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[[oktatas:programozás:java:java_json|< Java JSON]]

====== Java JSON - Jackson-Databind ======

  * **Szerző:** Sallai András
  * Copyright (c) 2023, Sallai András
  * Licenc: [[https://creativecommons.org/licenses/by-sa/4.0/|CC Attribution-Share Alike 4.0 International]]
  * Web: https://szit.hu


===== Beszerzés =====

Maven függőségek:

<code xml>
  <dependencies>
    <dependency>
        <groupId>com.fasterxml.jackson.datatype</groupId>
        <artifactId>jackson-datatype-jsr310</artifactId>
        <version>2.15.2</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.15.2</version>
    </dependency>
    
  </dependencies>
</code>


===== JSON =====

<code javascript emp.json>
[
    {
        "id": 1,
        "name": "Parlag Ferenc",
        "city": "Szeged",
        "birth": {
            "place": "Szeged",
            "date": "2001-05-18"
        }
    },
    {
        "id": 2,
        "name": "Erős István",
        "city": "Szeged",
        "birth": {
            "place": "Szeged",
            "date": "2000-03-25"
        }
    }
]
</code>


===== Program =====

<code java Birth.java>
import java.time.LocalDate;

public class Birth {
    public String place;
    public LocalDate date;
}
</code>


<code java Employee.java>
public class Employee {
    public int id;
    public String name;
    public String city;
    public Birth birth;
    
    public Employee() {
    }
}
</code>

<code java Conv.java>
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;

import com.fasterxml.jackson.core.exc.StreamReadException;
import com.fasterxml.jackson.databind.DatabindException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.type.CollectionType;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

public class Conv {
    
    public void conv() {
        try {
            tryConv();
        }catch(StreamReadException e) {
            System.err.println("Hiba! A folyam olvasása sikertelen!");
        }catch(DatabindException e) {
            System.err.println("Hiba! A csatolás sikertelen!");
            System.err.println(e.getMessage());
        }catch(IOException e) {
            System.err.println("Hiba! A beolvasás sikertelen!");
        }
    }
    public void tryConv() throws IOException {
        ObjectMapper om = new ObjectMapper();

        om.registerModule(new JavaTimeModule());
        om.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);        

        CollectionType ct = om.getTypeFactory()
        .constructCollectionType(ArrayList.class, Employee.class);
        ArrayList<Employee> empList = om.readValue(new File("emp.json"),
        ct);


        System.out.println(empList.get(0).birth.date);
    }
}
</code>

<code java App.java>
public class App 
{
    public static void main( String[] args )
    {
        new Conv().conv();
    }
}

</code>