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Android example source code file (SQLiteQueryBuilder.java)

This example Android source code file (SQLiteQueryBuilder.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

all, android, by, cursor, database, having, illegalargumentexception, iterator, limit, order, provider, regex, set, sqlitequerybuilder, string, stringbuilder, union, util, utilities, where

The SQLiteQueryBuilder.java Android example source code

/*
 * Copyright (C) 2006 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.
 */

package android.database.sqlite;

import android.database.Cursor;
import android.database.DatabaseUtils;
import android.provider.BaseColumns;
import android.text.TextUtils;
import android.util.Log;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import java.util.regex.Pattern;

/**
 * This is a convience class that helps build SQL queries to be sent to
 * {@link SQLiteDatabase} objects.
 */
public class SQLiteQueryBuilder
{
    private static final String TAG = "SQLiteQueryBuilder";
    private static final Pattern sLimitPattern =
            Pattern.compile("\\s*\\d+\\s*(,\\s*\\d+\\s*)?");

    private Map<String, String> mProjectionMap = null;
    private String mTables = "";
    private StringBuilder mWhereClause = null;  // lazily created
    private boolean mDistinct;
    private SQLiteDatabase.CursorFactory mFactory;
    private boolean mStrictProjectionMap;

    public SQLiteQueryBuilder() {
        mDistinct = false;
        mFactory = null;
    }

    /**
     * Mark the query as DISTINCT.
     *
     * @param distinct if true the query is DISTINCT, otherwise it isn't
     */
    public void setDistinct(boolean distinct) {
        mDistinct = distinct;
    }

    /**
     * Returns the list of tables being queried
     *
     * @return the list of tables being queried
     */
    public String getTables() {
        return mTables;
    }

    /**
     * Sets the list of tables to query. Multiple tables can be specified to perform a join.
     * For example:
     *   setTables("foo, bar")
     *   setTables("foo LEFT OUTER JOIN bar ON (foo.id = bar.foo_id)")
     *
     * @param inTables the list of tables to query on
     */
    public void setTables(String inTables) {
        mTables = inTables;
    }

    /**
     * Append a chunk to the WHERE clause of the query. All chunks appended are surrounded
     * by parenthesis and ANDed with the selection passed to {@link #query}. The final
     * WHERE clause looks like:
     *
     * WHERE (<append chunk 1><append chunk2>) AND (<query() selection parameter>)
     *
     * @param inWhere the chunk of text to append to the WHERE clause.
     */
    public void appendWhere(CharSequence inWhere) {
        if (mWhereClause == null) {
            mWhereClause = new StringBuilder(inWhere.length() + 16);
        }
        if (mWhereClause.length() == 0) {
            mWhereClause.append('(');
        }
        mWhereClause.append(inWhere);
    }

    /**
     * Append a chunk to the WHERE clause of the query. All chunks appended are surrounded
     * by parenthesis and ANDed with the selection passed to {@link #query}. The final
     * WHERE clause looks like:
     *
     * WHERE (<append chunk 1><append chunk2>) AND (<query() selection parameter>)
     *
     * @param inWhere the chunk of text to append to the WHERE clause. it will be escaped
     * to avoid SQL injection attacks
     */
    public void appendWhereEscapeString(String inWhere) {
        if (mWhereClause == null) {
            mWhereClause = new StringBuilder(inWhere.length() + 16);
        }
        if (mWhereClause.length() == 0) {
            mWhereClause.append('(');
        }
        DatabaseUtils.appendEscapedSQLString(mWhereClause, inWhere);
    }

    /**
     * Sets the projection map for the query.  The projection map maps
     * from column names that the caller passes into query to database
     * column names. This is useful for renaming columns as well as
     * disambiguating column names when doing joins. For example you
     * could map "name" to "people.name".  If a projection map is set
     * it must contain all column names the user may request, even if
     * the key and value are the same.
     *
     * @param columnMap maps from the user column names to the database column names
     */
    public void setProjectionMap(Map<String, String> columnMap) {
        mProjectionMap = columnMap;
    }

