Add scripts and basic tests for unit conversion #19

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

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+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 refered 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.
+	 * 
+	 * @param aliasOptions String with the format "<symbolA>: <aliasA1> <aliasA2>,
+	 *                     <symbolB>: <aliasB2> ..."
+	 */
+	public IcatUnits(String aliasOptions) {
+		for (String unitAliases : aliasOptions.split(",")) {
+			String[] splitUnitAliases = unitAliases.split(":");
+			Unit<?> unit = unitFormat.parse(splitUnitAliases[0].trim());
+			for (String alias : splitUnitAliases[1].trim().split("\\s+")) {
+				unitFormat.alias(unit, alias);
+			}
+		}
+	}
+
+}

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

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+package org.icatproject.utils;
+
+import static org.junit.Assert.assertEquals;
+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");
+		assertEquals(null, systemValue.units);
+		assertEquals(null, systemValue.value);
+
+		// Unit parsed, value null
+		systemValue = icatUnits.new SystemValue(null, "K");
+		assertEquals("Kelvin", systemValue.units);
+		assertEquals(null, 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");
+		assertEquals(null, systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "degC");
+		assertEquals(null, systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "kelvin");
+		assertEquals(null, systemValue.units);
+
+		icatUnits = new IcatUnits("\u2103: celsius degC, K: kelvin");
+		systemValue = icatUnits.new SystemValue(null, "celsius");
+		assertEquals("Kelvin", systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "degC");
+		assertEquals("Kelvin", systemValue.units);
+		systemValue = icatUnits.new SystemValue(null, "kelvin");
+		assertEquals("Kelvin", systemValue.units);
+	}
+}