/*
* Copyright 2013 The Android Open Source Project
*
* 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.
*/
/*
* Modifications:
* -Imported from AOSP frameworks/base/core/java/com/android/internal/content
* -Changed package name
*/
package com.example.android.common.db;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.text.TextUtils;
import android.util.Log;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
/**
* Helper for building selection clauses for {@link SQLiteDatabase}.
*
* <p>This class provides a convenient frontend for working with SQL. Instead of composing statements
* manually using string concatenation, method calls are used to construct the statement one
* clause at a time. These methods can be chained together.
*
* <p>If multiple where() statements are provided, they're combined using {@code AND}.
*
* <p>Example:
*
* <pre>
* SelectionBuilder builder = new SelectionBuilder();
* Cursor c = builder.table(FeedContract.Entry.TABLE_NAME) // String TABLE_NAME = "entry"
* .where(FeedContract.Entry._ID + "=?", id); // String _ID = "_ID"
* .query(db, projection, sortOrder)
*
* </pre>
*
* <p>In this example, the table name and filters ({@code WHERE} clauses) are both explicitly
* specified via method call. SelectionBuilder takes care of issuing a "query" command to the
* database, and returns the resulting {@link Cursor} object.
*
* <p>Inner {@code JOIN}s can be accomplished using the mapToTable() function. The map() function
* can be used to create new columns based on arbitrary (SQL-based) criteria. In advanced usage,
* entire subqueries can be passed into the map() function.
*
* <p>Advanced example:
*
* <pre>
* // String SESSIONS_JOIN_BLOCKS_ROOMS = "sessions "
* // + "LEFT OUTER JOIN blocks ON sessions.block_id=blocks.block_id "
* // + "LEFT OUTER JOIN rooms ON sessions.room_id=rooms.room_id";
*
* // String Subquery.BLOCK_NUM_STARRED_SESSIONS =
* // "(SELECT COUNT(1) FROM "
* // + Tables.SESSIONS + " WHERE " + Qualified.SESSIONS_BLOCK_ID + "="
* // + Qualified.BLOCKS_BLOCK_ID + " AND " + Qualified.SESSIONS_STARRED + "=1)";
*
* String Subqery.BLOCK_SESSIONS_COUNT =
* Cursor c = builder.table(Tables.SESSIONS_JOIN_BLOCKS_ROOMS)
* .map(Blocks.NUM_STARRED_SESSIONS, Subquery.BLOCK_NUM_STARRED_SESSIONS)
* .mapToTable(Sessions._ID, Tables.SESSIONS)
* .mapToTable(Sessions.SESSION_ID, Tables.SESSIONS)
* .mapToTable(Sessions.BLOCK_ID, Tables.SESSIONS)
* .mapToTable(Sessions.ROOM_ID, Tables.SESSIONS)
* .where(Qualified.SESSIONS_BLOCK_ID + "=?", blockId);
* </pre>
*
* <p>In this example, we have two different types of {@code JOIN}s: a left outer join using a
* modified table name (since this class doesn't directly support these), and an inner join using
* the mapToTable() function. The map() function is used to insert a count based on specific
* criteria, executed as a sub-query.
*
* This class is <em>not</em> thread safe.
*/
public class SelectionBuilder {
private static final String TAG = "basicsyncadapter";
private String mTable = null;
private Map<String, String> mProjectionMap = new HashMap<String, String>();
private StringBuilder mSelection = new StringBuilder();
private ArrayList<String> mSelectionArgs = new ArrayList<String>();
/**
* Reset any internal state, allowing this builder to be recycled.
*
* <p>Calling this method is more efficient than creating a new SelectionBuilder object.
*
* @return Fluent interface
*/
public SelectionBuilder reset() {
mTable = null;
mSelection.setLength(0);
mSelectionArgs.clear();
return this;
}
/**
* Append the given selection clause to the internal state. Each clause is
* surrounded with parenthesis and combined using {@code AND}.
*
* <p>In the most basic usage, simply provide a selection in SQL {@code WHERE} statement format.
*
* <p>Example:
*
* <pre>
* .where("blog_posts.category = 'PROGRAMMING');
* </pre>
*
* <p>User input should never be directly supplied as as part of the selection statement.
* Instead, use positional parameters in your selection statement, then pass the user input
* in via the selectionArgs parameter. This prevents SQL escape characters in user input from
* causing unwanted side effects. (Failure to follow this convention may have security
* implications.)
*
* <p>Positional parameters are specified using the '?' character.
*
* <p>Example:
* <pre>
* .where("blog_posts.title contains ?, userSearchString);
* </pre>
*
* @param selection SQL where statement
* @param selectionArgs Values to substitute for positional parameters ('?' characters in
* {@code selection} statement. Will be automatically escaped.
* @return Fluent interface
*/
public SelectionBuilder where(String selection, String... selectionArgs) {
if (TextUtils.isEmpty(selection)) {
if (selectionArgs != null && selectionArgs.length > 0) {
throw new IllegalArgumentException(
"Valid selection required when including arguments=");
}
// Shortcut when clause is empty
return this;
}
if (mSelection.length() > 0) {
mSelection.append(" AND ");
}
mSelection.append("(").append(selection).append(")");
if (selectionArgs != null) {
Collections.addAll(mSelectionArgs, selectionArgs);
}
return this;
}
/**
* Table name to use for SQL {@code FROM} statement.
*
* <p>This method may only be called once. If multiple tables are required, concatenate them
* in SQL-format (typically comma-separated).
