BeanCursor.java

package org.robobinding.itempresentationmodel;

import java.lang.reflect.InvocationTargetException;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.robobinding.internal.java_beans.PropertyDescriptor;
import org.robobinding.property.PropertyUtils;

import android.database.AbstractCursor;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

/**
 * 
 * @since 1.0
 * @version $Revision: 1.0 $
 * @author Cheng Wei
 */
public class BeanCursor<T> extends AbstractCursor implements TypedCursor<T> {

	private final List<T> beans;
	private final Map<String, PropertyDescriptor> propertyDescriptorMap;

	BeanCursor(List<T> beans, Map<String, PropertyDescriptor> propertyDescriptorMap) {
		this.beans = beans;
		this.propertyDescriptorMap = propertyDescriptorMap;
	}

	@Override
	public int getCount() {
		return beans.size();
	}

	private transient volatile String[] propertyNamesCache;

	@Override
	public String[] getColumnNames() {
		if (propertyNamesCache == null) {
			Set<String> propertyNames = propertyDescriptorMap.keySet();
			propertyNamesCache = propertyNames.toArray(new String[0]);
		}
		return propertyNamesCache;
	}

	@Override
	public String getString(int column) {
		return (String) getColumnValue(column);
	}

	@Override
	public short getShort(int column) {
		return (Short) getColumnValue(column);
	}

	@Override
	public int getInt(int column) {
		return (Integer) getColumnValue(column);
	}

	@Override
	public long getLong(int column) {
		return (Long) getColumnValue(column);
	}

	@Override
	public float getFloat(int column) {
		return (Float) getColumnValue(column);
	}

	@Override
	public double getDouble(int column) {
		return (Double) getColumnValue(column);
	}

	@Override
	public boolean isNull(int column) {
		Object value = getColumnValue(column);
		return value == null;
	}

	private Object getColumnValue(int column) {
		Preconditions.checkArgument(column < getNumColumns(), "column '" + column + "' is out of bound");
		PropertyDescriptor descriptor = mapColumnToPropertyDescriptor(column);
		try {
			return descriptor.getReadMethod().invoke(getBean(), new Object[0]);
		} catch (IllegalAccessException e) {
			throw new RuntimeException(e);
		} catch (IllegalArgumentException e) {
			throw new RuntimeException(e);
		} catch (InvocationTargetException e) {
			throw new RuntimeException(e);
		}
	}

	private PropertyDescriptor mapColumnToPropertyDescriptor(int column) {
		String propertyName = mapColumnToPropertyName(column);
		PropertyDescriptor descriptor = propertyDescriptorMap.get(propertyName);

		return descriptor;
	}

	private String mapColumnToPropertyName(int column) {
		return getColumnName(column);
	}

	private int getNumColumns() {
		return propertyDescriptorMap.size();
	}

	private Object getBean() {
		return beans.get(getPosition());
	}

	@Override
	public T getObjectAtPosition(int position) {
		Preconditions.checkArgument(position < getCount(), "Invalid requested position '" + position + "', as the cursor size is '" + getCount() + "'");
		return beans.get(position);
	}

	public static <T> BeanCursor<T> create(Collection<T> beans, Class<T> beanClass) {
		Preconditions.checkNotNull(beans, "beans can not be null");
		Preconditions.checkNotNull(beanClass, "beanClass can not be null");
		return new BeanCursor<T>(Lists.newArrayList(beans), getPropertyDescriptorMap(beanClass));
	}
	
	private static Map<String, PropertyDescriptor> getPropertyDescriptorMap(Class<?> beanClass) {
		Map<String, PropertyDescriptor> propertyDescriptorMap = Maps.newHashMap();
		for(PropertyDescriptor descriptor : PropertyUtils.getPropertyDescriptors(beanClass)) {
			propertyDescriptorMap.put(descriptor.getName(), descriptor);
		}
		return propertyDescriptorMap;
	}
}