[SCB-2629] use SystemUtils.JAVA_IO_TMPDIR (#3170)

diff --git a/common/common-rest/src/main/java/org/apache/servicecomb/common/rest/RestConst.java b/common/common-rest/src/main/java/org/apache/servicecomb/common/rest/RestConst.java
index f388695..b35997d 100644
--- a/common/common-rest/src/main/java/org/apache/servicecomb/common/rest/RestConst.java
+++ b/common/common-rest/src/main/java/org/apache/servicecomb/common/rest/RestConst.java
@@ -17,6 +17,8 @@
 
 package org.apache.servicecomb.common.rest;
 
+import org.apache.commons.lang3.SystemUtils;
+
 public final class RestConst {
   private RestConst() {
   }
@@ -65,9 +67,7 @@
 
   public static final String UPLOAD_DIR = "servicecomb.uploads.directory";
 
-  public static final String UPLOAD_DEFAULT_ENV_VARIABLE = "java.io.tmpdir";
-
-  public static final String UPLOAD_DEFAULT_DIR = System.getProperty(UPLOAD_DEFAULT_ENV_VARIABLE);
+  public static final String UPLOAD_DEFAULT_DIR = SystemUtils.JAVA_IO_TMPDIR;
 
   // limit of one upload file, only available for servlet rest transport
   public static final String UPLOAD_MAX_FILE_SIZE = "servicecomb.uploads.maxFileSize";