FEAT first ResourceManager impl

src/main/java/de/nclazz/resources/ResourceManager.java

@@ -0,0 +1,26 @@
+package de.nclazz.resources;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+public class ResourceManager {
+
+    private Map<String, ResourceMapping> mappings = new HashMap<>();
+
+
+    public Optional<ResourceMapping> getMapping(String key) {
+        return Optional.ofNullable(this.mappings.get(key));
+    }
+
+
+    public ResourceManager addMapping(String key, ResourceMapping mapping) {
+        this.mappings.put(key, mapping);
+        return this;
+    }
+
+    public Optional<Resource> getResource(String key) {
+        return getMapping(key)
+                .flatMap(ResourceMapping::fetchResource);
+    }
+}

src/main/java/de/nclazz/resources/ResourceMapping.java

@@ -4,6 +4,7 @@ import lombok.Builder;
 import lombok.Data;
 import lombok.Singular;
 
+import java.util.Optional;
 import java.util.Set;
 
 @Builder
@@ -27,4 +28,14 @@ public class ResourceMapping {
         return this.definedResource != null || this.defaultResource != null;
     }
 
+    public Optional<Resource> fetchResource() {
+        if (this.definedResource != null) {
+            return Optional.of(this.definedResource);
+        }
+        if (this.defaultResource != null) {
+            return Optional.of(this.defaultResource);
+        }
+        return Optional.empty();
+    }
+
 }

src/test/java/de/nclazz/resources/ResourceManagerTest.java

@@ -0,0 +1,60 @@
+package de.nclazz.resources;
+
+import lombok.SneakyThrows;
+import org.apache.commons.io.IOUtils;
+import org.junit.jupiter.api.Test;
+
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ResourceManagerTest {
+
+    ResourceManager createManager() {
+
+        ResourceManager manager = new ResourceManager();
+        manager.addMapping("test.resource.exists", ResourceMapping.builder()
+                .defaultResource(Resource.fromClasspath("/airplane.png"))
+                .build())
+                .addMapping("test.resource.helloworld.default", ResourceMapping.builder()
+                        .defaultResource(Resource.fromClasspath("/helloworld.txt"))
+                        .build())
+                .addMapping("test.resource.helloworld", ResourceMapping.builder()
+                        .definedResource(Resource.fromClasspath("/hellospecific.txt"))
+                        .build());
+
+        return manager;
+    }
+
+    @SneakyThrows
+    String stringFromInputStream(InputStream stream) {
+        return IOUtils.toString(stream, StandardCharsets.UTF_8);
+    }
+
+    @Test
+    void getResourceForKey() {
+        ResourceManager manager = createManager();
+
+        assertTrue(manager.getMapping("test.resource.exists").isPresent());
+        assertFalse(manager.getMapping("test.resource.noexists").isPresent());
+    }
+
+    @Test
+    void getDefaultOrDefinedResource() {
+
+        ResourceManager manager = createManager();
+
+        assertEquals("Hello World!", manager.getResource("test.resource.helloworld.default")
+                .flatMap(Resource::getInputStream)
+                .map(this::stringFromInputStream)
+                .orElse(""));
+
+        assertEquals("Hello Specific!", manager.getResource("test.resource.helloworld")
+                .flatMap(Resource::getInputStream)
+                .map(this::stringFromInputStream)
+                .orElse(""));
+    }
+
+
+}

src/test/resources/hellospecific.txt

@@ -0,0 +1 @@
+Hello Specific!

src/test/resources/helloworld.txt

@@ -0,0 +1 @@
+Hello World!