Implement OSS features - Enterprise Distributed Application Service

This topic provides an example to describe how to implement Object Storage Service (OSS) features in an on-premises Spring Cloud application and deploy the application to Enterprise Distributed Application Service (EDAS).

Why is OSS used?

OSS is developed by Alibaba Cloud to provide secure, cost-effective, and highly reliable storage services. It allows you to store large amounts of data in the cloud. OSS provides platform-independent RESTful API operations and allows you to store and access all the types of data in applications that are developed by using Spring Cloud.

Prerequisites

Before you implement OSS features in an application, a bucket is created in OSS by using your Alibaba Cloud account.

Implement OSS features in an on-premises environment

Create a Maven project named oss-example.

Add the following dependencies to the pom.xml file:

In the following sample code, Spring Boot 2.1.4.RELEASE and Spring Cloud Greenwich.SR1 are added as dependencies.

 <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
     <version>2.1.4.RELEASE</version>
     <relativePath/>
 </parent>

  <dependencies>
     <dependency>
         <groupId>com.alibaba.cloud</groupId>
         <artifactId>spring-cloud-starter-alicloud-oss</artifactId>
         <version>2.1.1.RELEASE</version>
     </dependency>
     <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
     </dependency>
 </dependencies>

 <dependencyManagement>
     <dependencies>
         <dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-dependencies</artifactId>
             <version>Finchley.SR1</version>
             <type>pom</type>
             <scope>import</scope>
         </dependency>
     </dependencies>
 </dependencyManagement>

Note

If you must use Spring Boot 1.x, we recommend that you use Spring Boot 1.5.x and Spring Cloud Edgware. The corresponding version of Spring Cloud Alibaba is 1.5.1.RELEASE.
Spring Boot 1.x has reached end of life. Therefore, we recommend that you use a later version of Spring Boot to develop your applications.

Create a package, such as spring.cloud.alicloud.oss, in the src/main/java directory.

Create a startup class named OssApplication for oss-example in the spring.cloud.alicloud.oss package.

    package spring.cloud.alicloud.oss;

    import com.aliyun.oss.OSS;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.ApplicationArguments;
    import org.springframework.boot.ApplicationRunner;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.annotation.Bean;

    import java.net.URISyntaxException;

    @SpringBootApplication
    public class OssApplication {
        public static final String BUCKET_NAME = "test-bucket";
        public static void main(String[] args) throws URISyntaxException {
            SpringApplication.run(OssApplication.class, args);
        }
        @Bean
        public AppRunner appRunner() {
            return new AppRunner();
        }
        class AppRunner implements ApplicationRunner {
            @Autowired
            private OSS ossClient;
            @Override
            public void run(ApplicationArguments args) throws Exception {
                try {
                    if (!ossClient.doesBucketExist(BUCKET_NAME)) {
                        ossClient.createBucket(BUCKET_NAME);
                    }
                } catch (Exception e) {
                    System.err.println("oss handle bucket error: " + e.getMessage());
                    System.exit(-1);
                }
            }
        }
    }

In the src/main/resources directory, add a sample file to be uploaded. The sample file is named oss-test.json in the example.
```
 {
   "name": "oss-test"
 }                        
```

Create a class named OssController in the spring.cloud.alicloud.oss package and add configurations to implement features, such as obtaining files by using the Resource interface of Spring, uploading data, and downloading data.

    package spring.cloud.alicloud.oss;

    import com.aliyun.oss.OSS;
    import com.aliyun.oss.common.utils.IOUtils;
    import com.aliyun.oss.model.OSSObject;
    import org.apache.commons.codec.CharEncoding;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.core.io.Resource;
    import org.springframework.util.StreamUtils;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;

    import java.nio.charset.Charset;

    @RestController
    public class OssController {
        @Autowired
        private OSS ossClient;
        @Value("oss://" + OssApplication.BUCKET_NAME + "/oss-test.json")
        private Resource file;
        @GetMapping("/upload")
        public String upload() {
            try {
                ossClient.putObject(OssApplication.BUCKET_NAME, "oss-test.json", this
                        .getClass().getClassLoader().getResourceAsStream("oss-test.json"));
            } catch (Exception e) {
                e.printStackTrace();
                return "upload fail: " + e.getMessage();
            }
            return "upload success";
        }
        @GetMapping("/file-resource")
        public String fileResource() {
            try {
                return "get file resource success. content: " + StreamUtils.copyToString(
                        file.getInputStream(), Charset.forName(CharEncoding.UTF_8));
            } catch (Exception e) {
                e.printStackTrace();
                return "get resource fail: " + e.getMessage();
            }
        }
        @GetMapping("/download")
        public String download() {
            try {
                OSSObject ossObject = ossClient.getObject(OssApplication.BUCKET_NAME, "oss-test.json");
                return "download success, content: " + IOUtils
                        .readStreamAsString(ossObject.getObjectContent(), CharEncoding.UTF_8);
            } catch (Exception e) {
                e.printStackTrace();
                return "download fail: " + e.getMessage();
            }
        }
    }

Obtain the AccessKey ID, AccessKey secret, and endpoint, and then add the configurations in your on-premises environment.
1. Go to the Security Management page and obtain the AccessKey ID and the AccessKey secret.
2. Obtain the endpoint based on the region where the bucket is deployed. For more information, see Regions and endpoints.
3. Create a file named application.properties in the src/main/resources directory and add the configurations of the AccessKey ID, AccessKey secret, and endpoint.
```
spring.application.name=oss-example
server.port=18084
# Specify the AccessKey ID.
spring.cloud.alicloud.access-key=xxxxx
# Specify the AccessKey secret.
spring.cloud.alicloud.secret-key=xxxxx
# Specify the endpoint.
spring.cloud.alicloud.oss.endpoint=xxx.aliyuncs.com
management.endpoints.web.exposure.include=*                                
```
Run the main function of OssApplication to start the service.

Verify the result

Visit http://127.0.0.1:18084/upload in your web browser.
If upload success appears, the sample file oss-test.json is uploaded. Otherwise, check the code in the on-premises environment for troubleshooting. Then, run the main function of OssApplication again to start the service.
Log on to the OSS console and go to the bucket that stores the uploaded file. Then, in the left-side navigation pane, click Files and check whether the sample file is in the file list.
If oss-test.json is in the file list, the file is uploaded. Otherwise, check the code in the on-premises environment for troubleshooting. Then, run the main function of OssApplication again to start the service.
Visit http://127.0.0.1:18084/download in your web browser to download the oss-test.json file.
```
 {
   "name": "oss-test"
 }                        
```
Visit http://127.0.0.1:18084/file-resource in your web browser to obtain the content of the sample file oss-test.json.
```
 {
   "name": "oss-test"
 }                        
```

Deploy the application to EDAS

Spring Cloud AliCloud OSS is developed to respond to the needs of migrating applications from their original development environments to EDAS. You can deploy applications to EDAS without the need to modify the code or configurations. For more information about deployment methods and steps, see Overview and Overview.