Add java bytecode class file version detection

Signed-off-by: Jorge Solórzano <jorsol@ongres.com>

Author: Jorge Solórzano

plexus-java/src/main/java/org/codehaus/plexus/languages/java/version/JavaClassfileVersion.java

@@ -0,0 +1,141 @@
+package org.codehaus.plexus.languages.java.version;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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
+ *
+ *   http://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.
+ */
+
+/**
+ * Reads the bytecode of a Java class to detect the major, minor and Java
+ * version that was compiled.
+ *
+ * @author Jorge Solórzano
+ */
+public final class JavaClassfileVersion {
+
+    private final int major;
+    private final int minor;
+
+    JavaClassfileVersion(int major, int minor) {
+        if (major < 45) {
+            throw new IllegalArgumentException("Java class major version must be 45 or above.");
+        }
+        this.major = major;
+        this.minor = minor;
+    }
+
+    /**
+     * Reads the bytecode of a Java class file and returns the
+     * {@link JavaClassfileVersion}.
+     *
+     * @param bytes {@code byte[]} of the Java class file
+     * @return the {@link JavaClassfileVersion} of the byte array
+     */
+    public static JavaClassfileVersion of(byte[] bytes) {
+        return JavaClassfileVersionParser.of(bytes);
+    }
+
+    /**
+     * Reads the bytecode of a Java class file and returns the
+     * {@link JavaClassfileVersion}.
+     *
+     * @param path {@link Path} of the Java class file
+     * @return the {@link JavaClassfileVersion} of the path java class
+     */
+    public static JavaClassfileVersion of(Path path) {
+        try {
+            byte[] readAllBytes = Files.readAllBytes(path);
+            return of(readAllBytes);
+        } catch (IOException ex) {
+            throw new UncheckedIOException(ex);
+        }
+    }
+
+    /**
+     * JavaVersion of the class file version detected.
+     *
+     * @return JavaVersion based on the major version of the class file.
+     */
+    public JavaVersion javaVersion() {
+        int javaVer = major - 44;
+        String javaVersion = javaVer < 9 ? "1." + javaVer : Integer.toString(javaVer);
+
+        return JavaVersion.parse(javaVersion);
+    }
+
+    /**
+     * Returns the major version of the parsed classfile.
+     *
+     * @return the major classfile version
+     */
+    public int majorVersion() {
+        return major;
+    }
+
+    /**
+     * Returns the minor version of the parsed classfile.
+     *
+     * @return the minor classfile version
+     */
+    public int minorVersion() {
+        return minor;
+    }
+
+    /**
+     * Returns if the classfile use preview features.
+     *
+     * @return {@code true} if the classfile use preview features.
+     */
+    public boolean isPreview() {
+        return minor == 65535;
+    }
+
+    /**
+     * Returns a String representation of the Java class file version, e.g.
+     * {@code 65.0 (Java 21)}.
+     *
+     * @return String representation of the Java class file version
+     */
+    @Override
+    public String toString() {
+        return major + "." + minor + " (Java " + javaVersion() + ")";
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + major;
+        result = prime * result + minor;
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (!(obj instanceof JavaClassfileVersion)) return false;
+        JavaClassfileVersion other = (JavaClassfileVersion) obj;
+        if (major != other.major) return false;
+        if (minor != other.minor) return false;
+        return true;
+    }
+}

plexus-java/src/main/java/org/codehaus/plexus/languages/java/version/JavaClassfileVersionParser.java

@@ -0,0 +1,55 @@
+package org.codehaus.plexus.languages.java.version;
+
+import java.io.ByteArrayInputStream;
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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
+ *
+ *   http://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.
+ */
+
+/**
+ * This class is intented to be package-private and consumed by
+ * {@link JavaClassfileVersion}.
+ *
+ * @author Jorge Solórzano
+ */
+final class JavaClassfileVersionParser {
+
+    private JavaClassfileVersionParser() {}
+
+    /**
+     * Reads the bytecode of a Java class file and returns the {@link JavaClassfileVersion}.
+     *
+     * @param in {@code byte[]} of the Java class file
+     * @return the {@link JavaClassfileVersion} of the input stream
+     */
+    public static JavaClassfileVersion of(byte[] bytes) {
+        try (final DataInputStream data = new DataInputStream(new ByteArrayInputStream(bytes))) {
+            if (0xCAFEBABE != data.readInt()) {
+                throw new IOException("Invalid java class file header");
+            }
+            int minor = data.readUnsignedShort();
+            int major = data.readUnsignedShort();
+            return new JavaClassfileVersion(major, minor);
+        } catch (IOException ex) {
+            throw new UncheckedIOException(ex);
+        }
+    }
+}

