This Java example is for Java developers to use and modify when they wish to make a VSAC FHIR API call from within their program.

import java.io.IOException;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

import org.apache.http.HttpResponse;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.springframework.http.HttpHeaders;

public class FhirClient {

	public static void main(String[] args) throws IOException {

		String fhirServerBase = "https://cts.nlm.nih.gov/fhir/";
		String username = "";
		String password = "d4c9d78b-83dc-499e-ae27-947cc00fb438"; // Assign an API key to password
		String valueToEncode = username + ":" + password;
	    String basicAuthHeader =  "Basic " + Base64.getEncoder().encodeToString(valueToEncode.getBytes());		

		HttpClient client = HttpClientBuilder.create().build();
		try {

			// Request sample 1: value set
			HttpGet httpGet = new HttpGet();
			httpGet.setHeader(HttpHeaders.AUTHORIZATION, basicAuthHeader);

			httpGet.setURI(new URIBuilder(fhirServerBase + "ValueSet/2.16.840.1.113762.1.4.1018.98").build()); // VSAC OID example
			HttpResponse response = client.execute(httpGet);
			String responseString = EntityUtils.toString(response.getEntity());
			System.out.println(responseString);

			// Request sample 2: code system lookup
			httpGet.setURI(new URIBuilder(fhirServerBase + "CodeSystem/$lookup?system=http://loinc.org&code=1963-8").build());

			response = client.execute(httpGet);
			responseString = EntityUtils.toString(response.getEntity());
			System.out.println(responseString);

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Last Reviewed: September 7, 2023