Cache

java.lang.Object
- de.umass.lastfm.cache.Cache

Direct Known Subclasses:

DatabaseCache, FileSystemCache, MemoryCache
```
public abstract class Cache
extends java.lang.Object
```
The Cache handles storing and loading to a permanent storage for last.fm api requests. This could be a file system or a sql database.

Author:

Janni Kovacs

See Also:

Caller.setCache(Cache), ExpirationPolicy

Constructor Summary

Constructors
Modifier Constructor and Description

protected Cache()

Constructors
Modifier	Constructor and Description
`protected`	`Cache()`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract void`	`clear()` Clears the cache by effectively removing all cached data.
`abstract boolean`	`contains(java.lang.String cacheEntryName)` Checks if the cache contains an entry with the given name.
`static java.lang.String`	`createCacheEntryName(java.lang.String method, java.util.Map<java.lang.String,java.lang.String> params)` Creates a unique entry name string for a request.
`ExpirationPolicy`	`getExpirationPolicy()` Returns the active `ExpirationPolicy`
`abstract boolean`	`isExpired(java.lang.String cacheEntryName)` Checks if the specified entry is expired.
`abstract java.io.InputStream`	`load(java.lang.String cacheEntryName)` Loads the specified entry from the cache and returns an InputStream to be read from.
`abstract void`	`remove(java.lang.String cacheEntryName)` Removes the specified entry from the cache if available.
`void`	`setExpirationPolicy(ExpirationPolicy expirationPolicy)` Sets the active `ExpirationPolicy`.
`static void`	`setHashCacheEntryNames(boolean hashCacheEntryNames)` If `hashCacheEntryNames` is set to true the `createCacheEntryName(java.lang.String, java.util.Map<java.lang.String, java.lang.String>)` method will return a hash of the original entry name instead of the name itself.
`abstract void`	`store(java.lang.String cacheEntryName, java.io.InputStream inputStream, long expirationDate)` Stores a request in the cache.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Cache
```
protected Cache()
```
- Method Detail
  - getExpirationPolicy
```
public ExpirationPolicy getExpirationPolicy()
```
    Returns the active ExpirationPolicy
    
    Returns:
    
    the ExpirationPolicy
  - setExpirationPolicy
```
public void setExpirationPolicy(ExpirationPolicy expirationPolicy)
```
    Sets the active ExpirationPolicy.
    
    Parameters:
    
    expirationPolicy - An ExpirationPolicy, not null
  - contains
```
public abstract boolean contains(java.lang.String cacheEntryName)
```
    Checks if the cache contains an entry with the given name.
    
    Parameters:
    
    cacheEntryName - An entry name
    
    Returns:
    
    true if the cache contains this entry
  - load
```
public abstract java.io.InputStream load(java.lang.String cacheEntryName)
```
    Loads the specified entry from the cache and returns an InputStream to be read from. Returns null if the cache does not contain the specified cacheEntryName.
    
    Parameters:
    
    cacheEntryName - An entry name
    
    Returns:
    
    an InputStream or null
  - remove
```
public abstract void remove(java.lang.String cacheEntryName)
```
    Removes the specified entry from the cache if available. Does nothing if no such entry is available.
    
    Parameters:
    
    cacheEntryName - An entry name
  - store
```
public abstract void store(java.lang.String cacheEntryName,
                           java.io.InputStream inputStream,
                           long expirationDate)
```
    Stores a request in the cache.
    
    Parameters:
    
    cacheEntryName - The entry name to be stored to
    
    inputStream - An InputStream containing the data to be cached
    
    expirationDate - The date of expiration represented in milliseconds since 1.1.1970
  - isExpired
```
public abstract boolean isExpired(java.lang.String cacheEntryName)
```
    Checks if the specified entry is expired.
    
    Parameters:
    
    cacheEntryName - An entry name
    
    Returns:
    
    true if the entry is expired
  - clear
```
public abstract void clear()
```
    Clears the cache by effectively removing all cached data.
  - createCacheEntryName
```
public static java.lang.String createCacheEntryName(java.lang.String method,
                                                    java.util.Map<java.lang.String,java.lang.String> params)
```
    Creates a unique entry name string for a request. It consists of the method name and all the parameter names and values concatenated in alphabetical order. It is used to identify cache entries in the backend storage. If hashCacheEntryNames is set to true this method will return a MD5 hash of the generated name.
    
    Parameters:
    
    method - The request method
    
    params - The request parameters
    
    Returns:
    
    a cache entry name
  - setHashCacheEntryNames
```
public static void setHashCacheEntryNames(boolean hashCacheEntryNames)
```
    If hashCacheEntryNames is set to true the createCacheEntryName(java.lang.String, java.util.Map<java.lang.String, java.lang.String>) method will return a hash of the original entry name instead of the name itself.
    
    Parameters:
    
    hashCacheEntryNames - true to generate hashes

Class Cache

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Cache

Method Detail

getExpirationPolicy

setExpirationPolicy

contains

load

remove

store

isExpired

clear

createCacheEntryName

setHashCacheEntryNames