GreenDao3 数据库升级问题

来源：互联网发布：java 树遍历treenode 编辑：程序博客网时间：2024/05/22 03:51

首先在试用GreenDao的时候，默认的数据库升级会先Drop表再Create，这样问题显而易见，如果版本已经上线必然不能接受

解决方法：网上有很多转载解决方案。一般是利用临时表转移2次数据

现在要说的问题：

当某张表需要添加一个Int类型的列时，升级数据库则会报NOT NULL约束不通过，原因是 GreenDao建表时Int 类型加了NOT NULL。而再数据转移的时候并没有Insert 该列。

下面对之前网上的代码做一些调整：

 for (int j = 0; j < daoConfig.properties.length; j++) {                String columnName = daoConfig.properties[j].columnName;                if (getColumns(db, tempTableName).contains(columnName)) {                    properties.add(columnName);                    propertiesQuery.add(columnName);                } else {                    try {                        if (getTypeByClass(daoConfig.properties[j].type).equals("INTEGER")) {                            propertiesQuery.add("0 as " + columnName);                            properties.add(columnName);                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                }            }

遍历新的表结构，发现新增的列的时候，从临时表查数据的时候，对应把新增的列默认填值 0 as columnName

该类全部代码如下：

public class GreenDaoUpgrade {    private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION = "MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";    private static GreenDaoUpgrade instance;    public static GreenDaoUpgrade getInstance() {        if (instance == null) {            instance = new GreenDaoUpgrade();        }        return instance;    }    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;    }    public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {        generateTempTables(db, daoClasses);        DaoMaster.dropAllTables(db, true);        DaoMaster.createAllTables(db, false);        restoreData(db, 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) {                        exception.printStackTrace();                    }                    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());        }    }    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();            ArrayList<String> propertiesQuery = 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);                    propertiesQuery.add(columnName);                } else {                    try {                        if (getTypeByClass(daoConfig.properties[j].type).equals("INTEGER")) {                            propertiesQuery.add("0 as " + columnName);                            properties.add(columnName);                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                }            }            StringBuilder insertTableStringBuilder = new StringBuilder();            insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");            insertTableStringBuilder.append(TextUtils.join(",", properties));            insertTableStringBuilder.append(") SELECT ");            insertTableStringBuilder.append(TextUtils.join(",", propertiesQuery));            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) || type.equals(int.class)) {            return "INTEGER";        }        if (type.equals(Boolean.class) || type.equals(boolean.class)) {            return "BOOLEAN";        }        Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));        exception.printStackTrace();        throw exception;    }}

0 0