src/main/java/org/osgi/util/converter/ConverterImpl.java

/*
 * Copyright (c) OSGi Alliance (2017). All Rights Reserved.
 *
 * Licensed 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.osgi.util.converter;

import java.lang.reflect.Method;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
import java.util.UUID;
import java.util.regex.Pattern;

import org.osgi.util.function.Function;

/**
 * Top-level implementation of the Converter. This class contains a number of
 * rules that cover 'special cases'.
 * <p>
 * Note that this class avoids lambda's and hard dependencies on Java-8 (or
 * later) types to also work under Java 7.
 *
 * @author $Id$
 */
class ConverterImpl implements InternalConverter {
	static final SimpleDateFormat ISO8601_DATE_FORMAT = new SimpleDateFormat(
			"yyyy-MM-dd'T'HH:mm:ssXXX");
	static {
		ISO8601_DATE_FORMAT.setTimeZone(TimeZone.getTimeZone("UTC"));
	}

	@Override
	public InternalConverting convert(Object obj) {
		return new ConvertingImpl(this, obj);
	}

	@Override
	public Functioning function() {
		return new FunctioningImpl(this);
	}

	void addStandardRules(ConverterBuilder cb) {
		// Not written using lambda's because this code needs to run with Java 7
		cb.rule(new Rule<Calendar,String>(new Function<Calendar,String>() {
			@Override
			public String apply(Calendar f) {
				synchronized (ISO8601_DATE_FORMAT) {
					return ISO8601_DATE_FORMAT.format(f.getTime());
				}
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,Calendar>(new Function<String,Calendar>() {
			@Override
			public Calendar apply(String f) {
				try {
					synchronized (ISO8601_DATE_FORMAT) {
						Calendar cc = Calendar.getInstance();
						cc.setTime(ISO8601_DATE_FORMAT.parse(f));
						return cc;
					}
				} catch (ParseException e) {
					throw new ConversionException(
							"Cannot convert " + f + " to Date", e);
				}
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Calendar,Long>(new Function<Calendar,Long>() {
			@Override
			public Long apply(Calendar f) {
				return Long.valueOf(f.getTime().getTime());
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Long,Calendar>(new Function<Long,Calendar>() {
			@Override
			public Calendar apply(Long f) {
				Calendar c = Calendar.getInstance();
				c.setTimeInMillis(f.longValue());
				return c;
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Character,Boolean>(new Function<Character,Boolean>() {
			@Override
			public Boolean apply(Character c) {
				return Boolean.valueOf(c.charValue() != 0);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Boolean,Character>(new Function<Boolean,Character>() {
			@Override
			public Character apply(Boolean b) {
				return Character
						.valueOf(b.booleanValue() ? (char) 1 : (char) 0);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Character,Integer>(new Function<Character,Integer>() {
			@Override
			public Integer apply(Character c) {
				return Integer.valueOf(c.charValue());
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Character,Long>(new Function<Character,Long>() {
			@Override
			public Long apply(Character c) {
				return Long.valueOf(c.charValue());
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,Character>(new Function<String,Character>() {
			@Override
			public Character apply(String f) {
				return Character
						.valueOf(f.length() > 0 ? f.charAt(0) : (char) 0);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,Class< ? >>(new Function<String,Class< ? >>() {
			@Override
			public Class< ? > apply(String cn) {
				return loadClassUnchecked(cn);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Date,Long>(new Function<Date,Long>() {
			@Override
			public Long apply(Date d) {
				return Long.valueOf(d.getTime());
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Long,Date>(new Function<Long,Date>() {
			@Override
			public Date apply(Long f) {
				return new Date(f.longValue());
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Date,String>(new Function<Date,String>() {
			@Override
			public String apply(Date d) {
				synchronized (ISO8601_DATE_FORMAT) {
					return ISO8601_DATE_FORMAT.format(d);
				}
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,Date>(new Function<String,Date>() {
			@Override
			public Date apply(String f) {
				try {
					synchronized (ISO8601_DATE_FORMAT) {
						return ISO8601_DATE_FORMAT.parse(f);
					}
				} catch (ParseException e) {
					throw new ConversionException(
							"Cannot convert " + f + " to Date", e);
				}
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,Pattern>(new Function<String,Pattern>() {
			@Override
			public Pattern apply(String ps) {
				return Pattern.compile(ps);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,UUID>(new Function<String,UUID>() {
			@Override
			public UUID apply(String uuid) {
				return UUID.fromString(uuid);
			}
		}) {
			// empty subclass to capture generics
		});

