如何在 Java 9 中使用新的 BeanInfo 注释

Question

JEP 256: BeanInfo Annotations provides for JavaBean and BeanProperty annotations. While there is not much documentation, I have been hoping this would allow us to use annotations to designate fields on a class as being JavaBean-style properties without having to create boilerplate getter/setter accessor/mutator methods.

所以这个：

public class Person {

    private String name ;

    public String getName( ) {
        return this.name ;
    }

    public void setName( String nameArg ) {
        this.name = nameArg ;
    }

}

……会变成这样：

import java.beans.BeanProperty;

public class Person {

    @BeanProperty
    public String name ;

}

然而，当我在 IntelliJ 2017.2.2 的 Java 9 项目中尝试此操作时，我在“@”注释的 IDE 中收到错误消息：

'@BeanProperty' not applicable to field

编译器报告错误：

Error:(8, 5) java: annotation type not applicable to this kind of declaration

➠ 我是否误解了这些新注释的用途？还是我有语法问题？

除了上面链接的 JEP 和 JavaDoc，我没有找到任何文档。

我正在试验 Java 9 的最新候选版本，目前在 macOS Sierra 10.12.6 上是 Java 9+181。

Answer 1

出于所有原因，javadoc says BeanProperty is @Target(METHOD). Looks like it’s a way to customize PropertyDescriptors without having to create a BeanInfo implementation. I don’t think it was intended to work like Lombok. (And thank goodness—see Why use getters and setters? 显式方法是一个好主意。）

如何在 Java 9 中使用新的 BeanInfo 注释

How to use new BeanInfo Annotations in Java 9

java

annotations

properties

javabeans

jep-256