org.eclipse.jgit.internal.storage.reftree

Class RefTreeDatabase

java.lang.Object

org.eclipse.jgit.lib.RefDatabase

org.eclipse.jgit.internal.storage.reftree.RefTreeDatabase

public class RefTreeDatabase
extends RefDatabase

Reference database backed by a RefTree.

The storage for RefTreeDatabase has two parts. The main part is a native Git tree object stored under the refs/txn namespace. To avoid cycles, references to refs/txn are not stored in that tree object, but instead in a "bootstrap" layer, which is a separate RefDatabase such as RefDirectory using local reference files inside of $GIT_DIR/refs.

Field Summary

Fields inherited from class org.eclipse.jgit.lib.RefDatabase

ALL, MAX_SYMBOLIC_REF_DEPTH, SEARCH_PATH

Constructor Summary

Constructors

Constructor and Description
RefTreeDatabase(Repository repo, RefDatabase bootstrap) Create a RefTreeDb for a repository.
RefTreeDatabase(Repository repo, RefDatabase bootstrap, String txnCommitted) Create a RefTreeDb for a repository.

Method Summary

Modifier and Type	Method and Description
void	close() Close any resources held by this database.
void	create() Initialize a new reference database at this location.
Ref	exactRef(String name) Read a single reference.
List<Ref>	getAdditionalRefs() Get the additional reference-like entities from the repository.
RefDatabase	getBootstrap() Get the bootstrap reference database
Ref	getRef(String name) Read a single reference.
Map<String,Ref>	getRefs(String prefix) Get a section of the reference namespace.
String	getTxnCommitted() Get name of bootstrap reference anchoring committed RefTree.
String	getTxnNamespace() Get namespace used by bootstrap layer.
boolean	isNameConflicting(String name) Determine if a proposed reference name overlaps with an existing one.
BatchRefUpdate	newBatchUpdate() Create a new batch update to attempt on this database.
RefRename	newRename(String fromName, String toName) Create a new update command to rename a reference.
RefUpdate	newUpdate(String name, boolean detach) Create a new update command to create, modify or delete a reference.
Ref	peel(Ref ref) Peel a possibly unpeeled reference by traversing the annotated tags.
boolean	performsAtomicTransactions() Whether the database is capable of performing batch updates as atomic transactions.
void	refresh() Triggers a refresh of all internal data structures.

Methods inherited from class org.eclipse.jgit.lib.RefDatabase

exactRef, findRef, firstExactRef, getConflictingNames, getRefs, getRefsByPrefix, hasRefs

Methods inherited from class java.lang.Object

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

Constructor Detail

RefTreeDatabase

public RefTreeDatabase(Repository repo,
                       RefDatabase bootstrap)

Create a RefTreeDb for a repository.

Parameters:

repo - the repository using references in this database.

bootstrap - bootstrap reference database storing the references that anchor the RefTree.

RefTreeDatabase

public RefTreeDatabase(Repository repo,
                       RefDatabase bootstrap,
                       String txnCommitted)

Create a RefTreeDb for a repository.

Parameters:

repo - the repository using references in this database.

bootstrap - bootstrap reference database storing the references that anchor the RefTree.

txnCommitted - name of the bootstrap reference holding the committed RefTree.

Method Detail

getBootstrap

public RefDatabase getBootstrap()

Get the bootstrap reference database

Returns:

the bootstrap reference database, which must be used to access getTxnCommitted(), getTxnNamespace().

getTxnCommitted

public String getTxnCommitted()

Get name of bootstrap reference anchoring committed RefTree.

Returns:

name of bootstrap reference anchoring committed RefTree.

getTxnNamespace

@Nullable
public String getTxnNamespace()

Get namespace used by bootstrap layer.

Returns:

namespace used by bootstrap layer, e.g. refs/txn/. Always ends in '/'.

create

public void create()
            throws IOException

Initialize a new reference database at this location.

Specified by:

create in class RefDatabase

Throws:

IOException - the database could not be created.

performsAtomicTransactions

public boolean performsAtomicTransactions()

Whether the database is capable of performing batch updates as atomic transactions.

If true, by default BatchRefUpdate instances will perform updates atomically, meaning either all updates will succeed, or all updates will fail. It is still possible to turn off this behavior on a per-batch basis by calling update.setAtomic(false).

If false, BatchRefUpdate instances will never perform updates atomically, and calling update.setAtomic(true) will cause the entire batch to fail with REJECTED_OTHER_REASON.

This definition of atomicity is stronger than what is provided by ReceivePack. ReceivePack will attempt to reject all commands if it knows in advance some commands may fail, even if the storage layer does not support atomic transactions. Here, atomicity applies even in the case of unforeseeable errors.

Overrides:

performsAtomicTransactions in class RefDatabase

Returns:

whether transactions are atomic by default.

refresh

public void refresh()

Triggers a refresh of all internal data structures.

