Wiki source code of EOF-Using EOF-Custom EOAdaptor

Last modified by Pascal Robert on 2012/09/22 15:33

version	line-number	content
8.1	1	It's surprisingly easy to create a simple custom EOAdaptor. You can look at JavaFSAdaptor, which is part of Project Wonder, and you can also look at JavaMemoryAdaptor, also in Wonder.
1.1	2
6.1	3	Here is a little example on how the create an EOAdaptor:
	4
7.1	5	Creating an EOAdaptor can be very straightforward (or very complicated)
8.1	6	depending on the underlying data source. In this example, and for the
	7	sake of keeping thing simple, I'm using the file system as a data source
	8	(well, at least, how java.io.File sees it).
	9	At a bare minimum you need to implement three classes: EOAdaptor,
	10	EOAdaptorContext, EOAdaptorChannel.
6.1	11
8.1	12	~[[[EOAdaptor JavaDoc>>url:http://wocommunity.org/documents/javadoc/WebObjects/5.4.2/com/webobjects/eoaccess/EOAdaptor.html?is-external=true\|\|shape="rect"]]]
6.1	13
7.1	14	Not much in here. The EOAdaptor is mostly a rendezvous point to access
8.1	15	other functionality in your adaptor. You need to implement a couple of
	16	abstract methods though:
6.1	17
8.1	18	(% class="alternate" %)
7.1	19	* assertConnectionDictionaryIsValid() to check the validity of a
8.1	20	connection dictionary.
6.1	21	* createAdaptorContext() to create your own EOAdaptorContext instance.
	22	* defaultExpressionClass() to return a relevant EOSQLExpression class.
7.1	23	* isValidQualifierType() to decide if a qualifier can be used in a SQL
8.1	24	where clause.
6.1	25	* synchronizationFactory() to return a EOSchemaGeneration helper.
	26
	27	In the case of a file system there is not much to do:
	28
	29	{{code}}
	30
7.1	31	public void assertConnectionDictionaryIsValid()
6.1	32	{
	33	}
7.1	34
6.1	35	public EOAdaptorContext createAdaptorContext()
	36	{
	37	return new FSAdaptorContext( this );
	38	}
7.1	39
6.1	40	public Class defaultExpressionClass()
	41	{
	42	throw new UnsupportedOperationException
	43	( "FSAdaptor.defaultExpressionClass" );
	44	}
7.1	45
6.1	46	public EOSQLExpressionFactory expressionFactory()
	47	{
	48	throw new UnsupportedOperationException
	49	( "FSAdaptor.expressionFactory" );
	50	}
7.1	51
6.1	52	public boolean isValidQualifierType(String aTypeName, EOModel aModel)
	53	{
	54	return true;
	55	}
7.1	56
6.1	57	public EOSchemaGeneration synchronizationFactory()
	58	{
	59	throw new UnsupportedOperationException
	60	( "FSAdaptor.synchronizationFactory" );
	61	}
	62
	63	{{/code}}
	64
	65	The only important method is createAdaptorContext().
	66
8.1	67	~[[[EOAdaptorContext JavaDoc>>url:http://wocommunity.org/documents/javadoc/WebObjects/5.4.2/com/webobjects/eoaccess/EOAdaptorContext.html?is-external=true\|\|shape="rect"]]]
6.1	68
7.1	69	The adaptor context handles "transactions". It's usually pretty simple
8.1	70	if your data store support that concept. Not much to do here for a file
	71	system:
6.1	72
	73	{{code}}
	74
7.1	75	public void beginTransaction()
6.1	76	{
	77	if ( _hasTransaction == false )
	78	{
	79	_hasTransaction = true;
	80
	81	this.transactionDidBegin();
	82	}
	83	}
7.1	84
6.1	85	public void commitTransaction()
	86	{
	87	if ( _hasTransaction == true )
	88	{
	89	_hasTransaction = false;
7.1	90
6.1	91	this.transactionDidCommit();
	92	}
	93	}
7.1	94
6.1	95	public EOAdaptorChannel createAdaptorChannel()
	96	{
	97	return new FSAdaptorChannel( this );
	98	}
7.1	99
6.1	100	public void handleDroppedConnection()
	101	{
	102	}
	103
	104	public void rollbackTransaction()
	105	{
	106	throw new UnsupportedOperationException
	107	( "FSAdaptorContext.rollbackTransaction" );
	108	}
	109
	110	{{/code}}
	111
7.1	112	Again createAdaptorChannel() is the only method that you really care
8.1	113	about in this case.
