# Conflicts:

#	dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/utils/FourLetterWordMain.java

dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/utils/FourLetterWordMain.java

@@ -29,13 +29,17 @@ import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
 import java.net.SocketTimeoutException;
-
+import java.util.Objects;
 
 public class FourLetterWordMain {
 
     private static final int DEFAULT_SOCKET_TIMEOUT = 5000;
     protected static final Logger LOG = LoggerFactory.getLogger(FourLetterWordMain.class);
 
+    private FourLetterWordMain() {
+        throw new IllegalStateException("FourLetterWordMain class");
+    }
+
     /**
      * Send the 4letterword
      * @param host the destination host
@@ -48,6 +52,7 @@ public class FourLetterWordMain {
             throws IOException {
         return send4LetterWord(host, port, cmd, DEFAULT_SOCKET_TIMEOUT);
     }
+
     /**
      * Send the 4letterword
      * @param host the destination host
@@ -59,12 +64,12 @@ public class FourLetterWordMain {
      */
     public static String send4LetterWord(String host, int port, String cmd, int timeout)
             throws IOException {
+        Objects.requireNonNull(cmd, "cmd must not be null");
         LOG.info("connecting to {} {}", host, port);
-        Socket sock = new Socket();
         InetSocketAddress hostaddress= host != null ? new InetSocketAddress(host, port) :
                 new InetSocketAddress(InetAddress.getByName(null), port);
-        BufferedReader reader = null;
+        
-        try {
+        try (Socket sock = new Socket()) {
             sock.setSoTimeout(timeout);
             sock.connect(hostaddress, timeout);
             OutputStream outstream = sock.getOutputStream();
@@ -73,22 +78,18 @@ public class FourLetterWordMain {
             // this replicates NC - close the output stream before reading
             sock.shutdownOutput();
 
-            reader =
+            try (BufferedReader reader =
                         new BufferedReader(
-                            new InputStreamReader(sock.getInputStream()));
+                            new InputStreamReader(sock.getInputStream()))) {
                 StringBuilder sb = new StringBuilder();
                 String line;
                 while ((line = reader.readLine()) != null) {
                     sb.append(line + "\n");
                 }
                 return sb.toString();
+            }
         } catch (SocketTimeoutException e) {
             throw new IOException("Exception while executing four letter word: " + cmd, e);
-        } finally {
-            sock.close();
-            if (reader != null) {
-                reader.close();
-            }
         }
     }
 }

dolphinscheduler-api/src/test/java/org/apache/dolphinscheduler/api/utils/FourLetterWordMainTest.java

