org.ehcache.spi.loaderwriter

Interface CacheLoaderWriter<K,V>

Type Parameters:

K - the key type processed by this loader-writer

V - the value type processed by this loader-writer //These are already linked

public interface CacheLoaderWriter<K,V>

A CacheLoaderWriter is used to keep a Cache in sync with another system.

Instances of this class should be thread safe.

Any Exception thrown by the loading methods of this interface will be wrapped into a CacheLoadingException by the Cache and will need to be handled by the user. Any java.lang.Exception thrown by the writing methods will be wrapped into a CacheWritingException.

WTF? A similar thing will happen for the bulk version of the loading and writing methods and create the bulk version of the related exceptions.

See Also:

CacheLoadingException, CacheWritingException, BulkCacheLoadingException, BulkCacheWritingException

Method Summary

Modifier and Type	Method and Description
void	delete(K key) Deletes a single mapping.
void	deleteAll(java.lang.Iterable<? extends K> keys) Deletes multiple mappings.
V	load(K key) Loads a single value.
java.util.Map<K,V>	loadAll(java.lang.Iterable<? extends K> keys) Loads multiple values.
void	write(K key, V value) Writes a single mapping.
void	writeAll(java.lang.Iterable<? extends java.util.Map.Entry<? extends K,? extends V>> entries) Writes multiple mappings.

Method Detail

load

V load(K key)
throws java.lang.Exception

Loads a single value.

When used with a cache any exception thrown by this method will be thrown back to the user as a CacheLoadingException.

Parameters:

key - the key for which to load the value

Returns:

the loaded value

Throws:

java.lang.Exception - if the value cannot be loaded

loadAll

java.util.Map<K,V> loadAll(java.lang.Iterable<? extends K> keys)
                    throws BulkCacheLoadingException,
                           java.lang.Exception

Loads multiple values.

The returned Map should contain null values for the keys that could not be found.

When used with a cache the mappings that will be installed are the keys as found in keys mapped to the results of loadAllResult.get(key). Any other mappings will be ignored.

By using a BulkCacheLoadingException implementors can report partial success. Any other exceptions will be thrown back to the Cache user through a BulkCacheLoadingException indicating a complete failure.

Parameters:

keys - the keys to load //Which null or not present?

Returns:

the Map of values for each key passed in, where no mapping means no value to map.

Throws:

BulkCacheLoadingException - in case of partial success

java.lang.Exception - in case no values could be loaded

write

void write(K key,
           V value)
    throws java.lang.Exception

Writes a single mapping.

The write may represent a brand new value or an update to an existing value.

When used with a Cache any exception thrown by this method will be thrown back to the user through a CacheWritingException.

Parameters:

key - the key to write

value - the value to write

Throws:

java.lang.Exception - if the write operation failed

writeAll

void writeAll(java.lang.Iterable<? extends java.util.Map.Entry<? extends K,? extends V>> entries)
       throws BulkCacheWritingException,
              java.lang.Exception

Writes multiple mappings.

The writes may represent a mix of brand new values and updates to existing values.

By using a BulkCacheWritingException implementors can report partial success. Any other exception will be thrown back to the Cache user through a BulkCacheWritingException indicating a complete failure.

Parameters:

entries - the mappings to write

Throws:

BulkCacheWritingException - in case of partial success

java.lang.Exception - in case no values could be written

delete

void delete(K key)
     throws java.lang.Exception

Deletes a single mapping.

Parameters:

key - the key to delete

Throws:

java.lang.Exception - if the write operation failed

deleteAll

void deleteAll(java.lang.Iterable<? extends K> keys)
        throws BulkCacheWritingException,
               java.lang.Exception

Deletes multiple mappings.

By using a BulkCacheWritingException implementors can report partial success. Any other exception will be thrown back to the Cache user through a BulkCacheWritingException indicating all deletes failed.

Parameters:

keys - the keys to delete

Throws:

BulkCacheWritingException - in case of partial success

java.lang.Exception - in case no values can be loaded