[[oktatas:programozás:java:java_rest_api_kliens|< Java REST API kliens]]

====== Java REST API Unirest és Gson használatával ======

  * **Szerző:** Sallai András
  * Copyright (c) 2024, Sallai András
  * Licenc: [[https://creativecommons.org/licenses/by-sa/4.0/|CC BY-SA 4.0]]
  * Web: https://szit.hu

===== Az Unirest-ről =====

Az Unirest számára minimum 11 Java szükséges. A háttérben az Apache HttpClient megvalósítást használja.

Az Unirest elérhetősége:

  * https://github.com/Kong/unirest-java (2024)
  * https://kong.github.io/unirest-java/ (2024)

==== JAR függőségek ====

Ha jar fájlokat használunk a következőkre van szükség:

  * commons-logging
  * httpasyncclient
  * httpclient
  * httpcore
  * httpcore-nio
  * unirest-java



===== Maven =====

<code xml pom.xml>
    <dependencyManagement>
  <dependencies>
      <!-- https://mvnrepository.com/artifact/com.konghq/unirest-java-bom --> 
      <dependency>
          <groupId>com.konghq</groupId>
          <artifactId>unirest-java-bom</artifactId>
          <version>4.4.0</version>
          <type>pom</type>
          <scope>import</scope>
      </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
    <!-- https://mvnrepository.com/artifact/com.konghq/unirest-java-core -->
    <dependency>
        <groupId>com.konghq</groupId>
        <artifactId>unirest-java-core</artifactId>
    </dependency>
    
    <!-- pick a JSON module if you want to parse JSON include one of these: -->
    <!-- Google GSON -->
    <dependency>
        <groupId>com.konghq</groupId>
        <artifactId>unirest-modules-gson</artifactId>
    </dependency>

    <!-- OR maybe you like Jackson better? -->
    <dependency>
        <groupId>com.konghq</groupId>
        <artifactId>unirest-modules-jackson</artifactId>
    </dependency>
</dependencies>
</code>

===== Példa GET metódusra =====

<code java src/main/java/lan/zold/Main.java>
package lan.zold;

import kong.unirest.core.HttpResponse;
import kong.unirest.core.JsonNode;
import kong.unirest.core.Unirest;


public class Main {
    public static void main(String[] args) {

        String url = "https://jsonplaceholder.typicode.com/todos";
        
        HttpResponse<JsonNode> apiResponse = Unirest.get(url).asJson();

        System.out.println(apiResponse.getBody().toPrettyString());
    }
}
</code>

===== Helyi URL =====

Ha hai-server-t használunk helyettesítő szervernek szükség lehet a localhost helyett: [::1] névre:

<code java src/main/java/lan/zold/Main.java>
package lan.zold;

import kong.unirest.core.HttpResponse;
import kong.unirest.core.JsonNode;
import kong.unirest.core.Unirest;

public class Main {
    public static void main(String[] args) {
        String url = "http://[::1]:8000/employees";
        HttpResponse<JsonNode> apiResponse = Unirest.get(url)
            .asJson();

        System.out.println(apiResponse.getBody().toPrettyString());
    }
}
</code>

===== CRUD műveletek =====

<code java src/main/java/lan/zold/Employee.java>
package lan.zold;

public class Employee {
  Integer id;
  String name;
  String city;
  Double salary;
  public Employee(Integer id, String name, String city, Double salary) {
    this.id = id;
    this.name = name;
    this.city = city;
    this.salary = salary;
  }
  public Employee(String name, String city, Double salary) { 
    this.name = name;
    this.city = city;
    this.salary = salary;
  }
}
</code>


<code java src/main/java/lan/zold/Api.java>
package lan.zold;

import java.util.ArrayList;
import java.util.Arrays;

import com.google.gson.Gson;

import kong.unirest.core.HttpResponse;
import kong.unirest.core.JsonNode;
import kong.unirest.core.Unirest;

public class Api {
  
  String url = "http://[::1]:8000/employees";

  public ArrayList<Employee> getEmployees() {    
    HttpResponse<JsonNode> apiResponse = 
    Unirest.get(url).asJson();
    String json = apiResponse.getBody().toString();
    Gson gson = new Gson();
    Employee[] employeeArray = 
    gson.fromJson(json, Employee[].class);
    ArrayList<Employee> employeeList = 
    new ArrayList<>(Arrays.asList(employeeArray));
    return employeeList;
  }

  public String createEmployee(Employee employee) {
    Gson gson = new Gson();
    String json = gson.toJson(employee);
    HttpResponse<String> apiResponse = Unirest.post(url)
        .header("Content-Type", "application/json")
        .body(json)
        .asString();
    return apiResponse.getBody();
  }

  public String updateEmployee(Employee employee) {
    Gson gson = new Gson();
    String json = gson.toJson(employee);
    HttpResponse<String> apiResponse = 
    Unirest.put(url + "/" + employee.id)
        .header("Content-Type", "application/json")
        .body(json)
        .asString();
    return apiResponse.getBody();
  }

  public String deleteEmployee(Integer id) {
    HttpResponse<String> apiResponse = 
    Unirest.delete(url + "/" + id)
        .asString();
    return apiResponse.getBody();
  }
}

</code>


<code java src/main/java/lan/zold/Main.java>
package lan.zold;

import java.util.ArrayList;

public class Main {
    static Api api = new Api();
    public static void main(String[] args) {
        getEmployees();
    }

    public static void getEmployees() {
        ArrayList<Employee> employees = api.getEmployees();
        for (Employee employee : employees) {
          System.out.println(employee.name);
        }
    }

    public static void createEmployee() {
        Employee employee = new Employee(
            "John", 
            "London", 
            1000.0);
        System.out.println(api.createEmployee(employee));       
    }

    public static void updateEmployee() {
        Employee employee = new Employee(4, "Árpád", "Szeged", 500.0);
        System.out.println(api.updateEmployee(employee));
    }

    public static void deleteEmployee() {
        System.out.println(api.deleteEmployee(5));
    }
}
</code>