| java.lang.Object | |
| ↳ | com.neomades.content.cache.CacheEntry |
 Known Direct Subclasses
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Class Overview
Data and metadata for an entry returned by the cache.
CacheEntry will describe the cache policy thanks to the methods
isExpired() and refreshNeeded().
In this implementation, isExpired() and refreshNeeded() are
both based on the time to live of the data in the server found in the
response header. This enables the cache to be updated automatically only when
the data are declared as invalid by the server. This implies some
configuration of the server to send the good header with the request
response. If not, the data will be considered as invalid each time a request
is sent and they will be downloaded again.
To fully understand this behavior, read the javadoc of setTtl(long),
setSoftTtl(long), isExpired() and refreshNeeded().
Summary
| Public Constructors | |||||||||||
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CacheEntry()
Creates a
CacheEntry. | |||||||||||
| Public Methods | |||||||||||
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| byte[] |
getData()
Returns the raw data in the cache.
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| Object |
getDeserializedData()
Returns the deserialized data in the cache.
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| String |
getEtag()
Gets the value associated with the
ETag header found when the
data was saved in the cache. | ||||||||||
| Map<String, String> |
getResponseHeaders()
Returns all the headers returned by the response that were used to download
the data.
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| long |
getServerDate()
Returns the date returned by the server in the header
Date when
the response with the data was returned (in ms). | ||||||||||
| long |
getSoftTTL()
Returns the time when the data will require an update.
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| long |
getTTL()
Returns the validity time in ms of the cache data.
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| boolean |
isExpired()
Returns if the entry is expired.
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| boolean |
refreshNeeded()
Returns
true if a refresh is needed from the original data
source. | ||||||||||
| void |
setData(byte[] data)
Inserts a byte array of data inside the cache entry in order to get it.
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| void |
setDeserializedData(Object data)
Inserts a deserialized object inside the cache entry in order to get it.
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| void |
setEtag(String etag)
Saves the value associated with the
ETag header found in the
response that get the data. | ||||||||||
| void |
setResponseHeaders(Map<String, String> responseHeaders)
Saves all the headers returned by the response that were used to download the
data.
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| void |
setServerDate(long serverDate)
Saves the date returned by the server in the header
Date when
the response with the data is returned (in ms). | ||||||||||
| void |
setSoftTtl(long softTtl)
Sets the time when the data will require an update.
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| void |
setTtl(long ttl)
Saves the validity time in ms of the cache data.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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Public Constructors
public CacheEntry ()
Creates a CacheEntry.
Public Methods
public byte[] getData ()
Returns the raw data in the cache.
Returns
- the raw data in the cache
public Object getDeserializedData ()
Returns the deserialized data in the cache.
Returns
- a deserialized object
public String getEtag ()
Gets the value associated with the ETag header found when the
data was saved in the cache. If the header was not sent by the server, the
value is null.
Returns
- the value associated with the
ETagheader found when the data was saved in the cache
public Map<String, String> getResponseHeaders ()
Returns all the headers returned by the response that were used to download the data.
Returns
- the headers returned by the response that were used to download the data
public long getServerDate ()
Returns the date returned by the server in the header Date when
the response with the data was returned (in ms). If the header was not sent by the
server, the value is 0.
Returns
- the date returned by the server in the header
Datewhen the response with the data was returned (in ms)
public long getSoftTTL ()
Returns the time when the data will require an update. Contrary to
getTTL(), when expired, the next request will trigger an update of
the data but while it is not done, the previous data will be used. The data
are invalid but we can still use them while they are not updated. This value
is used by refreshNeeded() to determine if a "soft" update is
required.
Returns
- the time when the data will require an update
public long getTTL ()
Returns the validity time in ms of the cache data. When expired, the data
will be considered as invalid and the next request will trigger a download
and the cache will be updated with new data. This value is used by
isExpired() to determine if the cache is invalid.
Returns
- the validity time in ms of the cache data
public boolean isExpired ()
Returns if the entry is expired.
An entry becomes expired when its time to live is outdated (it is older than
the current time). To understand how the time to live is calculated, refer to
setTtl(long).
