我做了一个Java项目,该项目只包含此类:
package test.processor;
public abstract class Processor {
public abstract void loadData(String objectId);
public abstract void processData();
public abstract void saveData(String objectId);
}
项目将导出为jar文件(processor.jar)
然后,我制作了另一个导入Processor.jar的项目,并且有一个扩展Processor的类:
package test.process;
import test.processor.Processor;
public class Process extends Processor{
@Override
public void loadData(String objectId) {
System.out.println("LOAD DATAAAAAAAAAAAA");
}
@Override
public void processData() {
System.out.println("PROCESS DATAAAAAAAAAAAA");
}
@Override
public void saveData(String objectId) {
System.out.println("SAVE DATAAAAAAAAAAAA");
}
}
该项目也被导出为jar(plugin.jar)。
最后,我编写了一些代码来动态加载插件:
import test.processor.Processor;
public class Test {
public void testPlugins(){
Processor plugin = (Processor) loadJar(
"C:\\Users\\...\\Desktop\\plugin.jar",
"test.process.Process");
processor.loadData("dada");
}
private Object loadJar(String jar, String className){
File jarFile = new File(jar);
Object instance = null;
try {
URL jarpath = jarFile.toURI().toURL();
String jarUrl = "jar:" + jarpath + "!/";
URL urls[] = { new URL(jarUrl) };
URLClassLoader child = new URLClassLoader(urls);
Class classToLoad = Class.forName(nomeClasse, true, child);
instance = classToLoad.newInstance();
} catch (Exception ex) {
ex.printStackTrace();
}
return instance;
}
}
如果我在主要方法中运行该代码,则该方法可以正常工作,一旦尝试在服务器中运行它,则在加载类时会出现问题,我将收到ClassNotFoundException(处理器)。
我尝试将jar放入tomcat / lib,project / WEB-INF / lib中,但没有任何更改。
知道我在做什么错吗?
最佳答案
我没有按照自己想要的方式解决它,但是我解决了它:
首先,我尝试手动加载process.jar:
private Object loadJars(String processJar, String pluginJar, String className){
File processJarFile = new File(processJar);
File pluginJarFile = new File(pluginJar);
Object instance = null;
try {
URL processJarPath = processJarFile.toURI().toURL();
String processJarUrl = "jar:" + processJarPath + "!/";
URL pluginJarPath = pluginJarFile.toURI().toURL();
String pluginJarUrl = "jar:" + pluginJarPath + "!/";
URL urls[] = { new URL(processJarUrl), new URL(pluginJarUrl) };
URLClassLoader child = new URLClassLoader(urls);
Class classToLoad = Class.forName(nomeClasse, true, child);
instance = classToLoad.newInstance();
} catch (Exception ex) {
ex.printStackTrace();
}
return instance;
}
正确加载Process类后,问题会在testPlugins方法中发生,一旦尝试将其强制转换为Processor(ClassCastException,无法将Process强制转换为Processor):
public void testPlugins(){
Processor plugin = (Processor) loadJars("C:\\Users\\...\\Desktop\\processor.jar",
"C:\\Users\\...\\Desktop\\plugin.jar",
"test.process.Process");
processor.loadData("dada");
}
仍然需要阅读很多有关类加载的信息,但是我想问题是它不能像从Webapp上下文加载的处理器一样识别从C:\ Users \ ... \ Desktop \ processor.jar加载的处理器。它“忘记”进程扩展了Processor。
我很着急,所以没有时间去研究,以解决我使用反射调用方法的问题:
public void modifiedTestPlugins(){
Object plugin = loadJar("C:\\Users\\...\\Desktop\\processor.jar",
"C:\\Users\\...\\Desktop\\plugin.jar",
"test.process.Process");
try {
Method processData = findMethod(obj.getClass(), "processData");
//here I invoke the processData method, it prints: PROCESS DATAAAAAAAAAAAA
loadData.invoke(processData, new Object[]{});
} catch (Exception e) {
e.printStackTrace();
}
}
private static Method findMethod(Class clazz, String methodName) throws Exception {
Method[] methods = clazz.getMethods();
for (int i = 0; i < methods.length; i++) {
if (methods[i].getName().equals(methodName))
return methods[i];
}
return null;
}