Java 動態載入Jar包，並使用

將一個jar包動態載入到java虛擬機中

import java.io.File;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;

import org.apache.commons.lang3.reflect.FieldUtils;

public class JarTools {

protected static Method addURL = null ;
static{
try {
addURL = URLClassLoader.class.getDeclaredMethod("addURL", new Class[] { URL.class }) ;
addURL.setAccessible(true);
} catch (Exception e) {
}
}

/**
* 動態載入Jar包到內存中
* */
public static Object loadJar(String jarFile, String className) {
try {
File file = new File( jarFile );
if (!file.exists) {
throw new RuntimeException(jarFile + "不存在");
}
addURL.invoke(ClassLoader.getSystemClassLoader, new Object { file.toURI.toURL });
return Class.forName( className ,false , ClassLoader.getSystemClassLoader ).newInstance;
} catch (Exception e) {
e.printStackTrace;
} finally {

}
return null;
}

public static void main(String[] args) throws Exception {
Object loadJar = loadJar("C:/commons-io-2.4.jar", "org.apache.commons.io.Charsets") ;
Field field = loadJar.getClass.getField("UTF_8");
System.out.println(FieldUtils.readDeclaredStaticField(loadJar.getClass, field.getName));
}
}

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