Add ServerErrorHandler to inject dependencies in annotations (#5446)

Motivation:
- It seems good to directly inject ServerErrorHandler via a bean.
- #5440

Modifications:
- Introduced `Optional<List<ServerErrorHandler>>` serverErrorHandlers in
the `armeriaServer` method to enable the injection of ServerErrorHandler
beans.
- Updated the `configureServerWithArmeriaSettings` method to incorporate
error handlers.

Result:
- Users can now define custom ServerErrorHandler beans and utilize an
Armeria server that has been pre-configured with these user-defined
error handlers.
- Closes #5443

Author: kth496

spring/boot3-autoconfigure/src/main/java/com/linecorp/armeria/internal/spring/ArmeriaConfigurationUtil.java

@@ -64,6 +64,7 @@
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 import com.linecorp.armeria.server.HttpService;
 import com.linecorp.armeria.server.ServerBuilder;
+import com.linecorp.armeria.server.ServerErrorHandler;
 import com.linecorp.armeria.server.encoding.EncodingService;
 import com.linecorp.armeria.server.metric.MetricCollectingService;
 import com.linecorp.armeria.server.metric.MetricCollectingServiceBuilder;
@@ -110,6 +111,7 @@ public static void configureServerWithArmeriaSettings(
             MeterIdPrefixFunction meterIdPrefixFunction,
             List<MetricCollectingServiceConfigurator> metricCollectingServiceConfigurators,
             List<DependencyInjector> dependencyInjectors,
+            List<ServerErrorHandler> serverErrorHandlers,
             BeanFactory beanFactory) {
 
         requireNonNull(server, "server");
@@ -203,6 +205,7 @@ public static void configureServerWithArmeriaSettings(
         if (settings.isEnableAutoInjection()) {
             server.dependencyInjector(SpringDependencyInjector.of(beanFactory), false);
         }
+        serverErrorHandlers.forEach(server::errorHandler);
     }
 
     private static void configureInternalService(ServerBuilder server, InternalServiceId serviceId,

spring/boot3-autoconfigure/src/main/java/com/linecorp/armeria/spring/AbstractArmeriaAutoConfiguration.java

@@ -40,6 +40,7 @@
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 import com.linecorp.armeria.server.Server;
 import com.linecorp.armeria.server.ServerBuilder;
+import com.linecorp.armeria.server.ServerErrorHandler;
 import com.linecorp.armeria.server.ServerPort;
 import com.linecorp.armeria.server.docs.DocService;
 import com.linecorp.armeria.server.healthcheck.HealthCheckService;
@@ -73,6 +74,7 @@ public Server armeriaServer(
             Optional<List<ArmeriaServerConfigurator>> armeriaServerConfigurators,
             Optional<List<Consumer<ServerBuilder>>> armeriaServerBuilderConsumers,
             Optional<List<DependencyInjector>> dependencyInjectors,
+            Optional<List<ServerErrorHandler>> serverErrorHandlers,
             BeanFactory beanFactory) {
 
         if (!armeriaServerConfigurators.isPresent() &&
@@ -98,6 +100,7 @@ public Server armeriaServer(
                                                    MeterIdPrefixFunction.ofDefault("armeria.server")),
                                            metricCollectingServiceConfigurators.orElse(ImmutableList.of()),
                                            dependencyInjectors.orElse(ImmutableList.of()),
+                                           serverErrorHandlers.orElse(ImmutableList.of()),
                                            beanFactory);
 
         return serverBuilder.build();

spring/boot3-autoconfigure/src/test/java/com/linecorp/armeria/spring/ArmeriaAutoConfigurationTest.java

