@interface
Use this annotation can be customized annotation, the class name is the annotation name. Can define custom annotations in the method, all the methods are no arguments no modifier, the return value is the basic data types, String, Classs, Annotation, Enum or a corresponding array.
Methods default setting default values.
Use annotations
The method may direct a single annotation annotation name ( value) method used
Multi-use method is annotated name (name = value method, the method name = value ...)
When there is a default value assignment process may not be displayed.
format
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface method name {
// value as a parameter, meaning the entry statement is to define a string value type parameter , a default value is empty
String value() default “”;
boolean isAlive() default false;
}
@Retention
Retention level defined annotations. ---- that is, when to use the annotation
His value is RetentionPolicy type, there are three values
The SOURCE : the presence of coding stage
The CLASS : stage compiling notes remain in the class file, need to keep the VM is running
RUNTIME : stage compiling notes remain in the class file remains comment VM runtime
@Target
Define the role of annotation objects. ---- That is where the use of the annotation
It ranges ElementType type, of the type commonly
The TYPE : class, interface (including notes), enumeration
The FIELD : member variables
The METHOD : member method
The PARAMETER : method parameters
ANNOTATION_TYPE : annotated notes
@Documented
Mark custom annotation tool javadoc should be recorded. ---- description that is marked annotated
This meta-annotation type is not a member of the
Related reflection
| The class name |
use |
| Class class |
On behalf of the class of entities in a Java application running represent classes and interfaces |
| Field class |
On behalf of the class member variables (also known as member variables of the class attribute) |
| Method class |
Method represents a class of |
| Constructor class |
Representative class constructor |
Class class
Get the class attribute
getDeclaredFields () : get all the properties of an object
getDeclaredField (String name): of a property objects
Obtaining a class method RELATED
getDeclaredMethods () : get all the class methods
The method of obtaining the relevant class constructor
getDeclaredConstructors () : get all class constructors
The method of obtaining the relevant class notes
getAnnotation (Class <A> annotationClass) : Returns the class object is a public annotation matching the parameter type
Obtain the relevant class method
getSimpleName () : get the name of the class
isAccessible()和setAccessible(true)
1. The isAccessible when () is allowed to access the result of reflection by the field to false
2. When This field private modified value derived isAccessible () is false, must be changed to true can access
3. So setAccessible (true); let's role is to get access to the private variable in the reflection