~~NOTRANS~~
~~Title: REST Storage Client~~

If you need data from a REST service, it's super easy to call the REST service with JVx. The JVx REST services are based on [[https://www.restlet.com/|RESTlet]] and the library should be available in your application as well. To try it out, simply create a unit test:

<file java ContactClient.java>
import java.util.List;
import java.util.Map;

import org.junit.Test;
import org.restlet.data.ChallengeScheme;
import org.restlet.resource.ClientResource;

import com.sibvisions.rad.server.http.rest.JSONUtil;
import com.sibvisions.util.type.StringUtil;

public class ContactClient
{
    //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    // Test methods
    //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    @Test
    public void getContacts() throws Exception
    {
        ClientResource cres = new ClientResource("https://cloud.sibvisions.com/demoerp/services/rest/DemoERP/Customers/data/customer/");
        cres.setChallengeResponse(ChallengeScheme.HTTP_BASIC, "manager", "manager");
        
        List<Map<String, Object>> list = JSONUtil.getObject(cres.get(), List.class);
        
        for (Map<String, Object> m : list)
        {
            //System.out.println(StringUtil.toString(m.keySet()));

            System.out.println(m.get("ID") + ": " + m.get("FIRSTNAME") + " " + m.get("SURNAME"));
        }
    }
}
</file>

The response is e.g.

<file json>
[
   {
      "ID":730,
      "COMPANY":"adsad",
      "FIRSTNAME":"alasafsd",
      "SURNAME":"asf test",
      "EMAIL":"sadadsaa",
      "ADDRESS":"1",
      "ZIP":"1",
      "CITY":"2",
      "CUSTOMERSINCE":"2016-04-30T22:00:00.000+0000",
      "TITL_ID":1,
      "TITL_TITLE":"Dr.",
      "SALU_ID":1,
      "SALU_SALUTATION":"Male",
      "CUSTOMER_NR":"CN - 730"
   },
   {
      "ID":634,
      "COMPANY":"helDFF",
      "FIRSTNAME":"Peter",
      "SURNAME":"Fall",
      "EMAIL":"oooo",
      "ADDRESS":"zjr",
      "ZIP":"1235",
      "CITY":"www",
      "CUSTOMERSINCE":"2016-03-09T23:00:00.000+0000",
      "TITL_ID":1,
      "TITL_TITLE":"Dr.",
      "SALU_ID":2,
      "SALU_SALUTATION":"Female",
      "CUSTOMER_NR":"CN - 634"
   },
   {
      "ID":2,
      "COMPANY":"Excompany",
      "FIRSTNAME":"ddddd",
      "SURNAME":"eeee",
      "EMAIL":"susi.summ@excompany.com",
      "ADDRESS":"Street 2",
      "ZIP":"1100",
      "CITY":"Vienna",
      "CUSTOMERSINCE":"2012-12-01T23:00:00.000+0000",
      "TITL_ID":1,
      "TITL_TITLE":"Dr.",
      "SALU_ID":1,
      "SALU_SALUTATION":"Male",
      "CUSTOMER_NR":"CN - 2"
   },
   {
      "ID":750,
      "COMPANY":"333",
      "FIRSTNAME":"abcefe",
      "SURNAME":"555",
      "EMAIL":"Schider.ngai@somehost.com",
      "ADDRESS":"Far Far Away",
      "ZIP":"55555",
      "CITY":"zxcvasd",
      "CUSTOMERSINCE":null,
      "TITL_ID":1,
      "TITL_TITLE":"Dr.",
      "SALU_ID":1,
      "SALU_SALUTATION":"Male",
      "CUSTOMER_NR":"CN - 750"
   }
]</file>

You could integrate the REST call in your business logic, see [[:jvx:communication:calling_server_action|Calling a server-side action]]. If you need the result in your GUI, it's also possible to create a custom storage. We use a simple [[jvx:server:storage:abstract_memory|statful storage]] for our example, but you could also implement a stateless storage. Here's the storage:

<file java ContactStorage.java>
public class ContactStorage extends AbstractMemStorage
{
    //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    // Initialization
    //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    /**
     * Creates a new instance of <code>ContactStorage</code>.
     */
    public ContactStorage()
    {
    }

    //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    // Abstract methods implementation
    //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    @Override
    public RowDefinition getRowDefinition() throws ModelException
    {
        RowDefinition rdef = new RowDefinition();
        rdef.addColumnDefinition(new ColumnDefinition("ID", new BigDecimalDataType()));
        rdef.addColumnDefinition(new ColumnDefinition("FIRST"));
        rdef.addColumnDefinition(new ColumnDefinition("LAST"));
        
        rdef.setPrimaryKeyColumnNames(new String[] {"ID"});
        
        rdef.setColumnView(null, new ColumnView(rdef));
        
        return rdef;
    }

    @Override
    public void loadData(MemDataBook pBook, ICondition pCondition) throws ModelException
    {
        pBook.close();
        pBook.open();
        
        ClientResource cres = new ClientResource("https://cloud.sibvisions.com/demoerp/services/rest/DemoERP/Customers/data/customer/");
        cres.setChallengeResponse(ChallengeScheme.HTTP_BASIC, "manager", "manager");
        
        try
        {
            List<Map<String, Object>> list = JSONUtil.getObject(cres.get(), List.class);
            
            for (Map<String, Object> m : list)
            {
                pBook.insert(false);
                pBook.setValues(new String[] {"ID", "FIRST", "LAST"}, 
                                new Object[] {new BigDecimal((BigInteger)m.get("ID")), m.get("FIRSTNAME"), m.get("SURNAME")} ); 
            }
            
            pBook.saveAllRows();
        }
        catch (IOException ioe)
        {
            throw new ModelException(ioe);
        }
    }

    @Override
    public void insert(DataBookEvent pEvent) throws ModelException
    {
    }

    @Override
    public void update(DataBookEvent pEvent) throws ModelException
    {
    }

    @Override
    public void delete(DataBookEvent pEvent) throws ModelException
    {
    }

}
</file>
Our storage doesn't support insert/update/delete/filtering/sort. Only fetching data is implemented. But if you use client filtering/sort, it will work well.

The storage is ready to use with life-cycle objects:

<file java Contacts.java>
public IStorage getContacts() throws Exception
{
    ContactStorage storage = (ContactStorage)get("contacts");
    
    if (storage == null)
    {
        storage = new ContactStorage();
        storage.open();

        put("contacts", storage);
    }
    
    return storage;
}
</file>

And on the client side, use a RemoteDataBook as usual:

<file java>
RemoteDataBook rdbContacts = new RemoteDataBook();
rdbContacts.setName("contacts");
rdbContacts.setDataSource(getDataSource());
//because our storage doesn't support remote filtering/sort
rdbContacts.setMemFilter(true);
rdbContacts.setMemSort(true);
rdbContacts.open();
</file>

And here's an example application:

{{ :jvx:contacts.png?nolink |}}

\\ 
**<fs 20px>Note</fs>**

It's also possible to use other REST libraries, like:

  * https://howtoprogram.xyz/java-technologies/java-rest-client-example/
  * https://stackoverflow.com/questions/221442/rest-clients-for-java

Using RESTlet may be an option because it's used from JVx and thanks to JSONUtil it's easy to access the JSON object from the Response.