в 17:44, 31 мая 2010

2010-05-31T17:44:26Z

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2010-05-31T15:19:22Z

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== Get annotation by Annotation class ==



<source lang="java">
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@interface MySingle {
int value(); // this variable name must be value
}
class Single {
@MySingle(100)
public static void myMeth() {
Single ob = new Single();
try {
Method m = ob.getClass().getMethod("myMeth");
MySingle anno = m.getAnnotation(MySingle.class);
System.out.println(anno.value()); // displays 100
} catch (NoSuchMethodException exc) {
System.out.println("Method Not Found.");
}
}
public static void main(String args[]) {
myMeth();
}
}</source>



== Get annotation by type ==



<source lang="java">
import java.lang.annotation.Annotation;
import javax.ejb.Entity;
public class GetAnnotation {
public static void main(String[] args) {
Annotation[] as = Person.class.getAnnotations();
for(int i=0;i<as.length;i++){
System.out.println(as[i].annotationType());
}
Annotation a =Person.class.getAnnotation(Entity.class);
System.out.println(a);
Annotation[] das = Person.class.getDeclaredAnnotations();
for(int i=0;i<das.length;i++){
System.out.println(das[i].annotationType());
}
}
}

///

import javax.ejb.Entity;
import javax.ejb.AccessType;
import javax.ejb.Id;
import javax.ejb.GeneratorType;
import java.io.Serializable;
@Entity(access = AccessType.FIELD)
public class Person implements Serializable {
@Id(generate = GeneratorType.AUTO)
Integer id;
String name;
}</source>



== Show all annotations for a class and a method. ==



<source lang="java">
import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnno {
String str();
int val();
}
@Retention(RetentionPolicy.RUNTIME)
@interface What {
String description();
}
@What(description = "An annotation test class")
@MyAnno(str = "Meta2", val = 99)
class Meta2 {
@What(description = "An annotation test method")
@MyAnno(str = "Testing", val = 100)
public static void myMeth() {
Meta2 ob = new Meta2();
try {
Annotation annos[] = ob.getClass().getAnnotations();
System.out.println("All annotations for Meta2:");
for (Annotation a : annos)
System.out.println(a);
Method m = ob.getClass().getMethod("myMeth");
annos = m.getAnnotations();
System.out.println("All annotations for myMeth:");
for (Annotation a : annos)
System.out.println(a);
} catch (NoSuchMethodException exc) {
System.out.println("Method Not Found.");
}
}
public static void main(String args[]) {
myMeth();
}
}</source>



== Use reflection to display the annotation associated with a method. ==



<source lang="java">
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnno {
String str();
int val();
}
class Meta {
@MyAnno(str = "Annotation Example", val = 100)
public static void myMeth() {
Meta ob = new Meta();
try {
Class c = ob.getClass();
Method m = c.getMethod("myMeth");
MyAnno anno = m.getAnnotation(MyAnno.class);
System.out.println(anno.str() + " " + anno.val());
} catch (NoSuchMethodException exc) {
System.out.println("Method Not Found.");
}
}
public static void main(String args[]) {
myMeth();
}
}</source>

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Java Tutorial/Reflection/Annotation - История изменений

в 17:44, 31 мая 2010

Admin: 1 версия