diff --git a/pom.xml b/pom.xml
index de5d9f93..af5642cc 100644
--- a/pom.xml
+++ b/pom.xml
@@ -58,7 +58,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.source>1.7</maven.compiler.source>
         <maven.compiler.target>1.7</maven.compiler.target>
-        <hadoop.version>3.3.3</hadoop.version>
+        <hadoop.version>2.8.5</hadoop.version>
         <cos_api.version>5.6.137.2</cos_api.version>
         <google.guava.version>24.1.1-jre</google.guava.version>
         <commons_lang3.version>3.1</commons_lang3.version>
diff --git a/src/main/java/org/apache/hadoop/fs/CosNFileSystem.java b/src/main/java/org/apache/hadoop/fs/CosNFileSystem.java
index b06d6f03..e10d6872 100644
--- a/src/main/java/org/apache/hadoop/fs/CosNFileSystem.java
+++ b/src/main/java/org/apache/hadoop/fs/CosNFileSystem.java
@@ -1527,28 +1527,19 @@ private Path makeAbsolute(Path path) {
         return new Path(workingDir, path);
     }
 
-    // key and path relate
-    public static String pathToKey(Path path) {
-        if (path.toUri().getScheme() != null && path.toUri().getPath().isEmpty()) {
-            // allow uris without trailing slash after bucket to refer to root,
-            // like cosn://mybucket
-            return "";
-        }
-        if (!path.isAbsolute()) {
-            throw new IllegalArgumentException("Path must be absolute: " + path);
-        }
-        String ret = path.toUri().getPath();
-        if (ret.endsWith("/") && (ret.indexOf("/") != ret.length() - 1)) {
-            ret = ret.substring(0, ret.length() - 1);
-        }
-        return ret;
+    /**
+     * 将一个 hadoop 的 path 路径转换为 COS 的 key 路径。
+     * 由于每个方法都会调用这个方法，因此这里调用了 checkPath 检查传入路径是否归属于当前的文件系统 URI。
+     *
+     * @param path hadoop 的 path 路径，原则上应是一个绝对路径。
+     * @return 传入的 hadoop 的 path 对应的 COS 的 key 路径。
+     */
+    public String pathToKey(Path path) {
+        super.checkPath(path);
+        return CosNUtils.pathToKey(path);
     }
 
-    public static Path keyToPath(String key) {
-        if (!key.startsWith(PATH_DELIMITER)) {
-            return new Path("/" + key);
-        } else {
-            return new Path(key);
-        }
+    public Path keyToPath(String key) {
+        return CosNUtils.keyToPath(key, PATH_DELIMITER);
     }
 }
diff --git a/src/main/java/org/apache/hadoop/fs/CosNUtils.java b/src/main/java/org/apache/hadoop/fs/CosNUtils.java
index 3d7c6228..a1545c0a 100644
--- a/src/main/java/org/apache/hadoop/fs/CosNUtils.java
+++ b/src/main/java/org/apache/hadoop/fs/CosNUtils.java
@@ -309,4 +309,27 @@ public static Configuration propagateBucketOptions(Configuration source, String
         return dest;
     }
 
+    public static String pathToKey(Path path) {
+        if (path.toUri().getScheme() != null && path.toUri().getPath().isEmpty()) {
+            // allow uris without trailing slash after bucket to refer to root,
+            // like cosn://mybucket
+            return "";
+        }
+        if (!path.isAbsolute()) {
+            throw new IllegalArgumentException("Path must be absolute: " + path);
+        }
+        String ret = path.toUri().getPath();
+        if (ret.endsWith("/") && (ret.indexOf("/") != ret.length() - 1)) {
+            ret = ret.substring(0, ret.length() - 1);
+        }
+        return ret;
+    }
+
+    public static Path keyToPath(String key, String pathDelimiter) {
+        if (!key.startsWith(pathDelimiter)) {
+            return new Path("/" + key);
+        } else {
+            return new Path(key);
+        }
+    }
 }
diff --git a/src/main/java/org/apache/hadoop/fs/RangerCredentialsClient.java b/src/main/java/org/apache/hadoop/fs/RangerCredentialsClient.java
index 0ac19ed1..acd3e009 100644
--- a/src/main/java/org/apache/hadoop/fs/RangerCredentialsClient.java
+++ b/src/main/java/org/apache/hadoop/fs/RangerCredentialsClient.java
@@ -68,7 +68,7 @@ public void doCheckPermission(Path f, RangerAccessType rangerAccessType, String
         }
 
         Path absolutePath = makeAbsolute(f, workingDirectory);
-        String allowKey = CosNFileSystem.pathToKey(absolutePath);
+        String allowKey = CosNUtils.pathToKey(absolutePath);
         if (allowKey.startsWith("/")) {
             allowKey = allowKey.substring(1);
         }