## Class TDbCache

Description

TDbCache class

TDbCache implements a cache application module by storing cached data in a database.

TDbCache relies on PDO to retrieve data from databases. In order to use TDbCache, you need to enable the PDO extension as well as the corresponding PDO DB driver. For example, to use SQLite database to store cached data, you need both php_pdo and php_pdo_sqlite extensions.

By default, TDbCache creates and uses an SQLite database under the application runtime directory. You may change this default setting by specifying the following properties:

- ConnectionID or
- ConnectionString, Username and Pasword.

The cached data is stored in a table in the specified database. By default, the name of the table is called 'pradocache'. If the table does not exist in the database, it will be automatically created with the following structure: (key CHAR(128) PRIMARY KEY, value BLOB, expire INT)

If you want to change the cache table name, or if you want to create the table by yourself, you may set CacheTableName and AutoCreateCacheTableName properties.

The following basic cache operations are implemented:

- get : retrieve the value with a key (if any) from cache
- set : store the value with a key into cache
- add : store the value only if cache does not have this key
- delete : delete the value with the specified key from cache
- flush : delete all values from cache

Each value is associated with an expiration time. The get operation ensures that any expired value will not be returned. The expiration time by the number of seconds. A expiration time 0 represents never expire.

By definition, cache does not ensure the existence of a value even if it never expires. Cache is not meant to be an persistent storage.

Do not use the same database file for multiple applications using TDbCache. Also note, cache is shared by all user sessions of an application.

Some usage examples of TDbCache are as follows,

     $cache=new TDbCache;  // TDbCache may also be loaded as a Prado application module
      $cache->init(null);
     $cache->add('object',$object);
     $object2=$cache->get('object');

If loaded, TDbCache will register itself with TApplication as the cache module. It can be accessed via TApplication::getCache().

TDbCache may be configured in application configuration file as follows

     <module id="cache" class="System.Caching.TDbCache" />

- since: 3.1.0
- version: $Id: TDbCache.php 2250 2007-09-27 02:30:10Z xue $
- author: Qiang Xue <qiang.xue@gmail.com>

Located in /Caching/TDbCache.php (line 77)

    TComponent
       |
       --TApplicationComponent
          |
          --TModule
             |
             --TCache
                |
                --TDbCache

Method Summary
void __destruct ()
boolean addValue (string $key, string $value, integer $expire)
TDbConnection createDbConnection (string 0)
boolean deleteValue (string $key)
void flush ()
boolean getAutoCreateCacheTable ()
string getCacheTableName ()
string getConnectionID ()
string getConnectionString ()
TDbConnection getDbConnection ()
string getPassword ()
string getUsername ()
string getValue (string $key)
void init (TXmlElement $config)
void setAutoCreateCacheTable (boolean $value)
void setCacheTableName (string $value)
void setConnectionID (string $value)
void setConnectionString (string $value)
void setPassword (string $value)
void setUsername (string $value)
boolean setValue (string $key, string $value, integer $expire)
Methods
Destructor __destruct (line 103)

Destructor.

Disconnect the db connection.

- access: public

void __destruct ()
addValue (line 339)

Stores a value identified by a key into cache if the cache does not contain this key.

This is the implementation of the method declared in the parent class.

- return: true if the value is successfully stored into cache, false otherwise
- access: protected

boolean addValue (string $key, string $value, integer $expire)

- string $key: the key identifying the value to be cached
- string $value: the value to be cached
- integer $expire: the number of seconds in which the cached value will expire. 0 means never expire.

Redefinition of:

TCache::addValue()
  Stores a value identified by a key into cache if the cache does not contain this key.

createDbConnection (line 150)

Creates the DB connection.

- return: the created DB connection
- access: protected
- throws: TConfigurationException if module ID is invalid or empty

TDbConnection createDbConnection (string 0)

- string 0: the module ID for TDataSourceConfig

deleteValue (line 362)

Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.

- return: if no error happens during deletion
- access: protected

boolean deleteValue (string $key)

- string $key: the key of the value to be deleted

Redefinition of:

TCache::deleteValue()
  Deletes a value with the specified key from cache This method should be implemented by child classes to delete the data from actual cache storage.

flush (line 374)

Deletes all values from cache.

Be careful of performing this operation if the cache is shared by multiple applications.

- access: public

void flush ()

Redefinition of:

TCache::flush()
  Deletes all values from cache.

getAutoCreateCacheTable (line 289)

- return: whether the cache DB table should be automatically created if not exists. Defaults to true.
- access: public
- see: TDbCache::setAutoCreateCacheTable()

boolean getAutoCreateCacheTable ()
getCacheTableName (line 266)

- return: the name of the DB table to store cache content. Defaults to 'pradocache'.
- access: public
- see: TDbCache::setAutoCreateCacheTable()

string getCacheTableName ()
getConnectionID (line 195)

- return: the ID of a TDataSourceConfig module. Defaults to empty string, meaning not set.
- access: public
- since: 3.1.1

string getConnectionID ()
getConnectionString (line 216)

- return: The Data Source Name, or DSN, contains the information required to connect to the database.
- access: public

string getConnectionString ()
getDbConnection (line 184)

- return: the DB connection instance
- access: public

TDbConnection getDbConnection ()
getPassword (line 249)

- return: the password for establishing DB connection. Defaults to empty string.
- access: public

string getPassword ()
getUsername (line 233)

- return: the username for establishing DB connection. Defaults to empty string.
- access: public

string getUsername ()
getValue (line 309)

Retrieves a value from cache with a specified key.

