Package com.jbstrap.core.meta

Class InMemoryDataDescriptor

java.lang.Object

com.jbstrap.core.meta.BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

com.jbstrap.core.meta.InMemoryDataDescriptor

All Implemented Interfaces:

DataDescriptor

public class InMemoryDataDescriptor
extends BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

In-Memory DataDescriptor

The InMemory is a special DataDescriptor that does not persist data in a file or a database. The saved data are stored in the server’s memory. If the DataDescriptor class is destroyed, the associated data are also lost.

There are two basic ways of working of an In-Memory DataDescriptor. By default, they locally store data, that is, every instance stores data values separately, without interfering each other. Use this concept to temporarily store data on a page.

If you switch the DataDescriptor to global mode using the setGlobal(boolean) method, the DataDescriptor stores data globally, meaning that data values will be the same in every DataDescriptor instance. If you delete a record from an instance, it disappears from all instances. Use this concept to cache data on application level.

Since:

4.0

Author:

JBStrap

Field Summary

Fields inherited from class com.jbstrap.core.meta.BaseDataDescriptor

access, columns, domainClass, name

Constructor Summary

Constructors

Constructor	Description
InMemoryDataDescriptor(String name)	Creates an In-Memory DataDescriptor.

Method Summary

Modifier and Type	Method	Description
InMemoryDataDescriptor	copy()	Creates a copy of the DataDescriptor
long	countData(NoTransaction transaction, Client client, Criteria criteria)	Gets the number of records in the database.
List<Record>	find(NoTransaction transaction, Client client, Criteria criteria, List<Order> orders, int startRow, int endRow)	Initiates a query by using the DataDescriptor.
Record	findById(NoTransaction transaction, Client client, Object... id)	Fetches a record from the database using the record’s unique ID.
boolean	isGlobal()	Checks if the DataDescriptor is global.
NoTransaction	openTransaction()	As the DataDescriptor does not support transaction handling, the method returns null.
List<Record>	remove(NoTransaction transaction, Client client, List<Record> records)	Initiates a delete operation by using a DataDescriptor. Use the method to delete one or more records from the database using a DataDescriptor.
List<Record>	save(NoTransaction transaction, Client client, List<Record> records)	Initiates a save operation using a DataDescriptor. Use the method to save one or more records to the database using the DataDescriptor.
InMemoryDataDescriptor	setGlobal(boolean global)	Sets if the DataDescriptor should use global or local data storage.

Methods inherited from class com.jbstrap.core.meta.BaseDataDescriptor

addColumn, addColumns, addParam, countData, countData, fetchData, fetchData, fetchData, fetchData, fetchData, fetchData, find, find, find, find, find, find, find, find, find, find, find, find, findById, findById, getAccess, getColumn, getColumns, getDefaultFilterCriteria, getName, getParam, getPrimaryKeyName, getPrimaryKeyNames, getRead, getWrite, isFilterable, remove, remove, remove, remove, remove, remove, remove, remove, remove, save, save, save, save, save, save, save, save, save, setAccess, setDefaultFilterCriteria, setParam, setRead, setWrite, sortColumn

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

InMemoryDataDescriptor

public InMemoryDataDescriptor(String name)

Creates an In-Memory DataDescriptor.

Parameters:

name - DataDescriptor name You can specify any name for the DataDescriptor. The name must be unique within the application.

Throws:

NullPointerException - Thrown if the specified DataDescriptor name is null

Method Details

setGlobal

public InMemoryDataDescriptor setGlobal(boolean global)

Sets if the DataDescriptor should use global or local data storage. By default, the DataDescriptor works locally, it only stores data in the specified instance. If you set it to global, the same data values are contained in every instance. If you save a new record to one of the instances, the new record is also there in every instance.

Parameters:

global - If you set a true value, the DataDescriptor works globally, otherwise it works locally

Returns:

In-Memory DataDescriptor instance

isGlobal

public boolean isGlobal()

Checks if the DataDescriptor is global.

