像吸气剂一样使用枚举？

Question

I have a util class that keeps track of important system variables:

public static final String REQUEST_ADDRESS = "http.request.address";  
public static final String REQUEST_PORT = "http.request.port";

public static final String get(String property) {
    return System.getProperty(property);
}

And I can retrieve these values like so:

String port = SystemPropertyHelper.get(SystemPropertyHelper.REQUEST_PORT);

Is it possible, in Java, to get these like an enum?

REQUEST_PORT {
    return System.getProperty("http.request.port");
}

String port = SystemPropertyHelper.REQUEST_PORT;

Answer 1

我会这样解决的。

public static final String REQUEST_PORT = System.getProperty("http.request.port");

Answer 2

        enum SystemPropertyHelper {
            REQUEST_PORT("http.request.port"), ...;

            private String key;

            Config(String key) {
                this.key = key;
            }

            public String get() {
             return System.getProperty(key);
            }
        }

and use it like SystemPropertyHelper.REQUEST_PORT.get();

Answer 3

Sure, you could create an enum like this, which would give you access to the property name, and the value:

public enum SystemPropertyEnum {
    REQUEST_PORT("http.request.port"),
    REQUEST_ADDRESS("http.request.address");

    private String propertyName;
    private String value;

    SystemPropertyEnum(final String propertyName) {
        this.propertyName = propertyName;
        this.value = System.getProperty(propertyName);
    }

    public String getPropertyName() {
        return propertyName;
    }

    public String getValue() {
        return value;
    }
}

However, you could avoid the need to call a getter by just using public static final String variables for your properties, as @halloei suggests.

Answer 4

Also you can do something like this:

public enum Properties {
    REQUEST_PORT("http.request.port"),
    REQUEST_USE_SSL("http.request.ssl");
    // Add others...

    private final String value;

    Properties(String value) {
        this.value = System.getProperty(value);
    }

    public String getValue() {
        return this.value;
    }
}

This can be use like:

String port = Properties.REQUEST_PORT.getValue();