@@ -0,0 +1,218 @@
+/*
+ * 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.dolphinscheduler.api.utils;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Ignore;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.powermock.api.mockito.PowerMockito;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.SocketTimeoutException;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.when;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest({FourLetterWordMain.class, Socket.class})
+public class FourLetterWordMainTest {
+
+    private static final Logger logger = 
+            LoggerFactory.getLogger(FourLetterWordMainTest.class);
+    private static final String NEW_LINE = "\n";
+
+    @InjectMocks
+    private FourLetterWordMain fourLetterWord;
+    @Mock
+    private Socket socket;
+    @Mock
+    private InetSocketAddress socketAddress;
+
+    private final String localHost = "127.0.0.1";
+    private final int zkPort = 2181;
+    private ByteArrayOutputStream byteArrayOutputStream;
+    private InputStream inputStream;
+
+    private String cmd;
+    private String testResult;
+    private String expectedStr;
+
+    @Before
+    public void setUp() {
+        // mock socket class
+        PowerMockito.mockStatic(Socket.class);
+        try {
+            PowerMockito.whenNew(Socket.class).withNoArguments()
+                    .thenReturn(socket);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    /**
+     * None mock test method, just to check zookeeper status.
+     * Comment @Before notation to run this test.
+     * Zookeeper status will be as:
+     * Zookeeper version: 3.4.11 ...
+     * Received: 6739707
+     * Sent: 6739773
+     * Connections: 20
+     * Outstanding: 0
+     * Zxid: 0x9ba
+     * Mode: standalone
+     * Node count: 263
+     */
+    public void testCmd() {
+        // "192.168.64.11"
+        // final String zkHost = localHost;
+        final String zkHost = "192.168.64.11";
+        cmd = "srvr";
+        try {
+            // Change localhost to right zk host ip.
+            final String result = FourLetterWordMain
+                    .send4LetterWord(zkHost, zkPort, cmd);
+            logger.info(cmd + ": " + result + "<<<");
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Test
+    public void testEmptyCmd() {
+        cmd = "";
+        expectedStr = "";
+        testSend4LetterWord(cmd, expectedStr);
+    }
+
+    @Test
+    public void testNullCmd() {
+        cmd = null;
+
+        try {
+            testResult = FourLetterWordMain
+                    .send4LetterWord(localHost, zkPort, cmd);
+        } catch (Exception e) {
+            testResult = e.getMessage();
+        }
+        
+        logger.info("testNullCmd result: " + testResult);
+        assertEquals("cmd must not be null", testResult);
+    }
+
+    @Test
+    public void testNullSocketOutput() {
+        cmd = "test null socket output";
+        expectedStr = null;
+        testSend4LetterWord(cmd, expectedStr);
+    }
+
+    @Test
+    public void testOneLineOutput() {
+        cmd = "line 1";
+
+        // line end without \n
+        expectedStr = "line 1" + NEW_LINE;
+        testSend4LetterWord(cmd, expectedStr);
+
+        // line end with \n
+        expectedStr = "line 1\n" + NEW_LINE;
+        testSend4LetterWord(cmd, expectedStr);
+    }
+
+    @Test
+    public void testMultiline() {
+        cmd = "line 1 " + NEW_LINE +
+                "line 2 " + NEW_LINE +
+                "line 3 " + NEW_LINE;
+
+        expectedStr = cmd + NEW_LINE;
+        testSend4LetterWord(cmd, expectedStr);
+
+        expectedStr = NEW_LINE + NEW_LINE + NEW_LINE;
+        testSend4LetterWord(cmd, expectedStr);
+    }
+
+    @Test
+    public void testSocketTimeOut() {
+        cmd = "test socket time out";
+
+        try {
+            doThrow(new SocketTimeoutException())
+                .when(socket)
+                .connect(any(InetSocketAddress.class), Mockito.anyInt());
+            testResult = FourLetterWordMain
+                .send4LetterWord(localHost, zkPort, cmd);
+        } catch (Exception e) {
+            testResult = e.getMessage();
+        }
+        
+        logger.info("testSocketTimeOut result: " + testResult);
+        assertEquals(
+                "Exception while executing four letter word: " + cmd,
+                testResult
+        );
+    }
+
+    /**
+     * Test FourLetterWordMain.send4LetterWord() with input cmd and output
+     * string. 
+     * @param cmd
+     * @param expectedStr
+     */
+    public void testSend4LetterWord(String cmd, String expectedStr) {
+        try {
+            final byte[] strBytes = cmd.getBytes();
+            byteArrayOutputStream = new ByteArrayOutputStream(strBytes.length);
+            byteArrayOutputStream.write(strBytes, 0, strBytes.length);
+            
+            inputStream = new ByteArrayInputStream(expectedStr.getBytes());
+
+            when(socket.getOutputStream())
+                    .thenReturn(byteArrayOutputStream);
+            when(socket.getInputStream()).thenReturn(inputStream);
+
+            final String result = FourLetterWordMain
+                    .send4LetterWord(localHost, zkPort, cmd);
+            logger.info(
+                    "testSend4LetterWord: " +
+                    "cmd: " + cmd + 
+                    ", expectedStr: " + expectedStr + 
+                    ", result: " + result + "."
+            );
+            Assert.assertEquals(expectedStr, result);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+}

pom.xml

@@ -687,6 +687,7 @@
                         <include>**/common/queue/*.java</include>
                         <include>**/api/utils/CheckUtilsTest.java</include>
                         <include>**/api/utils/FileUtilsTest.java</include>
+                        <include>**/api/utils/FourLetterWordTest.java</include>
                         <include>**/api/utils/exportprocess/DataSourceParamTest.java</include>
                         <include>**/api/utils/exportprocess/DependentParamTest.java</include>
                         <include>**/api/enums/*.java</include>