Android Open Source - LitePal Upgrader

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License

The source code is released under:

Apache License

Java Source Code

/*
 * Copyright (C)  Tony Green, Litepal Framework Open Source Project
 */*from  w  w  w. j  av a2  s  .  com*/
 * 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 org.litepal.tablemanager;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.litepal.tablemanager.model.TableModel;
import org.litepal.util.BaseUtility;
import org.litepal.util.LogUtil;

import android.database.sqlite.SQLiteDatabase;

/**
 * Upgrade the database. The first step is to remove the columns that can not
 * find the corresponding field in the model class. Then add the new added field
 * as new column into the table. At last it will check all the types of columns
 * to see which are changed.
 * 
 * @author Tony Green
 * @since 1.0
 */
public class Upgrader extends AssociationUpdater {
  /**
   * Model class for table.
   */
  protected TableModel mTableModel;

  /**
   * Analyzing the table model, them remove the dump columns and add new
   * columns of a table.
   */
  @Override
  protected void createOrUpgradeTable(SQLiteDatabase db, boolean force) {
    mDb = db;
    for (TableModel tableModel : getAllTableModels()) {
      mTableModel = tableModel;
      upgradeTable();
    }
  }

  /**
   * Upgrade table actions. Include remove dump columns, add new columns and
   * change column types. All the actions above will be done by the
   * description order.
   */
  private void upgradeTable() {
    removeColumns(findColumnsToRemove(), mTableModel.getTableName());
    addColumn(findColumnsToAdd());
    changeColumnsType(findColumnTypesToChange());
  }

  /**
   * It will find the difference between class model and table model. If
   * there's a field in the class without a corresponding column in the table,
   * this field is a new added column. This method find all new added columns.
   * 
   * @return A map contains all new columns with column name as key and column
   *         type as value.
   */
  private Map<String, String> findColumnsToAdd() {
    Map<String, String> newColumnsMap = new HashMap<String, String>();
    for (String columnName : mTableModel.getColumnNames()) {
      boolean isNewColumn = true;
      for (String dbColumnName : getTableModelFromDB(mTableModel.getTableName())
          .getColumnNames()) {
        if (columnName.equalsIgnoreCase(dbColumnName)) {
          isNewColumn = false;
          break;
        }
      }
      if (isNewColumn) {
        // add column action
        if (!isIdColumn(columnName)) {
          newColumnsMap.put(columnName, mTableModel.getColumns().get(columnName));
        }
      }
    }
    return newColumnsMap;
  }

  /**
   * This method helps find the difference between table model from class and
   * table model from database. Database should always be synchronized with
   * model class. If there're some fields are removed from class, the table
   * model from database will be compared to find out which fields are
   * removed. But there're still some exceptions. The columns named id or _id
   * won't ever be removed. The foreign key column will be checked some where
   * else, not from here.
   * 
   * @return A list with column names need to remove.
   */
  private List<String> findColumnsToRemove() {
    TableModel tableModelDB = getTableModelFromDB(mTableModel.getTableName());
    List<String> removeColumns = new ArrayList<String>();
    Map<String, String> dbColumnsMap = tableModelDB.getColumns();
    Set<String> dbColumnNames = dbColumnsMap.keySet();
    for (String dbColumnName : dbColumnNames) {
      if (isNeedToRemove(dbColumnName)) {
        removeColumns.add(dbColumnName);
      }
    }
    for (String removeColumn : removeColumns) {
      LogUtil.d(TAG, "remove column is >> " + removeColumn);
    }
    return removeColumns;
  }

  /**
   * It will check each class in the mapping list. Find their types for each
   * field is changed or not by comparing with the types in table columns. If
   * there's a column have same name as a field in class but with different
   * type, then it's a type changed column.
   * 
   * @return A map contains all type changed columns with column name as key
   *         and column type as value.
   */
  private Map<String, String> findColumnTypesToChange() {
    Map<String, String> changeTypeColumns = new HashMap<String, String>();
    TableModel tableModelDB = getTableModelFromDB(mTableModel.getTableName());
    for (String columnNameDB : tableModelDB.getColumnNames()) {
      for (String columnName : mTableModel.getColumnNames()) {
        if (columnNameDB.equalsIgnoreCase(columnName)) {
          String columnTypeDB = tableModelDB.getColumns().get(columnNameDB);
          String columnType = mTableModel.getColumns().get(columnName);
          if (!columnTypeDB.equalsIgnoreCase(columnType)) {
            // column type is changed
            changeTypeColumns.put(columnName, columnType);
          }
        }
      }
    }
    return changeTypeColumns;
  }

  /**
   * Tell LitePal the column is need to remove or not. The column can be
   * remove only on the condition that the following three rules are all
   * passed. First the corresponding field for this column is removed in the
   * class. Second this column is not an id column. Third this column is not a
   * foreign key column.
   * 
   * @param columnName
   *            The column name to judge
   * @return Need to remove return true, otherwise return false.
   */
  private boolean isNeedToRemove(String columnName) {
    return isRemovedFromClass(columnName) && !isIdColumn(columnName)
        && !isForeignKeyColumn(mTableModel, columnName);
  }

  /**
   * Read a column name from database, and judge the corresponding field in
   * class is removed or not.
   * 
   * @param columnName
   *            The column name to judge.
   * @return If it's removed return true, or return false.
   */
  private boolean isRemovedFromClass(String columnName) {
    return !BaseUtility.containsIgnoreCases(mTableModel.getColumnNames(), columnName);
  }

  /**
   * Generate a SQL for add new column into the existing table.
   * 
   * @param columnName
   *            The new column name.
   * @param columnType
   *            The new column type.
   * @return A SQL to add new column.
   */
  private String generateAddColumnSQL(String columnName, String columnType) {
    return generateAddColumnSQL(mTableModel.getTableName(), columnName, columnType);
  }

  /**
   * This method create a SQL array for the all new columns to add them into
   * table.
   * 
   * @param newColumnsMap
   *            A column map with column name as key and column type as value.
   * @return A SQL array contains add all new columns job.
   */
  private String[] getAddColumnSQLs(Map<String, String> newColumnsMap) {
    List<String> sqls = new ArrayList<String>();
    for (String columnName : newColumnsMap.keySet()) {
      sqls.add(generateAddColumnSQL(columnName, newColumnsMap.get(columnName)));
    }
    return sqls.toArray(new String[0]);
  }

  /**
   * When some fields are added into the class after last upgrade, the table
   * should synchronize the changes by adding the corresponding columns.
   * 
   * @param columnsMap
   *            A map contains all the new columns need to add with column
   *            names as key and column types as value.
   */
  private void addColumn(Map<String, String> columnsMap) {
    execute(getAddColumnSQLs(columnsMap), mDb);
  }

  /**
   * When some fields type are changed in class, the table should drop the
   * before columns and create new columns with same name but new types.
   * 
   * @param changeTypeColumns
   *            A map contains all the columns need to change type with column
   *            names as key and column types as value.
   */
  private void changeColumnsType(Map<String, String> changeTypeColumns) {
    removeColumns(changeTypeColumns.keySet(), mTableModel.getTableName());
    addColumn(changeTypeColumns);
  }

}

Java Source Code List

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