Package org.apache.activemq.store.kahadb.disk.page

Class Transaction

java.lang.Object

org.apache.activemq.store.kahadb.disk.page.Transaction

All Implemented Interfaces:

Iterable<Page>

public class Transaction
extends Object
implements Iterable<Page>

The class used to read/update a PageFile object. Using a transaction allows you to do multiple update operations in a single unit of work.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Transaction.CallableClosure<R,T extends Throwable>	This closure interface is intended for the end user implement callbacks for the Transaction.exectue() method.
static interface	Transaction.Closure<T extends Throwable>	This closure interface is intended for the end user implement callbacks for the Transaction.exectue() method.
class	Transaction.InvalidPageIOException	The InvalidPageIOException is thrown if try to load/store a a page with an invalid page id.
class	Transaction.PageOverflowIOException	The PageOverflowIOException occurs when a page write is requested and it's data is larger than what would fit into a single page.

Method Summary

Modifier and Type	Method	Description
<T> Page<T>	allocate()	Allocates a free page that you can write data to.
<T> Page<T>	allocate(int count)	Allocates a block of free pages that you can write data to.
void	commit()	Commits the transaction to the PageFile as a single 'Unit of Work'.
<R, T extends Throwable> R	execute(Transaction.CallableClosure<R,T> closure)	Executes a closure and if it does not throw any exceptions, then it commits the transaction.
<T extends Throwable> void	execute(Transaction.Closure<T> closure)	Executes a closure and if it does not throw any exceptions, then it commits the transaction.
void	free(long pageId)	Frees up a previously allocated page so that it can be re-allocated again.
void	free(long pageId, int count)	Frees up a previously allocated sequence of pages so that it can be re-allocated again.
<T> void	free(Page<T> page)	Frees up a previously allocated page so that it can be re-allocated again.
<T> void	free(Page<T> page, int count)	Frees up a previously allocated sequence of pages so that it can be re-allocated again.
PageFile	getPageFile()
protected File	getTempFile()
boolean	isReadOnly()
Iterator<Page>	iterator()	Allows you to iterate through all active Pages in this object.
Iterator<Page>	iterator(boolean includeFreePages)	Allows you to iterate through all active Pages in this object.
<T> Page<T>	load(long pageId, Marshaller<T> marshaller)	Loads a page from disk.
<T> void	load(Page<T> page, Marshaller<T> marshaller)	Loads a page from disk.
InputStream	openInputStream(Page p)
OutputStream	openOutputStream(Page page, boolean overflow)
void	rollback()	Rolls back the transaction.
<T> void	store(Page<T> page, Marshaller<T> marshaller, boolean overflow)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Method Details

getPageFile

public PageFile getPageFile()

Returns:

the page file that created this Transaction

allocate

public <T> Page<T> allocate()
                     throws IOException

Allocates a free page that you can write data to.

Returns:

a newly allocated page.

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

allocate

public <T> Page<T> allocate(int count)
                     throws IOException

Allocates a block of free pages that you can write data to.

Parameters:

count - the number of sequential pages to allocate

Returns:

the first page of the sequential set.

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

free

public void free(long pageId)
          throws IOException

Frees up a previously allocated page so that it can be re-allocated again.

Parameters:

pageId - the page to free up

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

free

public void free(long pageId,
 int count)
          throws IOException

Frees up a previously allocated sequence of pages so that it can be re-allocated again.

Parameters:

pageId - the initial page of the sequence that will be getting freed

count - the number of pages in the sequence

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

free

public <T> void free(Page<T> page,
 int count)
              throws IOException

Frees up a previously allocated sequence of pages so that it can be re-allocated again.

Parameters:

page - the initial page of the sequence that will be getting freed

count - the number of pages in the sequence

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

free

public <T> void free(Page<T> page)
              throws IOException

Frees up a previously allocated page so that it can be re-allocated again.

Parameters:

page - the page to free up

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

store

public <T> void store(Page<T> page,
 Marshaller<T> marshaller,
 boolean overflow)
               throws IOException

Parameters:

page - the page to write. The Page object must be fully populated with a valid pageId, type, and data.

marshaller - the marshaler to use to load the data portion of the Page, may be null if you do not wish to write the data.

overflow - If true, then if the page data marshalls to a bigger size than can fit in one page, then additional overflow pages are automatically allocated and chained to this page to store all the data. If false, and the overflow condition would occur, then the PageOverflowIOException is thrown.

Throws:

IOException - If an disk error occurred.

Transaction.PageOverflowIOException - If the page data marshalls to size larger than maximum page size and overflow was false.

IllegalStateException - if the PageFile is not loaded

openOutputStream

public OutputStream openOutputStream(Page page,
 boolean overflow)
                              throws IOException

Throws:

IOException

load

public <T> Page<T> load(long pageId,
 Marshaller<T> marshaller)
                 throws IOException

Loads a page from disk.

Parameters:

pageId - the id of the page to load

marshaller - the marshaler to use to load the data portion of the Page, may be null if you do not wish to load the data.

Returns:

The page with the given id

Throws:

IOException - If an disk error occurred.

IllegalStateException - if the PageFile is not loaded

load

public <T> void load(Page<T> page,
 Marshaller<T> marshaller)
              throws IOException

Loads a page from disk.

Parameters:

page - - The pageId field must be properly set

marshaller - the marshaler to use to load the data portion of the Page, may be null if you do not wish to load the data.

Throws:

IOException - If an disk error occurred.

Transaction.InvalidPageIOException - If the page is is not valid.

IllegalStateException - if the PageFile is not loaded

openInputStream

public InputStream openInputStream(Page p)
                            throws IOException

Throws:

IOException

See Also:

• load(org.apache.activemq.store.kahadb.disk.page.Page, org.apache.activemq.store.kahadb.disk.util.Marshaller)

iterator

public Iterator<Page> iterator()

Allows you to iterate through all active Pages in this object. Pages with type Page.FREE_TYPE are not included in this iteration. Pages removed with Iterator.remove() will not actually get removed until the transaction commits.

Specified by:

iterator in interface Iterable<Page>

Throws:

IllegalStateException - if the PageFile is not loaded

iterator

public Iterator<Page> iterator(boolean includeFreePages)

Allows you to iterate through all active Pages in this object. You can optionally include free pages in the pages iterated.

Parameters:

includeFreePages - - if true, free pages are included in the iteration

Throws:

IllegalStateException - if the PageFile is not loaded

commit

public void commit()
            throws IOException

Commits the transaction to the PageFile as a single 'Unit of Work'. Either all page updates associated with the transaction are written to disk or none will.

Throws:

IOException

rollback

public void rollback()
              throws IOException

Rolls back the transaction.

Throws:

IOException

getTempFile

protected File getTempFile()

isReadOnly

public boolean isReadOnly()

Returns:

true if there are no uncommitted page file updates associated with this transaction.

execute

public <T extends Throwable> void execute(Transaction.Closure<T> closure)
                                   throws T,
IOException

Executes a closure and if it does not throw any exceptions, then it commits the transaction. If the closure throws an Exception, then the transaction is rolled back.

Type Parameters:

T -

Parameters:

closure - - the work to get exectued.

Throws:

T - if the closure throws it

IOException - If the commit fails.

execute

public <R,
T extends Throwable> R execute(Transaction.CallableClosure<R,T> closure)
                                  throws T,
IOException

Executes a closure and if it does not throw any exceptions, then it commits the transaction. If the closure throws an Exception, then the transaction is rolled back.

Type Parameters:

T -

Parameters:

closure - - the work to get exectued.

Throws:

T - if the closure throws it

IOException - If the commit fails.