In case the RefDatabase implementation has internal caches this method will trigger that all these caches are cleared.

Implementors should overwrite this method if they use any kind of caches.

Overrides:

refresh in class RefDatabase

close

public void close()

Close any resources held by this database.

Specified by:

close in class RefDatabase

getRef

public Ref getRef(String name)
           throws IOException

Read a single reference.

Aside from taking advantage of RefDatabase.SEARCH_PATH, this method may be able to more quickly resolve a single reference name than obtaining the complete namespace by getRefs(ALL).get(name).

To read a specific reference without using @{link #SEARCH_PATH}, see RefDatabase.exactRef(String).

Specified by:

getRef in class RefDatabase

Parameters:

name - the name of the reference. May be a short name which must be searched for using the standard RefDatabase.SEARCH_PATH.

Returns:

the reference (if it exists); else null.

Throws:

IOException - the reference space cannot be accessed.

exactRef

public Ref exactRef(String name)
             throws IOException

Read a single reference.

Unlike RefDatabase.getRef(java.lang.String), this method expects an unshortened reference name and does not search using the standard RefDatabase.SEARCH_PATH.

Overrides:

exactRef in class RefDatabase

Parameters:

name - the unabbreviated name of the reference.

Returns:

the reference (if it exists); else null.

Throws:

IOException - the reference space cannot be accessed.

getRefs

public Map<String,Ref> getRefs(String prefix)
                        throws IOException

Get a section of the reference namespace.

Specified by:

getRefs in class RefDatabase

Parameters:

prefix - prefix to search the namespace with; must end with /. If the empty string (RefDatabase.ALL), obtain a complete snapshot of all references.

Returns:

modifiable map that is a complete snapshot of the current reference namespace, with prefix removed from the start of each key. The map can be an unsorted map.

Throws:

IOException - the reference space cannot be accessed.

getAdditionalRefs

public List<Ref> getAdditionalRefs()
                            throws IOException

Get the additional reference-like entities from the repository.

The result list includes non-ref items such as MERGE_HEAD and FETCH_RESULT cast to be refs. The names of these refs are not returned by getRefs() but are accepted by RefDatabase.getRef(String) and RefDatabase.exactRef(String).

Specified by:

getAdditionalRefs in class RefDatabase

Returns:

a list of additional refs

Throws:

IOException - the reference space cannot be accessed.

peel

public Ref peel(Ref ref)
         throws IOException

Peel a possibly unpeeled reference by traversing the annotated tags.

If the reference cannot be peeled (as it does not refer to an annotated tag) the peeled id stays null, but Ref.isPeeled() will be true.

Implementors should check Ref.isPeeled() before performing any additional work effort.

Specified by:

peel in class RefDatabase

Parameters:

ref - The reference to peel

Returns:

ref if ref.isPeeled() is true; otherwise a new Ref object representing the same data as Ref, but isPeeled() will be true and getPeeledObjectId() will contain the peeled object (or null).

Throws:

IOException - the reference space or object space cannot be accessed.

isNameConflicting

public boolean isNameConflicting(String name)
                          throws IOException

Determine if a proposed reference name overlaps with an existing one.

Reference names use '/' as a component separator, and may be stored in a hierarchical storage such as a directory on the local filesystem.

If the reference "refs/heads/foo" exists then "refs/heads/foo/bar" must not exist, as a reference cannot have a value and also be a container for other references at the same time.

If the reference "refs/heads/foo/bar" exists than the reference "refs/heads/foo" cannot exist, for the same reason.

Specified by:

isNameConflicting in class RefDatabase

Parameters:

name - proposed name.

Returns:

true if the name overlaps with an existing reference; false if using this name right now would be safe.

Throws:

IOException - the database could not be read to check for conflicts.

See Also:

RefDatabase.getConflictingNames(String)

newBatchUpdate

public BatchRefUpdate newBatchUpdate()

Create a new batch update to attempt on this database.

The default implementation performs a sequential update of each command.

Overrides:

newBatchUpdate in class RefDatabase

Returns:

a new batch update object.

newUpdate

public RefUpdate newUpdate(String name,
                           boolean detach)
                    throws IOException

Create a new update command to create, modify or delete a reference.

Specified by:

newUpdate in class RefDatabase

Parameters:

name - the name of the reference.

detach - if true and name is currently a SymbolicRef, the update will replace it with an ObjectIdRef. Otherwise, the update will recursively traverse SymbolicRefs and operate on the leaf ObjectIdRef.

Returns:

a new update for the requested name; never null.

Throws:

IOException - the reference space cannot be accessed.

newRename

public RefRename newRename(String fromName,
                           String toName)
                    throws IOException

Create a new update command to rename a reference.

Specified by:

newRename in class RefDatabase

Parameters:

fromName - name of reference to rename from

toName - name of reference to rename to

Returns:

an update command that knows how to rename a branch to another.

Throws:

IOException - the reference space cannot be accessed.