattern)
        JsonObject jsonObj = Json.createObjectBuilder()
            .add("name", "Adithya")
            .add("age", 25)
            .add("salary", 40000)
            .add("address", Json.createObjectBuilder()
                .add("street", "Madhapur")
                .add("city", "Hyderabad")
                .add("zipCode", "500084")
            )
            .add("phoneNumber", Json.createArrayBuilder()
                .add("9959984000")
                .add("7702144400")
            )
            .build();
        
        // Write ra String
        StringWriter stringWriter = new StringWriter();
        JsonWriter writer = Json.createWriter(stringWriter);
        writer.writeObject(jsonObj);
        writer.close();
        
        System.out.println(stringWriter.toString());
    }
}

Output

{"name":"Adithya","age":25,"salary":40000,"address":{"street":"Madhapur","city":"Hyderabad","zipCode":"500084"},"phoneNumber":["9959984000","7702144400"]}

Các cách tạo JsonWriter

• Json.createWriter(Writer) - ghi ra Writer.
• Json.createWriter(OutputStream) - ghi ra OutputStream (auto UTF-8).
• JsonWriterFactory.createWriter(...) - reuse config cho multiple writers.

Streaming API (Alternative trong javax.json)

// Streaming write - memory efficient cho large JSON
JsonGenerator gen = Json.createGenerator(outputStream);
gen.writeStartObject()
   .write("name", "Adithya")
   .write("age", 25)
   .writeEndObject()
   .close();

So sánh Object Model vs Streaming

Dependency (Jakarta EE 9+)

<dependency>
    <groupId>jakarta.platform</groupId>
    <artifactId>jakarta.json-api</artifactId>
    <version>2.0.1</version>
</dependency>
<dependency>
    <groupId>org.glassfish</groupId>
    <artifactId>jakarta.json</artifactId>
    <version>2.0.1</version>
</dependency>