如何对动态填充注解 [英] How-to dynamically fill a annotation

问题描述

可悲的是，我忘了今天接受来自工作code和我在一起。但也许这个小例子来阐明的东西。

Sadly, I forgot to take the code from work with me today. But maybe this little example will clarify things.

我使用Hibernate映射一个bean来表。

I use hibernate to map a bean to a table.

示例：

import javax.persistence.column;
….
String columnameA;
….
@Column(name="columnameA")
public String getColumname(){
  return columnameA
}
….

我不想硬code中的COLUMNNAME在我的源代码code（ columnameA 的），因为我需要切换columname无需构建整个项目。
我想用这样的：

I do not want to hardcode the columnname ("columnameA") in my sourcecode, because I need to switch the columname without building the entire project. I wanted to use something like:

@Column(name=getColumnName())

这是行不通的。的想法是，要在JNDI树的地方写COLUMNNAME，并在启动时使用它。所以我只需要重新启动才能改变COLUMNNAME应用程序。

This does not work. The idea is, to to write the columnname somewhere in the jndi tree and use it at startup. So i only need to restart the application to change the columnname.

解决这个问题的唯一途径 - 这是我能想到的 - 是我自己写的注释，它扩展了休眠类。是否有这样做的一个简单的方法？

The only way around this problem – which I can think of – is to write my own annotation, which extends the hibernate class. Is there a simpler way of doing this?

推荐答案

您不能用注解达到这个目的，但你的具体问题的解决方案是实现自定义的 NamingStrategy ：

You can't achieve this with annotations, but a solution to your specific problem is to implement a custom NamingStrategy:

public class NamingStrategyWrapper implements NamingStrategy {
    private NamingStrategy target;

    public NamingStrategyWrapper(NamingStrategy target) {
        this.target = target;
    }

    public String columnName(String arg0) {
        if ("columnameA".equals(arg0)) return getColumnName();
        else return target.columnName(arg0);        
    }

    ...
}

-

AnnotationConfiguration cfg = new AnnotationConfiguration();
cfg.setNamingStrategy(new NamingStrategyWrapper(cfg.getNamingStrategy()));
factory = cfg.configure().buildSessionFactory();

这篇关于如何对动态填充注解的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！