打个比方，我们有一个书籍管理系统，用数据库存储每一本书籍数据，我们基于此封装一个BooksStoreManager的书籍管理系统。
import { relationalStore } from "@kit.ArkData";
import { BusinessError } from "@kit.BasicServicesKit";
/// 书籍模型
export class BookInfoModel {
id: number | undefined
name: string | undefined
icon: string | undefined
remark: string | undefined
chapter: string | undefined
}
/// 书籍管理数据库
export class BooksStoreManager{
private static instance: BooksStoreManager | null
private constructor() {}
static getInstance(): BooksStoreManager {
if (BooksStoreManager.instance == null) {
BooksStoreManager.instance =
AppStorage.get<BooksStoreManager>('BooksStoreManager') as BooksStoreManager;
if (!BooksStoreManager.instance) {
BooksStoreManager.instance = new BooksStoreManager();
AppStorage.setOrCreate('BooksStoreManager', BooksStoreManager.instance);
}
}
return BooksStoreManager.instance
}
/// RdbStore对象
private rdbBookStore?: relationalStore.RdbStore
/// 表名
private tableName: string = 'BooksTable'
/// Rdb数据库配置
/// name:数据库名称
/// securityLevel:数据库安全级别
private readonly BookStoreConfig:relationalStore.StoreConfig = {
name: "BookListInfo.db",
securityLevel: relationalStore.SecurityLevel.S1
}
/// 数据库创建sql语句(不支持分号分隔的多条语句)
private sqlCreate: string = `CREATE TABLE IF NOT EXISTS ${this.tableName}(
id INTEGER NULL,
name TEXT NULL,
icon TEXT NULL,
remark TEXT NULL,
chapter TEXT NULL)`
/// 数据字段
private dbColumns:Array<string> = ['id', 'name', 'icon', 'remark', 'chapter']
/// 初始化任务
initBookDB(context: Context) {
relationalStore.getRdbStore(context,this.BookStoreConfig,(err, rdbStore) => {
if (err) {
console.log('testTag', '获取rdb失败');
return
}
rdbStore.executeSql(this.sqlCreate)
/// ....... 或者去创建其他的表
console.log('创建表成功');
this.rdbBookStore = rdbStore
})
}
/// 查询所有书籍
async getBookList(): Promise<BookInfoModel[]> {
let predicates = new relationalStore.RdbPredicates(this.tableName)
let result = await this.rdbBookStore?.query(predicates,this.dbColumns)
let booksList: BookInfoModel[] = []
while (!result?.isAtLastRow) {
result?.goToNextRow()
let bookInfo:BookInfoModel = new BookInfoModel()
bookInfo.id = result?.getLong(result.getColumnIndex('id'))
bookInfo.name = result?.getString(result.getColumnIndex('name'))
bookInfo.icon = result?.getString(result.getColumnIndex('icon'))
bookInfo.remark = result?.getString(result.getColumnIndex('remark'))
bookInfo.chapter = result?.getString(result.getColumnIndex('chapter'))
booksList.push(bookInfo)
}
result?.close();// 释放数据集的内存,若不释放可能会引起fd泄露与内存泄露.
return booksList
}
/// 增加一本书籍
addBookInfo(item: BookInfoModel):Promise<number|void|null> {
const data: relationalStore.ValuesBucket = {
id:item.id ?? 0,
name: item.name ?? '',
icon: item.icon ?? '',
remark: item.remark ?? '',
chapter: item.chapter ?? '',
};
if (!this.rdbBookStore){
return Promise.resolve(null)
}
return this.rdbBookStore.insert(this.tableName, data)
.then(res => res)
.catch((err: BusinessError) => {
console.info("bookInfo failed, err: " + err)
})
}
/// 通过id查询并返回一条数据。如果为null,则表示数据库中没有这条数据.
async findBookById(id: number):Promise<BookInfoModel | null> {
let predicate = new relationalStore.RdbPredicates(this.tableName)
predicate.equalTo('id', id) /// 谓词匹配id
/// 第二个参数this.dbColumns,表示要查询的列.
let resultSet:relationalStore.ResultSet|undefined = await this.rdbBookStore?.query(predicate, this.dbColumns)
let bookInfo: BookInfoModel | null = null
// resultSet是一个数据集合的游标,默认指向第-1个记录,有效的数据从0开始.
while (resultSet?.goToNextRow()){
bookInfo = new BookInfoModel()
bookInfo.id = resultSet?.getLong(resultSet.getColumnIndex('id'))
bookInfo.name = resultSet?.getString(resultSet.getColumnIndex('name'))
bookInfo.icon = resultSet?.getString(resultSet.getColumnIndex('icon'))
bookInfo.remark = resultSet?.getString(resultSet.getColumnIndex('remark'))
bookInfo.chapter = resultSet?.getString(resultSet.getColumnIndex('chapter'))
}
resultSet?.close();
return bookInfo
}
/// 根据id判断书籍是否存在
async isBookExists(id: number):Promise<boolean>{
let predicate = new relationalStore.RdbPredicates(this.tableName)
predicate.equalTo('id', id)
let resultSet:relationalStore.ResultSet|undefined =
await this.rdbBookStore?.query(predicate, this.dbColumns)
resultSet?.close();
return resultSet?.goToNextRow() ?? false
}
/// 通过id删除某一本书
deleteBookById(id: number, callback: () => void) {
let predicate = new relationalStore.RdbPredicates(this.tableName)
predicate.equalTo('id', id)
return this.rdbBookStore?.delete(predicate,
(err: BusinessError, rows: number) => {
if (err) {
console.info("Delete failed, err: " + err)
return
}
callback();
})
}
/// 通过书籍id删除某一些书籍
clearBooksByIds(ids: Array<number>, callback: () => void) {
let predicate = new relationalStore.RdbPredicates(this.tableName)
ids.forEach((id: number, index: number) => {
predicate = predicate.equalTo('id', id)
if (index < ids.length - 1) {
predicate = predicate.or() /// 拼接谓词"逻辑或",以便可以匹配多本书籍.
}
})
return this.rdbBookStore?.delete(predicate, (err: BusinessError, rows: number) => {
if (err) {
console.info("Clear failed, err: " + err)
return
}
callback();
})
}
/// 更新某本书籍的数据库信息
updateBookInfoById(id: number, item: BookInfoModel) {
let predicate = new relationalStore.RdbPredicates(this.tableName)
predicate.equalTo('id', id) /// 通过id匹配到这本书
const data: relationalStore.ValuesBucket = {
id:item.id ?? 0,
name: item.name ?? '',
icon: item.icon ?? '',
remark: item.remark ?? '',
chapter: item.chapter ?? '',
};
return this.rdbBookStore?.update(data, predicate)
}
}
最后，我们需要在EntryAbility类的onCreate生命周期方法中初始化数据库
onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onCreate');
/// 初始化书籍数据库
BooksStoreManager.getInstance().initBookDB(this.context)
}
