说明

仅仅记录自己学习及使用该框架的过程和代码
框架版本大致可以分为

1.x
2.x 增加build.gradle插件
3.x 增加注解,build.gradle插件,加密

为什么用GreenDao

没有该框架之前，其实本人一直在使用手动封装的ORM。该ORM是我看起来融合我现有掌握的知识很自然的框架。因为它仅仅做的事情是。编译时生产出数据库业务相关的代码，这样简单理解为它就是一个工具。仅仅而已。
The best way to access the SQLite就像它宣传的含义一样。

简单概念

想玩转数据库，再我看来，必须要懂概念性东西。比如关系型数据库的基础。

Master
抽象基类，定义Session生成等等
Schema
如果数据库比作图书馆，那么每个藏书的房间就是Schema，它描述了这个房间的基本信息，如几个书架，藏书什么类型，借阅的开放时间等等。那么表就代表书架，那么字段就是书架的分类签。行内容就是一本本书了。
Session
每一次数据库链接的会话，记得有缓存功能！。可以理解为你打算今天去图书馆看书一天。
4.Dao
相当于你获得了借阅哪个书架的资格

1.x配置

我的工程目录如图，
生成数据库相关代码如下：

image.png

package com.example.ltx.orm_greendao.db.generator;

import de.greenrobot.daogenerator.DaoGenerator;
import de.greenrobot.daogenerator.Entity;
import de.greenrobot.daogenerator.Schema;

/**
 * Created by ltx on 2017/12/19.
 */

public class GreenDaoGenerator {

    private static void addTaskDetail(Schema schema) {
        //创建User表
        Entity entityUser = schema.addEntity("User");
        entityUser.addIdProperty().primaryKey().autoincrement();;
        entityUser.addStringProperty("userId").notNull();
        entityUser.addStringProperty("userName");
        entityUser.addIntProperty("age");
        entityUser.addStringProperty("phone");
        entityUser.addDateProperty("createTime");
        entityUser.addDateProperty("modifyTime");

        //创建NetCache表
        Entity entityNetCache = schema.addEntity("NetCache");
        entityNetCache.addIdProperty().primaryKey().autoincrement();;
        entityNetCache.addLongProperty("netId").notNull();
        entityNetCache.addStringProperty("url");
        entityNetCache.addStringProperty("json");
        entityNetCache.addDateProperty("createTime");
        entityNetCache.addDateProperty("modifyTime");
    }

    public static void main(String[] args) throws Exception {
        //定义Scheme，可以有多个，通常一个就可以了。Scheme相当于房间，表相当于书架子。
        //参数二代表包的路径，生成文件所在位置。
        //需要注意的是，Scheme版本更新，DaoSession
        Schema schema = new Schema(1, "com.example.ltx.orm_greendao.db.entity");
        addTaskDetail(schema);
        try {
            new DaoGenerator().generateAll(schema, "../ORM-GreenDao/app/src/main/java/");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

接下来，为了方便使用。单例来管理Session。我们知道，一般IO操作，包括网络，数据库的读写，文件读写都是IO，那么IO就最好严格执行异步，因此这里还会有GreenDao提供的AsyncSession对象

image.png

package com.example.ltx.orm_greendao.db;

import android.app.Application;
import android.content.Context;

import com.example.ltx.orm_greendao.db.entity.DaoMaster;
import com.example.ltx.orm_greendao.db.entity.DaoSession;

import de.greenrobot.dao.async.AsyncSession;

/**
 * Created by ltx on 2017/12/20.
 */

public class DBHelper {
    private static String DB_NAME = "test";

    private static DaoSession session  = null;
    private static AsyncSession asyncSession  = null;

    /**
     * DaoSession单利
     * @return
     */
    public static DaoSession getSessionInstance(){
        if(session==null)
            synchronized (DBHelper.class) {
                if(session==null){
                    Context appContext = new Application().getApplicationContext();
                    DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(appContext, DB_NAME, null);
                    DaoMaster master = new DaoMaster(helper.getWritableDatabase());
                    session = master.newSession();
                }
            }
        return session;
    }

    /**
     * AsyncSession单利
     * @return
     */
    public static AsyncSession getAsyncSessionInstance(){
        if(asyncSession==null)
            synchronized (DBHelper.class) {
                if(asyncSession==null){
                    if(session==null){
                        session = getSessionInstance();
                    }
                    asyncSession = session.startAsyncSession();