    /**
     * Sets the cursor factory to be used for the query.  You can use
     * one factory for all queries on a database but it is normally
     * easier to specify the factory when doing this query.  @param
     * factory the factor to use
     */
    public void setCursorFactory(SQLiteDatabase.CursorFactory factory) {
        mFactory = factory;
    }

    /**
     * @hide
     */
    public void setStrictProjectionMap(boolean flag) {
        mStrictProjectionMap = flag;
    }

    /**
     * Build an SQL query string from the given clauses.
     *
     * @param distinct true if you want each row to be unique, false otherwise.
     * @param tables The table names to compile the query against.
     * @param columns A list of which columns to return. Passing null will
     *            return all columns, which is discouraged to prevent reading
     *            data from storage that isn't going to be used.
     * @param where A filter declaring which rows to return, formatted as an SQL
     *            WHERE clause (excluding the WHERE itself). Passing null will
     *            return all rows for the given URL.
     * @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 the SQL query string
     */
    public static String buildQueryString(
            boolean distinct, String tables, String[] columns, String where,
            String groupBy, String having, String orderBy, String limit) {
        if (TextUtils.isEmpty(groupBy) && !TextUtils.isEmpty(having)) {
            throw new IllegalArgumentException(
                    "HAVING clauses are only permitted when using a groupBy clause");
        }
        if (!TextUtils.isEmpty(limit) && !sLimitPattern.matcher(limit).matches()) {
            throw new IllegalArgumentException("invalid LIMIT clauses:" + limit);
        }

        StringBuilder query = new StringBuilder(120);

        query.append("SELECT ");
        if (distinct) {
            query.append("DISTINCT ");
        }
        if (columns != null && columns.length != 0) {
            appendColumns(query, columns);
        } else {
            query.append("* ");
        }
        query.append("FROM ");
        query.append(tables);
        appendClause(query, " WHERE ", where);
        appendClause(query, " GROUP BY ", groupBy);
        appendClause(query, " HAVING ", having);
        appendClause(query, " ORDER BY ", orderBy);
        appendClause(query, " LIMIT ", limit);

        return query.toString();
    }

    private static void appendClause(StringBuilder s, String name, String clause) {
        if (!TextUtils.isEmpty(clause)) {
            s.append(name);
            s.append(clause);
        }
    }

    private static void appendClauseEscapeClause(StringBuilder s, String name, String clause) {
        if (!TextUtils.isEmpty(clause)) {
            s.append(name);
            DatabaseUtils.appendEscapedSQLString(s, clause);
        }
    }

    /**
     * Add the names that are non-null in columns to s, separating
     * them with commas.
     */
    public static void appendColumns(StringBuilder s, String[] columns) {
        int n = columns.length;

        for (int i = 0; i < n; i++) {
            String column = columns[i];

            if (column != null) {
                if (i > 0) {
                    s.append(", ");
                }
                s.append(column);
            }
        }
        s.append(' ');
    }

    /**
     * Perform a query by combining all current settings and the
     * information passed into this method.
     *
     * @param db the database to query on
     * @param projectionIn A list of which columns to return. Passing
     *   null will return all columns, which is discouraged to prevent
     *   reading data from storage that isn't going to be used.
     * @param selection A filter declaring which rows to return,
     *   formatted as an SQL WHERE clause (excluding the WHERE
     *   itself). Passing null will return all rows for the given URL.
     * @param selectionArgs You may include ?s in selection, which
     *   will be replaced by the values from selectionArgs, in order
     *   that they appear in the selection. The values will be bound
     *   as Strings.
     * @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 sortOrder 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 cursor over the result set
     * @see android.content.ContentResolver#query(android.net.Uri, String[],
     *      String, String[], String)
     */
    public Cursor query(SQLiteDatabase db, String[] projectionIn,
            String selection, String[] selectionArgs, String groupBy,
            String having, String sortOrder) {
        return query(db, projectionIn, selection, selectionArgs, groupBy, having, sortOrder,
                null /* limit */);
    }

