Packages:
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Classes:
Keyword

Class TMemCache

TComponent
   |
   --TApplicationComponent
      |
      --TModule
         |
         --TCache
            |
            --TMemCache

TMemCache class

TMemCache implements a cache application module based on memcached.

TMemCache can be configured with the Host and Port properties, which specify the host and port of the memcache server to be used. By default, they take the value 'localhost' and 11211, respectively. These properties must be set before init is invoked.

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 can be specified by the number of seconds (maximum 60*60*24*30) or a UNIX timestamp. 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.

Also note, there is no security measure to protected data in memcache. All data in memcache can be accessed by any process running in the system.

To use this module, the memcache PHP extension must be loaded.

Some usage examples of TMemCache are as follows,

  1. $cache=new TMemCache; // TMemCache may also be loaded as a Prado application module
  2. $cache->init(null);
  3. $cache->add('object',$object);
  4. $object2=$cache->get('object');

You can configure TMemCache two different ways. If you only need one memcache server you may use the method as follows.

  1. <module id="cache" class="System.Caching.TMemCache" Host="localhost" Port="11211" />

If you want a more complex configuration, you may use the method as follows.

  1. <module id="cache" classs="System.Caching.TMemCache">
  2. <server Host="localhost" Port="11211" Weight="1" Timeout="300" RetryInterval="15" />
  3. <server Host="anotherhost" Port="11211" Weight="1" Timeout="300" RetryInterval="15" />
  4. </module>

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

TMemCache may be configured in application configuration file as follows

  1. <module id="cache" class="System.Caching.TMemCache" Host="localhost" Port="11211" />
where Host and Port are configurable properties of TMemCache.

Since: 3.0
Author: Qiang Xue <qiang.xue@gmail.com>

Method Summary
protected  boolean
addValue ( string $key, string $value, integer $expire)
Stores a value identified by a key into cache if the cache does not contain this key.
protected  boolean
deleteValue ( string $key)
Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.
void
flush ()
Deletes all values from cache.
string
getHost ()
integer
getPort ()
protected  string
getValue ( string $key)
Retrieves a value from cache with a specified key.
void
init ( TApplication $config, TXmlElement 1)
Initializes this module.
void
setHost ( string $value)
void
setPort ( integer $value)
protected  boolean
setValue ( string $key, string $value, integer $expire)
Stores a value identified by a key in cache.
Methods Inherited From TCache
TCache::add(), TCache::delete(), TCache::flush(), TCache::generateUniqueKey(), TCache::get(), TCache::getKeyPrefix(), TCache::getPrimaryCache(), TCache::init(), TCache::offsetExists(), TCache::offsetGet(), TCache::offsetSet(), TCache::offsetUnset(), TCache::set(), TCache::setKeyPrefix(), TCache::setPrimaryCache(),
Methods Inherited From TModule
TModule::getID(), TModule::init(), TModule::setID()
Methods Inherited From TApplicationComponent
TApplicationComponent::getApplication(), TApplicationComponent::getRequest(), TApplicationComponent::getResponse(), TApplicationComponent::getService(), TApplicationComponent::getSession(), TApplicationComponent::getUser(), TApplicationComponent::publishAsset(), TApplicationComponent::publishFilePath()
Methods 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()

Method Details

addValue

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

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.

Input
string$keythe key identifying the value to be cached
string$valuethe value to be cached
integer$expirethe number of seconds in which the cached value will expire. 0 means never expire.
Output
boolean true if the value is successfully stored into cache, false otherwise
Exception

deleteValue

protected boolean deleteValue (string $key )

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

Input
string$keythe key of the value to be deleted
Output
boolean if no error happens during deletion
Exception

flush

public void flush ()

Deletes all values from cache.

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

Output
Exception

getHost

public string getHost ()

Output
string host name of the memcache server
Exception

getPort

public integer getPort ()

Output
integer port number of the memcache server
Exception

getValue

protected string getValue (string $key )

Retrieves a value from cache with a specified key.

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

Input
string$keya unique key identifying the cached value
Output
string the value stored in cache, false if the value is not in the cache or expired.
Exception

init

public void init (TApplication $config , TXmlElement 1 )

Initializes this module.

This method is required by the IModule interface. It makes sure that UniquePrefix has been set, creates a Memcache instance and connects to the memcache server.

Input
TApplication$configPrado application, can be null
TXmlElement1configuration for this module, can be null
Output
Exception
throwsTConfigurationException if memcache extension is not installed or memcache sever connection fails

setHost

public void setHost (string $value )

Input
string$valuehost name of the memcache server
Output
Exception
throwsTInvalidOperationException if the module is already initialized

setPort

public void setPort (integer $value )

Input
integer$valueport number of the memcache server
Output
Exception
throwsTInvalidOperationException if the module is already initialized

setValue

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

Stores a value identified by a key in cache.

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

Input
string$keythe key identifying the value to be cached
string$valuethe value to be cached
integer$expirethe number of seconds in which the cached value will expire. 0 means never expire.
Output
boolean true if the value is successfully stored into cache, false otherwise
Exception