refact: unify pom & remove useless file (#100)

diff --git a/hugegraph-common/LICENSE b/hugegraph-common/LICENSE
deleted file mode 100644
index e06d208..0000000
--- a/hugegraph-common/LICENSE
+++ /dev/null
@@ -1,202 +0,0 @@
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diff --git a/hugegraph-common/checkstyle.xml b/hugegraph-common/checkstyle.xml
deleted file mode 100644
index 9373a70..0000000
--- a/hugegraph-common/checkstyle.xml
+++ /dev/null
@@ -1,89 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE module PUBLIC
-        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
-        "https://checkstyle.org/dtds/configuration_1_3.dtd">
-<!-- 参考:https://checkstyle.sourceforge.io/checks.html -->
-<module name="Checker">
-    <!--检查不通过时被判定的违规级别,必须修复后才能使build通过-->
-    <property name="severity" value="error"/>
-    <!--对java文件做检查-->
-    <property name="fileExtensions" value="java"/>
-    <!--对UTF-8编码的文件做检查-->
-    <property name="charset" value="UTF-8"/>
-    <!--文件中不允许包含制表符-->
-    <module name="FileTabCharacter">
-        <property name="eachLine" value="true"/>
-    </module>
-
-    <!--检查java源文件并定义一些适用于检查此类文件的一些属性-->
-    <module name="TreeWalker">
-        <!--检查行长度-->
-        <module name="LineLength">
-            <property name="max" value="80"/>
-            <!--可以忽略的行-->
-            <property name="ignorePattern"
-                      value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
-        </module>
-        <!--检查没有import语句使用*号-->
-        <module name="AvoidStarImport"/>
-        <!--检查是否存在多余的import语句,比如重复的,java自带的包,相同包下的其他类-->
-        <module name="RedundantImport"/>
-        <!--检查是否存在没有使用的import语句-->
-        <module name="UnusedImports"/>
-        <!--检查包名称是否遵守命名规约-->
-        <module name="PackageName">
-            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
-        </module>
-        <!--检查局部变量的名称是否遵守命名规约-->
-        <module name="LocalVariableName">
-            <property name="format" value="^[a-z][a-zA-Z0-9_]*$"/>
-        </module>
-        <!--检查成员变量(非静态字段)的名称是否遵守命名规约-->
-        <module name="MemberName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
-        </module>
-        <!--检查方法名称是否遵守命名规约-->
-        <module name="MethodName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
-        </module>
-        <!--检查参数名称是否遵守命名规约-->
-        <module name="ParameterName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
-        </module>
-        <!--检查常量(用static final修饰的字段)的名称是否遵守命名规约-->
-        <module name="ConstantName">
-            <property name="format" value="^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$"/>
-        </module>
-        <!--检查数组是否属于java风格,方括号放在类型后面,而不是变量后面,比如:int[] nums(合法),int nums[](不合法)-->
-        <module name="ArrayTypeStyle">
-            <property name="javaStyle" value="true"/>
-        </module>
-        <!--long类型的字面量如果要以"L"结尾,必须是大写的"L",而非小写的"l"-->
-        <module name="UpperEll"/>
-        <!--代码换行时,运算符必须在当前行的末尾,比如:+、&&、?、: 等-->
-        <module name="OperatorWrap">
-            <property name="option" value="eol"/>
-        </module>
-        <!--检查指定标记的周围是否有空格,比如:if、for、while、synchoronized 等-->
-        <module name="WhitespaceAround"/>
-        <!--左圆括号之后和右圆括号之前是否需要有一个空格,不需要-->
-        <module name="ParenPad"/>
-        <!--检查修饰符是否符合Java建议,顺序是:public、protected、private、abstract、default、static、final、transient、volatile、synchronized、native、strictfp-->
-        <module name="ModifierOrder"/>
-        <!--检查代码块的左花括号的放置位置,必须在当前行的末尾-->
-        <module name="LeftCurly">
-            <property name="option" value="eol"/>
-            <property name="ignoreEnums" value="false"/>
