在Java中从字符串创建实例

Question

如果我有两个类，“A”和“B”，我该如何创建一个通用工厂，以便只需将类名作为字符串传递即可接收实例？

例如：

public static void factory(String name) {
     // An example of an implmentation I would need, this obviously doesn't work
      return new name.CreateClass();
}

Thanks!

Joel

- Joel

Answer 1

Class c= Class.forName(className);
return c.getDeclaredConstructor().newInstance();//assuming you aren't worried about constructor .

• javadoc

用于调用带参数的构造函数

 public static Object createObject(Constructor constructor,
      Object[] arguments) {

    System.out.println("Constructor: " + constructor.toString());
    Object object = null;

    try {
      object = constructor.newInstance(arguments);
      System.out.println("Object: " + object.toString());
      return object;
    } catch (InstantiationException e) {
      //handle it
    } catch (IllegalAccessException e) {
      //handle it
    } catch (IllegalArgumentException e) {
      //handle it
    } catch (InvocationTargetException e) {
      //handle it
    }
    return object;
  }
}

请点击这里查看相关IT技术内容。

- jmj

---

如何向构造函数传递参数？ - Joel

System.out.println(e);请不要这样做！为什么不直接声明异常呢？当你真的想通过报告来处理它时，请使用e.printStackTrace()。 - maaartinus

newInstance()现已被弃用，替换为clazz.getDeclaredConstructor().newInstance()。 - boardtc

Answer 2

您可以查看反射相关内容：

import java.awt.Rectangle;

public class SampleNoArg {

   public static void main(String[] args) {
      Rectangle r = (Rectangle) createObject("java.awt.Rectangle");
      System.out.println(r.toString());
   }

   static Object createObject(String className) {
      Object object = null;
      try {
          Class classDefinition = Class.forName(className);
          object = classDefinition.newInstance();
      } catch (InstantiationException e) {
          System.out.println(e);
      } catch (IllegalAccessException e) {
          System.out.println(e);
      } catch (ClassNotFoundException e) {
          System.out.println(e);
      }
      return object;
   }
}

- Darin Dimitrov