GreenDao数据库升级问题

前面博客中有介绍轻量级的数据库GreenDao的整合。本文介绍如何对GreenDao数据库进行升级。

为什么要进行数据库升级呢？

在项目建立之初，数据库的表结构基本上以满足现阶段的业务而建立，随着后面业务的增加需要更多的column，或者废弃掉表中的某些column,此时如果直接去修改表结构，就会与之前已有的表冲突，导致Crash，此时我们就需要升级数据库中的表。

数据库升级的思路

删除重建

这种方法是最简单直接的。直接将之前的数据库删除后，再重新建立数据库。这样会使得之前保存的数据丢失。不需要持久化的保存数据，可以采用这种方式。

逐级版本迭代升级

比如当前版本为1，最新版本为3，此方案就是先从1–>2–>3. 这种方法实际应用中用起来相当的繁琐，要维护每个版本，所以不做过多介绍。

备份数据库，建立新数据库，然后将备份导入

如题，，奖原来的表删除，之后再将临时表插入到新建的表之中，然后再将临时表给删除了。以此完成数据迁移。

在原表基础上直接添加新的column

对比原表，增加或者删除column

代码实现

首先创建一个数据库帮助类

/**
 * description: GreenDao帮助类
 * author: bear .
 * Created date:  2017/5/17.
 */
public class MyOpenHelper extends DaoMaster.DevOpenHelper {


    public MyOpenHelper(Context context, String name) {
        super(context, name);
    }

    public MyOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
        super(context, name, factory);
    }

    @Override
    public void onUpgrade(Database db, int oldVersion, int newVersion) {
       /*此处不用super，因为父类中包含了
       dropAllTables(db, true);
        onCreate(db);
        需要自己定制升级
        */
    }
}

修改greenDao的版本号，在内层的gradle中的buildTypes节点下添加

greendao{
            schemaVersion 1
         // 这个地方是自动生成的配置文件存放在哪个位置的
            targetGenDir 'src/main/java'
        }

以下是更新方式：

1. 删除再新建

/**
    * 删除原表重新再建立一个表
    * @param db
    */
   public void dropAndCreate(Database db){
       DaoMaster.dropAllTables(db, true);
       DaoMaster.createAllTables(db, false);
   }

1. 备份数据库，建立新数据库，然后将备份导入

/**
     * 备份还原
     * @param db
     * @param daoClasses
     */
    public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        generateTempTables(db, daoClasses);
        DaoMaster.dropAllTables(db, true);
        DaoMaster.createAllTables(db, false);
        restoreData(db, daoClasses);
    }
    /**
     * 数据库备份
     * @param db
     * @param daoClasses
     */
    private void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        for (int i = 0; i < daoClasses.length; i++) {
            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String divider = "";
            String tableName = daoConfig.tablename;
            String tempTableName = daoConfig.tablename.concat("_TEMP");
            ArrayList<String> properties = new ArrayList<>();

            StringBuilder createTableStringBuilder = new StringBuilder();

            createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" (");

            for (int j = 0; j < daoConfig.properties.length; j++) {
                String columnName = daoConfig.properties[j].columnName;

                if (getColumns(db, tableName).contains(columnName)) {
                    properties.add(columnName);

                    String type = null;

                    try {
                        type = getTypeByClass(daoConfig.properties[j].type);
                    } catch (Exception exception) {
                    }

                    createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);

                    if (daoConfig.properties[j].primaryKey) {
                        createTableStringBuilder.append(" PRIMARY KEY");
                    }

                    divider = ",";
                }
            }
            createTableStringBuilder.append(");");

            db.execSQL(createTableStringBuilder.toString());

