1 files changed, 121 insertions, 0 deletions
diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/compat/ProtocolManager.java b/zookeeper-server/src/main/java/org/apache/zookeeper/compat/ProtocolManager.java
new file mode 100644
index 000000000..5633b81c1
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+++ b/zookeeper-server/src/main/java/org/apache/zookeeper/compat/ProtocolManager.java
@@ -0,0 +1,121 @@
+/*
+ * 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.zookeeper.compat;
+
+import java.io.IOException;
+import org.apache.jute.InputArchive;
+import org.apache.zookeeper.proto.ConnectRequest;
+import org.apache.zookeeper.proto.ConnectResponse;
+
+/**
+ * A manager for switching behaviours between difference wire protocol.
+ * <p>
+ * Basically, wire protocol should be backward and forward compatible between minor versions.
+ * However, there are several cases that it's different due to Jute's limitations.
+ */
+public final class ProtocolManager {
+    private volatile Boolean isReadonlyAvailable = null;
+
+    public boolean isReadonlyAvailable() {
+        return isReadonlyAvailable != null && isReadonlyAvailable;
+    }
+
+    /**
+     * Deserializing {@link ConnectRequest} should be specially handled for request from client
+     * version before and including ZooKeeper 3.3 which doesn't understand readOnly field.
+     */
+    public ConnectRequest deserializeConnectRequest(InputArchive inputArchive) throws IOException {
+        if (isReadonlyAvailable != null) {
+            if (isReadonlyAvailable) {
+                return deserializeConnectRequestWithReadonly(inputArchive);
+            } else {
+                return deserializeConnectRequestWithoutReadonly(inputArchive);
+            }
+        }
+
+        final ConnectRequest request = deserializeConnectRequestWithoutReadonly(inputArchive);
+        try {
+            request.setReadOnly(inputArchive.readBool("readOnly"));
+            this.isReadonlyAvailable = true;
+        } catch (Exception e) {
+            request.setReadOnly(false); // old version doesn't have readonly concept
+            this.isReadonlyAvailable = false;
+        }
+        return request;
+    }
+
+    private ConnectRequest deserializeConnectRequestWithReadonly(InputArchive inputArchive) throws IOException {
+        final ConnectRequest request = new ConnectRequest();
+        request.deserialize(inputArchive, "connect");
+        return request;
+    }
+
+    private ConnectRequest deserializeConnectRequestWithoutReadonly(InputArchive inputArchive) throws IOException {
+        final ConnectRequest request = new ConnectRequest();
+        inputArchive.startRecord("connect");
+        request.setProtocolVersion(inputArchive.readInt("protocolVersion"));
+        request.setLastZxidSeen(inputArchive.readLong("lastZxidSeen"));
+        request.setTimeOut(inputArchive.readInt("timeOut"));
+        request.setSessionId(inputArchive.readLong("sessionId"));
+        request.setPasswd(inputArchive.readBuffer("passwd"));
+        inputArchive.endRecord("connect");
+        return request;
+    }
+
+    /**
+     * Deserializing {@link ConnectResponse} should be specially handled for response from server
+     * version before and including ZooKeeper 3.3 which doesn't understand readOnly field.
+     */
+    public ConnectResponse deserializeConnectResponse(InputArchive inputArchive) throws IOException {
+        if (isReadonlyAvailable != null) {
+            if (isReadonlyAvailable) {
+                return deserializeConnectResponseWithReadonly(inputArchive);
+            } else {
+                return deserializeConnectResponseWithoutReadonly(inputArchive);
+            }
+        }
+
+        final ConnectResponse response = deserializeConnectResponseWithoutReadonly(inputArchive);
+        try {
+            response.setReadOnly(inputArchive.readBool("readOnly"));
+            this.isReadonlyAvailable = true;
+        } catch (Exception e) {
+            response.setReadOnly(false); // old version doesn't have readonly concept
+            this.isReadonlyAvailable = false;
+        }
+        return response;
+    }
+
+    private ConnectResponse deserializeConnectResponseWithReadonly(InputArchive inputArchive) throws IOException {
+        final ConnectResponse response = new ConnectResponse();
+        response.deserialize(inputArchive, "connect");
+        return response;
+    }
+
+    private ConnectResponse deserializeConnectResponseWithoutReadonly(InputArchive inputArchive) throws IOException {
+        final ConnectResponse response = new ConnectResponse();
+        inputArchive.startRecord("connect");
+        response.setProtocolVersion(inputArchive.readInt("protocolVersion"));
+        response.setTimeOut(inputArchive.readInt("timeOut"));
+        response.setSessionId(inputArchive.readLong("sessionId"));
+        response.setPasswd(inputArchive.readBuffer("passwd"));
+        inputArchive.endRecord("connect");
+        return response;
+    }
+}