动态加载

在特定的场所，动态加载可以是程序更加灵活，减少复杂的逻辑运算带来的内存消耗，同时有利于代码维护。

 

import java.io.File;
import java.lang.reflect.Method;

public class Example {
	
	private static final String DEFAULT_LIB_DIR = "../lib";
	
	/**
	 * 
	 * @param path 类路径
	 * @param method 要运行的方法
	 */
	public Example(String path, String method){
		
        try {
        	ClassLoader parent = Thread.currentThread().getContextClassLoader();
            if (parent == null) {
                parent = this.getClass().getClassLoader();
                if (parent == null) {
                    parent = ClassLoader.getSystemClassLoader();
                }
            }

            File libDir;
            final String workingDirectory = System.getProperty("appdir");
            if (workingDirectory == null) {
                libDir = new File(DEFAULT_LIB_DIR);
            }
            else {
                libDir = new File(new File(workingDirectory), "lib");
            }
            
            final ClassLoader loader = new JiveClassLoader(parent, libDir);

            Thread.currentThread().setContextClassLoader(loader);

            Class sparkClass = loader.loadClass(path);// 获取要加载的类
            Object instanceOfSpark = sparkClass.newInstance();//创建实例


            Method startupMethod = sparkClass.getMethod(method);//获得要调用的方法
            startupMethod.invoke(instanceOfSpark);//调用方法
        }
        catch (Exception e) {
            e.printStackTrace();
        }
	}

}