6.1	114
8.1	115	~[[[EOAdaptorChannel JavaDoc>>url:http://wocommunity.org/documents/javadoc/WebObjects/5.4.2/com/webobjects/eoaccess/EOAdaptorChannel.html?is-external=true\|\|shape="rect"]]]
6.1	116
7.1	117	That's the real thing. It's where most of the work is done. It's
8.1	118	important to get this one right. Depending on your back end, it's simply
	119	an exercise in translating EOQualifiers into something that your data
	120	storage will understand. Here a the most important methods:
6.1	121
8.1	122	(% class="alternate" %)
7.1	123	* deleteRowsDescribedByQualifier() to handle deletion of "row" or
8.1	124	something equivalent.
6.1	125	* insertRow() to create a "row".
	126	* updateValuesInRowsDescribedByQualifier() to update a "row".
	127
7.1	128	Finally, fetching "rows" is a two steps process: first you need to setup
8.1	129	the "context" of what you are going to fetch and then fetch it:
6.1	130
8.1	131	(% class="alternate" %)
6.1	132	* selectAttributes() is where you set your fetch "context".
	133	* fetchRow is the actual fetching one row at the time.
	134
	135	In the case of a file system here is what you could have:
	136
8.1	137	(% class="alternate" %)
7.1	138	* deleteRowsDescribedByQualifier will delete some files (aka "rows"
8.1	139	based) on a qualifier.
6.1	140
	141	{{code}}
	142
7.1	143	public int deleteRowsDescribedByQualifier(EOQualifier aQualifier,
6.1	144	EOEntity anEntity)
	145	{
	146	if ( aQualifier != null )
	147	{
	148	if ( anEntity != null )
	149	{
7.1	150	NSArray someFiles =
6.1	151	FSQualifierHandler.filesWithQualifier( aQualifier );
7.1	152
6.1	153	if ( someFiles != null )
	154	{
	155	someFiles = this.filteredArrayWithEntity( someFiles, anEntity );
7.1	156
6.1	157	if ( someFiles != null )
	158	{
	159	int count = someFiles.count();
	160	int counter = 0;
7.1	161
6.1	162	for ( int index = 0; index < count; index++ )
	163	{
	164	File aFile = (File) someFiles.objectAtIndex( index );
7.1	165
6.1	166	if ( aFile.delete() == true )
	167	{
	168	counter += 1;
	169	}
	170	}
7.1	171
6.1	172	return counter;
	173	}
	174	}
	175
	176	return 0;
	177	}
	178
	179	throw new IllegalArgumentException
	180	( "FSAdaptorChannel.deleteRowsDescribedByQualifier: null entity." );
	181	}
	182
	183	throw new IllegalArgumentException
	184	( "FSAdaptorChannel.deleteRowsDescribedByQualifier: null qualifier." );
	185	}
	186
	187	{{/code}}
	188
8.1	189	(% class="alternate" %)
	190	* insertRow will create a file or directory.
6.1	191
	192	{{code}}
	193
7.1	194	public void insertRow(NSDictionary aRow, EOEntity anEntity)
6.1	195	{
	196	if ( aRow != null )
	197	{
	198	if ( anEntity != null )
	199	{
	200	String aPath = (String) aRow.objectForKey( "absolutePath" );
7.1	201
6.1	202	if ( aPath != null )
	203	{
	204	File aFile = new File( aPath );
7.1	205
6.1	206	try
	207	{
	208	if ( anEntity.name().equals( "FSDirectory" ) == true )
	209	{
	210	aFile.mkdirs();
	211	}
	212	else
	213	{
	214	aFile.createNewFile();
	215	}
	216	}
	217	catch(Exception anException)
	218	{
	219	throw new RuntimeException
	220	( "FSAdaptorChannel.insertRow: " + anException );
	221	}
7.1	222
6.1	223	return;
	224	}
	225
	226	throw new IllegalArgumentException
	227	( "FSAdaptorChannel.insertRow: null absolutePath." );
	228	}
	229
	230	throw new IllegalArgumentException
	231	( "FSAdaptorChannel.insertRow: null entity." );
	232	}
7.1	233
6.1	234	throw new IllegalArgumentException
	235	( "FSAdaptorChannel.insertRow: null row." );
	236	}
	237
	238	{{/code}}
	239
8.1	240	(% class="alternate" %)
	241	* updateValuesInRowsDescribedByQualifier will change a file attributes.
