JAVA-8279 Split or move core java module

core-java-modules/core-java-uuid/README.md

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+## Core Java UUID
+
+### Relevant Articles: 
+- [Generating Alphanumeric UUID String in Java](https://www.baeldung.com/java-generate-alphanumeric-uuid)
+- [Guide to UUID in Java](http://www.baeldung.com/java-uuid)

core-java-modules/core-java-uuid/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-uuid</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-uuid</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>${log4j.version}</version>
+        </dependency>
+        <dependency> <!-- needed to bridge to slf4j for projects that use the log4j APIs directly -->
+            <groupId>org.slf4j</groupId>
+            <artifactId>log4j-over-slf4j</artifactId>
+            <version>${org.slf4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-uuid</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>copy-dependencies</id>
+                        <phase>prepare-package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}/libs</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <configuration>
+                    <executable>java</executable>
+                    <mainClass>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</mainClass>
+                    <arguments>
+                        <argument>-Xmx300m</argument>
+                        <argument>-XX:+UseParallelGC</argument>
+                        <argument>-classpath</argument>
+                        <classpath />
+                        <argument>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</argument>
+                    </arguments>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>${maven-javadoc-plugin.version}</version>
+                <configuration>
+                    <source>${source.version}</source>
+                    <target>${target.version}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <profiles>
+        <profile>
+            <id>integration</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>integration-test</phase>
+                                <goals>
+                                    <goal>test</goal>
+                                </goals>
+                                <configuration>
+                                    <excludes>
+                                        <exclude>**/*ManualTest.java</exclude>
+                                    </excludes>
+                                    <includes>
+                                        <include>**/*IntegrationTest.java</include>
+                                        <include>**/*IntTest.java</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                        <configuration>
+                            <systemPropertyVariables>
+                                <test.mime>json</test.mime>
+                            </systemPropertyVariables>
+                        </configuration>
+                    </plugin>
+                    <plugin>
+                        <groupId>org.codehaus.mojo</groupId>
+                        <artifactId>exec-maven-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>run-benchmarks</id>
+                                <!-- <phase>integration-test</phase> -->
+                                <phase>none</phase>
+                                <goals>
+                                    <goal>exec</goal>
+                                </goals>
+                                <configuration>
+                                    <classpathScope>test</classpathScope>
+                                    <executable>java</executable>
+                                    <arguments>
+                                        <argument>-classpath</argument>
+                                        <classpath />
+                                        <argument>org.openjdk.jmh.Main</argument>
+                                        <argument>.*</argument>
+                                    </arguments>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
+
+    <properties>
+        <assertj-core.version>3.10.0</assertj-core.version>
+        <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
+        <source.version>1.8</source.version>
+        <target.version>1.8</target.version>
+    </properties>
+
+</project>

core-java-modules/core-java-uuid/src/main/java/com/baeldung/uuid/UUIDGenerator.java

