Initialize required extensions when system starts up (#2274)

#### What type of PR is this?

/kind improvement
/area core
/milestone 2.0

#### What this PR does / why we need it:

This PR makes required extensions got initialized when system starts up. Of course, we can stop the initialization by setting property `halo.required-extension-disabled=true`.

Secondly, we are using [PathMatchingResourcePatternResolver](https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/core/io/support/PathMatchingResourcePatternResolver.html) support more functional Extension locations, please see the doc for more.

#### Does this PR introduce a user-facing change?

```release-note
None
```

src/main/java/run/halo/app/infra/ExtensionResourceInitializer.java

@@ -1,21 +1,17 @@
 package run.halo.app.infra;
 
 import java.io.IOException;
-import java.nio.file.Files;
+import java.util.HashSet;
-import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.List;
 import java.util.Set;
-import java.util.stream.Stream;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.boot.context.event.ApplicationReadyEvent;
 import org.springframework.context.ApplicationListener;
-import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.Resource;
+import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
 import org.springframework.lang.NonNull;
 import org.springframework.stereotype.Component;
 import org.springframework.util.CollectionUtils;
-import org.thymeleaf.util.StringUtils;
 import run.halo.app.extension.ExtensionClient;
 import run.halo.app.extension.Unstructured;
 import run.halo.app.infra.properties.HaloProperties;
@@ -32,6 +28,9 @@ import run.halo.app.infra.utils.YamlUnstructuredLoader;
 @Slf4j
 @Component
 public class ExtensionResourceInitializer implements ApplicationListener<ApplicationReadyEvent> {
+
+    public static final Set<String> REQUIRED_EXTENSION_LOCATIONS =
+        Set.of("classpath:/extensions/*.yaml", "classpath:/extensions/*.yml");
     private final HaloProperties haloProperties;
     private final ExtensionClient extensionClient;
 
@@ -43,15 +42,25 @@ public class ExtensionResourceInitializer implements ApplicationListener<Applica
 
     @Override
     public void onApplicationEvent(@NonNull ApplicationReadyEvent event) {
-        Set<String> extensionLocations = haloProperties.getInitialExtensionLocations();
+        var locations = new HashSet<String>();
-        if (!CollectionUtils.isEmpty(extensionLocations)) {
+        if (!haloProperties.isRequiredExtensionDisabled()) {
+            locations.addAll(REQUIRED_EXTENSION_LOCATIONS);
+        }
+        if (haloProperties.getInitialExtensionLocations() != null) {
+            locations.addAll(haloProperties.getInitialExtensionLocations());
+        }
 
-            Resource[] resources = extensionLocations.stream()
+        if (CollectionUtils.isEmpty(locations)) {
-                .map(this::listYamlFiles)
+            return;
+        }
+
+        var resources = locations.stream()
+            .map(this::listResources)
             .flatMap(List::stream)
+            .distinct()
             .toArray(Resource[]::new);
 
-            log.debug("Initialization loaded [{}] resources to establish.", resources.length);
+        log.info("Initializing [{}] extensions in locations: {}", resources.length, locations);
 
         new YamlUnstructuredLoader(resources).load()
             .forEach(unstructured -> extensionClient.fetch(unstructured.groupVersionKind(),
@@ -59,24 +68,20 @@ public class ExtensionResourceInitializer implements ApplicationListener<Applica
                 .ifPresentOrElse(persisted -> {
                     unstructured.getMetadata()
                         .setVersion(persisted.getMetadata().getVersion());
+                    // TODO Patch the unstructured instead of update it in the future
                     extensionClient.update(unstructured);
                 }, () -> extensionClient.create(unstructured)));
+
+        log.info("Initialized [{}] extensions in locations: {}", resources.length, locations);
+    }
+
+    private List<Resource> listResources(String location) {
+        var resolver = new PathMatchingResourcePatternResolver();
+        try {
+            return List.of(resolver.getResources(location));
+        } catch (IOException ie) {
+            throw new IllegalArgumentException("Invalid extension location: " + location, ie);
         }
     }
 