6.1	242
	243	{{code}}
	244
7.1	245	public int updateValuesInRowsDescribedByQualifier(NSDictionary
6.1	246	aRow, EOQualifier aQualifier, EOEntity anEntity)
	247	{
	248	if ( aRow != null )
	249	{
	250	if ( aQualifier != null )
	251	{
	252	if ( anEntity != null )
	253	{
7.1	254	NSArray someFiles =
6.1	255	FSQualifierHandler.filesWithQualifier( aQualifier );
7.1	256
6.1	257	if ( someFiles != null )
	258	{
	259	someFiles = this.filteredArrayWithEntity( someFiles, anEntity );
7.1	260
6.1	261	if ( someFiles != null )
	262	{
	263	int count = someFiles.count();
7.1	264
6.1	265	for ( int index = 0; index < count; index++ )
	266	{
	267	File aFile = (File) someFiles.objectAtIndex( index );
	268	NSArray someKeys = aRow.allKeys();
	269	int keyCount = someKeys.count();
7.1	270
6.1	271	for ( int keyIndex = 0; keyIndex < count; keyIndex++ )
	272	{
	273	Object aKey = someKeys.objectAtIndex( keyIndex );
7.1	274	EOAttribute anAttribute =
6.1	275	anEntity.attributeNamed( aKey.toString() );
7.1	276
6.1	277	if ( anAttribute != null )
	278	{
	279	Object aValue = aRow.objectForKey( aKey );
7.1	280
	281
	282	NSKeyValueCoding.DefaultImplementation.takeValueForKey( aFile, aValue,
6.1	283	anAttribute.columnName() );
	284	}
	285	}
7.1	286
6.1	287	}
7.1	288
6.1	289	return count;
	290	}
	291	}
	292
	293	return 0;
	294	}
	295
	296	throw new IllegalArgumentException
7.1	297	( "FSAdaptorChannel.updateValuesInRowsDescribedByQualifier: null
6.1	298	entity." );
	299	}
7.1	300
6.1	301	throw new IllegalArgumentException
7.1	302	( "FSAdaptorChannel.updateValuesInRowsDescribedByQualifier: null
6.1	303	qualifier." );
	304	}
7.1	305
6.1	306	throw new IllegalArgumentException
	307	( "FSAdaptorChannel.updateValuesInRowsDescribedByQualifier: null row." );
	308	}
	309
	310	{{/code}}
	311
8.1	312	(% class="alternate" %)
	313	* selectAttributes will retrieve some files based on a qualifier.
6.1	314
	315	{{code}}
	316
7.1	317	public void selectAttributes(NSArray someAttributes,
	318	EOFetchSpecification aFetchSpecification, boolean shouldLock, EOEntity
6.1	319	anEntity)
	320	{
	321	if ( someAttributes != null )
	322	{
	323	this.setAttributesToFetch( someAttributes );
7.1	324
6.1	325	if ( aFetchSpecification != null )
	326	{
	327	if ( anEntity != null )
	328	{
7.1	329	NSArray someFiles =
6.1	330	FSQualifierHandler.filesWithQualifier( aFetchSpecification.qualifier() );
7.1	331
6.1	332	if ( someFiles != null )
	333	{
	334	NSArray someSortOrderings = aFetchSpecification.sortOrderings();
7.1	335
6.1	336	if ( someSortOrderings != null )
	337	{
7.1	338	someFiles =
	339	EOSortOrdering.sortedArrayUsingKeyOrderArray( someFiles,
6.1	340	someSortOrderings );
	341	}
7.1	342
6.1	343	someFiles = this.filteredArrayWithEntity( someFiles, anEntity );
7.1	344
6.1	345	if ( someFiles != null )
	346	{
	347	this.files().addObjectsFromArray( someFiles );
	348	}
	349	}
7.1	350
6.1	351	return;
	352	}
	353
	354	throw new IllegalArgumentException
	355	( "FSAdaptorChannel.selectAttributes: null entity." );
	356	}
	357
	358	throw new IllegalArgumentException
	359	( "FSAdaptorChannel.selectAttributes: null fetch specification." );
	360	}
7.1	361
6.1	362	throw new IllegalArgumentException
	363	( "FSAdaptorChannel.selectAttributes: null attributes." );
	364	}
	365
	366	{{/code}}
	367
8.1	368	(% class="alternate" %)
	369	* fetchRow will "fetch" a dictionary representation of a file.
