2.7.0版本getContextPath方法：
```
protected String getContextPath(URL url) {
        String contextPath = url.getPath();
        return contextPath.endsWith("/") ? contextPath.substring(0,contextPath.length()-1) : contextPath;
    }
```
无法将方法置入web容器中，退回2.6.5版本的方法：
```
protected String getContextPath(URL url) {
        int pos = url.getPath().lastIndexOf("/");
        return pos > 0 ? url.getPath().substring(0, pos) : "";
    }
```
使用正常，两个方法应该不等价的。
import static org.apache.dubbo.common.Constants.QOS_PORT;
import static org.apache.dubbo.common.Constants.REFER_KEY;
import static org.apache.dubbo.common.Constants.REGISTER_IP_KEY;
import static org.apache.dubbo.common.Constants.REGISTER_KEY;
import static org.apache.dubbo.common.Constants.REGISTRY_KEY;
import static org.apache.dubbo.common.Constants.REGISTRY_PROTOCOL;
import static org.apache.dubbo.common.Constants.ROUTERS_CATEGORY;
import static org.apache.dubbo.common.Constants.SIMPLIFIED_KEY;
import static org.apache.dubbo.common.Constants.VALIDATION_KEY;
import static org.apache.dubbo.common.utils.UrlUtils.classifyUrls;
/**
 * RegistryProtocol
 */
public class RegistryProtocol implements Protocol {
    private final static Logger logger = LoggerFactory.getLogger(RegistryProtocol.class);
    private static RegistryProtocol INSTANCE;
    private final Map<URL, NotifyListener> overrideListeners = new ConcurrentHashMap<>();
    private final Map<String, ServiceConfigurationListener> serviceConfigurationListeners = new ConcurrentHashMap<>();
    private final ProviderConfigurationListener providerConfigurationListener = new ProviderConfigurationListener();
    
    
    private final ConcurrentMap<String, ExporterChangeableWrapper<?>> bounds = new ConcurrentHashMap<>();
    private Cluster cluster;
    private Protocol protocol;
    private RegistryFactory registryFactory;
    private ProxyFactory proxyFactory;
    public RegistryProtocol() {
        INSTANCE = this;
    }
    public static RegistryProtocol getRegistryProtocol() {