IdentifiableFilePersistence<T extends IIdentifiable<K>, K>

Extends: IdentifiableMemoryPersistence<T, K>

Description

The IdentifiableFilePersistence class allows you to create persistence components that store data in flat files and implement a number of CRUD operations over data items with unique ids.

Important points

• The data items must implement the IIdentifiable interface.
• In basic scenarios child classes shall only override getPageByFilter, getListByFilter or deleteByFilter operations with a specific filter function. All other operations can be used out of the box.
• In complex scenarios child classes can implement additional operations by accessing cached items via the self._items property and calling the save method on updates.

Configuration parameters

• path: path to the file where data is stored

• options:

  • max_page_size: maximum number of items returned in a single page (default: 100)

References

• *:logger:*:*:1.0 - (optional) (../../../components/log/ilogger) components to pass log messages

Constructors

Creates a new instance of the persistence.

public IdentifiableFilePersistence(Class type, JsonFilePersister persister)

• persister: JsonFilePersister - (optional) a persister component that loads and saves data from/to flat file.

Fields

Instance methods

configure

Configures component by passing configuration parameters.

public void configure(ConfigParams config) throws ConfigException

• config: ConfigParams - configuration parameters to be set.

Examples

{@code
  class MyFilePersistence extends IdentifiableFilePersistence<MyData, String> {
    public MyFilePersistence(String path) {
      super(MyData.class, new JsonPersister(path));
    }
  
    private Predicate<MyData> composeFilter(FilterParams filter) {
        filter = filter != null ? filter : new FilterParams();
        String name = filter.getAsNullableString("name");
        return (item) -> {
            if (name != null && item.name != name)
                return false;
            return true;
        };
    }
  
    public DataPage<MyData> getPageByFilter(IContext context, FilterParams filter, PagingParams paging) {
        super.getPageByFilter(context, this.composeFilter(filter), paging, null, null);
    }
  
  }
  
  MyFilePersistence persistence = new MyFilePersistence("./data/data.json");
  
  MyData item = persistence.create("123", new MyData("1", "ABC"));
  DataPage<MyData> mydata = persistence.getPageByFilter(
          "123",
          FilterParams.fromTuples("name", "ABC"),
          null, null, null);
  System.out.println(page.getData().toString());          // Result: { id: "1", name: "ABC" }
  persistence.deleteById("123", "1");
  ...
  }

See also

• MemoryPersistence