6.1	370
	371	{{code}}
	372
7.1	373	public NSMutableDictionary fetchRow()
6.1	374	{
	375	File aFile = (File) this.files().lastObject();
7.1	376
6.1	377	if ( aFile != null )
	378	{
	379	this.files().removeLastObject();
7.1	380
	381	return this.dictionaryForFileWithAttributes( aFile,
6.1	382	this.attributesToFetch() );
	383	}
7.1	384
6.1	385	return null;
	386	}
	387
	388	{{/code}}
	389
7.1	390	That could be it. Nothing to involved. However there is two extra
8.1	391	methods that make sense to implement: describeTableNames and
	392	describeModelWithTableNames.
6.1	393
8.1	394	(% class="alternate" %)
7.1	395	* describeTableNames() return an array of "table" (or something
8.1	396	conceptually equivalent) existing in you data back end.
7.1	397	* describeModelWithTableNames() will create a default model for some of
8.1	398	these "tables".
6.1	399
7.1	400	This is very useful to get you started in EOModeler instead of having to
8.1	401	create the entire model by hand. In the case of a file system, there is
	402	only one model:
6.1	403
	404	{{code}}
	405
7.1	406	public EOModel describeModelWithTableNames(NSArray anArray)
6.1	407	{
	408	return new EOModel( this.defaultModelPath() );
	409	}
	410
	411	{{/code}}
	412
	413	And voilà. No you have a toy file system adaptor (aka JavaFSAdaptor).
	414
8.1	415	(% class="alternate" %)
7.1	416	* To "fetch" some files, simply create a qualifier with some path
8.1	417	attributes (eg absolutePath):
6.1	418
	419	{{code}}
	420
	421	EOQualifier aPathQualifier = new EOKeyValueQualifier
	422	( "absolutePath", EOQualifier.QualifierOperatorEqual, System.getProperty
	423	( "user.home" ) );
	424
	425	{{/code}}
	426
8.1	427	(% class="alternate" %)
	428	* To get all the files in a directory, use the "parent" attribute:
6.1	429
	430	{{code}}
	431
7.1	432	EOQualifier aPathQualifier = new EOKeyValueQualifier( "parent",
6.1	433	EOQualifier.QualifierOperatorEqual, System.getProperty( "user.home" ) );
	434
	435	{{/code}}
	436
7.1	437	Once you have your qualifier, simply build a fetch specification for it
8.1	438	and get your "file" EOs:
6.1	439
	440	{{code}}
	441
	442	EOFetchSpecification aFetchSpecification = new EOFetchSpecification
	443	( "FSDirectory", aQualifier, null );
7.1	444	NSArray someObjects =
6.1	445	anEditingContext.objectsWithFetchSpecification( aFetchSpecification );
	446
	447	{{/code}}
	448
7.1	449	You can use FSFile to retrieve files only. FSDirectory for, er,
8.1	450	directories. And FSItem for both. FSDirectory have two handy
	451	relationships: "files" and "directories". Check the attached model.
6.1	452
8.1	453	(% class="alternate" %)
7.1	454	* To "create" a file (or directory), you can do something along those
8.1	455	lines:
6.1	456
	457	{{code}}
	458
7.1	459	EOClassDescription aClassDescription =
6.1	460	EOClassDescription.classDescriptionForEntityName( "FSDirectory" );
7.1	461	EOEnterpriseObject anObject =
	462	aClassDescription.createInstanceWithEditingContext( anEditingContext,
6.1	463	null );
7.1	464
6.1	465	anObject.takeValueForKey
	466	( "/Users/rszwarc/tmp/JavaFSAdaptor/TestFSDirectory", "absolutePath" );
7.1	467
6.1	468	anEditingContext.insertObject( anObject );
7.1	469
6.1	470	anEditingContext.saveChanges();
	471
	472	{{/code}}
	473
8.1	474	(% class="alternate" %)
	475	* Finally, do delete a file:
6.1	476
	477	{{code}}
	478
	479	anEditingContext.deleteObject( anObject );
	480
	481	anEditingContext.saveChanges();
	482
	483	{{/code}}

Wiki source code of EOF-Using EOF-Custom EOAdaptor

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