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+package com.baeldung.uuid;
+
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteOrder;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.time.Duration;
+import java.time.LocalDateTime;
+import java.util.Arrays;
+import java.util.Random;
+import java.util.UUID;
+
+public class UUIDGenerator {
+
+    private static final char[] hexArray = "0123456789ABCDEF".toCharArray();
+
+    /**
+     * Type 1 UUID Generation
+     */
+    public static UUID generateType1UUID() {
+
+        long most64SigBits = get64MostSignificantBitsForVersion1();
+        long least64SigBits = get64LeastSignificantBitsForVersion1();
+
+        return new UUID(most64SigBits, least64SigBits);
+    }
+
+    private static long get64LeastSignificantBitsForVersion1() {
+        Random random = new Random();
+        long random63BitLong = random.nextLong() & 0x3FFFFFFFFFFFFFFFL;
+        long variant3BitFlag = 0x8000000000000000L;
+        return random63BitLong + variant3BitFlag;
+    }
+
+    private static long get64MostSignificantBitsForVersion1() {
+        LocalDateTime start = LocalDateTime.of(1582, 10, 15, 0, 0, 0);
+        Duration duration = Duration.between(start, LocalDateTime.now());
+        long seconds = duration.getSeconds();
+        long nanos = duration.getNano();
+        long timeForUuidIn100Nanos = seconds * 10000000 + nanos * 100;
+        long least12SignificatBitOfTime = (timeForUuidIn100Nanos & 0x000000000000FFFFL) >> 4;
+        long version = 1 << 12;
+        return (timeForUuidIn100Nanos & 0xFFFFFFFFFFFF0000L) + version + least12SignificatBitOfTime;
+    }
+
+    /**
+     * Type 3 UUID Generation
+     *
+     * @throws UnsupportedEncodingException
+     */
+    public static UUID generateType3UUID(String namespace, String name) throws UnsupportedEncodingException {
+
+        byte[] nameSpaceBytes = bytesFromUUID(namespace);
+        byte[] nameBytes = name.getBytes("UTF-8");
+        byte[] result = joinBytes(nameSpaceBytes, nameBytes);
+
+        return UUID.nameUUIDFromBytes(result);
+    }
+
+    /**
+     * Type 4 UUID Generation
+     */
+    public static UUID generateType4UUID() {
+        UUID uuid = UUID.randomUUID();
+        return uuid;
+    }
+
+    /**
+     * Type 5 UUID Generation
+     *
+     * @throws UnsupportedEncodingException
+     */
+    public static UUID generateType5UUID(String namespace, String name) throws UnsupportedEncodingException {
+
+        byte[] nameSpaceBytes = bytesFromUUID(namespace);
+        byte[] nameBytes = name.getBytes("UTF-8");
+        byte[] result = joinBytes(nameSpaceBytes, nameBytes);
+
+        return type5UUIDFromBytes(result);
+    }
+
+    public static UUID type5UUIDFromBytes(byte[] name) {
+        MessageDigest md;
+        try {
+            md = MessageDigest.getInstance("SHA-1");
+        } catch (NoSuchAlgorithmException nsae) {
+            throw new InternalError("SHA-1 not supported", nsae);
+        }
+        byte[] bytes = Arrays.copyOfRange(md.digest(name), 0, 16);
+        bytes[6] &= 0x0f; /* clear version        */
+        bytes[6] |= 0x50; /* set to version 5     */
+        bytes[8] &= 0x3f; /* clear variant        */
+        bytes[8] |= 0x80; /* set to IETF variant  */
+        return constructType5UUID(bytes);
+    }
+
+    private static UUID constructType5UUID(byte[] data) {
+        long msb = 0;
+        long lsb = 0;
+        assert data.length == 16 : "data must be 16 bytes in length";
+
+        for (int i = 0; i < 8; i++)
+            msb = (msb << 8) | (data[i] & 0xff);
+
+        for (int i = 8; i < 16; i++)
+            lsb = (lsb << 8) | (data[i] & 0xff);
+        return new UUID(msb, lsb);
+    }
+
+    /**
+     * Unique Keys Generation Using Message Digest and Type 4 UUID
+     *
+     * @throws NoSuchAlgorithmException
+     * @throws UnsupportedEncodingException
+     */
+    public static String generateUniqueKeysWithUUIDAndMessageDigest() throws NoSuchAlgorithmException, UnsupportedEncodingException {
+        MessageDigest salt = MessageDigest.getInstance("SHA-256");
+        salt.update(UUID.randomUUID()
+                .toString()
+                .getBytes("UTF-8"));
+        String digest = bytesToHex(salt.digest());
+        return digest;
+    }
+
+    private static String bytesToHex(byte[] bytes) {
+        char[] hexChars = new char[bytes.length * 2];
+        for (int j = 0; j < bytes.length; j++) {
+            int v = bytes[j] & 0xFF;
+            hexChars[j * 2] = hexArray[v >>> 4];
+            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
+        }
+        return new String(hexChars);
+    }
+
+    private static byte[] bytesFromUUID(String uuidHexString) {
+        String normalizedUUIDHexString = uuidHexString.replace("-", "");
+
+        assert normalizedUUIDHexString.length() == 32;
+
+        byte[] bytes = new byte[16];
+        for (int i = 0; i < 16; i++) {
+            byte b = hexToByte(normalizedUUIDHexString.substring(i * 2, i * 2 + 2));
+            bytes[i] = b;
+        }
+        return bytes;
+    }
+
+    public static byte hexToByte(String hexString) {
+        int firstDigit = Character.digit(hexString.charAt(0), 16);
+        int secondDigit = Character.digit(hexString.charAt(1), 16);
+        return (byte) ((firstDigit << 4) + secondDigit);
+    }
+
+    public static byte[] joinBytes(byte[] byteArray1, byte[] byteArray2) {
+        int finalLength = byteArray1.length + byteArray2.length;
+        byte[] result = new byte[finalLength];
+
+        for (int i = 0; i < byteArray1.length; i++) {
+            result[i] = byteArray1[i];
+        }
+
+        for (int i = 0; i < byteArray2.length; i++) {
+            result[byteArray1.length + i] = byteArray2[i];
+        }
+
+        return result;
+    }
+
+    public static UUID generateType5UUID(String name) {
+
+        try {
+
+            byte[] bytes = name.getBytes(StandardCharsets.UTF_8);
+            MessageDigest md = MessageDigest.getInstance("SHA-1");
+
+            byte[] hash = md.digest(bytes);
+
+            long msb = getLeastAndMostSignificantBitsVersion5(hash, 0);
+            long lsb = getLeastAndMostSignificantBitsVersion5(hash, 8);
+            // Set the version field
+            msb &= ~(0xfL << 12);
+            msb |= ((long) 5) << 12;
+            // Set the variant field to 2
+            lsb &= ~(0x3L << 62);
+            lsb |= 2L << 62;
+            return new UUID(msb, lsb);
+
+        } catch (NoSuchAlgorithmException e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    private static long getLeastAndMostSignificantBitsVersion5(final byte[] src, final int offset) {
+        long ans = 0;
+        for (int i = offset + 7; i >= offset; i -= 1) {
+            ans <<= 8;
+            ans |= src[i] & 0xffL;
+        }
+        return ans;
+    }
+}

