Multi-Release Virtual Thread Methods (#470)

- Avoid reflection when checking if the thread is virtual
- use `threadId` over the deprecated `getId`

Author: SentryMan

json-core/pom.xml

@@ -36,6 +36,42 @@
       <version>1.7</version>
       <scope>test</scope>
     </dependency>
-
   </dependencies>
+  
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>compile-java-21</id>
+            <phase>compile</phase>
+            <goals>
+              <goal>compile</goal>
+            </goals>
+            <configuration>
+              <release>21</release>
+              <compileSourceRoots>
+                <compileSourceRoot>
+                  ${project.basedir}/src/main/java21</compileSourceRoot>
+              </compileSourceRoots>
+              <multiReleaseOutput>true</multiReleaseOutput>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-jar-plugin</artifactId>
+        <configuration>
+          <archive>
+            <manifestEntries>
+              <Multi-Release>true</Multi-Release>
+            </manifestEntries>
+          </archive>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
 </project>

json-core/src/main/java/io/avaje/json/stream/core/HybridBufferRecycler.java

@@ -5,10 +5,7 @@
 
 import java.io.InputStream;
 import java.lang.invoke.MethodHandle;
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.MethodType;
 import java.util.concurrent.atomic.AtomicReferenceArray;
-import java.util.function.Predicate;
 
 /**
  * This is a custom implementation of the Jackson's RecyclerPool intended to work equally well with
@@ -37,10 +34,9 @@ final class HybridBufferRecycler implements BufferRecycler {
 
   private static final HybridBufferRecycler INSTANCE = new HybridBufferRecycler();
 
-  private static final Predicate<Thread> isVirtual = VirtualPredicate.findIsVirtualPredicate();
-
   private static final BufferRecycler NATIVE_RECYCLER = ThreadLocalPool.shared();
   private static final BufferRecycler VIRTUAL_RECYCLER = StripedLockFreePool.shared();
+  private static final boolean VT_ENABLED = Runtime.version().feature() >= 21;
 
   private HybridBufferRecycler() {
   }
@@ -51,21 +47,21 @@ static HybridBufferRecycler shared() {
 
   @Override
   public JsonGenerator generator(JsonOutput target) {
-    return isVirtual.test(Thread.currentThread())
+    return VT_ENABLED && ThreadFunctions.isVirtual()
       ? VIRTUAL_RECYCLER.generator(target)
       : NATIVE_RECYCLER.generator(target);
   }
 
   @Override
   public JsonParser parser(byte[] bytes) {
-    return isVirtual.test(Thread.currentThread())
+    return VT_ENABLED && ThreadFunctions.isVirtual()
       ? VIRTUAL_RECYCLER.parser(bytes)
       : NATIVE_RECYCLER.parser(bytes);
   }
 
   @Override
   public JsonParser parser(InputStream in) {
-    return isVirtual.test(Thread.currentThread())
+    return VT_ENABLED && ThreadFunctions.isVirtual()
       ? VIRTUAL_RECYCLER.parser(in)
       : NATIVE_RECYCLER.parser(in);
   }
@@ -131,9 +127,8 @@ public JsonGenerator generator(JsonOutput target) {
         if (generatorStacks.compareAndSet(index, currentHead, currentHead.next)) {
           currentHead.next = null;
           return currentHead.value.prepare(target);
-        } else {
-          currentHead = generatorStacks.get(index);
         }
+        currentHead = generatorStacks.get(index);
       }
     }
 
@@ -149,9 +144,8 @@ private JsonParser parser() {
         if (parserStacks.compareAndSet(index, currentHead, currentHead.next)) {
           currentHead.next = null;
           return currentHead.value;
-        } else {
-          currentHead = parserStacks.get(index);
         }
+        currentHead = parserStacks.get(index);
       }
     }
 
@@ -166,9 +160,8 @@ public void recycle(JsonGenerator recycler) {
         if (generatorStacks.compareAndSet(vThreadBufferRecycler.slot, next, newHead)) {
           newHead.next = next;
           return;
-        } else {
-          next = generatorStacks.get(vThreadBufferRecycler.slot);
         }
+        next = generatorStacks.get(vThreadBufferRecycler.slot);
       }
     }
 
@@ -183,9 +176,8 @@ public void recycle(JsonParser recycler) {
         if (parserStacks.compareAndSet(vThreadBufferRecycler.slot, next, newHead)) {
           newHead.next = next;
           return;
-        } else {
-          next = parserStacks.get(vThreadBufferRecycler.slot);
         }
+        next = parserStacks.get(vThreadBufferRecycler.slot);
       }
     }
 
@@ -236,35 +228,6 @@ private VThreadJParser(int slot) {
     }
   }
 
-  private static final class VirtualPredicate {
-    private static final MethodHandle virtualMh = findVirtualMH();
-
-    private static MethodHandle findVirtualMH() {
-      try {
-        return MethodHandles.publicLookup()
-          .findVirtual(Thread.class, "isVirtual", MethodType.methodType(boolean.class));
-      } catch (Exception e) {
-        return null;
-      }
-    }
-
-    private static Predicate<Thread> findIsVirtualPredicate() {
-      return virtualMh == null ? VirtualPredicate::notVirtual : VirtualPredicate::isVirtual;
-    }
-
-    private static boolean isVirtual(Thread thread) {
-      try {
-        return (boolean) virtualMh.invokeExact(thread);
-      } catch (Throwable e) {
-        throw new RuntimeException(e);
-      }
-    }
-
-    private static boolean notVirtual(Thread thread) {
-      return false;
-    }
-  }
-
   private static final class XorShiftThreadProbe {
 
     private final int mask;
@@ -282,7 +245,7 @@ private int probe() {
       // 0x9e3779b9 is the integral part of the Golden Ratio's fractional part 0.61803398875…
       // (sqrt(5)-1)/2
       // multiplied by 2^32, which has the best possible scattering properties.
-      int probe = (int) ((Thread.currentThread().getId() * 0x9e3779b9) & Integer.MAX_VALUE);
+      int probe = (int) ((ThreadFunctions.getId() * 0x9e3779b9) & Integer.MAX_VALUE);
       // xorshift
       probe ^= probe << 13;
       probe ^= probe >>> 17;

json-core/src/main/java/io/avaje/json/stream/core/ThreadFunctions.java

@@ -0,0 +1,13 @@
+package io.avaje.json.stream.core;
+
+final class ThreadFunctions {
+  private ThreadFunctions() {}
+
+  static long getId() {
+    return Thread.currentThread().getId();
+  }
+
+  static boolean isVirtual() {
+    return false;
+  }
+}

json-core/src/main/java21/io/avaje/json/stream/core/ThreadFunctions.java

@@ -0,0 +1,13 @@
+package io.avaje.json.stream.core;
+
+final class ThreadFunctions {
+  private ThreadFunctions() {}
+
+  static long getId() {
+    return Thread.currentThread().threadId();
+  }
+
+  static boolean isVirtual() {
+    return Thread.currentThread().isVirtual();
+  }
+}