判断一个类到底是从哪个jar包中调用的工具类

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.security.CodeSource;
import java.security.ProtectionDomain;

public class SystemUtils {

    /**
     * 获取一个class类的实际位置
     * @param cls
     * @return
     */
    public static URL getClassLocation(final Class<?> cls) {

        //非空判断
        if (cls == null) {
            throw new IllegalArgumentException("null input: cls");
        }
        
        
        URL result = null;
        final String clsAsResource = cls.getName().replace(‘.‘, ‘/‘).concat(".class");
        
        final ProtectionDomain pd = cls.getProtectionDomain();
        
        if (pd != null) {
            final CodeSource cs = pd.getCodeSource();
            if (cs != null) {
                result = cs.getLocation();
            }
                
            if (result != null) {
                if ("file".equals(result.getProtocol())) {
                    try {
                        if (result.toExternalForm().endsWith(".jar") || result.toExternalForm().endsWith(".zip")) {
                            result = new URL("jar:".concat(result.toExternalForm()).concat("!/").concat(clsAsResource));
                        } else if (new File(result.getFile()).isDirectory()) {
                            result = new URL(result, clsAsResource);
                        }
                    } catch (MalformedURLException ignore) {
                        
                    }
                }
            }
        }
        
        if (result == null) {
            final ClassLoader clsLoader = cls.getClassLoader();
            result = clsLoader != null ? clsLoader.getResource(clsAsResource) : ClassLoader.getSystemResource(clsAsResource);
        }
        
        return result;
    }

}