PersistenceService (JNLP API Reference 1.5)
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javax.jnlp
Interface PersistenceService
public interface PersistenceService
PersistenceService provides methods for storing data
locally on the client system, even for applications that are running
in the untrusted execution environment. The service is somewhat
similar to that which the cookie mechanism provides to HTML-based
applications.
Each entry in the persistence data store is named with a URL.
This provides a similar hierarchical structure as a traditional file
system.
An application is only allowed to access data stored with a URL that
is based on its codebase. For example, given the codebase
http://www.mysite.com/apps/App1/, the application
would be allowed to access the data at the associated URLs:
http://www.mysite.com/apps/App1/
http://www.mysite.com/apps/
http://www.mysite.com/
This scheme allows sharing of data between different applications from
the same host. For example, if another application is located at
http://www.mysite.com/apps/App2/, then they can share data
between them in the http://www.mysite.com/ and
http://www.mysite.com/apps/ directories.
A JNLP client should track the amount of storage that a given
application uses. A PersistenceService implementation
provides methods to get the current storage usage and limits and to
request more storage. Storage is allocated on a per file basis, but a
JNLP Client will typically grant or deny the request based on the total
storage is use by an application.
Data stored using this mechanism is intended to be a local copy of
data stored on a remote server. The individual entries can be
tagged as either cached, meaning the server has an up-to-date
copy, dirty, meaning the server does not have an up-to-date
copy, or temporary, meaning that the file can always be
recreated.
Since:
1.0
Field Summary
static int
CACHED
static int
DIRTY
static int
TEMPORARY
Method Summary
long
create(java.net.URL url,
long maxsize)
Creates a new persistent storage entry on the client side named with
the given URL.
void
delete(java.net.URL url)
Removes the stream associated with the given URL from the
client-side date persistence store.
FileContents
get(java.net.URL url)
Returns a FileContents object representing the contents
of this file.
java.lang.String[]
getNames(java.net.URL url)
Returns an array of Strings containing the names of all the
entries for a given URL.
int
getTag(java.net.URL url)
Returns an int corresponding to the current value
of the tag for the persistent data store entry associated with the
given URL.
void
setTag(java.net.URL url,
int tag)
Tags the persistent data store entry associated with the given URL
with the given tag value.
Field Detail
CACHED
static final int CACHED
See Also:Constant Field Values
TEMPORARY
static final int TEMPORARY
See Also:Constant Field Values
DIRTY
static final int DIRTY
See Also:Constant Field Values
Method Detail
create
long create(java.net.URL url,
long maxsize)
throws java.net.MalformedURLException,
java.io.IOException
Creates a new persistent storage entry on the client side named with
the given URL.
Parameters:url - the URL representing the name of the entry in the
persistent data store.maxsize - maximum size of storage that can be written to this
entry.
Returns:the maximum size of storage that got granted, in bytes.
Throws:
java.net.MalformedURLException - if the application is denied access to
the persistent data store represented by
the given URL.
java.io.IOException - if an I/O exception occurs, or the entry already exists.
get
FileContents get(java.net.URL url)
throws java.net.MalformedURLException,
java.io.IOException,
java.io.FileNotFoundException
Returns a FileContents object representing the contents
of this file.
Parameters:url - the URL representing the persistent data store entry.
Returns:the file contents as a FileContents.
Throws:
java.io.IOException - if an I/O error occurs.
java.net.MalformedURLException - if the application is denied access to
the persistent data store represented by
the given URL.
java.io.FileNotFoundException - if a persistence store for the given URL
is not found.
delete
void delete(java.net.URL url)
throws java.net.MalformedURLException,
java.io.IOException
Removes the stream associated with the given URL from the
client-side date persistence store.
Parameters:url - the URL representing the entry to delete from
the persistent data store.
Throws:
java.net.MalformedURLException - if the application is denied access to
the persistent data store represented by
the given URL.
java.io.IOException - if an I/O exception occurs.
getNames
java.lang.String[] getNames(java.net.URL url)
throws java.net.MalformedURLException,
java.io.IOException
Returns an array of Strings containing the names of all the
entries for a given URL.
Parameters:url - the URL representing the root directory to search for
entry names.
Returns:a String array containing the entries
names.
Throws:
java.net.MalformedURLException - if the application is denied access to
the persistent data store represented by
the given URL.
java.io.IOException - if an I/O exception occurs.
getTag
int getTag(java.net.URL url)
throws java.net.MalformedURLException,
java.io.IOException
Returns an int corresponding to the current value
of the tag for the persistent data store entry associated with the
given URL.
Parameters:url - the URL representing the persistent data store entry
for which the tag value is requested.
Returns:an int containing one of the following
tag values:
CACHED
TEMPORARY
DIRTY
Throws:
java.net.MalformedURLException - if the application is denied access to
the persistent data store represented by
the given URL.
java.io.IOException - if an I/O exception occurs.
setTag
void setTag(java.net.URL url,
int tag)
throws java.net.MalformedURLException,
java.io.IOException
Tags the persistent data store entry associated with the given URL
with the given tag value.
Parameters:url - the URL representing the persistent data store entry
for which to set the tag value.tag - the tag value to set.
Throws:
java.net.MalformedURLException - if the application is denied access to
the persistent data store represented by
the given URL.
java.io.IOException - if an I/O exception occurs.
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Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved
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