		// Special conversions between character arrays and String
		cb.rule(new Rule<char[],String>(new Function<char[],String>() {
			@Override
			public String apply(char[] ca) {
				return charArrayToString(ca);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Character[],String>(
				new Function<Character[],String>() {
					@Override
					public String apply(Character[] ca) {
						return characterArrayToString(ca);
					}
				}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,char[]>(new Function<String,char[]>() {
			@Override
			public char[] apply(String s) {
				return stringToCharArray(s);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<String,Character[]>(
				new Function<String,Character[]>() {
					@Override
					public Character[] apply(String s) {
						return stringToCharacterArray(s);
					}
				}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Number,Boolean>(new Function<Number,Boolean>() {
			@Override
			public Boolean apply(Number obj) {
				return Boolean.valueOf(obj.longValue() != 0);
			}
		}) {
			// empty subclass to capture generics
		});

		cb.rule(new Rule<Number,Character>(new Function<Number,Character>() {
			@Override
			public Character apply(Number obj) {
				return Character.valueOf((char) obj.intValue());
			}
		}) {
			// empty subclass to capture generics
		});

		reflectiveAddJavaTimeRule(cb, "java.time.LocalDateTime");
		reflectiveAddJavaTimeRule(cb, "java.time.LocalDate");
		reflectiveAddJavaTimeRule(cb, "java.time.LocalTime");
		reflectiveAddJavaTimeRule(cb, "java.time.OffsetDateTime");
		reflectiveAddJavaTimeRule(cb, "java.time.OffsetTime");
		reflectiveAddJavaTimeRule(cb, "java.time.ZonedDateTime");
	}

	private void reflectiveAddJavaTimeRule(ConverterBuilder cb,
			String timeClsName) {
		try {
			final Class< ? > toCls = getClass().getClassLoader()
					.loadClass(timeClsName);
			final Method toMethod = toCls.getMethod("parse",
					CharSequence.class);

			cb.rule(new TypeRule<String,Object>(String.class, toCls,
					new Function<String,Object>() {
						@Override
						public Object apply(String f) {
							try {
								return toMethod.invoke(null, f);
							} catch (Exception e) {
								throw new ConversionException(
										"Problem converting to " + toCls, e);
							}
						}
					}));
			cb.rule(new TypeRule<Object,String>(toCls, String.class,
					new Function<Object,String>() {
						@Override
						public String apply(Object t) {
							return t.toString();
						}
					}));
		} catch (Exception ex) {
			// Class not available, do not add rule for it
		}
	}

	String charArrayToString(char[] ca) {
		StringBuilder sb = new StringBuilder(ca.length);
		for (char c : ca) {
			sb.append(c);
		}
		return sb.toString();
	}

	String characterArrayToString(Character[] ca) {
		return charArrayToString(convert(ca).to(char[].class));
	}

	char[] stringToCharArray(String s) {
		char[] ca = new char[s.length()];

		for (int i = 0; i < s.length(); i++) {
			ca[i] = s.charAt(i);
		}
		return ca;
	}

	Character[] stringToCharacterArray(String s) {
		return convert(stringToCharArray(s)).to(Character[].class);
	}

	Class< ? > loadClassUnchecked(String className) {
		try {
			return getClass().getClassLoader().loadClass(className);
		} catch (ClassNotFoundException e) {
			throw new NoClassDefFoundError(className);
		}
	}

	@Override
	public ConverterBuilderImpl newConverterBuilder() {
		return new ConverterBuilderImpl(this);
	}
}