Add full set of RecyclerPool implementations

src/main/java/com/fasterxml/jackson/core/json/JsonGeneratorImpl.java

@@ -245,6 +245,10 @@ public JacksonFeatureSet<StreamWriteCapability> getWriteCapabilities() {
         return JSON_WRITE_CAPABILITIES;
     }
 
+    public IOContext _getIoContext() {
+        return _ioContext;
+    }
+
     /*
     /**********************************************************
     /* Shared helper methods

src/test/java/com/fasterxml/jackson/core/write/BufferRecyclerPoolTest.java → src/test/java/com/fasterxml/jackson/core/io/BufferRecyclerPoolTest.java

@@ -1,8 +1,10 @@
-package com.fasterxml.jackson.core.write;
+package com.fasterxml.jackson.core.io;
 
 import com.fasterxml.jackson.core.BaseTest;
 import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.json.JsonGeneratorImpl;
+import com.fasterxml.jackson.core.util.BufferRecycler;
 import com.fasterxml.jackson.core.util.BufferRecyclerPool;
 
 import java.io.IOException;
@@ -11,36 +13,49 @@
 public class BufferRecyclerPoolTest extends BaseTest
 {
     public void testNoOp() {
-        checkBufferRecyclerPoolImpl(BufferRecyclerPool.NonRecyclingPool.shared());
+        // no-op pool doesn't actually pool anything, so avoid checking it
+        checkBufferRecyclerPoolImpl(BufferRecyclerPool.NonRecyclingPool.shared(), false);
     }
 
     public void testThreadLocal() {
-        checkBufferRecyclerPoolImpl(BufferRecyclerPool.ThreadLocalPool.shared());
+        checkBufferRecyclerPoolImpl(BufferRecyclerPool.ThreadLocalPool.shared(), true);
     }
 
     public void testLockFree() {
-        checkBufferRecyclerPoolImpl(BufferRecyclerPool.LockFreePool.nonShared());
+        checkBufferRecyclerPoolImpl(BufferRecyclerPool.LockFreePool.shared(), true);
     }
 
     public void testConcurrentDequeue() {
-        checkBufferRecyclerPoolImpl(BufferRecyclerPool.ConcurrentDequePool.nonShared());
+        checkBufferRecyclerPoolImpl(BufferRecyclerPool.ConcurrentDequePool.shared(), true);
     }
 
-    private void checkBufferRecyclerPoolImpl(BufferRecyclerPool pool) {
+    private void checkBufferRecyclerPoolImpl(BufferRecyclerPool pool, boolean checkPooledResource) {
         JsonFactory jsonFactory = JsonFactory.builder()
                 .bufferRecyclerPool(pool)
                 .build();
-        assertEquals(6, write("test", jsonFactory));
+        BufferRecycler usedBufferRecycler = write("test", jsonFactory, 6);
+        if (checkPooledResource) {
+            // acquire the pooled BufferRecycler again and check if it is the same instance used before
+            BufferRecycler pooledBufferRecycler = pool.acquireBufferRecycler();
+            try {
+                assertSame(usedBufferRecycler, pooledBufferRecycler);
+            } finally {
+                pooledBufferRecycler.release();
+            }
+        }
     }
 
-    protected final int write(Object value, JsonFactory jsonFactory) {
+    protected final BufferRecycler write(Object value, JsonFactory jsonFactory, int expectedSize) {
+        BufferRecycler bufferRecycler;
         NopOutputStream out = new NopOutputStream();
         try (JsonGenerator gen = jsonFactory.createGenerator(out)) {
+            bufferRecycler = ((JsonGeneratorImpl) gen)._getIoContext()._bufferRecycler;
             gen.writeObject(value);
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
-        return out.size();
+        assertEquals(expectedSize, out.size);
+        return bufferRecycler;
     }
 
     public class NopOutputStream extends OutputStream {