greenDAO: Android ORM for your SQLite database
一.什么是GreenDao
Demo链接: https://github.com/liumaomao0209/GreenDaoDemo
GreenDAO是一个开源的AndroidORM,使SQLite数据库的开发再次变得有趣。它在节省开发时间的同时,减轻了开发人员对低级别数据库需求的处理。SQLite是一个令人敬畏的嵌入式关系数据库。尽管如此,编写SQL和解析查询结果仍然是非常繁琐和耗时的任务。GreenDAO通过将Java对象映射到数据库表(称为奥姆,“对象/关系映射”)。通过这种方式,您可以使用简单的面向对象API来存储、更新、删除和查询Java对象。
二.GreenDao的特点
GreenDAO的特点一目了然
- 性能强大 (可能是Android最快的ORM)
- 易用 有强大的API
- 极小内存消耗
- 体积小 GreenDAO小于100KB,所以对于应用程序APK的大小影响很小。
- 数据库加密 支持SQLCiPHER,以确保用户数据的安全
当性能很重要时(数据访问频繁),GreenDao是一个很快的解决方案,它能够支持数千条记录的CRUD每秒,和OrmLite相比,GreenDAO要快几乎4.5倍。(准确数据请自行benchmark)。
三.GreenDao的配置
1.导入插件
在project:build.gradle添加如下两行(位置已注释)
// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
repositories {
google()
jcenter()
mavenCentral() // 添加
}
dependencies {
classpath 'com.android.tools.build:gradle:3.1.2'
classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2' // 添加
}
}
allprojects {
repositories {
google()
jcenter()
}
}
task clean(type: Delete) {
delete rootProject.buildDir
}
2.添加依赖和数据库配置
(1)在app:build.gradle添加library和plugin(位置已经注释为// apply plugin // add library)
(2)数据库配置信息,在android节点下
apply plugin: 'com.android.application'
apply plugin: 'org.greenrobot.greendao' // apply plugin
android {
compileSdkVersion 28
defaultConfig {
applicationId "com.maomao.technology.greendaodemo"
minSdkVersion 27
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
greendao {
schemaVersion 1 //数据库版本号,数据库升级使用
daoPackage 'com.maomao.technology.greendaodemo.greendao' //代表GreenDao自动生成的有关数据库操作工具类所要存放的包名
targetGenDir 'src/main/java' //路径
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation 'org.greenrobot:greendao:3.2.2' // add library
}
四.GreenDao的使用
首先大概看一下整体构建的样子:
base:数据库操作的基类
db:对用户表专门自定义的操作类.
greendao:建表时自动生成的类.
1.创建一个用户类
Generated之下是build后自动生成的.
项目的build目录下或者自己设定的目录下还可以看到自动生成的三个类文件:
DaoMaster
DaoSession
UserDao
@Entity
public class UserBean {
@Id(autoincrement = true)
long id;
@NotNull
String name;
String age;
@Generated(hash = 47803367)
public UserBean(long id, @NotNull String name, String age) {
this.id = id;
this.name = name;
this.age = age;
}
@Generated(hash = 1203313951)
public UserBean() {
}
public long getId() {
return this.id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return this.age;
}
public void setAge(String age) {
this.age = age;
}
}
注解说明:
@Id 注解选择 long / Long 属性作为实体ID。在数据库术语中,它是主键。参数自动增量,是使ID值不断增加(不会选用旧值)的标志。
@Property 让你定义一个非默认的列名,其属性映射到。如果不存在,greenDAO将在SQL杂交方式使用字段名(大写,下划线,而不是骆驼情况下,例如 customName将成为 CUSTOM_NAME)。注意:您目前只能使用内联常量来指定列名。
@Transient 表明这个字段不会被写入数据库,只是作为一个普通的java类字段,用来临时存储数据的,不会被持久化
@Entity 定义实体
@nameInDb 在数据库中的名字,如不写则为实体中类名
@indexes 索引
@schema 指定架构名称为实体
@active 无论是更新生成都刷新
@NotNull 不为null
@Unique 唯一约束
@ToMany 一对多
@OrderBy 排序
@ToOne 一对一
@Transient 不存储在数据库中
@generated 由greendao产生的构造函数或方法
2.构建两个管理DB的基类
1.BaseDBManager 所有的数据库操作类都继承自此
public class BaseDBManager {
private AbstractDao mDao;
public BaseDBManager(AbstractDao dao) {
this.mDao = dao;
}
public void insert(T item) {
mDao.insert(item);
}
public void insert(T... items) {
mDao.insertInTx(items);
}
public void insert(List items) {
mDao.insertInTx(items);
}
public void insertOrUpdate(T item) {
mDao.insertOrReplace(item);
}
public void insertOrUpdate(T... items) {
mDao.insertOrReplaceInTx(items);
}
public void insertOrUpdate(List items) {
mDao.insertOrReplaceInTx(items);
}
public void deleteByKey(K key) {
mDao.deleteByKey(key);
}
public void delete(T item) {
mDao.delete(item);
}
public void delete(T... items) {
mDao.deleteInTx(items);
}
public void delete(List items) {
mDao.deleteInTx(items);
}
public void deleteAll() {
mDao.deleteAll();
}
public void update(T item) {
