19 unit conversion

pom.xml

@@ -2,7 +2,7 @@
 <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/maven-v4_0_0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.icatproject</groupId>
-	<version>4.16.2-SNAPSHOT</version>
+	<version>4.17.0-SNAPSHOT</version>
 	<artifactId>icat.utils</artifactId>
 	<packaging>jar</packaging>
 	<name>ICAT Utils</name>
@@ -63,6 +63,18 @@
 			<scope>test</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>javax.measure</groupId>
+			<artifactId>unit-api</artifactId>
+			<version>2.1.3</version>
+		</dependency>
+
+		<dependency>
+			<groupId>tech.units</groupId>
+			<artifactId>indriya</artifactId>
+			<version>2.1.3</version>
+		</dependency>
+
 	</dependencies>
 
 	<build>

src/main/java/org/icatproject/utils/IcatUnits.java

@@ -0,0 +1,89 @@
+package org.icatproject.utils;
+
+import javax.measure.IncommensurableException;
+import javax.measure.UnconvertibleException;
+import javax.measure.Unit;
+import javax.measure.UnitConverter;
+import javax.measure.format.MeasurementParseException;
+
+import tech.units.indriya.format.SimpleUnitFormat;
+
+/**
+ * Utility to perform conversions to SI (System) units.
+ */
+public class IcatUnits {
+
+	/**
+	 * Holds the SI units and value for a quantity. If the units provided at
+	 * construction could not be parsed, then these will be null.
+	 */
+	public class SystemValue {
+		public String units = null;
+		public Double value = null;
+
+		/**
+		 * Converts value units into an SI quantity.
+		 * 
+		 * @param value Quantity in (potentially) non-SI units.
+		 * @param units Units of the provided value.
+		 */
+		public SystemValue(Double value, String units) {
+			try {
+				Unit<?> unit = unitFormat.parse(units);
+				Unit<?> systemUnit = unit.getSystemUnit();
+				this.units = systemUnit.getName();
+				if (value == null) {
+					return;
+				}
+				UnitConverter converter = unit.getConverterToAny(systemUnit);
+				this.value = converter.convert(value.doubleValue());
+			} catch (MeasurementParseException | UnconvertibleException | IncommensurableException e) {
+				// If the units can't be parsed, or the value converted, then just return
+				return;
+			}
+		}
+	}
+
+	private static final SimpleUnitFormat unitFormat = SimpleUnitFormat.getInstance();
+
+	/**
+	 * Creates instance with any aliasing.
+	 */
+	public IcatUnits() {
+	}
+
+	/**
+	 * In addition to the standard names and prefixes, allows aliasing other terms
+	 * for a unit. Note that Unit should be referred to by the symbol specified in
+	 * the
+	 * <a href=
+	 * "https://javadoc.io/doc/tech.units/indriya/latest/tech/units/indriya/unit/Units.html">Indriya
+	 * documentation</a>, but the aliases can be any string. However, OoM prefixes
+	 * will not be applied to aliases. For example, "mK" would be understood as
+	 * 0.001K, but if "Kelvin" is aliased than "mKelvin" will not be understood.
+	 * 
+	 * If needed, a conversion factor can be provided alongside an alias, for
+	 * example to alias "eV" as a unit of energy, a factor of 1.602176634e-19 should
+	 * be applied to convert to the SI unit J.
+	 * 
+	 * @param aliasOptions String with the format
+	 *                     <code>symbolA: aliasA1, aliasA2 factorA2; symbolB: aliasB1 ...</code>
+	 */
+	public IcatUnits(String aliasOptions) {
+		if (!aliasOptions.equals("")) {
+			for (String unitAliases : aliasOptions.split(";")) {
+				String[] splitUnitAliases = unitAliases.split(":");
+				Unit<?> unit = unitFormat.parse(splitUnitAliases[0].trim());
+				for (String alias : splitUnitAliases[1].trim().split(",")) {
+					String[] aliasSplit = alias.trim().split("\\s+");
+					if (aliasSplit.length == 2) {
+						unitFormat.alias(unit.multiply(new Double(aliasSplit[1])), aliasSplit[0]);
+					} else {
+						unitFormat.alias(unit, aliasSplit[0]);
+					}
+				}
+			}
+		}
+	}
+
+}

src/test/java/org/icatproject/utils/TestIcatUnits.java

@@ -0,0 +1,51 @@
+package org.icatproject.utils;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import org.icatproject.utils.IcatUnits.SystemValue;
+import org.junit.Test;
+
+public class TestIcatUnits {
+	@Test
+	public void testArguments() {
+		// Both null
+		IcatUnits icatUnits = new IcatUnits();
+		SystemValue systemValue = icatUnits.new SystemValue(null, "impossible to parse");
+		assertNull(systemValue.units);
+		assertNull(systemValue.value);
+
+		// Unit parsed, value null
+		systemValue = icatUnits.new SystemValue(null, "K");
+		assertEquals("Kelvin", systemValue.units);
+		assertNull(systemValue.value);
+
+		// Unit parsed, value converted
+		systemValue = icatUnits.new SystemValue(1., "GK");
+		assertEquals("Kelvin", systemValue.units);
+		assertEquals(new Double(1e9), systemValue.value);
+	}
+
+	@Test
+	public void testAliasing() {
+		IcatUnits icatUnits = new IcatUnits();
+		SystemValue systemValue = icatUnits.new SystemValue(null, "celsius");
+		assertNull(systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "degC");
+		assertNull(systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "kelvin");
+		assertNull(systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "eV");
+		assertNull(systemValue.units);
+
+		new IcatUnits("\u2103: celsius, degC; K: kelvin; J: eV 1.602176634e-19");
+		new IcatUnits();
+		systemValue = icatUnits.new SystemValue(null, "celsius");
+		assertEquals("Kelvin", systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "degC");
+		assertEquals("Kelvin", systemValue.units);
+		systemValue = icatUnits.new SystemValue(1., "eV");
+		assertEquals("Joule", systemValue.units);
+		assertEquals(new Double(1.602176634e-19), systemValue.value);
+	}
+}