core-java-modules/core-java-uuid/src/main/resources/log4j.properties

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+log4j.rootLogger=DEBUG, A1
+
+log4j.appender.A1=org.apache.log4j.ConsoleAppender
+
+log4j.appender.A1.layout=org.apache.log4j.PatternLayout
+log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

core-java-modules/core-java-uuid/src/main/resources/log4j2.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="WARN">
+    <Appenders>
+        <Console name="Console" target="SYSTEM_OUT">
+            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level - %msg%n"/>
+        </Console>
+    </Appenders>
+    <Loggers>
+        <Root level="debug">
+            <AppenderRef ref="Console"/>
+        </Root>
+    </Loggers>
+</Configuration>

core-java-modules/core-java-uuid/src/main/resources/log4jstructuraldp.properties

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+
+# Root logger 
+log4j.rootLogger=INFO, file, stdout
+
+# Write to console
+log4j.appender.stdout=org.apache.log4j.ConsoleAppender
+log4j.appender.stdout.Target=System.out
+log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

core-java-modules/core-java-uuid/src/main/resources/logback.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework" level="WARN" />
+    <logger name="org.springframework.transaction" level="WARN" />
+
+    <!-- in order to debug some marshalling issues, this needs to be TRACE -->
+    <logger name="org.springframework.web.servlet.mvc" level="WARN" />
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/UUIDGeneratorUnitTest.java

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+package com.baeldung.uuid;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.UnsupportedEncodingException;
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class UUIDGeneratorUnitTest {
+
+    private static final String NAMESPACE_URL = "6ba7b811-9dad-11d1-80b4-00c04fd430c8";
+    private static final String NAMESPACE_DNS = "6ba7b810-9dad-11d1-80b4-00c04fd430c8";
+
+    @Test
+    public void version_1_UUID_is_generated_with_correct_length_version_and_variant() {
+
+        UUID uuid = UUIDGenerator.generateType1UUID();
+
+        assertEquals(36, uuid.toString().length());
+        assertEquals(1, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_3_UUID_is_correctly_generated_for_domain_baeldung_com() throws UnsupportedEncodingException {
+
+        UUID uuid = UUIDGenerator.generateType3UUID(NAMESPACE_DNS, "baeldung.com");
+
+        assertEquals("23785b78-0132-3ac6-aff6-cfd5be162139", uuid.toString());
+        assertEquals(3, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_3_UUID_is_correctly_generated_for_domain_d() throws UnsupportedEncodingException {
+
+        UUID uuid = UUIDGenerator.generateType3UUID(NAMESPACE_DNS, "d");
+
+        assertEquals("dbd41ecb-f466-33de-b309-1468addfc63b", uuid.toString());
+        assertEquals(3, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_4_UUID_is_generated_with_correct_length_version_and_variant() {
+
+        UUID uuid = UUIDGenerator.generateType4UUID();
+
+        assertEquals(36, uuid.toString().length());
+        assertEquals(4, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_5_UUID_is_correctly_generated_for_domain_baeldung_com() throws UnsupportedEncodingException {
+
+        UUID uuid = UUIDGenerator.generateType5UUID(NAMESPACE_URL, "baeldung.com");
+
+        assertEquals("aeff44a5-8a61-52b6-bcbe-c8e5bd7d0300", uuid.toString());
+        assertEquals(5, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_5_UUID_is_correctly_generated_for_domain_baeldung_name() {
+
+        UUID uuid = UUIDGenerator.generateType5UUID("baeldung.com");
+
+        assertEquals("efd5462b-b07a-52a3-94ea-bf575c0e0e75", uuid.toString());
+        assertEquals(5, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+}

core-java-modules/core-java-uuid/src/test/resources/log4j.properties

@@ -0,0 +1,6 @@
+log4j.rootLogger=DEBUG, A1
+
+log4j.appender.A1=org.apache.log4j.ConsoleAppender
+
+log4j.appender.A1.layout=org.apache.log4j.PatternLayout
+log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

core-java-modules/core-java-uuid/src/test/resources/log4j2.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="WARN">
+    <Appenders>
+        <Console name="Console" target="SYSTEM_OUT">
+            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level - %msg%n"/>
+        </Console>
+    </Appenders>
+    <Loggers>
+        <Root level="debug">
+            <AppenderRef ref="Console"/>
+        </Root>
+    </Loggers>
+</Configuration>

core-java-modules/core-java-uuid/src/test/resources/log4jstructuraldp.properties

@@ -0,0 +1,9 @@
+
+# Root logger 
+log4j.rootLogger=INFO, file, stdout
+
+# Write to console
+log4j.appender.stdout=org.apache.log4j.ConsoleAppender
+log4j.appender.stdout.Target=System.out
+log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

core-java-modules/core-java-uuid/src/test/resources/logback.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework" level="WARN" />
+    <logger name="org.springframework.transaction" level="WARN" />
+
+    <!-- in order to debug some marshalling issues, this needs to be TRACE -->
+    <logger name="org.springframework.web.servlet.mvc" level="WARN" />
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>