mDao.update(item);
}
public void update(T... items) {
mDao.updateInTx(items);
}
public void update(List items) {
mDao.updateInTx(items);
}
/**
* 根据主键查询数据 如果没有涉及主键 则会报错
*
* @param key 主键
* @return T
*/
public T query(K key) {
return mDao.load(key);
}
public List queryAll() {
return mDao.loadAll();
}
public List query(String where, String... params) {
return mDao.queryRaw(where, params);
}
public QueryBuilder getQueryBuilder() {
return mDao.queryBuilder();
}
public long count() {
return mDao.count();
}
public void refresh(T item) {
mDao.refresh(item);
}
public void detach(T item) {
mDao.detach(item);
}
}
2.库名类
public interface DBConfig {
String DB_NAME = "User.db";
}
3.编写USER库的操作类
三个类分别为
UserDBFactory 用户数据库工厂类 通过这个类统一下面两个类的功能,使用时调用这个类.
UserDBManage 数据库管理类,用于创建 删除 关闭数据库 获取session
UserInfoManage 用户信息管理类 对用户列表的增删改查放这里
public class UserDBFactory {
private static UserDBFactory mInstance = null;
private UserInfoManage userInfoManage;
public static UserDBFactory getInstance() {
if (mInstance == null) {
synchronized (UserDBFactory.class) {
if (mInstance == null) {
mInstance = new UserDBFactory();
}
}
}
return mInstance;
}
public UserInfoManage getUserInfoManage() {
if (userInfoManage == null) {
userInfoManage = new UserInfoManage(UserDBManage.getInstance(MyApplication.getApplication()).getDaoSession().getUserBeanDao());
}
return userInfoManage;
}
}
public class UserDBManage {
private static UserDBManage dbManage;
private Context context;
public static UserDBManage getInstance(Context context) {
if (dbManage == null) {
synchronized (UserDBManage.class) {
if (dbManage == null) {
dbManage = new UserDBManage(context);
}
}
}
return dbManage;
}
private UserDBManage(Context context) {
this.context = context;
}
private DaoMaster.DevOpenHelper mHelper;
private DaoMaster mDaoMaster;
private DaoSession mDaoSession;
/**
* 获取DaoSession * * @return
*/
public synchronized DaoSession getDaoSession() {
if (null == mDaoSession) {
mDaoSession = getDaoMaster().newSession();
}
return mDaoSession;
}
/**
* 关闭数据库
*/
public synchronized void closeDataBase() {
closeHelper();
closeDaoSession();
}
/**
* 判断数据库是否存在,如果不存在则创建 * * @return
*/
private DaoMaster getDaoMaster() {
if (null == mDaoMaster) {
mHelper = new DaoMaster.DevOpenHelper(context, DBConfig.DB_NAME, null);
mDaoMaster = new DaoMaster(mHelper.getWritableDb());
}
return mDaoMaster;
}
private void closeDaoSession() {
if (null != mDaoSession) {
mDaoSession.clear();
mDaoSession = null;
}
}
private void closeHelper() {
if (mHelper != null) {
mHelper.close();
mHelper = null;
}
}
}
/**
* Describe:DB操作类
*/
public class UserInfoManage extends BaseDBManager {
public UserInfoManage(AbstractDao dao) {
super(dao);
}
}
五.增删改查功能实现
1.布局和代码目录展示
布局和条目布局代码我就不写在这里了,各位自行定义.列表使用的是recyclerview;
2.自定义适配器
package com.maomao.technology.greendaodemo;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.List;
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* 创建日期:2019/4/19 on 15:45
* 作 者:刘喵喵
* 邮 箱:[email protected]
* 描 述:
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
public class MyAdapter extends RecyclerView.Adapter {
private final int mLayoutId;
private final List mData;
private final Context mContext;
private final LayoutInflater inflater;
public MyAdapter(List mData, int mLayoutId, Context mContext) {
this.mData = mData;
this.mLayoutId = mLayoutId;
this.mContext = mContext;
inflater = LayoutInflater.from(mContext);
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
View view = inflater.inflate(mLayoutId, parent, false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder viewHolder, int i) {
MyViewHolder holder = (MyViewHolder) viewHolder;
