code optimization (#3167)

code optimization

Author: CrazyHZM

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/AbstractResult.java

@@ -16,6 +16,8 @@
  */
 package org.apache.dubbo.rpc;
 
+import org.apache.dubbo.common.utils.StringUtils;
+
 import java.util.HashMap;
 import java.util.Map;
 
@@ -58,7 +60,7 @@ public String getAttachment(String key) {
     @Override
     public String getAttachment(String key, String defaultValue) {
         String result = attachments.get(key);
-        if (result == null || result.length() == 0) {
+        if (StringUtils.isEmpty(result)) {
             result = defaultValue;
         }
         return result;

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/RpcContext.java

@@ -20,6 +20,7 @@
 import org.apache.dubbo.common.URL;
 import org.apache.dubbo.common.threadlocal.InternalThreadLocal;
 import org.apache.dubbo.common.utils.NetUtils;
+import org.apache.dubbo.common.utils.StringUtils;
 
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
@@ -364,7 +365,7 @@ public String getLocalAddressString() {
      */
     public String getLocalHostName() {
         String host = localAddress == null ? null : localAddress.getHostName();
-        if (host == null || host.length() == 0) {
+        if (StringUtils.isEmpty(host)) {
             return getLocalHost();
         }
         return host;

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/RpcException.java

@@ -34,7 +34,10 @@
     public static final int SERIALIZATION_EXCEPTION = 5;
     public static final int NO_INVOKER_AVAILABLE_AFTER_FILTER = 6;
     private static final long serialVersionUID = 7815426752583648734L;
-    private int code; // RpcException cannot be extended, use error code for exception type to keep compatibility
+    /**
+     * RpcException cannot be extended, use error code for exception type to keep compatibility
+     */
+    private int code;
 
     public RpcException() {
         super();

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/RpcInvocation.java

@@ -18,6 +18,7 @@
 
 import org.apache.dubbo.common.Constants;
 import org.apache.dubbo.common.URL;
+import org.apache.dubbo.common.utils.StringUtils;
 
 import java.io.Serializable;
 import java.lang.reflect.Method;
@@ -198,7 +199,7 @@ public String getAttachment(String key, String defaultValue) {
             return defaultValue;
         }
         String value = attachments.get(key);
-        if (value == null || value.length() == 0) {
+        if (StringUtils.isEmpty(value)) {
             return defaultValue;
         }
         return value;

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/service/GenericService.java

@@ -31,7 +31,7 @@ public interface GenericService {
      * @param parameterTypes Parameter types
      * @param args           Arguments
      * @return invocation return value
-     * @throws Throwable potential exception thrown from the invocation
+     * @throws GenericException potential exception thrown from the invocation
      */
     Object $invoke(String method, String[] parameterTypes, Object[] args) throws GenericException;