如何在子文件夹中访问java类 [英] How to access java classes in a subfolder

问题描述

我试图创建一个程序，可以从子文件夹插件加载未知的插件集。所有这些插件都实现相同的接口。我需要知道的是如何找到这个文件夹中的所有类，以便我可以实例化和使用它们？

解决方案

MyInterface.java

存根接口。

 包测试; 
 public interface MyInterface {
 public void printSomething（）; 
} 
  

---

TestClass。 java

要加载的测试类，实现您的界面。

 code> import test.MyInterface; 
 public class TestClass implements MyInterface {
 public void printSomething（）{
 System.out.println（Hello World，from TestClass）; 
} 
} 
  

（编译类文件放在子文件夹 ）

---

Test.java

一个完整的测试程序，从子文件夹/加载所有类文件，并实例化并运行接口方法。

 包装测试; 
 import java.io.File; 
 
 public class Test {
 public static void main（String [] args）{
 
 try {
 ClassLoader cl = ClassLoader.getSystemClassLoader 
文件子文件夹=新文件（子文件夹）; 
 
 for（File f：subfolder.listFiles（））{
 String s = f.getName（）; 
 System.out.println（Loading+ s）; 
 Class cls = cl.loadClass（s​​.substring（0，s.lastIndexOf（'。'）））; 
 
 MyInterface o =（MyInterface）cls.newInstance（）; 
 o.printSomething（）; 
} 
} catch（ClassNotFoundException e）{
} catch（InstantiationException e）{
} catch（IllegalAccessException e）{
} 
} 
} 
  

---

$

$

$

b $ b

I'm trying to make a program that can load an unknown set of plugins from a sub-folder, "Plugins". All of these plugins implement the same interface. What I need to know is how do I find all of the classes in this folder so that I can instantiate and use them?

解决方案

MyInterface.java

A stub interface.

package test;
public interface MyInterface {
    public void printSomething();
}

---

TestClass.java

A test class to be loaded, implementing your interface.

import test.MyInterface;
public class TestClass implements MyInterface {
    public void printSomething() {
        System.out.println("Hello World, from TestClass");
    }
}

(Compiled class file placed in "subfolder/".)

---

Test.java

A complete test program that loads all class files from "subfolder/" and instantiates and runs the interface method on it.

package test;
import java.io.File;

public class Test {
    public static void main(String[] args) {

        try {
            ClassLoader cl = ClassLoader.getSystemClassLoader();
            File subfolder = new File("subfolder");

            for (File f : subfolder.listFiles()) {
                String s = f.getName();
                System.out.println("Loading " + s);
                Class cls = cl.loadClass(s.substring(0, s.lastIndexOf('.')));

                MyInterface o = (MyInterface) cls.newInstance();
                o.printSomething();
            }
        } catch (ClassNotFoundException e) {
        } catch (InstantiationException e) {
        } catch (IllegalAccessException e) {
        }
    }
}

---

Output from Test program above:

Loading TestClass.class
Hello World, from TestClass

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