make VersionUtil more robust

Signed-off-by: Ceki Gulcu <ceki@qos.ch>

slf4j-log4j12/src/main/java/org/slf4j/impl/VersionUtil.java

@@ -1,33 +1,63 @@
+/**
+ * Copyright (c) 2004-2022 QOS.ch Sarl (Switzerland)
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free  of charge, to any person obtaining
+ * a  copy  of this  software  and  associated  documentation files  (the
+ * "Software"), to  deal in  the Software without  restriction, including
+ * without limitation  the rights to  use, copy, modify,  merge, publish,
+ * distribute,  sublicense, and/or sell  copies of  the Software,  and to
+ * permit persons to whom the Software  is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The  above  copyright  notice  and  this permission  notice  shall  be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
+ * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
+ * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
 package org.slf4j.impl;
 
-import java.lang.reflect.Method;
-
 import org.slf4j.helpers.Util;
 
 public class VersionUtil {
-	static final int MINIMAL_VERSION = 5;
+    static final int DEFAULT_GUESS = 8;
+
+    static public int getJavaMajorVersion() {
+        String javaVersionString = Util.safeGetSystemProperty("java.version");
+        return getJavaMajorVersion(javaVersionString);
+    }
 
-	static public int getJavaMajorVersion() {
-		String javaVersionString = Util.safeGetSystemProperty("java.version");
-		return getJavaMajorVersion(javaVersionString);
-	}
+    static public int getJavaMajorVersion(String versionString) {
+        if (versionString == null)
+            return DEFAULT_GUESS;
+        if (versionString.startsWith("1.")) {
+            return versionString.charAt(2) - '0';
+        } else {
+            String firstDigits = extractFirstDigits(versionString);
+            try {
+                return Integer.parseInt(firstDigits);
+             } catch(NumberFormatException e) {
+                 return DEFAULT_GUESS;
+             }
+        }
+    }
 
-	static int getJavaMajorVersion(String versionString) {
-		if (versionString == null)
-			return MINIMAL_VERSION;
-		if (versionString.startsWith("1.")) {
-			return versionString.charAt(2) - '0';
-		} else {
-			// we running under Java 9 or later
-			try {
-				Method versionMethod = Runtime.class.getMethod("version");
-				Object versionObj = versionMethod.invoke(null);
-				Method majorMethod = versionObj.getClass().getMethod("major");
-				Integer resultInteger = (Integer) majorMethod.invoke(versionObj);
-				return resultInteger.intValue();
-			} catch (Exception e) {
-				return MINIMAL_VERSION;
-			}
-		}
-	}
+    private static String extractFirstDigits(String versionString) {
+        StringBuffer buf = new StringBuffer();
+        for(char c : versionString.toCharArray()) {
+            if(Character.isDigit(c))
+                buf.append(c);
+            else
+                break;
+        }
+        return buf.toString();
+
+    }
 }

slf4j-log4j12/src/test/java/org/slf4j/impl/VersionUtilTest.java

@@ -0,0 +1,56 @@
+/**
+ * Copyright (c) 2004-2022 QOS.ch Sarl (Switzerland)
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free  of charge, to any person obtaining
+ * a  copy  of this  software  and  associated  documentation files  (the
+ * "Software"), to  deal in  the Software without  restriction, including
+ * without limitation  the rights to  use, copy, modify,  merge, publish,
+ * distribute,  sublicense, and/or sell  copies of  the Software,  and to
+ * permit persons to whom the Software  is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The  above  copyright  notice  and  this permission  notice  shall  be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
+ * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
+ * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+package org.slf4j.impl;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class VersionUtilTest {
+
+    @Test
+    public void test() {
+        System.out.println(System.getProperty("java.version"));
+        assertEquals(6, VersionUtil.getJavaMajorVersion("1.6"));
+        assertEquals(7, VersionUtil.getJavaMajorVersion("1.7.0_21-b11"));
+        assertEquals(8, VersionUtil.getJavaMajorVersion("1.8.0_25"));
+    }
+
+    @Test 
+    public void testJava9() {
+        assertEquals(9, VersionUtil.getJavaMajorVersion("9"));
+        assertEquals(9, VersionUtil.getJavaMajorVersion("9.12"));
+        assertEquals(9, VersionUtil.getJavaMajorVersion("9ea"));
+
+    }
+
+    @Test 
+    public void testJava11() {
+        assertEquals(11, VersionUtil.getJavaMajorVersion("11"));
+        assertEquals(11, VersionUtil.getJavaMajorVersion("11.612"));
+
+    }
+
+}