docs(readme): add endpoint

Author: bytestarter

README.md

@@ -1,26 +1,31 @@
 # Volcengine SDK for Java
 
 ## Table of Contents
+
 * Requirements
 * Usage
 * API Dosc
 * Note
 
 ### Requirements ###
+
 运行 SDK需要jdk **Java 1.7+**. 你可以下载最新的版本： http://developers.sun.com/downloads/.
 如果 SDK版本 高于或者等于 **Java 9** 请依赖javax.annotation-api
 由于在高于或者等于 **Java 9** 中 javax.annotation-api 被移除
 
 请在使用中引用
+
 ```xml
+
 <dependency>
-  <groupId>javax.annotation</groupId>
-  <artifactId>javax.annotation-api</artifactId>
-  <version>1.3.2</version>
+    <groupId>javax.annotation</groupId>
+    <artifactId>javax.annotation-api</artifactId>
+    <version>1.3.2</version>
 </dependency>
 ```
 
 ### Usage ###
+
 * Getting Started
 * Example
 
@@ -31,58 +36,62 @@
 建议使用Maven构建自己的项目，添加需要的相应模块的依赖，示例如下：
 
 ##### Init maven setting.xml #####
+
 如果您使用的版本大于0.1.27 可以不进行设置 直接使用中央仓库进行依赖
 
 如果您使用的版本小于或者等于0.1.27
 需要使用字节跳动的maven仓库来完成依赖，请先到maven安装目录的conf/setting.xml
 在<mirrors/>标签中增加
 
 ```xml
+
 <mirror>
-     <id>bytedanceMaven</id>
-     <mirrorOf>my-repo-id</mirrorOf>
-     <name>字节跳动maven仓库</name>
-     <url>https://artifact.bytedance.com/repository/releases/</url>
+    <id>bytedanceMaven</id>
+    <mirrorOf>my-repo-id</mirrorOf>
+    <name>字节跳动maven仓库</name>
+    <url>https://artifact.bytedance.com/repository/releases/</url>
 </mirror>
 ```
 
 ##### Importing the pom #####
 
 ```xml
+
 <dependencyManagement>
-  <dependencies>
-    <dependency>
-      <groupId>com.volcengine</groupId>
-	  <artifactId>volcengine-java-sdk-bom</artifactId>
-       <version>0.2.4</version>
-	  <type>pom</type>
-      <scope>import</scope>
-    </dependency>
-  </dependencies>
+    <dependencies>
+        <dependency>
+            <groupId>com.volcengine</groupId>
+            <artifactId>volcengine-java-sdk-bom</artifactId>
+            <version>0.2.4</version>
+            <type>pom</type>
+            <scope>import</scope>
+        </dependency>
+    </dependencies>
 </dependencyManagement>
 ```
 
-
 ##### Using the SDK Maven modules #####
 
 ```xml
+
 <dependencies>
-  <dependency>
-    <groupId>com.volcengine</groupId>
-    <artifactId>volcengine-java-sdk-vpc</artifactId>
-   <version>0.2.4</version>
-  </dependency>
-  <dependency>
-    <groupId>com.volcengine</groupId>
-    <artifactId>volcengine-java-sdk-ecs</artifactId>
-   <version>0.2.4</version>
-  </dependency>
+    <dependency>
+        <groupId>com.volcengine</groupId>
+        <artifactId>volcengine-java-sdk-vpc</artifactId>
+        <version>0.2.4</version>
+    </dependency>
+    <dependency>
+        <groupId>com.volcengine</groupId>
+        <artifactId>volcengine-java-sdk-ecs</artifactId>
+        <version>0.2.4</version>
+    </dependency>
 </dependencies>
 ```
 
 ##### Credentials 配置 #####
 
 **通过环境变量导入**:
+
 ```
 export VOLCENGINE_ACCESS_KEY=your ak
 export VOLCENGINE_SECRET_KEY=your sk
@@ -93,12 +102,34 @@ export VOLCENGINE_SESSION_TOKEN=token
 **代码方式引入**：
 
 ```java
-Credentials credentials = Credentials.getCredentials(ak,sk);
+Credentials credentials = Credentials.getCredentials(ak, sk);
 //如果使用token
-Credentials credentials = Credentials.getCredentials(ak,sk，token);
+Credentials credentials = Credentials.getCredentials(ak, sk，token);
 ```
 
+##### Endpoint 设置 #####
+
+如果您要自定义SDK的Endpoint，可以按照以下示例代码设置：
+
+```java
+ApiClient apiClient = new ApiClient()
+        .setCredentials(Credentials.getCredentials(ak, sk))
+        .setRegion(region).setEndpoint("ecs.cn-beijing-autodriving.volcengineapi.com");
+```
+
+火山引擎标准的Endpoint规则说明：
+
+| Regional 服务                                                                                                                            | Global 服务                                                                          |
+|----------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------|
+| `{service}.{region}.volcengineapi.com` <br> 例如：云服务ecs在cn-beijing-autodriving Region域名为： `ecs.cn-beijing-autodriving.volcengineapi.com` | `{service}.volcengineapi.com` <br> 例如：访问控制iam为Global服务，域名为：`iam.volcengineapi.com` |
+
+注：
+
+- Service中存在_符号时，Endpoint时需转为-符号。存在大写字母时需转成小写。
+- 并非所有云产品和Region都支持标准域名，具体请前往您所使用的产品-API参考中查看。
+
 #### Example ####
+
 ```java
 import com.volcengine.ApiClient;
 import com.volcengine.ApiException;
@@ -111,26 +142,26 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TestVpc {
-  public static void main(String[] args)throws Exception {
-    String ak = "your ak";
-    String sk = "your sk";
-    String region = "cn-beijing";
-
-    ApiClient apiClient = new ApiClient()
-            .setCredentials(Credentials.getCredentials(ak,sk))
-            .setRegion(region);
-    VpcApi vpcApi = new VpcApi(apiClient);
-    DescribeVpcsRequest request = new DescribeVpcsRequest();
-    List<String> list = new ArrayList<>();
-    list.add("vpc-13fpdgwk7rxfk3n6nu44wisg7");
-    request.setVpcIds(list);
-    try {
-      DescribeVpcsResponse response = vpcApi.describeVpcs(request);
-      System.out.println(response);
-    } catch (ApiException e) {
-      System.out.println(e.getResponseBody());
+    public static void main(String[] args) throws Exception {
+        String ak = "your ak";
+        String sk = "your sk";
+        String region = "cn-beijing";
+
+        ApiClient apiClient = new ApiClient()
+                .setCredentials(Credentials.getCredentials(ak, sk))
+                .setRegion(region);
+        VpcApi vpcApi = new VpcApi(apiClient);
+        DescribeVpcsRequest request = new DescribeVpcsRequest();
+        List<String> list = new ArrayList<>();
+        list.add("vpc-13fpdgwk7rxfk3n6nu44wisg7");
+        request.setVpcIds(list);
+        try {
+            DescribeVpcsResponse response = vpcApi.describeVpcs(request);
+            System.out.println(response);
+        } catch (ApiException e) {
+            System.out.println(e.getResponseBody());
+        }
     }
-  }
 }
 
 ```