            StringBuilder insertTableStringBuilder = new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" (");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(") SELECT ");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(" FROM ").append(tableName).append(";");

            db.execSQL(insertTableStringBuilder.toString());
        }
    }
    /**
     * 数据库恢复
     * @param db
     * @param daoClasses
     */
    private void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        for (int i = 0; i < daoClasses.length; i++) {
            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String tableName = daoConfig.tablename;
            String tempTableName = daoConfig.tablename.concat("_TEMP");
            ArrayList<String> properties = new ArrayList();

            for (int j = 0; j < daoConfig.properties.length; j++) {
                String columnName = daoConfig.properties[j].columnName;

                if (getColumns(db, tempTableName).contains(columnName)) {
                    properties.add(columnName);
                }
            }

            StringBuilder insertTableStringBuilder = new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(") SELECT ");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");

            StringBuilder dropTableStringBuilder = new StringBuilder();

            dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);

            db.execSQL(insertTableStringBuilder.toString());
            db.execSQL(dropTableStringBuilder.toString());
        }
    }
    private String getTypeByClass(Class<?> type) throws Exception {
        if (type.equals(String.class)) {
            return "TEXT";
        }
        if (type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class)) {
            return "INTEGER";
        }
        if (type.equals(Boolean.class)) {
            return "BOOLEAN";
        }

        Exception exception =
                new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));
        throw exception;
    }

    private static List<String> getColumns(Database db, String tableName) {
        List<String> columns = new ArrayList<>();
        Cursor cursor = null;
        try {
            cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null);
            if (cursor != null) {
                columns = new ArrayList<>(Arrays.asList(cursor.getColumnNames()));
            }
        } catch (Exception e) {
            Log.v(tableName, e.getMessage(), e);
            e.printStackTrace();
        } finally {
            if (cursor != null) cursor.close();
        }
        return columns;
    }

1. 对比表差异，向原表中直接插入column

/**
     * 对比差异，在原表中直接添加column,赞不做删除操作
     * @param db
     * @param daoClasses
     */
    public void contrastDiff(Database db,ArrayList<String>properties, Class<? extends AbstractDao<?, ?>>... daoClasses){
     for(int i=0;i<daoClasses.length;i++){
         DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
         String tableName=daoConfig.tablename;
         if(properties!=null&&properties.size()>0){
             ArrayList<String>tem=new ArrayList<>();
             StringBuilder sqlBuilder=new StringBuilder();
             for(int j=0;j<properties.size();j++){
                 if(getColumns(db,tableName).contains(properties.get(j))){
                     continue;
                 }
                 tem.add(properties.get(j));
             }
             sqlBuilder.append("INSERT INTO ").append(tableName).append(" (");
             sqlBuilder.append(TextUtils.join(",", tem));
             sqlBuilder.append(") SELECT ");
             sqlBuilder.append(TextUtils.join(",", tem));
             sqlBuilder.append(" FROM ").append(tableName).append(";");
             db.execSQL(sqlBuilder.toString());
         }
        }
    }

下面贴出，完整的数据库升级帮助类

/**
 * description: greenDao升级帮助
 * author: bear .
 * Created date:  2017/5/17.
 */
public class MigrationHelper {

    private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION =
            "MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";
    private static MigrationHelper instance;

    public static MigrationHelper getInstance() {
        if (instance == null) {
            instance = new MigrationHelper();
        }
        return instance;
    }

    /**
     * 备份还原
     * @param db
     * @param daoClasses
     */
    public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        generateTempTables(db, daoClasses);
        DaoMaster.dropAllTables(db, true);
        DaoMaster.createAllTables(db, false);
        restoreData(db, daoClasses);
    }

