枚举类型为类时如何使用Java反射？
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How to use Java reflection when the enum type is a Class?
提问by David G
I was using an enum in which the constant was a Class. I needed to invoke a method on the constant but could not introduce a compile time dependency and the enum was not always available at runtime (part of optional install). Therefore, I wanted to use reflection.
我正在使用一个枚举，其中常量是一个类。我需要对常量调用一个方法，但无法引入编译时依赖，并且枚举在运行时并不总是可用（可选安装的一部分）。因此，我想使用反射。
This is easy, but I hadn't used reflection with enums before.
这很容易，但我之前没有对枚举使用反射。
The enum looked something like this:
枚举看起来像这样：
public enum PropertyEnum {
SYSTEM_PROPERTY_ONE("property.one.name", "property.one.value"),
SYSTEM_PROPERTY_TWO("property.two.name", "property.two.value");
private String name;
private String defaultValue;
PropertyEnum(String name) {
this.name = name;
}
PropertyEnum(String name, String value) {
this.name = name;
this.defaultValue = value;
}
public String getName() {
return name;
}
public String getValue() {
return System.getProperty(name);
}
public String getDefaultValue() {
return defaultValue;
}
}
What is an example of invoking a method of the constant using reflection?
使用反射调用常量方法的示例是什么？
采纳答案by David G
import java.lang.reflect.Method;
class EnumReflection
{
public static void main(String[] args)
throws Exception
{
Class<?> clz = Class.forName("test.PropertyEnum");
/* Use method added in Java 1.5. */
Object[] consts = clz.getEnumConstants();
/* Enum constants are in order of declaration. */
Class<?> sub = consts[0].getClass();
Method mth = sub.getDeclaredMethod("getDefaultValue");
String val = (String) mth.invoke(consts[0]);
/* Prove it worked. */
System.out.println("getDefaultValue " +
val.equals(PropertyEnum.SYSTEM_PROPERTY_ONE.getDefaultValue()));
}
}
