harmony 鸿蒙Managing Cookies and Data Storage

2023-06-24
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Managing Cookies and Data Storage

Cookie Management

A cookie is a segment of data sent from the server to the client to uniquely identify a user during network access. The client may hold the data and provide it to the server at later interactions so that the server can quickly identify the client identity and status.

The Web component provides the WebCookieManager class for you to manage cookie information, which is stored in the /proc/{pid}/root/data/storage/el2/base/cache/web/Cookiesd file in the application sandbox path.

The following uses setCookie() as an example to describe how to set a cookie’s value to test for www.example.com. For details about functions and usage of other APIs, see WebCookieManager().

// xxx.ets
import web_webview from '@ohos.web.webview';
import business_error from '@ohos.base';

@Entry
@Component
struct WebComponent {
  controller: web_webview.WebviewController = new web_webview.WebviewController();

  build() {
    Column() {
      Button('setCookie')
        .onClick(() => {
          try {
            web_webview.WebCookieManager.setCookie('https://www.example.com', 'value=test');
          } catch (error) {
            let e: business_error.BusinessError = error as business_error.BusinessError;
            console.error(`ErrorCode: ${e.code},  Message: ${e.message}`);
          }
        })
      Web({ src: 'www.example.com', controller: this.controller })
    }
  }
}

Cache and Storage Management

Network resource requests are relatively time-consuming during website access. You can store resources locally by means of cache and Dom Storage to fasten the access to the same website.

Cache

Use cacheMode() to configure the cache mode for page resources. Four cache modes are supported:

Default: Page resources in a cache that has not expired are preferentially used. If the cache does not exist, page resources are obtained from the network.
None: Page resources are loaded from the cache. If the cache does not exist, page resources are obtained from the network.
Online: Page resources are not loaded from the cache. All resources are obtained from the network.
Only: Page resources are only loaded from the cache.

In the following example, the cache mode is set to None.

// xxx.ets
import web_webview from '@ohos.web.webview';

@Entry
@Component
struct WebComponent {
  @State mode: CacheMode = CacheMode.None;
  controller: web_webview.WebviewController = new web_webview.WebviewController();
  build() {
    Column() {
      Web({ src: 'www.example.com', controller: this.controller })
        .cacheMode(this.mode)
    }
  }
}

To obtain up-to-date resources, you can use removeCache() to clear cached resources. The sample code is as follows:

// xxx.ets
import web_webview from '@ohos.web.webview';
import business_error from '@ohos.base';

@Entry
@Component
struct WebComponent {
  @State mode: CacheMode = CacheMode.None;
  controller: web_webview.WebviewController = new web_webview.WebviewController();
  build() {
    Column() {
      Button('removeCache')
        .onClick(() => {
          try {
            // If this parameter is set to true, the cache in both the ROM and RAM is cleared. If this parameter is set to false, only the cache in the RAM is cleared.
            this.controller.removeCache(true);
          } catch (error) {
            let e: business_error.BusinessError = error as business_error.BusinessError;
            console.error(`ErrorCode: ${e.code},  Message: ${e.message}`);
          }
        })
      Web({ src: 'www.example.com', controller: this.controller })
        .cacheMode(this.mode)
    }
  }
}

Dom Storage

Dom Storage falls into Session Storage and Local Storage. Wherein, Session Storage applies to the temporary data, and its data storage and release follow the session lifecycle; Local Storage applies to the persistent data, which is flushed to the application directory. In both storage modes, data is stored in a form of key-value pair, and is usually used when a page that needs to be stored on the client is accessed. You can use domStorageAccess() to enable Dom Storage. The following is the sample code:

// xxx.ets
import web_webview from '@ohos.web.webview';

@Entry
@Component
struct WebComponent {
  controller: web_webview.WebviewController = new web_webview.WebviewController();
  build() {
    Column() {
      Web({ src: 'www.example.com', controller: this.controller })
        .domStorageAccess(true)
    }
  }
}