-        </module>
-        <!--代码中不允许有空语句,也就是单独的;符号-->
-        <module name="EmptyStatement"/>
-        <!--覆盖equals()方法的类必须也覆盖了hashCode()方法-->
-        <module name="EqualsHashCode"/>
-        <!--switch语句必须含有default子句-->
-        <module name="MissingSwitchDefault"/>
-        <!--switch语句的default必须放在所有的case分支之后-->
-        <module name="DefaultComesLast"/>
-        <!--覆盖clone()方法时调用了super.clone()方法-->
-        <module name="SuperClone"/>
-    </module>
-</module>
diff --git a/hugegraph-common/pom.xml b/hugegraph-common/pom.xml
index 2f6a818..871b98e 100644
--- a/hugegraph-common/pom.xml
+++ b/hugegraph-common/pom.xml
@@ -4,15 +4,15 @@
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <parent>
-        <groupId>com.baidu.hugegraph</groupId>
+        <groupId>org.apache.hugegraph</groupId>
         <artifactId>hugegraph-commons</artifactId>
-        <version>2.1.2</version>
+        <version>${revision}</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
     <artifactId>hugegraph-common</artifactId>
-    <name>hugegraph-common</name>
-    <url>https://github.com/hugegraph/hugegraph-common</url>
+    <name>${artifactId}</name>
+    <url>https://github.com/apache/incubator-hugegraph-commons/tree/master/hugegraph-common</url>
     <description>
         hugegraph-common is a common module for HugeGraph and its peripheral components.
         hugegraph-common encapsulates locks, configurations, events, iterators, rest and some
@@ -212,7 +212,7 @@
                 <artifactId>maven-checkstyle-plugin</artifactId>
                 <version>3.1.0</version>
                 <configuration>
-                    <configLocation>checkstyle.xml</configLocation>
+                    <configLocation>../checkstyle.xml</configLocation>
                     <encoding>UTF-8</encoding>
                     <consoleOutput>true</consoleOutput>
                     <failsOnError>true</failsOnError>
diff --git a/hugegraph-common/src/main/java/com/baidu/hugegraph/util/UnitUtil.java b/hugegraph-common/src/main/java/com/baidu/hugegraph/util/UnitUtil.java
index 60c626f..069ab00 100644
--- a/hugegraph-common/src/main/java/com/baidu/hugegraph/util/UnitUtil.java
+++ b/hugegraph-common/src/main/java/com/baidu/hugegraph/util/UnitUtil.java
@@ -62,7 +62,7 @@
                         "expect format like '10 MB'", valueWithUnit);
         String unit = valueWithUnit.substring(spacePos + 1);
 
-        long factor = 0L;
+        long factor;
         switch (unit.trim().toUpperCase()) {
             case "B":
             case "BYTE":
diff --git a/hugegraph-rpc/LICENSE b/hugegraph-rpc/LICENSE
deleted file mode 100644
index e06d208..0000000
--- a/hugegraph-rpc/LICENSE
+++ /dev/null
@@ -1,202 +0,0 @@
-Apache License
-                           Version 2.0, January 2004
-                        http://www.apache.org/licenses/
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-      "Legal Entity" shall mean the union of the acting entity and all
-      other entities that control, are controlled by, or are under common
-      control with that entity. For the purposes of this definition,
-      "control" means (i) the power, direct or indirect, to cause the
-      direction or management of such entity, whether by contract or
-      otherwise, or (ii) ownership of fifty percent (50%) or more of the
-      outstanding shares, or (iii) beneficial ownership of such entity.
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-      "You" (or "Your") shall mean an individual or Legal Entity
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-      source, and configuration files.
