Support exception mapper extension

Author: mytang0

dubbo-rpc/dubbo-rpc-rest/src/main/java/org/apache/dubbo/rpc/protocol/rest/BaseRestProtocolServer.java

@@ -25,6 +25,7 @@
 import java.util.concurrent.ConcurrentHashMap;
 
 import static org.apache.dubbo.common.constants.CommonConstants.COMMA_SPLIT_PATTERN;
+import static org.apache.dubbo.rpc.protocol.rest.Constants.EXCEPTION_MAPPER_KEY;
 import static org.apache.dubbo.rpc.protocol.rest.Constants.EXTENSION_KEY;
 
 public abstract class BaseRestProtocolServer implements RestProtocolServer {
@@ -38,8 +39,8 @@ public void start(URL url) {
         getDeployment().getMediaTypeMappings().put("json", "application/json");
         getDeployment().getMediaTypeMappings().put("xml", "text/xml");
         getDeployment().getProviderClasses().add(RpcContextFilter.class.getName());
-        // TODO users can override this mapper, but we just rely on the current priority strategy of resteasy
-        getDeployment().getProviderClasses().add(RpcExceptionMapper.class.getName());
+
+        loadProviders(url.getParameter(EXCEPTION_MAPPER_KEY, RpcExceptionMapper.class.getName()));
 
         loadProviders(url.getParameter(EXTENSION_KEY, ""));
 

dubbo-rpc/dubbo-rpc-rest/src/main/java/org/apache/dubbo/rpc/protocol/rest/Constants.java

@@ -35,4 +35,7 @@ public interface Constants {
     String TOMCAT = "tomcat";
 
     String NETTY = "netty";
+
+    // exception mapper
+    String EXCEPTION_MAPPER_KEY = "exception.mapper";
 }

dubbo-rpc/dubbo-rpc-rest/src/main/java/org/apache/dubbo/rpc/protocol/rest/RpcExceptionMapper.java

@@ -28,24 +28,21 @@ public class RpcExceptionMapper implements ExceptionMapper<RpcException> {
 
     @Override
     public Response toResponse(RpcException e) {
-        // TODO do more sophisticated exception handling and output
         if (e.getCause() instanceof ConstraintViolationException) {
             return handleConstraintViolationException((ConstraintViolationException) e.getCause());
         }
         // we may want to avoid exposing the dubbo exception details to certain clients
-        // TODO for now just do plain text output
         return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity("Internal server error: " + e.getMessage()).type(ContentType.TEXT_PLAIN_UTF_8).build();
     }
 
     protected Response handleConstraintViolationException(ConstraintViolationException cve) {
         ViolationReport report = new ViolationReport();
         for (ConstraintViolation<?> cv : cve.getConstraintViolations()) {
             report.addConstraintViolation(new RestConstraintViolation(
-                    cv.getPropertyPath().toString(),
-                    cv.getMessage(),
-                    cv.getInvalidValue() == null ? "null" : cv.getInvalidValue().toString()));
+                cv.getPropertyPath().toString(),
+                cv.getMessage(),
+                cv.getInvalidValue() == null ? "null" : cv.getInvalidValue().toString()));
         }
-        // TODO for now just do xml output
         return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity(report).type(ContentType.TEXT_XML_UTF_8).build();
     }
 }

dubbo-rpc/dubbo-rpc-rest/src/test/java/org/apache/dubbo/rpc/protocol/rest/RestProtocolTest.java

@@ -38,18 +38,21 @@
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.ExceptionMapper;
 import java.util.Map;
 
 import static org.apache.dubbo.remoting.Constants.SERVER_KEY;
+import static org.apache.dubbo.rpc.protocol.rest.Constants.EXCEPTION_MAPPER_KEY;
 import static org.apache.dubbo.rpc.protocol.rest.Constants.EXTENSION_KEY;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.nullValue;
 import static org.hamcrest.MatcherAssert.assertThat;
 
 class RestProtocolTest {
-    private Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getExtension("rest");
-    private ProxyFactory proxy = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
+    private final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getExtension("rest");
+    private final ProxyFactory proxy = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
     private final int availablePort = NetUtils.getAvailablePort();
     private final URL exportUrl = URL.valueOf("rest://127.0.0.1:" + availablePort + "/rest?interface=org.apache.dubbo.rpc.protocol.rest.DemoService");
     private final ModuleServiceRepository repository = ApplicationModel.defaultModel().getDefaultModule().getServiceRepository();
@@ -246,6 +249,29 @@ void testDefaultPort() {
         assertThat(protocol.getDefaultPort(), is(80));
     }
 
+    @Test
+    void testExceptionMapper() {
+        DemoService server = new DemoServiceImpl();
+
+        URL url = this.registerProvider(exportUrl, server, DemoService.class);
+
+        URL exceptionUrl = url.addParameter(EXCEPTION_MAPPER_KEY, TestExceptionMapper.class.getName());
+
+        protocol.export(proxy.getInvoker(server, DemoService.class, exceptionUrl));
+
+        DemoService referDemoService = this.proxy.getProxy(protocol.refer(DemoService.class, exceptionUrl));
+
+        Assertions.assertEquals("test-exception", referDemoService.error());
+    }
+
+    public static class TestExceptionMapper implements ExceptionMapper<RuntimeException> {
+
+        @Override
+        public Response toResponse(RuntimeException e) {
+            return Response.ok("test-exception").build();
+        }
+    }
+
     private URL registerProvider(URL url, Object impl, Class<?> interfaceClass) {
         ServiceDescriptor serviceDescriptor = repository.registerService(interfaceClass);
         ProviderModel providerModel = new ProviderModel(