HarmonyOS入门之应用数据持久化

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Datcon 2024-07-30 17:56:21 博主文章分类：Harmony ©著作权

文章标签 数据持久化数据库 Preferences 文章分类 Android 移动开发

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根据提供的资料，我们可以进一步扩展之前的博客文章，加入键值型数据库（KV-Store）和关系型数据库（RelationalStore）的内容。下面是整合后的完整博客草稿，包含了所有必要的代码示例：

HarmonyOS 应用数据持久化指南

引言

在HarmonyOS应用开发中，数据持久化是一项重要的功能。本文将介绍三种常见的数据持久化方式：用户首选项（Preferences）、键值型数据库（KV-Store）以及关系型数据库（RelationalStore），并给出相应的代码示例。

用户首选项（Preferences）

用户首选项是一种简单的数据持久化方式，适合存储少量配置信息。

示例代码

import dataPreferences from '@ohos.data.preferences';

// 获取Preferences实例
function getPreferences(context, storeName) {
  try {
    dataPreferences.getPreferences(context, storeName, (err, preferences) => {
      if (err) {
        console.error(`Failed to get preferences. Code:${err.code},message:${err.message}`);
        return;
      }
      console.info('Succeeded in getting preferences.');
      // 进行相关数据操作
    });
  } catch (err) {
    console.error(`Failed to get preferences. Code:${err.code},message:${err.message}`);
  }
}

// 写入数据
function putData(preferences, key, value) {
  try {
    preferences.put(key, value, (err) => {
      if (err) {
        console.error(`Failed to put data. Code:${err.code}, message:${err.message}`);
        return;
      }
      console.info('Succeeded in putting data.');
    });
  } catch (err) {
    console.error(`Failed to put data. Code: ${err.code},message:${err.message}`);
  }
}

// 读取数据
function getData(preferences, key, defaultValue) {
  try {
    preferences.get(key, defaultValue, (err, val) => {
      if (err) {
        console.error(`Failed to get value of '${key}'. Code:${err.code}, message:${err.message}`);
        return;
      }
      console.info(`Succeeded in getting value of '${key}'. val: ${val}.`);
    });
  } catch (err) {
    console.error(`Failed to get value of '${key}'. Code:${err.code}, message:${err.message}`);
  }
}

// 删除数据
function deleteData(preferences, key) {
  try {
    preferences.delete(key, (err) => {
      if (err) {
        console.error(`Failed to delete the key '${key}'. Code:${err.code}, message:${err.message}`);
        return;
      }
      console.info(`Succeeded in deleting the key '${key}'.`);
    });
  } catch (err) {
    console.error(`Failed to delete the key '${key}'. Code:${err.code}, message:${err.message}`);
  }
}

// 数据持久化
function flushData(preferences) {
  try {
    preferences.flush((err) => {
      if (err) {
        console.error(`Failed to flush. Code:${err.code}, message:${err.message}`);
        return;
      }
      console.info('Succeeded in flushing.');
    });
  } catch (err) {
    console.error(`Failed to flush. Code:${err.code}, message:${err.message}`);
  }
}

键值型数据库（KV-Store）

键值型数据库适用于存储无复杂关系的数据。

示例代码

import distributedKVStore from '@ohos.data.distributedKVStore';

// 获取KVManager实例
function createKVManager(context, bundleName) {
  const kvManagerConfig = {
    context: context,
    bundleName: bundleName
  };
  try {
    const kvManager = distributedKVStore.createKVManager(kvManagerConfig);
    console.info('Succeeded in creating KVManager.');
    return kvManager;
  } catch (e) {
    console.error(`Failed to create KVManager. Code:${e.code},message:${e.message}`);
    return null;
  }
}

// 创建并获取键值数据库
function getKVStore(kvManager, storeId, options) {
  try {
    kvManager.getKVStore(storeId, options, (err, kvStore) => {
      if (err) {
        console.error(`Failed to get KVStore. Code:${err.code},message:${err.message}`);
        return;
      }
      console.info('Succeeded in getting KVStore.');
      // 进行相关数据操作
    });
  } catch (e) {
    console.error(`An unexpected error occurred. Code:${e.code},message:${e.message}`);
  }
}

