利用java类加载以及反射-动态加载jar包实现热部署

业务背景：
1.a.jar中的test方法依赖两个其他的jar包分别为b.jar和c.jar，类路径com.Product
2.a.jar中的test方法调用b.jar的test方法，使a产品加工成b产品，再调用c.jar中的test方法使b产品加工成c产品。由于线上环境活动频繁变动，所以使用类加载以及反射实现更新应用而不重启应用的热部署。
代码实现如下：

`
/**

• This is the entrance of the test program. please do not modify the modifiers

• of this class and methods. Please do not modify the input and output

• parameters.

• @author tom
  */
  public class Test {

  public static void main(String[] args) throws IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchMethodException, MalformedURLException, ClassNotFoundException {
  new Test().test(new File(“b.jar”),new File(“b.jar”),“helloWorld!”);
  }
  /**

  • By calling this function. Call the functions in the three jar packages and

  • return data.

  • @param jarFileB

  • @param jarFileC

  • @param text original string

  • @return final decrypted string
    */
    public String test( File jarFileB, File jarFileC, String text) throws MalformedURLException, ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
    URL urlB = new URL(“file:”+jarFileB.getPath());
    URLClassLoader classLoaderA = new URLClassLoader(new URL[]{urlB}, Thread.currentThread()
    .getContextClassLoader());
    Class<?> product = classLoaderA.loadClass(“com.Product”);
    //获取实例
    Object obj = product.newInstance();
    //获取方法
    Method method=product.getDeclaredMethod(“test”,String.class);
    //执行方法
    Object result1 = method.invoke(obj, text);

    Object result2 = execute(jarFileC, result1.toString());
    execute(new File(“a.jar”),result2.toString());

    // TODO According to the requirements , write the implementation code.
    return null;

  }

  private Object execute(File file,String text) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException, InstantiationException, ClassNotFoundException, MalformedURLException {
  URL url1 = new URL(“file:”+file.getPath());
  URLClassLoader classLoaderA = new URLClassLoader(new URL[]{url1}, Thread.currentThread()
  .getContextClassLoader());
  Class<?> product = classLoaderA.loadClass(“com.Product”);
  //获取实例
  Object obj = product.newInstance();
  //获取方法
  Method method=product.getDeclaredMethod(“test”,String.class);
  //执行方法
  Object result = method.invoke(obj, text);
  return result;
  }

}`)