27 Java动态加载第三方jar包中的类

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我加载的方法是:
//参数fileName是jar包的路径，processorName 是业务类的包名+类名
public static A load(String fileName, String processorName) {
            String filePath = fileName;
              A processor = null;
  URL url;
try {
  url = new URL(filePath);
} catch (MalformedURLException e1) {
e1.printStackTrace();
log.error("文件不存在");
return null;
}
URLClassLoader loader = new URLClassLoader(new URL[] { url });
try {
Class<?> processorClass = loader.loadClass(processorName);
processor = (A)processorClass.newInstance();
} catch (Exception e) {
log.error("创建业务类失败");
e.printStackTrace();
return null;
}
return processor;
}
问题：用main方法来调用这个load方法是能加载jar包中业务类a的，但是如果在自己系统里面按照正常流程走的时候调用load方法的时候却报错：接口类A找不到，但是接口类A是明明定义在系统内部的,（两次调用load方法的入参都是一样的）

解决方法：

parentClassLoader，即Thread.currentThread().getContextClassLoader(),就能从当前程序中查找接口类A

package com.main.java;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;/**
*/
public class TestClassLoad2 {
private static Logger LOGGER = LoggerFactory.getLogger(TestClassLoad2.class);
public static void main(String[] args) {
args=new String[]{"file://F:/bin/lib/test.jar","com.main.java.TestProcess"};
LOGGER.info("start");
load(args[],args[]);
}
public static Process load(String fileName, String processorName) {
String filePath = fileName;
Process processor = null;
URL url;
try {
url = new URL(filePath);
} catch (MalformedURLException e1) {
e1.printStackTrace();
LOGGER.info("文件不存在");
return null;
}
URLClassLoader loader = new URLClassLoader(new URL[]{url},Thread.currentThread().getContextClassLoader());
//URLClassLoader loader = new URLClassLoader(new URL[] { url });
try {
Class<?> processorClass = loader.loadClass(processorName);
processor = (Process)processorClass.newInstance();
processor.display();
} catch (Exception e) {
LOGGER.info("创建业务类失败");
e.printStackTrace();
return null;
}
return processor;
}
}