@@ -54,6 +54,7 @@
 import com.linecorp.armeria.common.grpc.GrpcSerializationFormats;
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 import com.linecorp.armeria.server.Server;
+import com.linecorp.armeria.server.ServerErrorHandler;
 import com.linecorp.armeria.server.ServerPort;
 import com.linecorp.armeria.server.ServiceRequestContext;
 import com.linecorp.armeria.server.annotation.ExceptionHandlerFunction;
@@ -170,6 +171,26 @@ public MetricCollectingServiceConfigurator metricCollectingServiceConfigurator()
                         return (statusCode >= 200 && statusCode < 400) || statusCode == 404;
                     });
         }
+
+        @Bean
+        public ServerErrorHandler serverErrorHandler1() {
+            return (ctx, cause) -> {
+                if (cause instanceof ArithmeticException) {
+                    return HttpResponse.of("ArithmeticException was handled by serverErrorHandler!");
+                }
+                return null;
+            };
+        }
+
+        @Bean
+        public ServerErrorHandler serverErrorHandler2() {
+            return (ctx, cause) -> {
+                if (cause instanceof IllegalStateException) {
+                    return HttpResponse.of("IllegalStateException was handled by serverErrorHandler!");
+                }
+                return null;
+            };
+        }
     }
 
     public static class IllegalArgumentExceptionHandler implements ExceptionHandlerFunction {
@@ -221,6 +242,21 @@ public AggregatedHttpResponse getV2() {
         public JsonNode post(@RequestObject JsonNode jsonNode) {
             return jsonNode;
         }
+
+        @Get("/unhandled1")
+        public AggregatedHttpResponse unhandled1() throws Exception {
+            throw new ArithmeticException();
+        }
+
+        @Get("/unhandled2")
+        public AggregatedHttpResponse unhandled2() throws Exception {
+            throw new IllegalStateException();
+        }
+
+        @Get("/unhandled3")
+        public AggregatedHttpResponse unhandled3() throws Exception {
+            throw new IllegalAccessException();
+        }
     }
 
     public static class HelloGrpcService extends TestServiceImplBase {
@@ -294,7 +330,7 @@ void testAnnotatedService() throws Exception {
     @Test
     void testThriftService() throws Exception {
         final TestService.Iface client = ThriftClients.newClient(newUrl("h1c") + "/thrift",
-                                                                  TestService.Iface.class);
+                                                                 TestService.Iface.class);
         assertThat(client.hello("world")).isEqualTo("hello world");
 
         final WebClient webClient = WebClient.of(newUrl("h1c"));
@@ -314,7 +350,7 @@ void testThriftService() throws Exception {
     @Test
     void testGrpcService() throws Exception {
         final TestServiceBlockingStub client = GrpcClients.newClient(newUrl("h2c") + '/',
-                                                                      TestServiceBlockingStub.class);
+                                                                     TestServiceBlockingStub.class);
         final HelloRequest request = HelloRequest.newBuilder()
                                                  .setName("world")
                                                  .build();
@@ -394,4 +430,38 @@ void testHealthCheckService() throws Exception {
         res = response.aggregate().get();
         assertThat(res.status()).isEqualTo(HttpStatus.SERVICE_UNAVAILABLE);
     }
+
+    /**
+     * When a ServerErrorHandler @Bean is present,
+     * Server.config().errorHandler() does not register a DefaultServerErrorHandler.
+     * Since DefaultServerErrorHandler is not public, test were forced to compare toString.
+     * Needs to be improved.
+     */
+    @Test
+    void testServerErrorHandlerRegistration() {
+        assertThat(server.config().errorHandler().toString()).isNotEqualTo("INSTANCE");
+    }
+
+    @Test
+    void testServerErrorHandler() throws Exception {
+        final WebClient client = WebClient.of(newUrl("h1c"));
+
+        // ArithmeticException will be handled by serverErrorHandler
+        final HttpResponse response1 = client.get("/annotated/unhandled1");
+        final AggregatedHttpResponse res1 = response1.aggregate().join();
+        assertThat(res1.status()).isEqualTo(HttpStatus.OK);
+        assertThat(res1.contentUtf8()).isEqualTo("ArithmeticException was handled by serverErrorHandler!");
+
+        // IllegalStateException will be handled by serverErrorHandler
+        final HttpResponse response2 = client.get("/annotated/unhandled2");
+        final AggregatedHttpResponse res2 = response2.aggregate().join();
+        assertThat(res2.status()).isEqualTo(HttpStatus.OK);
+        assertThat(res2.contentUtf8()).isEqualTo("IllegalStateException was handled by serverErrorHandler!");
+
+        // IllegalAccessException will be handled by DefaultServerErrorHandler which is used as the
+        // final fallback when all customized handlers return null
+        final HttpResponse response3 = client.get("/annotated/unhandled3");
+        final AggregatedHttpResponse res3 = response3.aggregate().join();
+        assertThat(res3.status()).isEqualTo(HttpStatus.INTERNAL_SERVER_ERROR);
+    }
 }

