Java Tutorial/Language/Annotations Reflection
Содержание
Getting all annotations for 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; // A simple annotation type. @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation {
String stringValue(); int intValue();
} @Retention(RetentionPolicy.RUNTIME) @interface What {
String description();
} @What(description = "An annotation test class") @MyAnnotation(stringValue = "for class", intValue = 100) public class MainClass {
// Annotate a method.
@What(description = "An annotation test method")
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod() {
}
public static void main(String[] arg) {
try {
MainClass ob = new MainClass();
Method m = ob.getClass( ).getMethod("myMethod");
Annotation[] annos = m.getAnnotations();
System.out.println("All annotations for myMeth:");
for(Annotation a : annos)
System.out.println(a);
} catch (Exception exc) {
}
}
}</source>
All annotations for myMeth: @What(description=An annotation test method) @MyAnnotation(stringValue=Annotation Example, intValue=100)
Obtaining All Annotations: getAnnotations( )
<source lang="java">
import java.lang.annotation.Annotation; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; // A simple annotation type. @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation {
String stringValue(); int intValue();
} @Retention(RetentionPolicy.RUNTIME) @interface What {
String description();
} @What(description = "An annotation test class") @MyAnnotation(stringValue = "for class", intValue = 100) public class MainClass {
// Annotate a method.
@What(description = "An annotation test method")
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod(String str, int i) {
}
public static void main(String[] arg) {
try {
MainClass ob = new MainClass();
Annotation[] annos = ob.getClass().getAnnotations();
System.out.println("All annotations for Meta2:");
for(Annotation a : annos)
System.out.println(a);
} catch (Exception exc) {
}
}
}</source>
All annotations for Meta2: @MyAnnotation(stringValue=for class, intValue=100) @What(description=An annotation test class)
Obtaining Annotations at Run Time by Use of Reflection
<source lang="java">
import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.reflect.Method; // A simple annotation type. @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation {
String stringValue(); int intValue();
} public class MainClass {
// Annotate a method.
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod() {
}
public static void main(String[] a) {
try {
MainClass ob = new MainClass();
Class c = ob.getClass();
Method m = c.getMethod("myMethod");
MyAnnotation anno = m.getAnnotation(MyAnnotation.class);
System.out.println(anno.stringValue() + " " + anno.intValue());
} catch (NoSuchMethodException exc) {
System.out.println("Method Not Found.");
}
}
}</source>
Annotation Example 100
Reflection: getMethod( ) with parameters
<source lang="java">
import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.reflect.Method; // A simple annotation type. @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation {
String stringValue(); int intValue();
} public class MainClass {
// Annotate a method.
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod(String str, int i) {
}
public static void main(String[] a) {
try {
MainClass ob = new MainClass();
Class c = ob.getClass();
Method m = c.getMethod("myMethod", String.class, int.class);
MyAnnotation anno = m.getAnnotation(MyAnnotation.class);
System.out.println(anno.stringValue() + " " + anno.intValue());
} catch (NoSuchMethodException exc) {
System.out.println("Method Not Found.");
}
}
}</source>
Annotation Example 100
