check conditions of build() in OpenSergoClient.Builder

Signed-off-by: Jiangnan Jia <[email protected]>

Author: jnan806

src/main/java/io/opensergo/OpenSergoClient.java

@@ -53,7 +53,7 @@ public class OpenSergoClient implements AutoCloseable {
     public static class Builder {
 
         private String host;
-        private int port;
+        private int port = 10246;
         private OpenSergoClientConfig openSergoConfig;
 
         public OpenSergoClient.Builder endpoint(String host, int port) {
@@ -68,6 +68,7 @@ public OpenSergoClient.Builder openSergoConfig(OpenSergoClientConfig openSergoCo
         }
 
         public OpenSergoClient build() {
+            AssertUtils.notEmpty(this.host, "host cannot be empty, maybe need to invoke endpoint(host, port)");
             if (this.openSergoConfig == null) {
                 this.openSergoConfig = new OpenSergoClientConfig();
             }