-    private List<FileSystemResource> listYamlFiles(String location) {
-        try (Stream<Path> walk = Files.walk(Paths.get(location))) {
-            return walk.filter(this::isYamlFile)
-                .map(path -> new FileSystemResource(path.toFile()))
-                .toList();
-        } catch (IOException e) {
-            throw new IllegalArgumentException(e);
-        }
-    }
-
-    private boolean isYamlFile(Path pathname) {
-        Path fileName = pathname.getFileName();
-        return StringUtils.endsWith(fileName, ".yaml")
-            || StringUtils.endsWith(fileName, ".yml");
-    }
 }

src/main/java/run/halo/app/infra/properties/HaloProperties.java

@@ -18,6 +18,13 @@ public class HaloProperties {
 
     private Set<String> initialExtensionLocations = new HashSet<>();
 
+    /**
+     * This property could stop initializing required Extensions defined in classpath.
+     * See {@link run.halo.app.infra.ExtensionResourceInitializer#REQUIRED_EXTENSION_LOCATIONS}
+     * for more.
+     */
+    private boolean requiredExtensionDisabled;
+
     private final ExtensionProperties extension = new ExtensionProperties();
 
     private final SecurityProperties security = new SecurityProperties();

src/test/java/run/halo/app/infra/ExtensionResourceInitializerTest.java

@@ -10,10 +10,12 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import org.json.JSONException;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -22,6 +24,7 @@ import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 import org.skyscreamer.jsonassert.JSONAssert;
 import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.util.FileSystemUtils;
 import run.halo.app.extension.ExtensionClient;
 import run.halo.app.extension.GroupVersionKind;
 import run.halo.app.extension.Unstructured;
@@ -46,13 +49,19 @@ class ExtensionResourceInitializerTest {
 
     private ExtensionResourceInitializer extensionResourceInitializer;
 
+    List<Path> dirsToClean;
+
     @BeforeEach
     void setUp() throws IOException {
         extensionResourceInitializer =
             new ExtensionResourceInitializer(haloProperties, extensionClient);
 
+        dirsToClean = new ArrayList<>(2);
+
         Path tempDirectory = Files.createTempDirectory("extension-resource-initializer-test");
-        Path multiDirectory = Files.createDirectories(tempDirectory.resolve("a/b/c"));
+        dirsToClean.add(tempDirectory);
+        Path multiDirectory =
+            Files.createDirectories(tempDirectory.resolve("a").resolve("b").resolve("c"));
         Files.writeString(tempDirectory.resolve("hello.yml"), """
                 kind: FakeExtension
                 apiVersion: v1
@@ -79,8 +88,9 @@ class ExtensionResourceInitializerTest {
             StandardCharsets.UTF_8);
 
         // test file in directory
-        Path filePath = Files.createTempDirectory("extension-resource-file-test")
+        Path secondTempDir = Files.createTempDirectory("extension-resource-file-test");
-            .resolve("good.yml");
+        dirsToClean.add(secondTempDir);
+        Path filePath = secondTempDir.resolve("good.yml");
         Files.writeString(filePath, """
                 kind: FakeExtension
                 apiVersion: v1
@@ -92,11 +102,23 @@ class ExtensionResourceInitializerTest {
             StandardCharsets.UTF_8);
 
         when(haloProperties.getInitialExtensionLocations())
-            .thenReturn(Set.of(tempDirectory.toString(), filePath.toString()));
+            .thenReturn(Set.of("file:" + tempDirectory + "/**/*.yaml",
+                "file:" + tempDirectory + "/**/*.yml",
+                "file:" + filePath));
+    }
+
+    @AfterEach
+    void cleanUp() throws IOException {
+        if (dirsToClean != null) {
+            for (var dir : dirsToClean) {
+                FileSystemUtils.deleteRecursively(dir);
+            }
+        }
     }
 
     @Test
     void onApplicationEvent() throws JSONException {
+        when(haloProperties.isRequiredExtensionDisabled()).thenReturn(true);
         ArgumentCaptor<Unstructured> argumentCaptor = ArgumentCaptor.forClass(Unstructured.class);
 
         when(extensionClient.fetch(any(GroupVersionKind.class), any()))