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-      transformation or translation of a Source form, including but
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-      form, that is based on (or derived from) the Work and for which the
-      editorial revisions, annotations, elaborations, or other modifications
-      represent, as a whole, an original work of authorship. For the purposes
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-      To apply the Apache License to your work, attach the following
-      boilerplate notice, with the fields enclosed by brackets "{}"
-      replaced with your own identifying information. (Don't include
-      the brackets!)  The text should be enclosed in the appropriate
-      comment syntax for the file format. We also recommend that a
-      file or class name and description of purpose be included on the
-      same "printed page" as the copyright notice for easier
-      identification within third-party archives.
-
-   Copyright {yyyy} {name of copyright owner}
-
-   Licensed under the Apache License, Version 2.0 (the "License");
-   you may not use this file except in compliance with the License.
-   You may obtain a copy of the License at
-
-       http://www.apache.org/licenses/LICENSE-2.0
-
-   Unless required by applicable law or agreed to in writing, software
-   distributed under the License is distributed on an "AS IS" BASIS,
-   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-   See the License for the specific language governing permissions and
-   limitations under the License.
-
diff --git a/hugegraph-rpc/checkstyle.xml b/hugegraph-rpc/checkstyle.xml
deleted file mode 100644
index 9373a70..0000000
--- a/hugegraph-rpc/checkstyle.xml
+++ /dev/null
@@ -1,89 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE module PUBLIC
-        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
-        "https://checkstyle.org/dtds/configuration_1_3.dtd">
-<!-- 参考:https://checkstyle.sourceforge.io/checks.html -->
-<module name="Checker">
-    <!--检查不通过时被判定的违规级别,必须修复后才能使build通过-->
-    <property name="severity" value="error"/>
-    <!--对java文件做检查-->
-    <property name="fileExtensions" value="java"/>
-    <!--对UTF-8编码的文件做检查-->
-    <property name="charset" value="UTF-8"/>
-    <!--文件中不允许包含制表符-->
-    <module name="FileTabCharacter">
-        <property name="eachLine" value="true"/>
-    </module>
-
-    <!--检查java源文件并定义一些适用于检查此类文件的一些属性-->
-    <module name="TreeWalker">
-        <!--检查行长度-->
-        <module name="LineLength">
-            <property name="max" value="80"/>
-            <!--可以忽略的行-->
-            <property name="ignorePattern"
-                      value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
-        </module>
-        <!--检查没有import语句使用*号-->
-        <module name="AvoidStarImport"/>
-        <!--检查是否存在多余的import语句,比如重复的,java自带的包,相同包下的其他类-->
-        <module name="RedundantImport"/>
-        <!--检查是否存在没有使用的import语句-->
-        <module name="UnusedImports"/>
-        <!--检查包名称是否遵守命名规约-->
-        <module name="PackageName">
-            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
-        </module>
-        <!--检查局部变量的名称是否遵守命名规约-->
-        <module name="LocalVariableName">
-            <property name="format" value="^[a-z][a-zA-Z0-9_]*$"/>
-        </module>
-        <!--检查成员变量(非静态字段)的名称是否遵守命名规约-->
-        <module name="MemberName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
-        </module>
-        <!--检查方法名称是否遵守命名规约-->
-        <module name="MethodName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
-        </module>
-        <!--检查参数名称是否遵守命名规约-->
-        <module name="ParameterName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
-        </module>
-        <!--检查常量(用static final修饰的字段)的名称是否遵守命名规约-->
-        <module name="ConstantName">
-            <property name="format" value="^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$"/>
-        </module>
-        <!--检查数组是否属于java风格,方括号放在类型后面,而不是变量后面,比如:int[] nums(合法),int nums[](不合法)-->
-        <module name="ArrayTypeStyle">
