Add a system config changed event (#7502)

application/src/main/java/run/halo/app/infra/SystemConfigChangedEvent.java

@@ -0,0 +1,17 @@
+package run.halo.app.infra;
+
+import org.springframework.context.ApplicationEvent;
+
+/**
+ * Event that is published when the system configuration changes.
+ *
+ * @author johnniang
+ * @since 2.21.0
+ */
+public class SystemConfigChangedEvent extends ApplicationEvent {
+
+    public SystemConfigChangedEvent(Object source) {
+        super(source);
+    }
+
+}

application/src/main/java/run/halo/app/infra/SystemConfigurableEnvironmentFetcher.java

@@ -12,6 +12,7 @@ import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicReference;
 import org.apache.commons.lang3.StringUtils;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.lang.NonNull;
 import org.springframework.stereotype.Component;
@@ -39,12 +40,15 @@ import run.halo.app.infra.utils.JsonUtils;
 public class SystemConfigurableEnvironmentFetcher implements Reconciler<Reconciler.Request> {
     private final ReactiveExtensionClient extensionClient;
     private final ConversionService conversionService;
+    private final ApplicationEventPublisher eventPublisher;
     private final AtomicReference<ConfigMap> configMapCache = new AtomicReference<>();
 
     public SystemConfigurableEnvironmentFetcher(ReactiveExtensionClient extensionClient,
-        ConversionService conversionService) {
+        ConversionService conversionService,
+        ApplicationEventPublisher eventPublisher) {
         this.extensionClient = extensionClient;
         this.conversionService = conversionService;
+        this.eventPublisher = eventPublisher;
     }
 
     public <T> Mono<T> fetch(String key, Class<T> type) {
@@ -172,6 +176,7 @@ public class SystemConfigurableEnvironmentFetcher implements Reconciler<Reconcil
             .switchIfEmpty(Mono.error(new IllegalStateException("System configMap not found.")))
             .doOnNext(configMapCache::set)
             .block();
+        eventPublisher.publishEvent(new SystemConfigChangedEvent(this));
         return Result.doNotRetry();
     }
 

application/src/test/java/run/halo/app/infra/SystemConfigurableEnvironmentFetcherTest.java

@@ -1,8 +1,11 @@
 package run.halo.app.infra;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.isA;
 import static org.mockito.Mockito.lenient;
+import static org.mockito.Mockito.verify;
 
 import java.util.LinkedHashMap;
 import org.json.JSONException;
@@ -13,11 +16,13 @@ import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 import org.skyscreamer.jsonassert.JSONAssert;
+import org.springframework.context.ApplicationEventPublisher;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 import run.halo.app.extension.ConfigMap;
 import run.halo.app.extension.Metadata;
 import run.halo.app.extension.ReactiveExtensionClient;
+import run.halo.app.extension.controller.Reconciler;
 import run.halo.app.infra.utils.JsonUtils;
 
 /**
@@ -32,6 +37,9 @@ class SystemConfigurableEnvironmentFetcherTest {
     @Mock
     private ReactiveExtensionClient client;
 
+    @Mock
+    ApplicationEventPublisher eventPublisher;
+
     @InjectMocks
     private SystemConfigurableEnvironmentFetcher environmentFetcher;
 
@@ -43,6 +51,13 @@ class SystemConfigurableEnvironmentFetcherTest {
             .thenReturn(Mono.just(system()));
     }
 
+    @Test
+    void shouldPublishSystemConfigChangedEvent() {
+        var result = environmentFetcher.reconcile(new Reconciler.Request("system"));
+        assertTrue(result == null || !result.reEnqueue());
+        verify(eventPublisher).publishEvent(isA(SystemConfigChangedEvent.class));
+    }
+
     @Test
     void loadConfigMap() {
         environmentFetcher.loadConfigMap()