英文:
Java reflection invoke on getDeclaringClass
问题
我有一个像这样的接口，一些类实现了这个接口：
public interface MyInterface {}
public class Informations implements MyInterface {
@Command("version")
public void getVersion() {
System.out.println("1.0-SNAPSHOT");
}
}
public class Systems implements MyInterface {
@Command("os")
public void getOs() {
System.out.println("Linux OS");
}
}
我正在收集所有带有@Command注解的方法，存储在一个Map中，就像这样：
/* String is command */
private Map<String, Method> commandMaps = new ConcurrentHashMap<>();
现在，我想调用这些方法：
Optional<String> optionalCommand = commandMaps.keySet().stream().filter(e -> e.equals(user_input_command)).findFirst();
if (optionalCommand.isPresent()) {
Method method = commandMaps.get(optionalCommand.get());
Class<?> declaringClass = method.getDeclaringClass();
System.out.println(">> " + method.getName());
System.out.println(">> " + declaringClass.getName());
method.invoke(declaringClass);
}
例如，用户输入了os命令，declaringClass.getName()引用了Systems类，但不能调用declaringClass。因此，这段代码会抛出IllegalArgumentException异常：
>> getOs
>> a.b.c.Systems
java.lang.IllegalArgumentException: object is not an instance of declaring class
如何修复这个问题？
英文:
I have a interface like this and some classes implemented this interface:
public interface MyInterface {}
public class Informations implements MyInterface {
@Command("version")
public void getVersion() {
System.out.println("1.0-SNAPSHOT");
}
}
public class Systems implements MyInterface {
@Command("os")
public void getOs() {
System.out.println("Linux OS");
}
}
I collecting all methods annotated @Command in a Map like this :
/* String is command */
private Map<String, Method> commandMaps = new ConcurrentHashMap<>();
Now , I want invoke this methods :
Optional<String> optionalCommand = commandMaps.keySet().stream().filter(e -> e.equals(user_input_command)).findFirst();
if (optionalCommand.isPresent()) {
Method method = commandMaps.get(optionalCommand.get());
Class<?> declaringClass = method.getDeclaringClass();
System.out.println(">> " + method.getName());
System.out.println(">> " + declaringClass.getName());
method.invoke(declaringClass);
}
for example user enter os command and declaringClass.getName() referenced to Systems class but can not invoking declaringClass .
so , this code result IllegalArgumentException exception :
>> getOs
>> a.b.c.Systems
java.lang.IllegalArgumentException: object is not an instance of declaring class
How can fix this problem ?
答案1
得分: 1
When you invoke a method via reflection, you need to pass the object you are calling the method on as the first parameter to Method#invoke.
// equivalent to s1.testParam("", obj)
testParamMethod.invoke(s1, "", obj);
英文:
When you invoke a method via reflection, you need to pass the object you are calling the method on as the first parameter to Method#invoke.
// equivalent to s1.testParam("", obj)
testParamMethod.invoke(s1, "", obj);
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