Returns:

If true is specified, the DataDescriptor works globally, otherwise it works locally

find

public List<Record> find(NoTransaction transaction,
 Client client,
 Criteria criteria,
 List<Order> orders,
 int startRow,
 int endRow)
                  throws FindException

Initiates a query by using the DataDescriptor.

Specified by:

find in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Parameters:

transaction - Transaction object used to initiated the query If If null is specified, the query does not use a transaction (it takes place outside of a transaction).

client - Client instance initiating the query If null is specified, user access to the data is not checked.

startRow - The index of the first row

endRow - The index of the last row

criteria - Criteria instance used as a filter criterion If null is specified, the query fetches all records from the database without filtering.

orders - A list containing Order objects used to the order the query results If null or an empty list is passed, the query results are not ordered.

Returns:

A list of Record instances returned by the query

Throws:

FindException - Occurs if an error was encountered during the query

DataAccessException - Occurs if the user in the specified client has no access to read the data

countData

public long countData(NoTransaction transaction,
 Client client,
 Criteria criteria)
               throws RowCountException

Gets the number of records in the database.

Specified by:

countData in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Parameters:

transaction - Transaction object used to initiated the query If If null is specified, the query does not use a transaction (it takes place outside of a transaction).

client - Client instance initiating the query If null is specified, user access to the data is not checked.

criteria - Criteria instance used as a filter criterion If null is specified, the query fetches all records from the database without filtering.

Returns:

The number of records corresponding to the specified criteria If no records correspond to the specified criteria, the method returns 0.

Throws:

RowCountException - Occurs if an error was encountered during the execution of the SQL instruction that does the counting.

DataAccessException - Occurs if the logged in user has no read access to the DataDescriptor

save

public List<Record> save(NoTransaction transaction,
 Client client,
 List<Record> records)
                  throws SaveException

Initiates a save operation using a DataDescriptor.
Use the method to save one or more records to the database using the DataDescriptor.

Specified by:

save in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Parameters:

transaction - Transaction object used to initiated the query If If null is specified, the query does not use a transaction (it takes place outside of a transaction).

client - Client instance initiating the query If null is specified, user access to the data (whether the user has the rights to update data) is not checked.

records - A list of records to be saved

Returns:

The saved record

Throws:

SaveException - Occurs if an error was encountered during the save.

DataAccessException - Occurs if the user on the specified client has no permission to save the record to the DataDescriptor.

remove

public List<Record> remove(NoTransaction transaction,
 Client client,
 List<Record> records)
                    throws RemoveException

Initiates a delete operation by using a DataDescriptor.
Use the method to delete one or more records from the database using a DataDescriptor.

Specified by:

remove in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Parameters:

transaction - Transaction object used to initiated the query If If null is specified, the query does not use a transaction (it takes place outside of a transaction).

client - Client instance initiating the query If null is specified, user access to the data (whether the user has the rights to update data) is not checked.

records - A list of records to be deleted

Throws:

RemoveException - Occurs if an error was encountered during the removal process

DataAccessException - Occurs if the user on the specified client has no access to write the data of the DataDescriptor.

findById

public Record findById(NoTransaction transaction,
 Client client,
 Object... id)

Fetches a record from the database using the record’s unique ID.

Specified by:

findById in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Parameters:

transaction - Transaction object used to initiated the query If If null is specified, the query does not use a transaction (it takes place outside of a transaction).

client - Client instance initiating the query If null is specified, user access to the data is not checked.

id - Record ID

Throws:

FindException - Occurs if an error was encountered during the query

DataAccessException - Occurs if the user in the specified client has no access to query the data.

openTransaction

public NoTransaction openTransaction()

As the DataDescriptor does not support transaction handling, the method returns null.

Specified by:

openTransaction in interface DataDescriptor

Specified by:

openTransaction in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Returns:

Transaction object

copy

public InMemoryDataDescriptor copy()

Creates a copy of the DataDescriptor

Specified by:

copy in interface DataDescriptor

Overrides:

copy in class BaseDataDescriptor<InMemoryDataDescriptor,NoTransaction>

Returns:

A new DataDescriptor, that is a perfect copy of the DataDescriptor