CassandraPersistence<T>

Implements: IReferenceable, IUnreferenceable, IConfigurable, IOpenable, ICleanable

Description

The CassandraPersistence class allows you to create abstract persistence components that store data in Cassandra using the default driver.

Important points

• 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._db or this._collection properties.

Configuration parameters

• table: (optional) Cassandra table name
• keyspace: (optional) Cassandra keyspace name
• connection(s):
  • discovery_key: (optional) key to retrieve the connection from IDiscovery
  • host: host name or IP address
  • port: port number (default: 27017)
  • uri: resource URI or connection string with all parameters in it
• credential(s):
  • store_key: (optional) key to retrieve the credentials from ICredentialStore
  • username: (optional) username
  • password: (optional) user’s password
• options:
  • connect_timeout: (optional) number of milliseconds to wait before timing out when connecting a new client (default: 0)
  • idle_timeout: (optional) number of milliseconds a client must sit idle in the pool and not be checked out (default: 10000)
  • max_pool_size: (optional) maximum number of clients the pool should contain (default: 10)

References

• *:logger:*:*:1.0 - (optional) ILogger components to pass log messages
• *:discovery:*:*:1.0 - (optional) IDiscovery services
• *:credential-store:*:*:1.0 - (optional) ICredentialStore to resolve credentials

Constructors

Creates a new instance of the persistence component.

public constructor(tableName?: string, keyspaceName?: string)

• tableName: string - (optional) table’s name.
• keyspaceName: string - (optional) keyspace’s name.

Fields

Instance methods

clear

Clears a component’s state.

public clear(context: IContext): Promise<void>

• context: IContext - (optional) a context to trace execution through a call chain.

clearSchema

Clears all auto-created objects

protected clearSchema(): void

close

Closes a component and frees the used resources.

public close(context: string): Promise<void>

• context: IContext - (optional) a context to trace execution through a call chain.

configure

Configures a component by passing its configuration parameters.

public configure(config: ConfigParams): void

• config:: ConfigParams - configuration parameters to be set.

convertFromPublic

Converts an object value from public to internal format.

protected convertFromPublic(value: any): any

• value: any - object in public format to convert.
• returns: any - converted object in internal format.

convertToPublic

Converts an object value from internal to public format.

protected convertToPublic(value: any): any

• value: any - object in internal format to convert.
• returns: any - converted object in public format.

create

Creates a data item.

public create(context: IContext, item: T): Promise<T>

• context: IContext - (optional) a context to trace execution through a call chain.
• item: T - item to be created.
• returns: Promise<T> - created item

createSchema

Checks if a table exists and if not, it creates the necessary database objects.

protected createSchema(context: IContext): Promise<void>

• context: IContext - (optional) a context to trace execution through a call chain.

defineSchema

Defines a database schema via auto-create objects or convenience methods.

protected defineSchema(): void

deleteByFilter

Deletes data items that match to a given filter. This method shall be called by a public deleteByFilter method from child class that receives FilterParams and converts them into a filter function.

protected deleteByFilter(context: IContext, filter: any): Promise<void>

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: any - (optional) filter function to filter items.

ensureIndex

Adds an index definition to create it on opening.

protected ensureIndex(keys: any, options)

• keys: any - index keys (fields)
• options: any - index options

ensureSchema

Adds a statement to a schema definition.

protected ensureSchema(schemaStatement: string): void

• schemaStatement: string - statement to be added to the schema

generateColumns

Generates a list of column names to use in SQL statements like: “column1,column2,column3”.

protected generateColumns(values: any): string

• values: any - array with column values or a key-value map
• returns: string - generated list of column names

generateParameters

Generates a list of value parameters to use in SQL statements like: “$1,$2,$3”

protected generateParameters(values: any): string

• values: any - array with values or a key-value map
• returns: string - generated list of value parameters

generateSetParameters

Generates a list of column sets to use in UPDATE statements like: column1=$1,column2=$2

protected generateSetParameters(values: any): string

• values: any - key-value map with columns and values
• returns: string - generated list of column sets

generateValues

Generates a list of column parameters.

protected generateValues(values: any): any[]

• values: any - key-value map with columns and values
• returns: any[] - generated list of column values

getCountByFilter

Gets a number of data items retrieved by a given filter.