holder.key.setText(mData.get(i).getId()+"");
holder.name.setText(mData.get(i).getName()+"");
holder.age.setText(mData.get(i).getAge()+"");
}
@Override
public int getItemCount() {
return mData.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
private final TextView age;
private final TextView name;
private final TextView key;
public MyViewHolder(View v) {
super(v);
name = v.findViewById(R.id.name);
age = v.findViewById(R.id.age);
key = v.findViewById(R.id.key);
}
}
}
3.主要功能逻辑
public class MainActivity extends Activity implements View.OnClickListener {
private UserInfoManage userInfoManage;
private List userBeanList = new ArrayList<>();
private RecyclerView recyclerView;
private MyAdapter myAdapter;
private EditText keyEdit;
private EditText valueEdit;
private TextView add;
private TextView delete;
private TextView search;
private TextView show;
private TextView update;
private UserBean userBean;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initview();
initdata();
UserDBFactory userDBFactory = new UserDBFactory();
userInfoManage = userDBFactory.getUserInfoManage();
}
private void initdata() {
myAdapter = new MyAdapter(userBeanList, R.layout.user_item, this);
recyclerView.setAdapter(myAdapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
}
private void initview() {
add = findViewById(R.id.add_btn);
delete = findViewById(R.id.delete_btn);
search = findViewById(R.id.search_btn);
show = findViewById(R.id.show_btn);
recyclerView = findViewById(R.id.recyclerView);
keyEdit = findViewById(R.id.key_edt);
valueEdit = findViewById(R.id.value_edt);
update = findViewById(R.id.update_btn);
add.setOnClickListener(this);
delete.setOnClickListener(this);
search.setOnClickListener(this);
show.setOnClickListener(this);
update.setOnClickListener(this);
}
@Override
public void onClick(View v) {
Random mRandom = new Random();
String key = keyEdit.getText().toString();
switch (v.getId()) {
case R.id.add_btn:
//添加数据
for (int i = 0; i < 10; i++) {
userBean = new UserBean();
userBean.setId(i + "");
int age = mRandom.nextInt(10) + 10;
userBean.setAge(age + "");
userBean.setName("瑶瑶" + i);
userInfoManage.insertOrUpdate(userBean);//插入或替换
}
myAdapter.notifyDataSetChanged();
//显示
show.performClick();
break;
case R.id.delete_btn:
//删除key为..的数据
userInfoManage.deleteByKey(key);
show.performClick();
break;
case R.id.show_btn:
userBeanList.clear();
//查询所有并显示
List userBeans = userInfoManage.queryAll();
userBeanList.addAll(userBeans);
myAdapter.notifyDataSetChanged();
break;
case R.id.search_btn:
//搜索key为..的数据
UserBean query = userInfoManage.query(key);
if (query != null) {
userBeanList.clear();
userBeanList.add(query);
myAdapter.notifyDataSetChanged();
} else {
Toast.makeText(this, "没有该条数据", Toast.LENGTH_SHORT).show();
}
break;
case R.id.update_btn:
//使用主键查询需要修改的数据
UserBean userBean = userInfoManage.query(key);
if (userBean != null) {
userBean.setName(valueEdit.getText().toString());
//修改
userInfoManage.update(userBean);
show.performClick();
} else {
Toast.makeText(this, "没有该条数据", Toast.LENGTH_SHORT).show();
}
break;
}
}
}
4.全局context
public class MyApplication extends Application {
//全局唯一的context
private static MyApplication application;
@Override
protected void attachBaseContext(Context base) {
super.attachBaseContext(base);
application = this;
}
public static Context getContext() {
return application;
}
@Override
public void onCreate() {
super.onCreate();
}
/**
* 获取全局唯一上下文
*
* @return BaseApplication
*/
public static MyApplication getApplication() {
return application;
}
}
最后再放一次我的Demo链接
https://github.com/liumaomao0209/GreenDaoDemo
官方网站:http://greendao-orm.com/