feat(bindings/java): support ConcurrentLimitLayer (#5168)

Signed-off-by: tison <wander4096@gmail.com>

bindings/java/src/layer.rs

@@ -22,6 +22,7 @@ use jni::sys::jboolean;
 use jni::sys::jfloat;
 use jni::sys::jlong;
 use jni::JNIEnv;
+use opendal::layers::ConcurrentLimitLayer;
 use opendal::layers::RetryLayer;
 use opendal::Operator;
 
@@ -49,3 +50,15 @@ pub extern "system" fn Java_org_apache_opendal_layer_RetryLayer_doLayer(
     }
     Box::into_raw(Box::new(op.clone().layer(retry))) as jlong
 }
+
+#[no_mangle]
+pub extern "system" fn Java_org_apache_opendal_layer_ConcurrentLimitLayer_doLayer(
+    _: JNIEnv,
+    _: JClass,
+    op: *mut Operator,
+    permits: jlong,
+) -> jlong {
+    let op = unsafe { &*op };
+    let concurrent_limit = ConcurrentLimitLayer::new(permits as usize);
+    Box::into_raw(Box::new(op.clone().layer(concurrent_limit))) as jlong
+}

bindings/java/src/main/java/org/apache/opendal/layer/ConcurrentLimitLayer.java

@@ -0,0 +1,52 @@
+/*
+ * 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.
+ */
+
+package org.apache.opendal.layer;
+
+import org.apache.opendal.Layer;
+
+/**
+ * Users can control how many concurrent connections could be established between
+ * OpenDAL and underlying storage services.
+ *
+ * @see <a href="https://docs.rs/opendal/latest/opendal/layers/struct.ConcurrentLimitLayer.html">ConcurrentLimitLayer's rustdoc</a>
+ */
+public class ConcurrentLimitLayer extends Layer {
+    private final long permits;
+
+    /**
+     * Create a new ConcurrentLimitLayer will specify permits.
+     *
+     * @param permits concurrent connections could be established
+     */
+    public ConcurrentLimitLayer(long permits) {
+        if (permits <= 0) {
+            throw new IllegalArgumentException("permits must be positive");
+        }
+
+        this.permits = permits;
+    }
+
+    @Override
+    protected long layer(long nativeOp) {
+        return doLayer(nativeOp, permits);
+    }
+
+    private static native long doLayer(long nativeHandle, long permits);
+}

bindings/java/src/main/java/org/apache/opendal/layer/RetryLayer.java

@@ -23,6 +23,12 @@
 import lombok.Builder;
 import org.apache.opendal.Layer;
 
+/**
+ * This layer will retry failed operations when {@code Error::is_temporary} returns {@code true}.
+ * If operation still failed, this layer will set error to Persistent which means error has been retried.
+ *
+ * @see <a href="https://docs.rs/opendal/latest/opendal/layers/struct.RetryLayer.html">RetryLayer's rustdoc</a>
+ */
 @Builder
 public class RetryLayer extends Layer {
 

bindings/java/src/test/java/org/apache/opendal/test/LayerTest.java

@@ -25,6 +25,7 @@
 import lombok.Cleanup;
 import org.apache.opendal.AsyncOperator;
 import org.apache.opendal.Layer;
+import org.apache.opendal.layer.ConcurrentLimitLayer;
 import org.apache.opendal.layer.RetryLayer;
 import org.junit.jupiter.api.Test;
 
@@ -38,4 +39,14 @@ void testOperatorWithRetryLayer() {
         @Cleanup final AsyncOperator layeredOp = op.layer(retryLayer);
         assertThat(layeredOp.info).isNotNull();
     }
+
+    @Test
+    void testOperatorWithConcurrentLimitLayer() {
+        final Map<String, String> conf = new HashMap<>();
+        conf.put("root", "/opendal/");
+        final Layer concurrentLimitLayer = new ConcurrentLimitLayer(1024);
+        @Cleanup final AsyncOperator op = AsyncOperator.of("memory", conf);
+        @Cleanup final AsyncOperator layeredOp = op.layer(concurrentLimitLayer);
+        assertThat(layeredOp.info).isNotNull();
+    }
 }