HarmonyOS 数据库getRdbStore问题？

Question

在getRdbStore中，读取本地的数据库文件（非getRdbStore直接创建），报错如下图。

Answer 1

解决方案

参考demo：

import fs, { ReadOptions } from '@ohos.file.fs';
import { resourceManager } from '@kit.LocalizationKit';

saveFileToCache(file:resourceManager.RawFileDescriptor, dbName:string) {
  // 创建缓存文件(当前是覆盖式创建)
  let cFile = getContext(this).getApplicationContext().databaseDir + "/entry/rdb/" + dbName
  let cacheFile = fs.openSync(cFile, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
  // 读取缓冲区大小
  let bufferSize = 30000
  let buffer = new ArrayBuffer(bufferSize); //创建buffer缓冲区
  // 要copy的文件的offset和length
  let currentOffset = file.offset;
  let lengthNeedToReed = file.length;
  let readOption:ReadOptions = {
    offset: currentOffset, //期望读取文件的位置。可选，默认从当前位置开始读
    length: bufferSize //每次期望读取数据的长度。可选，默认缓冲区长度
  }
  // 后面len会一直减，直到没有
  while(true) {
    // 读取buffer容量的内容
    let readLength = fs.readSync(file.fd, buffer, readOption);
    // 写入buffer容量的内容
    fs.writeSync(cacheFile.fd, buffer, {length:readLength}) //写到cacheFile里
    // 判断后续内容 修改读文件的参数
    // buffer没读满代表文件读完了
    if (readLength < bufferSize) {
      break;
    }
    if (readOption.offset != undefined){
      readOption.offset += readLength;
    }
  }
  console.log("Copy Success!!!")
  fs.close(cacheFile);
}

Answer 2

你的问题可以理解为如何读取本地/预制数据库吗？
如果是的话，试试以下两个步骤：

1. 将db文件推到数据存储沙箱路径：/data/app/el2/100/database/(bundleName)/entry/rdb/下,实现方式为用文件管理的接口打开本地数据库，读取本地数据库内容并写入沙箱路径下的db文件中。

import { fileIo, ReadOptions } from '@kit.CoreFileKit';
import { resourceManager } from '@kit.LocalizationKit';
import { relationalStore } from '@kit.ArkData';

let context = getContext(this);
let RDBDirectory = getContext(this).getApplicationContext().databaseDir;
let resource = getContext(this).resourceManager;

function saveFileToCache(file: resourceManager.RawFileDescriptor, dbName: string) {
  // 创建缓存文件(当前是覆盖式创建)
  let cFile = RDBDirectory + '/entry/rdb/' + dbName;
  let cacheFile = fileIo.openSync(cFile, fileIo.OpenMode.READ_WRITE | fileIo.OpenMode.CREATE);

  // 读取缓冲区大小
  let bufferSize = 30000;
  let buffer = new ArrayBuffer(bufferSize); //创建buffer缓冲区

  // 要copy的文件的offset
  let currentOffset = file.offset;

  let readOption: ReadOptions = {
    offset: currentOffset, //期望读取文件的位置。可选，默认从当前位置开始读
    length: bufferSize //每次期望读取数据的长度。可选，默认缓冲区长度
  };

  // 后面len会一直减，直到没有
  while (true) {
    // 读取buffer容量的内容
    let readLength = fileIo.readSync(file.fd, buffer, readOption);
    // 写入buffer容量的内容
    fileIo.writeSync(cacheFile.fd, buffer, { length: readLength }); //写到cacheFile里
    // 判断后续内容 修改读文件的参数
    // buffer没读满代表文件读完了
    if (readLength < bufferSize) {
      break;
    }
    if (readOption.offset != undefined) {
      readOption.offset += readLength;
    }
  }
  console.log('Copy Success!!!')
  fileIo.close(cacheFile);
}

function INIT() {
  // 创建数据库沙箱目录
  try {
    let dirPath = RDBDirectory + '/entry';
    fileIo.mkdirSync(dirPath);
    dirPath = dirPath + '/rdb';
    fileIo.mkdirSync(dirPath);
  } catch (error) {
    console.error(`mkdir rdbPath failed, error code: ${error.code}, message: ${error.message}.`);
  }

  //数据库名称
  let dbName: string = 'Company.db';

  //读取rawfile目录下db文件
  try {
    resource.getRawFd('rdb/' + dbName, (error, value) => {
      if (error != null) {
        console.log(`callback getRawFd failed error code: ${error.code}, message: ${error.message}.`);
      } else {
        console.info(value.length.toString());
        saveFileToCache(value, dbName);
      }
    });
  } catch (error) {
    console.error(`callback getRawFd failed, error code: ${error.code}, message: ${error.message}.`);
  }
}

2. 通过getRdbStore获取保存在沙箱路径下的db文件

   function getRDB(): relationalStore.RdbStore | undefined {
     let result: relationalStore.RdbStore | undefined = undefined;
     const STORE_CONFIG: relationalStore.StoreConfig = {
    name: 'Company.db',
    securityLevel: relationalStore.SecurityLevel.S1
     };
   
     relationalStore.getRdbStore(context, STORE_CONFIG, (err, store) => {
    if (err) {
      console.error(`Failed to get RdbStore. Code:${err.code}, message:${err.message}`);
      return;
    } else {
      console.info(`Succeeded in getting RdbStore.`);
    }
    result = store;
     })
     return result;
   }