Fixes #2618 - ProcessorUtilsTest fragile.

Introduced ProcessorUtils.setAvailableProcessor(int) to allow
usage in embedded code without resorting to system properties.

Refactored the static initializer to be testable.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>

jetty-util/src/main/java/org/eclipse/jetty/util/ProcessorUtils.java

@@ -19,40 +19,48 @@
 package org.eclipse.jetty.util;
 
 /**
- * ProcessorUtils provides access to runtime info about processors, that may be 
- * overridden by system properties of environment variables.   This can be useful
- * in virtualised environments where the runtime may miss report the available 
- * resources.
+ * <p>ProcessorUtils provides access to runtime info about processors, that may be
+ * overridden by system properties or environment variables.</p>
+ * <p>This can be useful in virtualized environments where the runtime may miss
+ * report the available resources.</p>
  */
 public class ProcessorUtils
 {
     public static final String AVAILABLE_PROCESSORS = "JETTY_AVAILABLE_PROCESSORS";
-    private static int __availableProcessors = Runtime.getRuntime().availableProcessors();
+    private static int __availableProcessors = init();
 
-    static
+    static int init()
     {
-        String avlProcEnv = System.getProperty(AVAILABLE_PROCESSORS,System.getenv(AVAILABLE_PROCESSORS));
-        if (avlProcEnv != null)
+        String processors = System.getProperty(AVAILABLE_PROCESSORS, System.getenv(AVAILABLE_PROCESSORS));
+        if (processors != null)
         {
             try
             {
-                __availableProcessors = Integer.parseInt( avlProcEnv );
+                return Integer.parseInt( processors );
             }
-            catch ( NumberFormatException e )
+            catch (NumberFormatException ignored)
             {
-                // ignore
             }
         }
+        return Runtime.getRuntime().availableProcessors();
     }
 
     /**
-     * Obtain the number of available processors, from System Property "JETTY_AVAILABLE_PROCESSORS",
-     * or if not set then environment variable "JETTY_AVAILABLE_PROCESSORS" or if not set then
-     * {@link Runtime#availableProcessors()}.
+     * Returns the number of available processors, from System Property "JETTY_AVAILABLE_PROCESSORS",
+     * or if not set then from environment variable "JETTY_AVAILABLE_PROCESSORS" or if not set then
+     * from {@link Runtime#availableProcessors()}.
+     *
      * @return the number of processors
      */
     public static int availableProcessors()
     {
         return __availableProcessors;
     }
+
+    public static void setAvailableProcessors(int processors)
+    {
+        if (processors < 1)
+            throw new IllegalArgumentException("Invalid number of processors: " + processors);
+        __availableProcessors = processors;
+    }
 }

jetty-util/src/test/java/org/eclipse/jetty/util/ProcessorUtilsTest.java

@@ -19,23 +19,48 @@
 package org.eclipse.jetty.util;
 
 import org.junit.Assert;
-import org.junit.BeforeClass;
 import org.junit.Test;
 
-/**
- * we cannot really add env var in a unit test... so only test we get default value
- */
 public class ProcessorUtilsTest
 {
-    @BeforeClass
-    public static void beforeClass()
+    @Test
+    public void testSystemProperty()
     {
-        System.setProperty("JETTY_AVAILABLE_PROCESSORS","42");
+        // Classloading will trigger the static initializer.
+        int original = ProcessorUtils.availableProcessors();
+
+        // Verify that the static initializer logic is correct.
+        System.setProperty(ProcessorUtils.AVAILABLE_PROCESSORS, "42");
+        int processors = ProcessorUtils.init();
+        Assert.assertEquals(42, processors);
+
+        // Make sure the original value is preserved.
+        Assert.assertEquals(original, ProcessorUtils.availableProcessors());
     }
 
     @Test
-    public void getPropertyValue()
+    public void testSetter()
     {
-        Assert.assertEquals(42, ProcessorUtils.availableProcessors());
+        // Classloading will trigger the static initializer.
+        int original = ProcessorUtils.availableProcessors();
+        try
+        {
+            try
+            {
+                ProcessorUtils.setAvailableProcessors(0);
+                Assert.fail();
+            }
+            catch (IllegalArgumentException expected)
+            {
+            }
+
+            int processors = 42;
+            ProcessorUtils.setAvailableProcessors(processors);
+            Assert.assertEquals(processors, ProcessorUtils.availableProcessors());
+        }
+        finally
+        {
+            ProcessorUtils.setAvailableProcessors(original);
+        }
     }
 }