*
* <p>If you need to do advanced {@code JOIN}s, they can also be specified here.
*
* See also: mapToTable()
*
* @param table Table name
* @return Fluent interface
*/
public SelectionBuilder table(String table) {
mTable = table;
return this;
}
/**
* Verify that a table name has been supplied using table().
*
* @throws IllegalStateException if table not set
*/
private void assertTable() {
if (mTable == null) {
throw new IllegalStateException("Table not specified");
}
}
/**
* Perform an inner join.
*
* <p>Map columns from a secondary table onto the current result set. References to the column
* specified in {@code column} will be replaced with {@code table.column} in the SQL {@code
* SELECT} clause.
*
* @param column Column name to join on. Must be the same in both tables.
* @param table Secondary table to join.
* @return Fluent interface
*/
public SelectionBuilder mapToTable(String column, String table) {
mProjectionMap.put(column, table + "." + column);
return this;
}
/**
* Create a new column based on custom criteria (such as aggregate functions).
*
* <p>This adds a new column to the result set, based upon custom criteria in SQL format. This
* is equivalent to the SQL statement: {@code SELECT toClause AS fromColumn}
*
* <p>This method is useful for executing SQL sub-queries.
*
* @param fromColumn Name of column for mapping
* @param toClause SQL string representing data to be mapped
* @return Fluent interface
*/
public SelectionBuilder map(String fromColumn, String toClause) {
mProjectionMap.put(fromColumn, toClause + " AS " + fromColumn);
return this;
}
/**
* Return selection string based on current internal state.
*
* @return Current selection as a SQL statement
* @see #getSelectionArgs()
*/
public String getSelection() {
return mSelection.toString();
}
/**
* Return selection arguments based on current internal state.
*
* @see #getSelection()
*/
public String[] getSelectionArgs() {
return mSelectionArgs.toArray(new String[mSelectionArgs.size()]);
}
/**
* Process user-supplied projection (column list).
*
* <p>In cases where a column is mapped to another data source (either another table, or an
* SQL sub-query), the column name will be replaced with a more specific, SQL-compatible
* representation.
*
* Assumes that incoming columns are non-null.
*
* <p>See also: map(), mapToTable()
*
* @param columns User supplied projection (column list).
*/
private void mapColumns(String[] columns) {
for (int i = 0; i < columns.length; i++) {
final String target = mProjectionMap.get(columns[i]);
if (target != null) {
columns[i] = target;
}
}
}
/**
* Return a description of this builder's state. Does NOT output SQL.
*
* @return Human-readable internal state
*/
@Override
public String toString() {
return "SelectionBuilder[table=" + mTable + ", selection=" + getSelection()
+ ", selectionArgs=" + Arrays.toString(getSelectionArgs()) + "]";
}
/**
* Execute query (SQL {@code SELECT}) against specified database.
*
* <p>Using a null projection (column list) is not supported.
*
* @param db Database to query.
* @param columns Database projection (column list) to return, must be non-NULL.
* @param orderBy How to order the rows, formatted as an SQL ORDER BY clause (excluding the
* ORDER BY itself). Passing null will use the default sort order, which may be
* unordered.
* @return A {@link Cursor} object, which is positioned before the first entry. Note that
* {@link Cursor}s are not synchronized, see the documentation for more details.
*/
public Cursor query(SQLiteDatabase db, String[] columns, String orderBy) {
return query(db, columns, null, null, orderBy, null);
}
/**
* Execute query ({@code SELECT}) against database.
*
* <p>Using a null projection (column list) is not supported.
*
* @param db Database to query.
* @param columns Database projection (column list) to return, must be non-null.
* @param groupBy A filter declaring how to group rows, formatted as an SQL GROUP BY clause
* (excluding the GROUP BY itself). Passing null will cause the rows to not be
* grouped.
* @param having A filter declare which row groups to include in the cursor, if row grouping is
* being used, formatted as an SQL HAVING clause (excluding the HAVING itself).
* Passing null will cause all row groups to be included, and is required when
* row grouping is not being used.
* @param orderBy How to order the rows, formatted as an SQL ORDER BY clause (excluding the
* ORDER BY itself). Passing null will use the default sort order, which may be
* unordered.
* @param limit Limits the number of rows returned by the query, formatted as LIMIT clause.
* Passing null denotes no LIMIT clause.
* @return A {@link Cursor} object, which is positioned before the first entry. Note that
* {@link Cursor}s are not synchronized, see the documentation for more details.
*/
public Cursor query(SQLiteDatabase db, String[] columns, String groupBy,
String having, String orderBy, String limit) {
assertTable();
if (columns != null) mapColumns(columns);
Log.v(TAG, "query(columns=" + Arrays.toString(columns) + ") " + this);
return db.query(mTable, columns, getSelection(), getSelectionArgs(), groupBy, having,
orderBy, limit);
}
/**
* Execute an {@code UPDATE} against database.
*
* @param db Database to query.
* @param values A map from column names to new column values. null is a valid value that will
* be translated to NULL
* @return The number of rows affected.
*/
public int update(SQLiteDatabase db, ContentValues values) {
assertTable();
Log.v(TAG, "update() " + this);
return db.update(mTable, values, getSelection(), getSelectionArgs());
}
/**
* Execute {@code DELETE} against database.
*
* @param db Database to query.
* @return The number of rows affected.
*/
public int delete(SQLiteDatabase db) {
assertTable();
Log.v(TAG, "delete() " + this);
return db.delete(mTable, getSelection(), getSelectionArgs());
}
}