    /**
     * Perform a query by combining all current settings and the
     * information passed into this method.
     *
     * @param db the database to query on
     * @param projectionIn A list of which columns to return. Passing
     *   null will return all columns, which is discouraged to prevent
     *   reading data from storage that isn't going to be used.
     * @param selection A filter declaring which rows to return,
     *   formatted as an SQL WHERE clause (excluding the WHERE
     *   itself). Passing null will return all rows for the given URL.
     * @param selectionArgs You may include ?s in selection, which
     *   will be replaced by the values from selectionArgs, in order
     *   that they appear in the selection. The values will be bound
     *   as Strings.
     * @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 sortOrder 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 cursor over the result set
     * @see android.content.ContentResolver#query(android.net.Uri, String[],
     *      String, String[], String)
     */
    public Cursor query(SQLiteDatabase db, String[] projectionIn,
            String selection, String[] selectionArgs, String groupBy,
            String having, String sortOrder, String limit) {
        if (mTables == null) {
            return null;
        }

        String sql = buildQuery(
                projectionIn, selection, selectionArgs, groupBy, having,
                sortOrder, limit);

        if (Log.isLoggable(TAG, Log.DEBUG)) {
            Log.d(TAG, "Performing query: " + sql);
        }
        return db.rawQueryWithFactory(
                mFactory, sql, selectionArgs,
                SQLiteDatabase.findEditTable(mTables));
    }

    /**
     * Construct a SELECT statement suitable for use in a group of
     * SELECT statements that will be joined through UNION operators
     * in buildUnionQuery.
     *
     * @param projectionIn A list of which columns to return. Passing
     *    null will return all columns, which is discouraged to
     *    prevent reading data from storage that isn't going to be
     *    used.
     * @param selection A filter declaring which rows to return,
     *   formatted as an SQL WHERE clause (excluding the WHERE
     *   itself).  Passing null will return all rows for the given
     *   URL.
     * @param selectionArgs You may include ?s in selection, which
     *   will be replaced by the values from selectionArgs, in order
     *   that they appear in the selection.  The values will be bound
     *   as Strings.
     * @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 sortOrder 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 the resulting SQL SELECT statement
     */
    public String buildQuery(
            String[] projectionIn, String selection, String[] selectionArgs,
            String groupBy, String having, String sortOrder, String limit) {
        String[] projection = computeProjection(projectionIn);

        StringBuilder where = new StringBuilder();
        boolean hasBaseWhereClause = mWhereClause != null && mWhereClause.length() > 0;

        if (hasBaseWhereClause) {
            where.append(mWhereClause.toString());
            where.append(')');
        }

        // Tack on the user's selection, if present.
        if (selection != null && selection.length() > 0) {
            if (hasBaseWhereClause) {
                where.append(" AND ");
            }

            where.append('(');
            where.append(selection);
            where.append(')');
        }

        return buildQueryString(
                mDistinct, mTables, projection, where.toString(),
                groupBy, having, sortOrder, limit);
    }

    /**
     * Construct a SELECT statement suitable for use in a group of
     * SELECT statements that will be joined through UNION operators
     * in buildUnionQuery.
     *
     * @param typeDiscriminatorColumn the name of the result column
     *   whose cells will contain the name of the table from which
     *   each row was drawn.
     * @param unionColumns the names of the columns to appear in the
     *   result.  This may include columns that do not appear in the
     *   table this SELECT is querying (i.e. mTables), but that do
     *   appear in one of the other tables in the UNION query that we
     *   are constructing.
     * @param columnsPresentInTable a Set of the names of the columns
     *   that appear in this table (i.e. in the table whose name is
     *   mTables).  Since columns in unionColumns include columns that
     *   appear only in other tables, we use this array to distinguish
     *   which ones actually are present.  Other columns will have
     *   NULL values for results from this subquery.
     * @param computedColumnsOffset all columns in unionColumns before
     *   this index are included under the assumption that they're
     *   computed and therefore won't appear in columnsPresentInTable,
     *   e.g. "date * 1000 as normalized_date"
     * @param typeDiscriminatorValue the value used for the
     *   type-discriminator column in this subquery
     * @param selection A filter declaring which rows to return,
     *   formatted as an SQL WHERE clause (excluding the WHERE
     *   itself).  Passing null will return all rows for the given
     *   URL.
     * @param selectionArgs You may include ?s in selection, which
     *   will be replaced by the values from selectionArgs, in order
     *   that they appear in the selection.  The values will be bound
     *   as Strings.
     * @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.
     * @return the resulting SQL SELECT statement
     */
    public String buildUnionSubQuery(
            String typeDiscriminatorColumn,
            String[] unionColumns,
            Set<String> columnsPresentInTable,
            int computedColumnsOffset,
            String typeDiscriminatorValue,
            String selection,
            String[] selectionArgs,
            String groupBy,
            String having) {
        int unionColumnsCount = unionColumns.length;
        String[] projectionIn = new String[unionColumnsCount];

