ClientAuthentication.
---------------------------

package client;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import javax.ws.rs.client.ClientRequestContext;
import javax.ws.rs.client.ClientRequestFilter;
import javax.ws.rs.core.MultivaluedMap;
import javax.xml.bind.DatatypeConverter;

public class ClientAuthentication implements ClientRequestFilter {

	private final String user;
    private final String password;

    public ClientAuthentication(String user, String password) {
        this.user = user;
        this.password = password;
    }

    public void filter(ClientRequestContext requestContext) throws IOException {
        MultivaluedMap<String, Object> headers = requestContext.getHeaders();
        final String basicAuthentication = getBasicAuthentication();
        headers.add("Authorization", basicAuthentication);

    }

    private String getBasicAuthentication() {
        String token = this.user + ":" + this.password;
        try {
            return "BASIC " + DatatypeConverter.printBase64Binary(token.getBytes("UTF-8"));
        } catch (UnsupportedEncodingException ex) {
            throw new IllegalStateException("Cannot encode with UTF-8", ex);
        }
    }
}


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Client.
--------
package client;
import javax.json.Json;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Invocation;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.Response;

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

public class Client {

	private String uri;
	private String user;
	private String password;

	public Client(String uri, String user, String password) {
		this.uri = uri;
		this.user = user;
		this.password = password;
	}

	public String getUri() {
		return uri;
	}

	public void setUri(String uri) {
		this.uri = uri;
	}

	public String getUser() {
		return user;
	}

	public void setUser(String user) {
		this.user = user;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public double add(double one, double two) {
		try {
			javax.ws.rs.client.Client client = ClientBuilder.newClient()
					.register(new ClientAuthentication(user, password));
			WebTarget target = client.target(uri);
			target = target.path("add").queryParam("num1", one).queryParam("num2", two);
			Invocation.Builder builder = target.request();
			Response jsonString = builder.get();
			String res = jsonString.readEntity(String.class);
			Gson g = new Gson();
			JsonObject resJson = g.fromJson(res, JsonObject.class);
			double value = resJson.get("result").getAsDouble();
			return value;
		} catch (Exception e) {
			return 0.0;
		}
	}

	public double multiply(double one, double two) {
		try {
			javax.ws.rs.client.Client client = ClientBuilder.newClient()
					.register(new ClientAuthentication(user, password));
			WebTarget target = client.target(uri);
			target = target.path("multiply").queryParam("num1", one).queryParam("num2", two);
			Invocation.Builder builder = target.request();
			Response jsonString = builder.get();
			String res = jsonString.readEntity(String.class);
			Gson g = new Gson();
			JsonObject resJson = g.fromJson(res, JsonObject.class);
			double value = resJson.get("result").getAsDouble();
			return value;
		} catch (Exception e) {
			return 0.0;
		}
	}

	public double sqrt(double squaret) {
		try {
			javax.ws.rs.client.Client client = ClientBuilder.newClient()
					.register(new ClientAuthentication(user, password));
			WebTarget target = client.target(uri);
			target = target.path("square").queryParam("sqrt", squaret);
			Invocation.Builder builder = target.request();
			Response jsonString = builder.get();
			String res = jsonString.readEntity(String.class);
			Gson g = new Gson();
			JsonObject resJson = g.fromJson(res, JsonObject.class);
			double value = resJson.get("result").getAsDouble();
			return value;
		} catch (Exception e) {
			return 0.0;
		}
	}
}