pip-services4-persistence-node/src/persistence/FilePersistence.ts

Persistence Components for Pip.Services in Node.js / ES2017

/** @module persistence */
import { ConfigParams } from 'pip-services4-components-node';
import { IConfigurable } from 'pip-services4-components-node';

import { JsonFilePersister } from './JsonFilePersister'
import { MemoryPersistence } from './MemoryPersistence';

/**
 * Abstract persistence component that stores data in flat files
 * and caches them in memory.
 * 
 * This is the most basic persistence component that is only
 * able to store data items of any type. Specific CRUD operations
 * over the data items must be implemented in child classes by
 * accessing this._items property and calling [[save]] method.
 * 
 * @see [[MemoryPersistence]]
 * @see [[JsonFilePersister]]
 * 
 * ### Configuration parameters ###
 * 
 * - path:                path to the file where data is stored
 * 
 * ### References ###
 * 
 * - <code>\*:logger:\*:\*:1.0</code>   (optional) [[https://pip-services4-node.github.io/pip-services4-components-node/interfaces/log.ilogger.html ILogger]] components to pass log messages
 * 
 * ### Example ###
 * 
 *     class MyJsonFilePersistence extends FilePersistence<MyData> {
 *         public constructor(path?: string) {
 *             super(new JsonPersister(path));
 *         }
 *     
 *         public async getByName(context: IContext, name: string): Promise<MyData> {
 *             let item = this._items.find((d) => d.name == name);
 *             retur item;
 *         }); 
 *     
 *         public async set(correlatonId: string, item: MyData): Promise<MyData> {
 *             this._items = this._items.filter((d) => d.name != name);
 *             this._items.push(item);
 *             await this.save(context);
 *             return item;
 *         }
 *       
 *     }
 */
export class FilePersistence<T> extends MemoryPersistence<T> implements IConfigurable {
    protected readonly _persister: JsonFilePersister<T>;

    /**
     * Creates a new instance of the persistence.
     * 
     * @param persister    (optional) a persister component that loads and saves data from/to flat file.
     */
    public constructor(persister?: JsonFilePersister<T>) {
        if (persister == null) {
            persister = new JsonFilePersister<T>();
        }

        super(persister, persister);

        this._persister = persister;
    }

    /**
     * Configures component by passing configuration parameters.
     * 
     * @param config    configuration parameters to be set.
     */
    public configure(config: ConfigParams): void {
        this._persister.configure(config);
    }

}