org.apache.juneau.annotation.BeanConstructor Maven / Gradle / Ivy
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package org.apache.juneau.annotation;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
import java.lang.annotation.*;
import org.apache.juneau.*;
/**
* Maps constructor arguments to property names on beans with read-only properties.
*
*
* This annotation can be used in the case of beans with properties whose values can only be set by passing them in
* through a constructor on the class.
*
Since method parameter names are lost during compilation, this annotation essentially redefines them so that they
* are available at runtime.
*
*
* The definition of a read-only bean is a bean with properties with only getters, like shown below...
*
* public class Person {
* private final String name ;
* private final int age ;
*
* @BeanConstructor (properties="name,age" })
* public Person(String name, int age) {
* this .name = name;
* this .age = age;
* }
*
* // Read only properties.
*
* public String getName() {
* return name ;
* }
*
* public int getAge() {
* return age ;
* }
* }
*
* String json = "{name:'John Smith',age:45}" ;
* Person p = JsonParser.DEFAULT .parse(json);
* String name = p.getName(); // "John Smith"
* int age = p.getAge(); // 45
*
*
*
* This annotation can only be applied to constructors and can only be applied to one constructor per class.
*
*
* When present, bean instantiation is delayed until the call to {@link BeanMap#getBean()}.
* Until then, bean property values are stored in a local cache until getBean() is called.
* Because of this additional caching step, parsing into read-only beans tends to be slower and use more memory than
* parsing into beans with writable properties.
*
*
* Attempting to call {@link BeanMap#put(String,Object)} on a read-only property after calling {@link BeanMap#getBean()}
* will result in a {@link BeanRuntimeException} being thrown.
* Multiple calls to {@link BeanMap#getBean()} will return the same bean instance.
*
*
* Beans can be defined with a combination of read-only and read-write properties.
*/
@Documented
@Target(CONSTRUCTOR)
@Retention(RUNTIME)
@Inherited
public @interface BeanConstructor {
/**
* The names of the properties of the constructor arguments.
*
*
* The number of properties listed must match the number of arguments in the constructor.
*/
String properties() default "";
}