From 79295cef1aae1dfd7adadf3814468e41275af474 Mon Sep 17 00:00:00 2001
From: hizumiaoba <56146205+hizumiaoba@users.noreply.github.com>
Date: Tue, 3 May 2022 12:40:31 +0900
Subject: [PATCH 1/1] feat: add JST calc class

---
 src/com/ranfa/lib/JST.java | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 src/test/JSTTest.java      | 15 ++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 src/com/ranfa/lib/JST.java
 create mode 100644 src/test/JSTTest.java

diff --git a/src/com/ranfa/lib/JST.java b/src/com/ranfa/lib/JST.java
new file mode 100644
index 0000000..cd6f348
--- /dev/null
+++ b/src/com/ranfa/lib/JST.java
@@ -0,0 +1,70 @@
+package com.ranfa.lib;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.Date;
+import java.util.Objects;
+
+import org.apache.commons.net.ntp.NTPUDPClient;
+import org.apache.commons.net.ntp.NtpV3Packet;
+import org.apache.commons.net.ntp.TimeInfo;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class JST {
+	
+	// Logger
+	private static final Logger LOG = LoggerFactory.getLogger(JST.class);
+	private static final String SERVER_NAME = "ntp.nict.jp";
+	
+	// private constructor
+	private JST() { /* do nothing */ }
+	
+	public static Date JSTNow() {
+		NTPUDPClient client = new NTPUDPClient();
+		InetAddress address = null;
+		try {
+			address = InetAddress.getByName(SERVER_NAME);
+		} catch (UnknownHostException e) {
+			// TODO 自動生成された catch ブロック
+			e.printStackTrace();
+		}
+		try {
+			client.open();
+		} catch (SocketException e) {
+			// TODO 自動生成された catch ブロック
+			e.printStackTrace();
+		}
+		TimeInfo info = null;
+		try {
+			info = client.getTime(Objects.requireNonNull(address));
+		} catch (IOException e) {
+			// TODO 自動生成された catch ブロック
+			e.printStackTrace();
+		}
+		NtpV3Packet packet = Objects.requireNonNull(info).getMessage();
+		info.computeDetails();
+		LOG.debug("NTPClient: {}", client);
+		LOG.debug("NetAddress: {}", address);
+		LOG.debug("Time info: {}", info);
+		long t1 = packet.getOriginateTimeStamp().getTime();
+		long t2 = packet.getReceiveTimeStamp().getTime();
+		long t3 = packet.getTransmitTimeStamp().getTime();
+		long t4 = info.getReturnTime();
+		long CalculatedOffset = (t2 - t1 + t3 - t4) / 2;
+		long receiveOffset = info.getOffset();
+		long offset = ( CalculatedOffset + receiveOffset ) / 2;
+		Date date = new Date(System.currentTimeMillis() + offset);
+		LOG.debug("Client originate Time: {}", t1);
+		LOG.debug("Server Received request Time: {}", t2);
+		LOG.debug("Server Transmit response Time: {}", t3);
+		LOG.debug("Client Received response Time: {}", t4);
+		LOG.info("Estimated time offset: {}", CalculatedOffset);
+		LOG.info("received time offset: {}", receiveOffset);
+		LOG.info("estimated JST: {}", date);
+		LOG.info("Current client date: {}", new Date(System.currentTimeMillis()));
+		return date;
+	}
+}
diff --git a/src/test/JSTTest.java b/src/test/JSTTest.java
new file mode 100644
index 0000000..05edfd5
--- /dev/null
+++ b/src/test/JSTTest.java
@@ -0,0 +1,15 @@
+package test;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+import com.ranfa.lib.JST;
+
+public class JSTTest {
+
+	@Test
+	public void JSTNonNullTest() {
+		assertNotNull(JST.JSTNow());
+	}
+}
-- 
2.11.0