Java: How can I access a class's field by a name stored in a variable?
How can I set or get a field in a class whose name is dynamic and stored in a string variable?
public class Test {
public String a1;
public String a2;
public Test(String key) {
th开发者_如何学Cis.key = 'found'; <--- error
}
}
You have to use reflection:
- Use
Class.getField()
to get aField
reference. If it's not public you'll need to callClass.getDeclaredField()
instead - Use
AccessibleObject.setAccessible
to gain access to the field if it's not public - Use
Field.set()
to set the value, or one of the similarly-named methods if it's a primitive
Here's an example which deals with the simple case of a public field. A nicer alternative would be to use properties, if possible.
import java.lang.reflect.Field;
class DataObject
{
// I don't like public fields; this is *solely*
// to make it easier to demonstrate
public String foo;
}
public class Test
{
public static void main(String[] args)
// Declaring that a method throws Exception is
// likewise usually a bad idea; consider the
// various failure cases carefully
throws Exception
{
Field field = DataObject.class.getField("foo");
DataObject o = new DataObject();
field.set(o, "new value");
System.out.println(o.foo);
}
}
Class<?> actualClass=actual.getClass();
Field f=actualClass.getDeclaredField("name");
The above code would suffice .
object.class.getField("foo");
Unfortunately the above code didn't work for me , since the class had empty field array.
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