1. non-simplify mode:
```
dubbo://120.0.0.1:20880/org.apache.dubbo.demo.DemoService?key=value
```
the store path of ZK will be: `/dubbo/porg.apache.dubbo.demo.DemoService/url`

2. simplify mode:
```
dubbo://120.0.0.1:20880/org.apache.dubbo.demo.DemoService?key=value
```
the store path of ZK will be: `/dubbo/porg.apache.dubbo.demo.DemoService/url`

3. simplify mode with path specified:
```
dubbo://120.0.0.1:20880/path-value?key=value
```
the store path of ZK will be: `/dubbo/path-value/url`
this.host = null;
        this.port = 0;
        this.path = null;
        this.parameters = null;
    }
    public URL(String protocol, String host, int port) {
        this(protocol, null, null, host, port, null, (Map<String, String>) null);
    }
    public URL(String protocol, String host, int port, String[] pairs) { 
        this(protocol, null, null, host, port, null, CollectionUtils.toStringMap(pairs));
    }
    public URL(String protocol, String host, int port, Map<String, String> parameters) {
        this(protocol, null, null, host, port, null, parameters);
    }
    public URL(String protocol, String host, int port, String path) {
        this(protocol, null, null, host, port, path, (Map<String, String>) null);
    }
    public URL(String protocol, String host, int port, String path, String... pairs) {
        this(protocol, null, null, host, port, path, CollectionUtils.toStringMap(pairs));
    }
    public URL(String protocol, String host, int port, String path, Map<String, String> parameters) {
        this(protocol, null, null, host, port, path, parameters);
    }
    public URL(String protocol, String username, String password, String host, int port, String path) {
        this(protocol, username, password, host, port, path, (Map<String, String>) null);
    }
    public URL(String protocol, String username, String password, String host, int port, String path, String... pairs) {
        this(protocol, username, password, host, port, path, CollectionUtils.toStringMap(pairs));
    }
    public URL(String protocol, String username, String password, String host, int port, String path, Map<String, String> parameters) {