spring/boot3-webflux-autoconfigure/src/main/java/com/linecorp/armeria/spring/web/reactive/ArmeriaReactiveWebServerFactory.java

@@ -64,6 +64,7 @@
 import com.linecorp.armeria.server.Route;
 import com.linecorp.armeria.server.Server;
 import com.linecorp.armeria.server.ServerBuilder;
+import com.linecorp.armeria.server.ServerErrorHandler;
 import com.linecorp.armeria.server.ServerPort;
 import com.linecorp.armeria.spring.ArmeriaServerConfigurator;
 import com.linecorp.armeria.spring.ArmeriaSettings;
@@ -167,6 +168,7 @@ public WebServer getWebServer(HttpHandler httpHandler) {
                                                meterIdPrefixFunctionOrDefault(),
                                                findBeans(MetricCollectingServiceConfigurator.class),
                                                findBeans(DependencyInjector.class),
+                                               findBeans(ServerErrorHandler.class),
                                                beanFactory);
         }
 

spring/boot3-webflux-autoconfigure/src/test/java/com/linecorp/armeria/spring/web/reactive/ArmeriaReactiveWebServerFactoryTest.java

@@ -28,6 +28,7 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
+import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.RootBeanDefinition;
@@ -62,12 +63,14 @@
 import com.linecorp.armeria.common.HttpData;
 import com.linecorp.armeria.common.HttpHeaderNames;
 import com.linecorp.armeria.common.HttpMethod;
+import com.linecorp.armeria.common.HttpResponse;
 import com.linecorp.armeria.common.MediaType;
 import com.linecorp.armeria.common.RequestHeaders;
 import com.linecorp.armeria.common.metric.PrometheusMeterRegistries;
 import com.linecorp.armeria.internal.common.util.PortUtil;
 import com.linecorp.armeria.internal.testing.MockAddressResolverGroup;
 import com.linecorp.armeria.server.HttpStatusException;
+import com.linecorp.armeria.server.ServerErrorHandler;
 import com.linecorp.armeria.server.annotation.Get;
 import com.linecorp.armeria.server.annotation.Param;
 import com.linecorp.armeria.server.healthcheck.HealthChecker;
@@ -567,4 +570,24 @@ void testManagementPort() throws JsonProcessingException {
                     .isEqualTo("/hello/foo");
         }
     }
+
+    @Test
+    void testServerErrorHandlerRegistration() {
+        beanFactory.registerBeanDefinition("armeriaSettings", new RootBeanDefinition(ArmeriaSettings.class));
+        registerInternalServices(beanFactory);
+
+        // Add ServerErrorHandler @Bean which handles all exceptions and returns 200 with empty string content.
+        final ServerErrorHandler handler = (ctx, req) -> HttpResponse.of("");
+        final BeanDefinition rbd2 = new RootBeanDefinition(ServerErrorHandler.class, () -> handler);
+        beanFactory.registerBeanDefinition("serverErrorHandler", rbd2);
+
+        final ArmeriaReactiveWebServerFactory factory = factory();
+        runServer(factory, (req, res) -> {
+            throw new IllegalArgumentException(); // Always raise exception handler
+        }, server -> {
+            final WebClient client = httpClient(server);
+            final AggregatedHttpResponse res1 = client.post("/hello", "hello").aggregate().join();
+            assertThat(res1.status()).isEqualTo(com.linecorp.armeria.common.HttpStatus.OK);
+        });
+    }
 }