Introduce ModuleResource for resources loaded from a given Module

Closes gh-28507

Author: jhoeller

spring-core/src/main/java/org/springframework/core/io/ModuleResource.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2002-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.io;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@link Resource} implementation for {@link java.lang.Module} resolution,
+ * performing {@link #getInputStream()} access via {@link Module#getResourceAsStream}.
+ *
+ * <p>Alternatively, consider accessing resources in a module path layout
+ * via {@link ClassPathResource} for exported resources, or specifically
+ * via {@link ClassPathResource#ClassPathResource(String, Class)}
+ * for local resolution within the containing module of a specific class.
+ *
+ * @author Juergen Hoeller
+ * @since 6.1
+ * @see Module#getResourceAsStream
+ * @see ClassPathResource
+ */
+public class ModuleResource extends AbstractResource {
+
+	private final Module module;
+
+	private final String path;
+
+
+	/**
+	 * Create a new {@code ModuleResource} for the given {@link Module}
+	 * and the given resource path.
+	 * @param module the runtime module to search within
+	 * @param path the resource path within the module
+	 */
+	public ModuleResource(Module module, String path) {
+		Assert.notNull(module, "Module must not be null");
+		Assert.notNull(path, "Path must not be null");
+		this.module = module;
+		this.path = path;
+	}
+
+
+	/**
+	 * Return the {@link Module} for this resource.
+	 */
+	public final Module getModule() {
+		return this.module;
+	}
+
+	/**
+	 * Return the path for this resource.
+	 */
+	public final String getPath() {
+		return this.path;
+	}
+
+
+	@Override
+	public InputStream getInputStream() throws IOException {
+		InputStream is = this.module.getResourceAsStream(this.path);
+		if (is == null) {
+			throw new FileNotFoundException(getDescription() + " cannot be opened because it does not exist");
+		}
+		return is;
+	}
+
+	@Override
+	public Resource createRelative(String relativePath) {
+		String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
+		return new ModuleResource(this.module, pathToUse);
+	}
+
+	@Override
+	public String getDescription() {
+		return "module resource [" + this.path + "]" +
+				(this.module.isNamed() ? " from module '" + this.module.getName() + "'" : "");
+	}
+
+
+	@Override
+	public boolean equals(@Nullable Object obj) {
+		return (this == obj || (obj instanceof ModuleResource that &&
+				this.module.equals(that.module) && this.path.equals(that.path)));
+	}
+
+	@Override
+	public int hashCode() {
+		return this.module.hashCode() * 31 + this.path.hashCode();
+	}
+
+}

spring-core/src/test/java/org/springframework/core/io/ModuleResourceTests.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2002-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.io;
+
+import java.beans.Introspector;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+/**
+ * Unit tests for the {@link ModuleResource} class.
+ *
+ * @author Juergen Hoeller
+ * @since 6.1
+ */
+class ModuleResourceTests {
+
+	@Test
+	void existingResource() throws IOException {
+		ModuleResource mr = new ModuleResource(Introspector.class.getModule(), "java/beans/Introspector.class");
+		assertThat(mr.exists()).isTrue();
+		assertThat(mr.isReadable()).isTrue();
+		assertThat(mr.isOpen()).isFalse();
+		assertThat(mr.isFile()).isFalse();
+		assertThat(mr.getDescription()).contains(mr.getModule().getName());
+		assertThat(mr.getDescription()).contains(mr.getPath());
+
+		Resource cpr = new ClassPathResource("java/beans/Introspector.class");
+		assertThat(mr.getContentAsByteArray()).isEqualTo(cpr.getContentAsByteArray());
+		assertThat(mr.contentLength()).isEqualTo(cpr.contentLength());
+	}
+
+	@Test
+	void nonExistingResource() {
+		ModuleResource mr = new ModuleResource(Introspector.class.getModule(), "java/beans/Introspecter.class");
+		assertThat(mr.exists()).isFalse();
+		assertThat(mr.isReadable()).isFalse();
+		assertThat(mr.isOpen()).isFalse();
+		assertThat(mr.isFile()).isFalse();
+		assertThat(mr.getDescription()).contains(mr.getModule().getName());
+		assertThat(mr.getDescription()).contains(mr.getPath());
+
+		assertThatExceptionOfType(FileNotFoundException.class).isThrownBy(mr::getContentAsByteArray);
+		assertThatExceptionOfType(FileNotFoundException.class).isThrownBy(mr::contentLength);
+	}
+
+	@Test
+	void equalsAndHashCode() {
+		Resource mr1 = new ModuleResource(Introspector.class.getModule(), "java/beans/Introspector.class");
+		Resource mr2 = new ModuleResource(Introspector.class.getModule(), "java/beans/Introspector.class");
+		Resource mr3 = new ModuleResource(Introspector.class.getModule(), "java/beans/Introspecter.class");
+		assertThat(mr1).isEqualTo(mr2);
+		assertThat(mr1).isNotEqualTo(mr3);
+		assertThat(mr1).hasSameHashCodeAs(mr2);
+		assertThat(mr1).doesNotHaveSameHashCodeAs(mr3);
+	}
+
+}