        for (int i = 0; i < unionColumnsCount; i++) {
            String unionColumn = unionColumns[i];

            if (unionColumn.equals(typeDiscriminatorColumn)) {
                projectionIn[i] = "'" + typeDiscriminatorValue + "' AS "
                        + typeDiscriminatorColumn;
            } else if (i <= computedColumnsOffset
                       || columnsPresentInTable.contains(unionColumn)) {
                projectionIn[i] = unionColumn;
            } else {
                projectionIn[i] = "NULL AS " + unionColumn;
            }
        }
        return buildQuery(
                projectionIn, selection, selectionArgs, groupBy, having,
                null /* sortOrder */,
                null /* limit */);
    }

    /**
     * Given a set of subqueries, all of which are SELECT statements,
     * construct a query that returns the union of what those
     * subqueries return.
     * @param subQueries an array of SQL SELECT statements, all of
     *   which must have the same columns as the same positions in
     *   their results
     * @param sortOrder 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 The limit clause, which applies to the entire union result set
     *
     * @return the resulting SQL SELECT statement
     */
    public String buildUnionQuery(String[] subQueries, String sortOrder, String limit) {
        StringBuilder query = new StringBuilder(128);
        int subQueryCount = subQueries.length;
        String unionOperator = mDistinct ? " UNION " : " UNION ALL ";

        for (int i = 0; i < subQueryCount; i++) {
            if (i > 0) {
                query.append(unionOperator);
            }
            query.append(subQueries[i]);
        }
        appendClause(query, " ORDER BY ", sortOrder);
        appendClause(query, " LIMIT ", limit);
        return query.toString();
    }

    private String[] computeProjection(String[] projectionIn) {
        if (projectionIn != null && projectionIn.length > 0) {
            if (mProjectionMap != null) {
                String[] projection = new String[projectionIn.length];
                int length = projectionIn.length;

                for (int i = 0; i < length; i++) {
                    String userColumn = projectionIn[i];
                    String column = mProjectionMap.get(userColumn);

                    if (column != null) {
                        projection[i] = column;
                        continue;
                    }

                    if (!mStrictProjectionMap &&
                            ( userColumn.contains(" AS ") || userColumn.contains(" as "))) {
                        /* A column alias already exist */
                        projection[i] = userColumn;
                        continue;
                    }

                    throw new IllegalArgumentException("Invalid column "
                            + projectionIn[i]);
                }
                return projection;
            } else {
                return projectionIn;
            }
        } else if (mProjectionMap != null) {
            // Return all columns in projection map.
            Set<Entry entrySet = mProjectionMap.entrySet();
            String[] projection = new String[entrySet.size()];
            Iterator<Entry entryIter = entrySet.iterator();
            int i = 0;

            while (entryIter.hasNext()) {
                Entry<String, String> entry = entryIter.next();

                // Don't include the _count column when people ask for no projection.
                if (entry.getKey().equals(BaseColumns._COUNT)) {
                    continue;
                }
                projection[i++] = entry.getValue();
            }
            return projection;
        }
        return null;
    }
}

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