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Wiki source code of EOF-Using EOF-Fetching

Last modified by David Avendasora on 2010/09/11 23:52
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1 == Overview ==
2
3 There are many ways to specify what Entities to fetch using EOF.
4
5 1. Model a Fetch Specification in EntityModeler
6 1. Create a FetchSpecification in code
7 1. Use EOUtilities helper methods
8 1. User helper fetch methods in your Entity.java (if generated using a more advanced EOGenerator* template).
9
10 *EOGenerator, Velocity EOGenerator, JavaEOGenerator
11
12 For complete details please read the [[EOF Documentation>>url:http://developer.apple.com/documentation/WebObjects/Enterprise_Objects/About/chapter_1_section_1.html||shape="rect"]], the rest of this article will give some simple examples of the different kinds of fetches.
13
14 == Examples ==
15
16 === Model a Fetch Specification in EntityModeler ===
17
18 ==== Create the Fetch Specfication ====
19
20 ~1. Open your model in EntityModeler and select an Entity to define a fetch spec for.
21 2. Click on the "New Fetch Specification" tool bar button.
22 3. In the Properties tab, give the new Fetch Specification a name. ie: userForLoginCredentials
23 4. Enter a qualifier string in the text area provided. ie:
24
25 {{code}}
26 (username = $username) and (password = $password)
27 {{/code}}
28
29 Binding variables (eg: $username) will be replaced by user supplied values when the Fetch Specification is called.
30
31 ==== Fetch using a Modeled Fetch Specification ====
32
33 {{code}}
34
35 String username; //Assume exists
36 String password; //Assume exists
37 EOEditingContext editingContext; //Assume exists
38 NSMutableDictionary bindings = new NSMutableDictionary();
39 bindings.takeValueForKey(username, Person.USERNAME_KEY);
40 bindings.takeValueForKey(password, Person.PASSWORD_KEY);
41 String fetchSpecName = "userForLoginCredentials";
42 String entityName = Person.ENTITY_NAME;
43 NSArray objects = EOUtilities.objectsWithFetchSpecificationAndBindings(editingContext, entityName, fetchSpecName, bindings);
44
45 {{/code}}
46
47 === Create a Fetch Specification in code ===
48
49 ==== Build a simple qualifier ====
50
51 {{code}}
52 EOKeyValueQualifier qualifier = new EOKeyValueQualifier(keyName, EOQualifier.QualifierOperatorEqual, value);
53 {{/code}}
54
55 ==== Build a more complex qualifier ====
56
57 {{code}}
58
59 EOKeyValueQualifier qual1 = new EOKeyValueQualifier(keyName1, EOQualifier.QualifierOperatorEqual, value1);
60 EOKeyValueQualifier qual2 = new EOKeyValueQualifier(keyName2, EOQualifier.QualifierOperatorEqual, value2);
61 EOAndQualifier finalQual = new EOAndQualifier(new NSArray(new object[] {qual1, qual2}));
62
63 {{/code}}
64
65 ==== Build a Fetch Specification ====
66
67 {{code}}
68
69 NSArray sortOrderings; // Assume Exists (or null for no defined sort)
70 EOQualifier qualifier; // Assume Exists (or null for all objects)
71 EOFetchSpecification fetchSpec = new EOFetchSpecification("EntityName", qualifier, sortOrderings);
72
73 {{/code}}
74
75 ==== Fetch with the Fetch Specification ====
76
77 {{code}}
78
79 String username; //Assume exists
80 String password; //Assume exists
81 EOEditingContext editingContext; //Assume exists
82 EOKeyValueQualifier usernameQual = new EOKeyValueQualifier(Person.USERNAME_KEY, EOQualifier.QualifierOperatorEqual, username);
83 EOKeyValueQualifier passwordQual = new EOKeyValueQualifier(Person.PASSWORD_KEY, EOQualifier.QualifierOperatorEqual, password);
84 EOAndQualifier credentialsQual = new EOAndQualifier(new NSArray(new object[] {usernameQual, passwordQual}));
85 EOFetchSpecification userForCredentialsFetchSpec = new EOFetchSpecification(Person.ENTITY_NAME, credentialsQual, null);
86 NSArray fetchedObjects = editingContext.objectsWithFetchSpecification(userForCredentialsFetchSpec);
87
88 {{/code}}
89
90 === EOUtilities ===
91
92 [[EOUtilities>>url:http://developer.apple.com/documentation/WebObjects/Reference/WO53_Reference/com/webobjects/eoaccess/EOUtilities.html||shape="rect"]] has several helper methods for simplifying your fetchs, we've already used "objectsWithFetchSpecificationAndBindings" above.
93
94 Also look at:
95
96 {{code}}String username; //Assume exists
97 EOEditingContext editingContext; //Assume exists
98 EOEnterpriseObject eo = EOUtilities.objectMatchingKeyAndValue(editingContext, Person.ENTITY_NAME, Person.USERNAME_KEY, username);{{/code}}
99
100 {{code}}EOEditingContext editingContext; //Assume exists
101 NSDictionary bindings; //Assume exists
102 EOEnterpriseObject eo = EOUtilities.objectMatchingValues(editingContext, Person.ENTITY_NAME, bindings);{{/code}}
103
104 {{code}}EOEditingContext editingContext; //Assume exists
105 NSArray objects = EOUtilities.objectsForEntityNamed(editingContext, Person.ENTITY_NAME);{{/code}}
106
107 {{code}}String username; //Assume exists
108 EOEditingContext editingContext; //Assume exist
109 NSArray objects = EOUtilities.objectsMatchingKeyAndValue(editingContext, Person.ENTITY_NAME, Person.USERNAME_KEY, username);{{/code}}
110
111 {{code}}
112
113 EOEditingContext editingContext; //Assume exists
114 NSDictionary bindings; //Assume exists
115 NSArray objects = EOUtilities.objectsMatchingValues(editingContext, Person.ENTITY_NAME, bindings);
116
117 {{/code}}
118
119 === EOGenerator Template Helper Methods. ===
120
121 Depending on your EOGenerator [[templates>>doc:WOL.Home.EOGenerator.EOGenerator Templates and Additions.WebHome]] you may have auto generated methods in your _Entity.java class that will make fetching objects easier. Look for methods like:
122
123 {{code}}EOEditingContext editingContext; //Assume exists
124 NSArray people Person.fetchAllPeople(editingContext);{{/code}}
125
126 {{code}}
127
128 EOEditingContext editingContext; //Assume exists
129 EOQualifier qualifer; //Assume exists
130 NSArray people Person.fetchPeople(editingContext, qualifier);
131
132 {{/code}}