// 插入数据
function putData(kvStore, key, value) {
  try {
    kvStore.put(key, value, (err) => {
      if (err !== undefined) {
        console.error(`Failed to put data. Code:${err.code},message:${err.message}`);
        return;
      }
      console.info('Succeeded in putting data.');
    });
  } catch (e) {
    console.error(`An unexpected error occurred. Code:${e.code},message:${e.message}`);
  }
}

// 获取数据
function getData(kvStore, key) {
  try {
    kvStore.get(key, (err, data) => {
      if (err !== undefined) {
        console.error(`Failed to get data. Code:${err.code},message:${err.message}`);
        return;
      }
      console.info(`Succeeded in getting data. data:${data}`);
    });
  } catch (e) {
    console.error(`Failed to get data. Code:${e.code},message:${e.message}`);
  }
}

// 删除数据
function deleteData(kvStore, key) {
  try {
    kvStore.delete(key, (err) => {
      if (err !== undefined) {
        console.error(`Failed to delete data. Code:${err.code},message:${err.message}`);
        return;
      }
      console.info('Succeeded in deleting data.');
    });
  } catch (e) {
    console.error(`An unexpected error occurred. Code:${e.code},message:${e.message}`);
  }
}

关系型数据库（RelationalStore）

关系型数据库适用于存储具有复杂关系的数据。

示例代码

import relationalStore from '@ohos.data.relationalStore';

// 获取RdbStore
function getRdbStore(context, config) {
  const SQL_CREATE_TABLE = 'CREATE TABLE IF NOT EXISTS EMPLOYEE (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT NOT NULL, AGE INTEGER, SALARY REAL, CODES BLOB)';
  try {
    relationalStore.getRdbStore(context, config, (err, store) => {
      if (err) {
        console.error(`Failed to get RdbStore. Code:${err.code}, message:${err.message}`);
        return;
      }
      console.info(`Succeeded in getting RdbStore.`);
      store.executeSql(SQL_CREATE_TABLE); // 创建数据表
      // 这里执行数据库的增、删、改、查等操作
    });
  } catch (e) {
    console.error(`Failed to get RdbStore. Code:${e.code}, message:${e.message}`);
  }
}

// 插入数据
function insertData(store, tableName, valueBucket) {
  store.insert(tableName, valueBucket, (err, rowId) => {
    if (err) {
      console.error(`Failed to insert data. Code:${err.code}, message:${err.message}`);
      return;
    }
    console.info(`Succeeded in inserting data. rowId:${rowId}`);
  });
}

// 更新数据
function updateData(store, valueBucket, tableName, name) {
  let predicates = new relationalStore.RdbPredicates(tableName);
  predicates.equalTo('NAME', name);
  store.update(valueBucket, predicates, (err, rows) => {
    if (err) {
      console.error(`Failed to update data. Code:${err.code}, message:${err.message}`);
      return;
    }
    console.info(`Succeeded in updating data. row count: ${rows}`);
  });
}

// 删除数据
function deleteData(store, tableName, name) {
  let predicates = new relationalStore.RdbPredicates(tableName);
  predicates.equalTo('NAME', name);
  store.delete(predicates, (err, rows) => {
    if (err) {
      console.error(`Failed to delete data. Code:${err.code}, message:${err.message}`);
      return;
    }
    console.info(`Delete rows: ${rows}`);
  });
}

// 查询数据
function queryData(store, tableName, name, columns) {
  let predicates = new relationalStore.RdbPredicates(tableName);
  predicates.equalTo('NAME', name);
  store.query(predicates, columns, (err, resultSet) => {
    if (err) {
      console.error(`Failed to query data. Code:${err.code}, message:${err.message}`);
      return;
    }
    console.info(`Succeeded in querying data.`);
    while (resultSet.next()) {
      console.log(`ID: ${resultSet.getInt('ID')}, Name: ${resultSet.getString('NAME')}, Age: ${resultSet.getInt('AGE')}, Salary: ${resultSet.getDouble('SALARY')}, Codes: ${resultSet.getBlob('CODES')}`);
    }
    resultSet.close();
  });
}