|
|
| Java Developers Desk: Annotations |
|
@Test_Target(doTestElement=”Hi ! How r
you”)
^
Error in javac compilation
2) Retention annotation:
These types of annotation specify where and
how long annotation with this types are to be
retained. There are three type of Retention
annotations are of three types.
- RetentionPolicy.SOURCE: This type of
annotation will be retained only at
source level and the compiler will ignore
them.
- RetentionPolicy.CLASS: This type of
annotation will be retained at the
compile time the virtual machine (VM) will
ignore them.
- RetentionPolicy.RUNTIME: Virtual
machine will retained the annotation of
this type and they can be read only at
run-time.
- Lets demonstrate that how this type of
annotations are applied by taking an
example using RetentionPolicy.RUNTIME.
Example:
@Retention(RetentionPolicy.RUNTIME)
public @interface Retention_Demo {
String doRetentionDemo();
} |
This example uses the annotation type @Retention(RetentionPolicy.RUNTIME) that
indicates the VM will retained your
Retention_Demo annotation so that it can be
read effectively at run-time.
3) Documented annotation:
This type of annotation should be documented
by the javadoc tool. javadoc does not include
the annotation by default. Include the
|
|
annotation type information by using @Documented in the generated document. In
this type of annotation all the processing is done
by javadoc-like tool.
The given example demonstrates the use of
the @Documented annotations.
Example:
@Documented
public @interface Documented_Demo {
String doTestDocumentedDemo();
}
Next, make changes in Test_Annotations class
as follows:
public class Test_Annotations {
public static void main(String arg[]) {
new
Test_Annotations().doTestRetentionDemo();
new
Test_Annotations().doTestDocumentedDemo();
}
@Retention_Demo
(doTestRetentionDemo=”Hello retention
annotation”)
public void doTestRetentionDemo() {
System.out.printf(“Testing ‘Retention’
annotation”);
}
@Documented_Demo
(doTestDocumentedDemo=”Hello Test
documentation”)
public void doTestDocumentedDemo() {
System.out.printf(“Testing ‘Documented’
annotation”);
}} |
4) Inherited Annotation:
This annotation is little bit complex. It inherits
the annotated class automatically. If you specify
@Inherited tag before defining a class then
apply the annotation at your class and finally
extend the class then the child class inherits the properties of the parent class automatically.
Lets demonstrate the benefits of using the
|
|
|
|
Jan 2008 | Java Jazz Up | 11 |
| |
|
| |
| View All Topics |
| All Pages of this Issue |
Pages:
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
23,
24,
25,
26,
27,
28,
29,
30,
31,
32,
33,
34,
35,
36,
37,
38,
39,
40,
41,
42,
43,
44,
45,
46,
47,
48,
49,
50,
51,
52,
53 ,
54,
55,
56,
57,
58,
59,
60,
61,
62,
63 ,
64,
65 ,
66 ,
67 ,
68 ,
69 ,
70 ,
71 ,
72 ,
73 ,
74 ,
75 ,
76 ,
77 ,
78 ,
79 ,
80 ,
81 ,
82 ,
83,
84 ,
85 ,
86,
87 ,
88,
89 ,
90 ,
91 ,
92 ,
93 ,
94 ,
95 ,
96 ,
97 ,
98 ,
99 ,
100 ,
101 ,
102 ,
103,
104 ,
105 ,
106,
107,
Download PDF |
|
|
|
|
|
|
| |
| |
|