-            <property name="javaStyle" value="true"/>
-        </module>
-        <!--long类型的字面量如果要以"L"结尾,必须是大写的"L",而非小写的"l"-->
-        <module name="UpperEll"/>
-        <!--代码换行时,运算符必须在当前行的末尾,比如:+、&&、?、: 等-->
-        <module name="OperatorWrap">
-            <property name="option" value="eol"/>
-        </module>
-        <!--检查指定标记的周围是否有空格,比如:if、for、while、synchoronized 等-->
-        <module name="WhitespaceAround"/>
-        <!--左圆括号之后和右圆括号之前是否需要有一个空格,不需要-->
-        <module name="ParenPad"/>
-        <!--检查修饰符是否符合Java建议,顺序是:public、protected、private、abstract、default、static、final、transient、volatile、synchronized、native、strictfp-->
-        <module name="ModifierOrder"/>
-        <!--检查代码块的左花括号的放置位置,必须在当前行的末尾-->
-        <module name="LeftCurly">
-            <property name="option" value="eol"/>
-            <property name="ignoreEnums" value="false"/>
-        </module>
-        <!--代码中不允许有空语句,也就是单独的;符号-->
-        <module name="EmptyStatement"/>
-        <!--覆盖equals()方法的类必须也覆盖了hashCode()方法-->
-        <module name="EqualsHashCode"/>
-        <!--switch语句必须含有default子句-->
-        <module name="MissingSwitchDefault"/>
-        <!--switch语句的default必须放在所有的case分支之后-->
-        <module name="DefaultComesLast"/>
-        <!--覆盖clone()方法时调用了super.clone()方法-->
-        <module name="SuperClone"/>
-    </module>
-</module>
diff --git a/hugegraph-rpc/pom.xml b/hugegraph-rpc/pom.xml
index 06dded6..43fcff4 100644
--- a/hugegraph-rpc/pom.xml
+++ b/hugegraph-rpc/pom.xml
@@ -4,15 +4,14 @@
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <parent>
-        <groupId>com.baidu.hugegraph</groupId>
+        <groupId>org.apache.hugegraph</groupId>
         <artifactId>hugegraph-commons</artifactId>
-        <version>2.1.2</version>
+        <version>${revision}</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
     <artifactId>hugegraph-rpc</artifactId>
-
-    <name>hugegraph-rpc</name>
+    <name>${artifactId}</name>
     <description>HugeGraph Database RPC component</description>
 
     <properties>
@@ -107,7 +106,7 @@
                 <artifactId>maven-checkstyle-plugin</artifactId>
                 <version>3.1.0</version>
                 <configuration>
-                    <configLocation>checkstyle.xml</configLocation>
+                    <configLocation>../checkstyle.xml</configLocation>
                     <encoding>UTF-8</encoding>
                     <consoleOutput>true</consoleOutput>
                     <failsOnError>true</failsOnError>
diff --git a/pom.xml b/pom.xml
index cee98a5..7bb8fc4 100644
--- a/pom.xml
+++ b/pom.xml
@@ -4,13 +4,13 @@
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
 
-    <groupId>com.baidu.hugegraph</groupId>
+    <groupId>org.apache.hugegraph</groupId>
     <artifactId>hugegraph-commons</artifactId>
-    <version>2.1.2</version>
+    <version>${revision}</version>
     <packaging>pom</packaging>
 
-    <name>hugegraph-commons</name>
-    <url>https://github.com/hugegraph/hugegraph-commons</url>
+    <name>${project.artifactId}</name>
+    <url>https://github.com/apache/incubator-hugegraph-commons</url>
     <description>
         hugegraph-commons is a common module for HugeGraph-Common and HugeGraph-Rpc with their peripheral components.
         It includes rpc frame, locks, configurations, events, iterators, rest and some
@@ -37,22 +37,8 @@
         <developerConnection>https://github.com/hugegraph/hugegraph-commons</developerConnection>
     </scm>
 
-    <developers>
-        <developer>
-            <name>lizhangmei</name>
-            <email>javaloveme@gmail.com</email>
-        </developer>
-        <developer>
-            <name>zhoney</name>
-            <email>zhangyi89817@126.com</email>
-        </developer>
-        <developer>
-            <name>liningrui</name>
-            <email>liningrui@vip.qq.com</email>
-        </developer>
-    </developers>
-
     <properties>
+        <revision>2.1.2</revision>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <top.level.dir>${project.basedir}/..</top.level.dir>
         <compiler.source>1.8</compiler.source>