This is the implementation of the method declared in the parent class.

- return: the value stored in cache, false if the value is not in the cache or expired.
- access: protected

string getValue (string $key)

- string $key: a unique key identifying the cached value

Redefinition of:

TCache::getValue()
  Retrieves a value from cache with a specified key.

init (line 119)

Initializes this module.

This method is required by the IModule interface. It checks if the DbFile property is set, and creates a SQLiteDatabase instance for it. The database or the cache table does not exist, they will be created. Expired values are also deleted.

- access: public
- throws: TConfigurationException if sqlite extension is not installed, DbFile is set invalid, or any error happens during creating database or cache table.

void init (TXmlElement $config)

- TXmlElement $config: configuration for this module, can be null

Redefinition of:

TCache::init()
  Initializes the cache module.

setAutoCreateCacheTable (line 298)

- access: public
- see: TDbCache::setCacheTableName()

void setAutoCreateCacheTable (boolean $value)

- boolean $value: whether the cache DB table should be automatically created if not exists.

setCacheTableName (line 280)

Sets the name of the DB table to store cache content.

Note, if AutoCreateCacheTable is false and you want to create the DB table manually by yourself, you need to make sure the DB table is of the following structure: (key CHAR(128) PRIMARY KEY, value BLOB, expire INT)

- access: public
- see: TDbCache::setAutoCreateCacheTable()

void setCacheTableName (string $value)

- string $value: the name of the DB table to store cache content

setConnectionID (line 208)

Sets the ID of a TDataSourceConfig module.

The datasource module will be used to establish the DB connection for this cache module. The database connection can also be specified via ConnectionString. When both ConnectionID and ConnectionString are specified, the former takes precedence.

- access: public
- since: 3.1.1

void setConnectionID (string $value)

- string $value: ID of the TDataSourceConfig module

setConnectionString (line 225)

- access: public
- see: http://www.php.net/manual/en/function.pdo-construct.php

void setConnectionString (string $value)

- string $value: The Data Source Name, or DSN, contains the information required to connect to the database.

setPassword (line 257)

- access: public

void setPassword (string $value)

- string $value: the password for establishing DB connection

setUsername (line 241)

- access: public

void setUsername (string $value)

- string $value: the username for establishing DB connection

setValue (line 324)

Stores a value identified by a key in cache.

This is the implementation of the method declared in the parent class.

- return: true if the value is successfully stored into cache, false otherwise
- access: protected

boolean setValue (string $key, string $value, integer $expire)

- string $key: the key identifying the value to be cached
- string $value: the value to be cached
- integer $expire: the number of seconds in which the cached value will expire. 0 means never expire.

Redefinition of:

TCache::setValue()
  Stores a value identified by a key in cache.

#### Inherited Methods

Inherited From TCache

> TCache::add()
> TCache::addValue()
> TCache::delete()
> TCache::deleteValue()
> TCache::flush()
> TCache::generateUniqueKey()
> TCache::get()
> TCache::getKeyPrefix()
> TCache::getPrimaryCache()
> TCache::getValue()
> TCache::init()
> TCache::set()
> TCache::setKeyPrefix()
> TCache::setPrimaryCache()
> TCache::setValue()

Inherited From TModule

> TModule::getID()
> TModule::init()
> TModule::setID()

Inherited From TApplicationComponent

> TApplicationComponent::getApplication()
> TApplicationComponent::getRequest()
> TApplicationComponent::getResponse()
> TApplicationComponent::getService()
> TApplicationComponent::getSession()
> TApplicationComponent::getUser()
> TApplicationComponent::publishAsset()
> TApplicationComponent::publishFilePath()

Inherited From TComponent

> TComponent::addParsedObject()
> TComponent::attachEventHandler()
> TComponent::canGetProperty()
> TComponent::canSetProperty()
> TComponent::createdOnTemplate()
> TComponent::detachEventHandler()
> TComponent::evaluateExpression()
> TComponent::evaluateStatements()
> TComponent::getEventHandlers()
> TComponent::getSubProperty()
> TComponent::hasEvent()
> TComponent::hasEventHandler()
> TComponent::hasProperty()
> TComponent::raiseEvent()
> TComponent::setSubProperty()
> TComponent::__get()
> TComponent::__set()

Documentation generated on Sun, 30 Sep 2007 19:15:56 -0400 by phpDocumentor 1.3.0RC4