java動態加載jar文件

public static void main(String[] args)
            throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException,
            SecurityException, ClassNotFoundException, InstantiationException, MalformedURLException {
//         String path =
//         "/xx/.m2/repository/org/apache/commons/commons-lang3/3.1/commons-lang3-3.1.jar";
        String path = "commons-lang3-3.1.jar";//jar文件需放在工程目錄下

        loadJar(path);
        Class<?> aClass = Class.forName("org.apache.commons.lang3.StringUtils");
        Object instance = aClass.newInstance();
        Object strip = aClass.getDeclaredMethod("strip", String.class, String.class).invoke(instance,
                "[1,2,3,4,5,6,2,3,5,1]", "[]");
        System.out.println(strip);

    }

    private static void loadJar(String jarPath) throws MalformedURLException {
        File jarFile = new File(jarPath); // 從URLClassLoader類中獲取類所在文件夾的方法，jar也可以認為是一個文件夾

        if (jarFile.exists() == false) {
            System.out.println("jar file not found.");
            return;
        }

        //獲取類加載器的addURL方法，准備動態調用
        Method method = null;
        try {
            method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
        } catch (NoSuchMethodException | SecurityException e1) {
            e1.printStackTrace();
        } 
        
        // 獲取方法的訪問權限，保存原始值
        boolean accessible = method.isAccessible();
        try {
            //修改訪問權限為可寫
            if (accessible == false) {
                method.setAccessible(true);
            }

            // 獲取系統類加載器
            URLClassLoader classLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
            
            //獲取jar文件的url路徑
            java.net.URL url = jarFile.toURI().toURL();
            
            //jar路徑加入到系統url路徑里
            method.invoke(classLoader, url);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //回寫訪問權限
            method.setAccessible(accessible);
        }

    }

 

參考文章：

Java動態加載jar及class文件