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123 lines
3.7 KiB
Java
123 lines
3.7 KiB
Java
/**
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* Copyright (c) 2012 Todoroo Inc
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*
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* See the file "LICENSE" for the full license governing this code.
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*/
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package com.todoroo.andlib.data;
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import android.database.Cursor;
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import android.database.CursorWrapper;
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import com.todoroo.andlib.data.Property.PropertyVisitor;
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import java.util.WeakHashMap;
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/**
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* AstridCursor wraps a cursor and allows users to query for individual
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* {@link Property} types or read an entire {@link AbstractModel} from
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* a database row.
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*
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* @author Tim Su <tim@todoroo.com>
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*
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* @param <TYPE> a model type that is returned by this cursor
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*/
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public class TodorooCursor<TYPE extends AbstractModel> extends CursorWrapper {
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/** Properties read by this cursor */
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private final Property<?>[] properties;
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/** Weakly cache field name to column id references for this cursor.
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* Because it's a weak hash map, entire keys can be discarded by GC */
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private final WeakHashMap<String, Integer> columnIndexCache;
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/** Property reading visitor */
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private static final CursorReadingVisitor reader = new CursorReadingVisitor();
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/**
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* Create an <code>AstridCursor</code> from the supplied {@link Cursor}
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* object.
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*
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* @param properties properties read from this cursor
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*/
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public TodorooCursor(Cursor cursor, Property<?>[] properties) {
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super(cursor);
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this.properties = properties;
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columnIndexCache = new WeakHashMap<>();
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}
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/**
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* Get the value for the given property on the underlying {@link Cursor}
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*
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* @param <PROPERTY_TYPE> type to return
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* @param property to retrieve
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*/
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public <PROPERTY_TYPE> PROPERTY_TYPE get(Property<PROPERTY_TYPE> property) {
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return (PROPERTY_TYPE)property.accept(reader, this);
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}
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/**
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* Gets entire property list
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*/
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public Property<?>[] getProperties() {
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return properties;
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}
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/**
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* Use cache to get the column index for the given field name
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*/
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public synchronized int getColumnIndexFromCache(String field) {
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Integer index = columnIndexCache.get(field);
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if(index == null) {
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index = getColumnIndexOrThrow(field);
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columnIndexCache.put(field, index);
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}
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return index;
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}
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/**
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* Visitor that reads the given property from a cursor
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*
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* @author Tim Su <tim@todoroo.com>
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*
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*/
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public static class CursorReadingVisitor implements PropertyVisitor<Object, TodorooCursor<?>> {
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@Override
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public Object visitInteger(Property<Integer> property,
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TodorooCursor<?> cursor) {
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int column = columnIndex(property, cursor);
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if(property.checkFlag(Property.PROP_FLAG_NULLABLE) && cursor.isNull(column)) {
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return null;
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}
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return cursor.getInt(column);
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}
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@Override
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public Object visitLong(Property<Long> property, TodorooCursor<?> cursor) {
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int column = columnIndex(property, cursor);
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if(property.checkFlag(Property.PROP_FLAG_NULLABLE) && cursor.isNull(column)) {
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return null;
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}
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return cursor.getLong(column);
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}
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@Override
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public Object visitString(Property<String> property,
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TodorooCursor<?> cursor) {
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int column = columnIndex(property, cursor);
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if(property.checkFlag(Property.PROP_FLAG_NULLABLE) && cursor.isNull(column)) {
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return null;
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}
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return cursor.getString(column);
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}
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private int columnIndex(Property<?> property, TodorooCursor<?> cursor) {
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return cursor.getColumnIndexFromCache(property.getColumnName());
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}
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}
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}
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