                }
            }
        return asyncSession;
    }



}

具体使用，代码：

package com.example.ltx.orm_greendao;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.example.ltx.orm_greendao.db.DBHelper;
import com.example.ltx.orm_greendao.db.entity.DaoSession;
import com.example.ltx.orm_greendao.db.entity.User;
import com.example.ltx.orm_greendao.db.entity.UserDao;

import de.greenrobot.dao.async.AsyncOperation;
import de.greenrobot.dao.async.AsyncOperationListener;
import de.greenrobot.dao.async.AsyncSession;

public class MainActivity extends Activity implements View.OnClickListener {
    private TextView mTvShow;
    private Button mBtnAdd,mBtnDel,mBtnUpdate,mBtnSelect;
    private AsyncSession mAsyncSession;
    private DaoSession mDaoSession;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mTvShow = findViewById(R.id.db_show);
        mBtnAdd = findViewById(R.id.db_add);
        mBtnDel = findViewById(R.id.db_delete);
        mBtnUpdate = findViewById(R.id.db_update);
        mBtnSelect = findViewById(R.id.db_select);


        mBtnAdd.setOnClickListener(this);
        mBtnDel.setOnClickListener(this);
        mBtnUpdate.setOnClickListener(this);
        mBtnSelect.setOnClickListener(this);

        mAsyncSession = DBHelper.getAsyncSessionInstance();
        mDaoSession = DBHelper.getSessionInstance();
    }


    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.db_add:
                User u = new User();
                u.setUserName("ltx");
                u.setAge(4);


                //异步操作
                mAsyncSession.insert(u);
                mAsyncSession.setListenerMainThread(new AsyncOperationListener() {
                    @Override
                    public void onAsyncOperationCompleted(AsyncOperation operation) {
                        operation.getResult();
                    }
                });



                mAsyncSession.runInTx(new Runnable() {
                    @Override
                    public void run() {
                        //不关心结果，且有多个顺序执行的操作
                    }
                });

                
                UserDao userDao = mDaoSession.getUserDao();
                //同步操作
                userDao.insert(u);


                break;

            case R.id.db_delete:


                break;

            case R.id.db_update:
                break;

            case R.id.db_select:
                break;
        }
    }
}

数据库升级

原表数据保留
表字段有增加（记得，表字段不要修改，不要删除，有新业务增加就行了）
有些表数据，数据库升级后不需要保留
要知道一点，GreenDao在数据库升级的回调方法中的操作是

DropAllTable();
CreateAllTable();

因此，默认全部表的数据是无法保留的。
若想升级时保留某个表数据。需要使用一个帮助类，帮助类代码

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.text.TextUtils;
import android.util.Log;

import com.crashlytics.android.Crashlytics;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import de.greenrobot.dao.AbstractDao;
import de.greenrobot.dao.internal.DaoConfig;
import greendao.DaoMaster;


/**
 * Created by pokawa on 18/05/15.
 */
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;
    }

    public void migrate(SQLiteDatabase db, Class>... daoClasses) {
        generateTempTables(db, daoClasses);
        DaoMaster.dropAllTables(db, true);
        DaoMaster.createAllTables(db, false);
        restoreData(db, daoClasses);
    }

    private void generateTempTables(SQLiteDatabase db, Class>... 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 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) {
                        Crashlytics.logException(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());
        }
    }

    private void restoreData(SQLiteDatabase db, Class>... 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 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()));
        Crashlytics.logException(exception);
        throw exception;
    }

    private static List getColumns(SQLiteDatabase db, String tableName) {
        List 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;
    }
}

DaoMaster中使用：

@Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by migrating all tables data");

        MigrationHelper.getInstance().migrate(db,
                UserDao.class,
                ItemDao.class);
    }

只要把想保留数据的表所对应的Dao.class 写在参数里就可以。

数据加密

GreenDao3.0 后直接支持SQLCipher的。SQLCipher是一个自定义使用256位的AES加密的SQLite.
依赖

compile 'net.zetetic:android-database-sqlcipher:3.5.2'

在Session创建时调用加密数据库

daoSession = new DaoMaster(dbHelper.getEncryptedWritableDb(DB_SCRET_KEY)).newSession();

GreenDao 配置及使用心得

说明