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Lightweight Object Relational Model (ORM) for persisting objects to SQL databases.
There is a newer version: 6.1
package com.j256.ormlite.field.types;

import java.lang.reflect.Field;
import java.sql.SQLException;

import com.j256.ormlite.field.BaseFieldConverter;
import com.j256.ormlite.field.DataPersister;
import com.j256.ormlite.field.FieldType;
import com.j256.ormlite.field.SqlType;

/**
 * Base data type that defines the default persistance methods for the various data types.
 * 
 * 
 * Here's a good page about the mapping for a number of
 * database types:
 * 
 * 
 * 
 * NOTE: If you are creating your own custom database persister, you probably will need to override the
 * {@link BaseFieldConverter#sqlArgToJava(FieldType, Object, int)} method as well which converts from a SQL data to
 * java.
 * 
 * 
 * @author graywatson
 */
public abstract class BaseDataType extends BaseFieldConverter implements DataPersister {

	private final static Class[] NO_CLASSES = new Class[0];

	/**
	 * Type of the data as it is persisted in SQL-land. For example, if you are storing a DateTime, you might consider
	 * this to be a {@link SqlType#LONG} if you are storing it as epoche milliseconds.
	 */
	private final SqlType sqlType;
	private final Class[] classes;

	/**
	 * @param sqlType
	 *            Type of the class as it is persisted in the databases.
	 * @param classes
	 *            Associated classes for this type. These should be specified if you want this type to be always used
	 *            for these Java classes. If this is a custom persister then this array should be empty.
	 */
	public BaseDataType(SqlType sqlType, Class[] classes) {
		this.sqlType = sqlType;
		this.classes = classes;
	}

	/**
	 * @param sqlType
	 *            Type of the class as it is persisted in the databases.
	 */
	public BaseDataType(SqlType sqlType) {
		this.sqlType = sqlType;
		this.classes = NO_CLASSES;
	}

	@Override
	public boolean isValidForField(Field field) {
		if (classes.length == 0) {
			// we can't figure out the types so we just say it is valid
			return true;
		}
		for (Class clazz : classes) {
			if (clazz.isAssignableFrom(field.getType())) {
				return true;
			}
		}
		// if classes are specified and one of them should match
		return false;
	}

	@Override
	public Class getPrimaryClass() {
		if (classes.length == 0) {
			return null;
		} else {
			return classes[0];
		}
	}

	@Override
	public SqlType getSqlType() {
		return sqlType;
	}

	@Override
	public Class[] getAssociatedClasses() {
		return classes;
	}

	@Override
	public String[] getAssociatedClassNames() {
		return null;
	}

	@Override
	public Object convertIdNumber(Number number) {
		// by default the type cannot convert an id number
		return null;
	}

	@Override
	public boolean isValidGeneratedType() {
		return false;
	}

	@Override
	public boolean isEscapedDefaultValue() {
		// default is to not escape the type if it is a number
		return isEscapedValue();
	}

	@Override
	public boolean isEscapedValue() {
		return true;
	}

	@Override
	public boolean isPrimitive() {
		return false;
	}

	@Override
	public boolean isComparable() {
		return true;
	}

	@Override
	public boolean isAppropriateId() {
		return true;
	}

	@Override
	public boolean isArgumentHolderRequired() {
		return false;
	}

	@Override
	public boolean isSelfGeneratedId() {
		return false;
	}

	@Override
	public Object generateId() {
		throw new IllegalStateException("Should not have tried to generate this type");
	}

	@Override
	public int getDefaultWidth() {
		return 0;
	}

	@Override
	public boolean dataIsEqual(Object fieldObj1, Object fieldObj2) {
		if (fieldObj1 == null) {
			return (fieldObj2 == null);
		} else if (fieldObj2 == null) {
			return false;
		} else {
			return fieldObj1.equals(fieldObj2);
		}
	}

	@Override
	public boolean isValidForVersion() {
		return false;
	}

	/**
	 * Move the current-value to the next value. Used for the version field.
	 * 
	 * @throws SQLException
	 *             For sub-classes.
	 */
	@Override
	public Object moveToNextValue(Object currentValue) throws SQLException {
		return null;
	}

	@Override
	public Object resultStringToJava(FieldType fieldType, String stringValue, int columnPos) throws SQLException {
		return sqlArgToJava(fieldType, parseDefaultString(fieldType, stringValue), columnPos);
	}

	@Override
	public String getSqlOtherType() {
		// here to be overridden by custom persisters
		return null;
	}
}