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refactorings for supporting custom endpoints with examples
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| # Sample application | ||
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| This module is to show simple examples of how to use the FHIR Gateway. The | ||
| minimal application is | ||
| [MainApp](src/main/java/com/google/fhir/gateway/MainApp.java). With this single | ||
| class, you can create an executable app with the Gateway [server](../server) and | ||
| all of the `AccessChecker` [plugins](../plugins), namely | ||
| [ListAccessChecker](../plugins/src/main/java/com/google/fhir/gateway/plugin/ListAccessChecker.java) | ||
| and | ||
| [PatientAccessChecker](../plugins/src/main/java/com/google/fhir/gateway/plugin/PatientAccessChecker.java). | ||
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| Two other classes are provided to show how to implement custom endpoints. |
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exec/src/main/java/com/google/fhir/gateway/CustomFhirEndpointExample.java
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| /* | ||
| * Copyright 2021-2023 Google LLC | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.google.fhir.gateway; | ||
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| import ca.uhn.fhir.context.FhirContext; | ||
| import ca.uhn.fhir.context.FhirVersionEnum; | ||
| import ca.uhn.fhir.parser.IParser; | ||
| import com.auth0.jwt.interfaces.Claim; | ||
| import com.auth0.jwt.interfaces.DecodedJWT; | ||
| import java.io.IOException; | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
| import javax.servlet.ServletException; | ||
| import javax.servlet.annotation.WebServlet; | ||
| import javax.servlet.http.HttpServlet; | ||
| import javax.servlet.http.HttpServletRequest; | ||
| import javax.servlet.http.HttpServletResponse; | ||
| import org.apache.http.HttpResponse; | ||
| import org.apache.http.HttpStatus; | ||
| import org.hl7.fhir.instance.model.api.IBaseResource; | ||
| import org.hl7.fhir.r4.model.ListResource; | ||
| import org.hl7.fhir.r4.model.ListResource.ListEntryComponent; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
|
|
||
| /** | ||
| * This is an example servlet that requires a valid JWT to be present as the Bearer Authorization | ||
| * header. Although it is not a standard FHIR query, but it uses the FHIR server to construct the | ||
| * response. In this example, it inspects the JWT and depending on its claims, constructs the list | ||
| * of Patient IDs that the user has access to. | ||
| * | ||
| * <p>The two types of tokens resemble {@link com.google.fhir.gateway.plugin.ListAccessChecker} and | ||
| * {@link com.google.fhir.gateway.plugin.PatientAccessChecker} expected tokens. But those are just | ||
| * picked as examples and this custom endpoint is independent of any {@link | ||
| * com.google.fhir.gateway.interfaces.AccessChecker}. | ||
| */ | ||
| @WebServlet("/myPatients") | ||
| public class CustomFhirEndpointExample extends HttpServlet { | ||
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| private static final Logger logger = LoggerFactory.getLogger(CustomFhirEndpointExample.class); | ||
| private final TokenVerifier tokenVerifier; | ||
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| private final HttpFhirClient fhirClient; | ||
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| public CustomFhirEndpointExample() throws IOException { | ||
| this.tokenVerifier = TokenVerifier.createFromEnvVars(); | ||
| this.fhirClient = FhirClientFactory.createFhirClientFromEnvVars(); | ||
| } | ||
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| @Override | ||
| protected void doGet(HttpServletRequest request, HttpServletResponse response) | ||
| throws ServletException, IOException { | ||
| // Check the Bearer token to be a valid JWT with required claims. | ||
| String authHeader = request.getHeader("Authorization"); | ||
| if (authHeader == null) { | ||
| throw new ServletException("No Authorization header provided!"); | ||
| } | ||
| List<String> patientIds = new ArrayList<>(); | ||
| // Note for a more meaningful HTTP status code, we can catch AuthenticationException in: | ||
| DecodedJWT jwt = tokenVerifier.decodeAndVerifyBearerToken(authHeader); | ||
| Claim claim = jwt.getClaim("patient_list"); | ||
| if (claim.asString() != null) { | ||
| logger.info("Found a 'patient_list' claim: {}", claim); | ||
| String listUri = "List/" + claim.asString(); | ||
| HttpResponse fhirResponse = fhirClient.getResource(listUri); | ||
| HttpUtil.validateResponseOrFail(fhirResponse, listUri); | ||
| if (fhirResponse.getStatusLine().getStatusCode() != HttpStatus.SC_OK) { | ||
| logger.error("Error while fetching {}", listUri); | ||
| response.setStatus(HttpStatus.SC_INTERNAL_SERVER_ERROR); | ||
| return; | ||
| } | ||
| FhirContext fhirContext = FhirContext.forCached(FhirVersionEnum.R4); | ||
| IParser jsonParser = fhirContext.newJsonParser(); | ||
| IBaseResource resource = jsonParser.parseResource(fhirResponse.getEntity().getContent()); | ||
| ListResource listResource = (ListResource) resource; | ||
| for (ListEntryComponent entry : listResource.getEntry()) { | ||
| patientIds.add(entry.getItem().getReference()); | ||
| } | ||
| } else { | ||
| claim = jwt.getClaim("patient_id"); | ||
| if (claim.asString() != null) { | ||
| logger.info("Found a 'patient_id' claim: {}", claim); | ||
| patientIds.add(claim.asString()); | ||
| } | ||
| } | ||
| if (claim.asString() == null) { | ||
| String error = "Found no patient claim in the token!"; | ||
| logger.error(error); | ||
| response.getOutputStream().print(error); | ||
| response.setStatus(HttpStatus.SC_INTERNAL_SERVER_ERROR); | ||
| return; | ||
| } | ||
| response.getOutputStream().print("Your patient are: " + String.join(" ", patientIds)); | ||
| response.setStatus(HttpStatus.SC_OK); | ||
| } | ||
| } |
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exec/src/main/java/com/google/fhir/gateway/CustomGenericEndpointExample.java
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| /* | ||
| * Copyright 2021-2023 Google LLC | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.google.fhir.gateway; | ||
|
|
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| import java.io.IOException; | ||
| import javax.servlet.annotation.WebServlet; | ||
| import javax.servlet.http.HttpServlet; | ||
| import javax.servlet.http.HttpServletRequest; | ||
| import javax.servlet.http.HttpServletResponse; | ||
| import org.apache.http.HttpStatus; | ||
|
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| /** | ||
| * This is an example servlet that can be used for any custom endpoint. It does not make any | ||
| * assumptions about authorization headers or accessing a FHIR server. | ||
| */ | ||
| @WebServlet("/custom/*") | ||
| public class CustomGenericEndpointExample extends HttpServlet { | ||
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| @Override | ||
| protected void doGet(HttpServletRequest request, HttpServletResponse resp) throws IOException { | ||
| String uri = request.getRequestURI(); | ||
| resp.getOutputStream().print("Successful request to the custom endpoint " + uri); | ||
|
Check warning Code scanning / CodeQL Cross-site scripting Medium
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| resp.setStatus(HttpStatus.SC_OK); | ||
| } | ||
| } | ||
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