如何让不添加任何code类配置？ [英] How to make a class configurable without adding any code?

问题描述

我希望能够写（在Java中）类似如下：

I would like to be able to write (in Java) something like the following:

public class A implements MagicallyConfigurable {

    @configuration_source_type{"xml"}
    @configuration_dir{"some/rel/path/"}

    /* or maybe some other annotations specifying a db-based configuration etc. */

    int length = 4 /* some kind of default */;
    char c = '*' /* some kind of default */;

    @do_not_configure
    String title;

    A(String title) {

        /* possibly, but hopefully no need to, something like:
        configure();
        call here. */

        this.title = title;
    }

    void goForIt() {
        System.out.println(title);
        for(int i=0; i < length; i++) {
            System.out.print(c);
        }
    }
}

和按预期工作。也就是说，我需要根据配置将加入​​一些注解，实现接口，并可能使一个函数调用（但不希望它）来初始化领域的唯一的事情。

and for it to work as expected. That is, the only thing I would need to initialize fields based on a configuration would be adding some annotations, implementing an interface and possibly making a single function call (but hopefully without it).

我敢肯定，这在理论上是可行的，问题在于是否有一个现有的库/框架/插件/的thingie这使得它。 （也许阿帕奇commons.configuration不知何故？有没有与它之前的工作。）

I'm sure this is theoretically doable, the question is whether there's an existing library/framework/add-on/thingie which enables it. (Maybe Apache commons.configuration somehow? Haven't worked with it before.)

推荐答案

你能做什么，是使用Spring 3.0 EL。一个例子可以在这里找到 ，但它是什么基本上可以归结为是，你可以做到以下几点：

What you can do, is to use Spring 3.0 EL. An example can be found here, but what it basically boils down to is that you can do the following:

@Value("#{systemProperties.databaseName}")
public void setDatabaseName(String dbName) { ... }

和您的属性将被自动设置。这将工作的制定者和属性。

And your properties will be automatically set. This will work on setters and on properties.

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