    /**
     * 对比差异，在原表中直接添加column,赞不做删除操作
     * @param db
     * @param daoClasses
     */
    public void contrastDiff(Database db,ArrayList<String>properties, Class<? extends AbstractDao<?, ?>>... daoClasses){
     for(int i=0;i<daoClasses.length;i++){
         DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
         String tableName=daoConfig.tablename;
         if(properties!=null&&properties.size()>0){
             ArrayList<String>tem=new ArrayList<>();
             StringBuilder sqlBuilder=new StringBuilder();
             for(int j=0;j<properties.size();j++){
                 if(getColumns(db,tableName).contains(properties.get(j))){
                     continue;
                 }
                 tem.add(properties.get(j));
             }
             sqlBuilder.append("INSERT INTO ").append(tableName).append(" (");
             sqlBuilder.append(TextUtils.join(",", tem));
             sqlBuilder.append(") SELECT ");
             sqlBuilder.append(TextUtils.join(",", tem));
             sqlBuilder.append(" FROM ").append(tableName).append(";");
             db.execSQL(sqlBuilder.toString());
         }
        }
    }

    /**
     * 删除原表重新再建立一个表
     * @param db
     */
    public void dropAndCreate(Database db){
        DaoMaster.dropAllTables(db, true);
        DaoMaster.createAllTables(db, false);
    }

    /**
     * 数据库备份
     * @param db
     * @param daoClasses
     */
    private void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        for (int i = 0; i < daoClasses.length; i++) {
            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String divider = "";
            String tableName = daoConfig.tablename;
            String tempTableName = daoConfig.tablename.concat("_TEMP");
            ArrayList<String> properties = new ArrayList<>();

            StringBuilder createTableStringBuilder = new StringBuilder();

            createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" (");

            for (int j = 0; j < daoConfig.properties.length; j++) {
                String columnName = daoConfig.properties[j].columnName;

                if (getColumns(db, tableName).contains(columnName)) {
                    properties.add(columnName);

                    String type = null;

                    try {
                        type = getTypeByClass(daoConfig.properties[j].type);
                    } catch (Exception exception) {
                    }

                    createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);

                    if (daoConfig.properties[j].primaryKey) {
                        createTableStringBuilder.append(" PRIMARY KEY");
                    }

                    divider = ",";
                }
            }
            createTableStringBuilder.append(");");

            db.execSQL(createTableStringBuilder.toString());

            StringBuilder insertTableStringBuilder = new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" (");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(") SELECT ");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(" FROM ").append(tableName).append(";");

            db.execSQL(insertTableStringBuilder.toString());
        }
    }

    /**
     * 数据库恢复
     * @param db
     * @param daoClasses
     */
    private void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        for (int i = 0; i < daoClasses.length; i++) {
            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String tableName = daoConfig.tablename;
            String tempTableName = daoConfig.tablename.concat("_TEMP");
            ArrayList<String> properties = new ArrayList();

            for (int j = 0; j < daoConfig.properties.length; j++) {
                String columnName = daoConfig.properties[j].columnName;

                if (getColumns(db, tempTableName).contains(columnName)) {
                    properties.add(columnName);
                }
            }

            StringBuilder insertTableStringBuilder = new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(") SELECT ");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");

            StringBuilder dropTableStringBuilder = new StringBuilder();

            dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);

            db.execSQL(insertTableStringBuilder.toString());
            db.execSQL(dropTableStringBuilder.toString());
        }
    }

    private String getTypeByClass(Class<?> type) throws Exception {
        if (type.equals(String.class)) {
            return "TEXT";
        }
        if (type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class)) {
            return "INTEGER";
        }
        if (type.equals(Boolean.class)) {
            return "BOOLEAN";
        }

        Exception exception =
                new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));
        throw exception;
    }

    private static List<String> getColumns(Database db, String tableName) {
        List<String> columns = new ArrayList<>();
        Cursor cursor = null;
        try {
            cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null);
            if (cursor != null) {
                columns = new ArrayList<>(Arrays.asList(cursor.getColumnNames()));
            }
        } catch (Exception e) {
            Log.v(tableName, e.getMessage(), e);
            e.printStackTrace();
        } finally {
            if (cursor != null) cursor.close();
        }
        return columns;
    }
}

以上是本人自己整理的一些升级方法，请大家批评指正。