plexus-java/src/main/java/org/codehaus/plexus/languages/java/version/JavaVersion.java

@@ -60,7 +60,7 @@ private JavaVersion(String rawVersion, boolean isMajor) {
      * Actual parsing is done when calling {@link #compareTo(JavaVersion)}
      *
      * @param s the version string, never {@code null}
-     * @return the version wrapped in a JavadocVersion
+     * @return the version wrapped in a JavaVersion
      */
     public static JavaVersion parse(String s) {
         return new JavaVersion(s, !s.startsWith("1."));

plexus-java/src/test/java/org/codehaus/plexus/languages/java/version/JavaClassVersionTest.java

@@ -0,0 +1,79 @@
+package org.codehaus.plexus.languages.java.version;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class JavaClassVersionTest {
+
+    @ParameterizedTest
+    @MethodSource("provideClassFiles")
+    void testFilesClassVersions(Path filePath) {
+        String fileName = filePath.getFileName().toString();
+        int javaVersion = Integer.valueOf(fileName.substring(fileName.indexOf("-") + 1, fileName.length() - 6));
+        JavaClassfileVersion classVersion = JavaClassfileVersion.of(filePath);
+        assertEquals(javaVersion + 44, classVersion.majorVersion());
+        assertEquals(0, classVersion.minorVersion());
+        assertEquals(JavaVersion.parse("" + javaVersion), classVersion.javaVersion());
+    }
+
+    static Stream<Path> provideClassFiles() {
+        List<Path> paths;
+        try (DirectoryStream<Path> directoryStream =
+                Files.newDirectoryStream(Paths.get("src/test/resources/classfile.version/"), "*-[0-9]?.class")) {
+            paths = StreamSupport.stream(directoryStream.spliterator(), false)
+                    .filter(Files::isRegularFile)
+                    .collect(Collectors.toList());
+        } catch (IOException ex) {
+            throw new UncheckedIOException(ex);
+        }
+        return paths.stream();
+    }
+
+    @Test
+    void testJavaClassPreview() {
+        Path previewFile = Paths.get("src/test/resources/classfile.version/helloworld-preview.class");
+        JavaClassfileVersion previewClass = JavaClassfileVersion.of(previewFile);
+        assertTrue(previewClass.isPreview());
+        assertEquals(20 + 44, previewClass.majorVersion());
+        assertEquals(JavaVersion.parse("20"), previewClass.javaVersion());
+    }
+
+    @Test
+    void testJavaClassVersionMajor45orAbove() {
+        assertThrows(
+                IllegalArgumentException.class,
+                () -> new JavaClassfileVersion(44, 0),
+                "Java class major version must be 45 or above.");
+    }
+
+    @Test
+    void equalsContract() {
+        JavaClassfileVersion javaClassVersion = new JavaClassfileVersion(65, 0);
+        JavaClassfileVersion previewFeature = new JavaClassfileVersion(65, 65535);
+        assertNotEquals(javaClassVersion, previewFeature);
+        assertNotEquals(javaClassVersion.hashCode(), previewFeature.hashCode());
+
+        JavaClassfileVersion javaClassVersionOther = new JavaClassfileVersion(65, 0);
+        assertEquals(javaClassVersion, javaClassVersionOther);
+        assertEquals(javaClassVersion.hashCode(), javaClassVersionOther.hashCode());
+        assertEquals(javaClassVersion.javaVersion(), javaClassVersionOther.javaVersion());
+        assertEquals(javaClassVersion.javaVersion(), previewFeature.javaVersion());
+    }
+}