This method shall be called by a public getCountByFilter method from the child class that receives FilterParams and converts them into a filter function.

protected getCountByFilter(context: IContext, filter: any): Promise<number>

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: any - (optional) JSON object filter
• returns: Promise<number> - number of filtered items.

getListByFilter

Gets a list of data items retrieved by a given filter and sorted according to sort parameters.

This method shall be called by a public getListByFilter method from a child class that receives FilterParams and converts them into a filter function.

protected getListByFilter(context: IContext, filter: any, sort: any, select: any): Promise<T[]>

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: any - (optional) filter function to filter items
• sort: any - (optional) sorting parameters
• select: any - (optional) projection parameters (not used yet)
• returns: Promise<T[]> - data list of results by filter.

getOneRandom

Gets a random item from items that match to a given filter.

This method shall be called by a public getOneRandom method from a child class that receives FilterParams and converts them into a filter function.

protected getOneRandom(context IContext, filter: any): Promise<T>

• context: Context - (optional) a context to trace execution through a call chain.
• filter: any - (optional) filter JSON object
• returns: Promise<T> - random item.

getPageByFilter

Gets a page of data items retrieved by a given filter and sorted according to sort parameters.

This method shall be called by a public getPageByFilter method from the a child class that receives FilterParams and converts them into a filter function.

protected getPageByFilter(context: IContext, filter: any, paging: PagingParams, sort: any, select: any): Promise<DataPage>

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: any - (optional) filter for JSON objects.
• paging: PagingParams - (optional) paging parameters
• sort: any - (optional) sorting JSON object
• select: any - (optional) projection JSON object
• returns: Promise<DataPage> - data page of results by the filter

isOpen

Checks if the component is open.

public isOpen(): boolean

• returns: boolean - true if the component is open and false otherwise.

open

Opens the component.

public open(context: IContext): Promise<void>

• context: IContext - (optional) a context to trace execution through a call chain.

quoteIdentifier

Adds single quotes to a string.

protected quoteIdentifier(value: string): string

• value: string - string where quotes need to be added
• returns: string - string with added quotes

quotedTableName

Adds the kespace’s name to a table’s name.

protected quotedTableName(): string

• returns: string - table’s name with added keyspace’s name on the left.

setReferences

Sets references to dependent components.

public setReferences(references: IReferences): void

• references: IReferences - references to locate the component dependencies.

unsetReferences

Unsets (clears) previously set references to dependent components.

public unsetReferences(): void

Examples

class MyCassandraPersistence extends CassandraPersistence<MyData> {
  public constructor() {
      super("mydata");
  }

  public getByName(context: Context, name: string): Promise<MyData> {
    let criteria = { name: name };
    return new Promise((resolve, reject) => {
      this._model.findOne(criteria, (err, item) => {
        if (err != null) {
          reject(err);
          return;
        }
        item = this.convertToPublic(item);
        resolve(item);
      });
     });
  }); 

  public set(correlatonId: string, item: MyData): Promise<MyData> {
    let criteria = { name: item.name };
    let options = { upsert: true, new: true };
    return new Promise((resolve, reject) => {
      this.findOneAndUpdate(criteria, item, options, (err, item) => {
        if (err != null) {
          reject(err);
          return;
        }
        item = this.convertToPublic(item);
        resolve(item);
      });
     });
  }
}

let persistence = new MyCassandraPersistence();
persistence.configure(ConfigParams.fromTuples(
    "host", "localhost",
    "port", 27017
));

await persitence.open("123");
let item = await persistence.set("123", { name: "ABC" });
item = await persistence.getByName("123", "ABC");
console.log(item);   // Result: { name: "ABC" }