When a ContentQuery is sent, if the entry is expired, the cache is
ignored, and the resource will be requested again through the network.
Returns
- true if the entry is expired.
public boolean refreshNeeded ()
Returns true if a refresh is needed from the original data
source.
A refresh is needed when the "soft" time to live is outdated (it is older
than the current time). To understand how the soft time to live is
calculated, refer to setSoftTtl(long).
When a ContentQuery is posted, if a refresh is needed, the entry is
sent as an intermediate response, but the cached resource is requested again
through the network to refresh it. If the refresh is not needed, the entry is
sent as a final response.
In this implementation of CacheEntry there is no difference between
setTtl(long) and setSoftTtl(long). Consequently,
isExpired() and refreshNeeded() will be true
or false at the same time. Since isExpired() is called
before refreshNeeded() in the internal implementation, it is always
a "strong" refresh that will be done.
To adapt this behavior, isExpired() and refreshNeeded()
must be overriden in a specific CacheEntry()
Returns
trueif a refresh is needed from the original data source
public void setData (byte[] data)
Inserts a byte array of data inside the cache entry in order to get it. This
method can be used in get(String) to save data in the
CacheEntry.
Parameters
| data | byte array of data to set in the CacheEntry
|
|---|
public void setDeserializedData (Object data)
Inserts a deserialized object inside the cache entry in order to get it. This
method can be used in get(String) to save data in the
CacheEntry.
Parameters
| data | data to set in the CacheEntry
|
|---|
public void setEtag (String etag)
Saves the value associated with the ETag header found in the
response that get the data.
The ETag value will be added to the headers of the request that
will be used to update the cache as the value of a If-None-Match
header. Doing this, the server will send the data only if the
ETag has changed for the requested resource.
Parameters
| etag | value associated with the ETag header
|
|---|
public void setResponseHeaders (Map<String, String> responseHeaders)
Saves all the headers returned by the response that were used to download the data.
Parameters
| responseHeaders | the headers returned by the response that were used to download the data |
|---|
public void setServerDate (long serverDate)
Saves the date returned by the server in the header Date when
the response with the data is returned (in ms).
The server date will be added to the headers of the request that will be used
to update the cache as the value of a If-Modified-Since header
(only if the value is not 0). Doing this, if the server understands the
header, it will send a response only if the data were updated.
Parameters
| serverDate | date of the server when the data were sent (in ms) |
|---|
public void setSoftTtl (long softTtl)
Sets the time when the data will require an update. Contrary to
setTtl(long), when expired, the next request will trigger an update
of the data but while it is not done, the previous data will be used. The
data are invalid but we can still use them while they are not updated. This
value is used by refreshNeeded() to determine if a "soft" update is
required.
In this implementation of CacheEntry there is no difference between
setTtl(long) and setSoftTtl(long). Consequently,
isExpired() and refreshNeeded() will be true
or false at the same time. Since isExpired() is called
before refreshNeeded() in the internal implementation, it is always
a "strong" refresh that will be done.
To adapt this behavior, isExpired() and refreshNeeded()
must be overriden in a specific CacheEntry()
Parameters
| softTtl | the time when the data will require an update |
|---|
See Also
public void setTtl (long ttl)
Saves the validity time in ms of the cache data. When expired, the data will
be considered as invalid and the next request will trigger a download and the
cache will be updated with new data. This value is used by
isExpired() to determine if the cache is invalid.
By default, this value is set when parsing the response header. If a
Cache-Control, max-age=xxx is found in the header, the ttl value
will be: System.currentTimeMillis() + maxAge * 1000;.
If there is no Cache-Control, max-age=xxx header, an
Expires header will be searched in the response headers. If
found the time to live will be equal to
System.currentTimeMillis() + (serverExpires - serverDate); where
serverExpires is the value of the Expires header
and serverDate is the value of the Date header.
If there is no header, its value will be 0 and the cache will be updated each
time a request is triggered.
Parameters
| ttl | the validity time in ms of the cache data |
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