Java

Scenarios

To use Java to call an API through app authentication, obtain the Java SDK, create a project or import an existing project, and then call the API by referring to the API calling example.

This section uses Eclipse 4.5.2 as an example.

Figure 1 API calling process

Prerequisites

• You have obtained the domain name, ID, request URL, and request method of the API to be called, and the AppKey and AppSecret of the App for calling the API. For more information, see Preparation.
• You have installed Eclipse 3.6.0 or a later version. If not, download Eclipse from the official Eclipse website and install it.

• You have installed Java Development Kit (JDK) 1.8.111 or a later version. If not, download JDK from the official Oracle website and install it.

Obtaining the SDK

1. Log in to the DataArts Studio console.
2. Click DataArts DataService.
3. In the navigation pane, choose DataArts DataService Exclusive > SDKs.
4. On the SDKs page, download the SDK package.
5. Verify integrity of the SDK package. In Windows, open the CLI and run the following command to generate the SHA-256 value of the downloaded SDK package. In the command, D:\java-sdk.zip is an example local path and name of the SDK package. Replace it with the actual value.

   certutil -hashfile D:\java-sdk.zip SHA256

   The following is an example command output:

   SHA-256 hash value of D:\java-sdk.zip
   3a86f1ba249a00727db506e4075ec9630e6cf74f312bddf6c3901c9d0786f53e
   CertUtil: -hashfile command executed.
   3a86f1ba249a00727db506e4075ec9630e6cf74f312bddf6c3901c9d0786f53e

   Compare the SHA-256 value of the downloaded SDK package with that provided in the following table. If they are the same, no tampering or packet loss occurred during the package download.

   Table 1 SDK packages and the corresponding SHA-256 values

   Language	SHA-256 Value of the SDK Package
   Java	3a86f1ba249a00727db506e4075ec9630e6cf74f312bddf6c3901c9d0786f53e
   Go	23734867eae2e7ef61427c64aa33aa89512571946f2f43a1a5fef5e801e3129f
   Python	57636d8bacc459cab9dc08c70d01ccc42391ace60e6960c4e947566da1dc5d26
   C#	e5a3b677f75c28ba3f1e16645d8171f7b6f34a42143f8a32a68bb18719b5e65d
   JavaScript	442ac2fcb41d84525dc0139ec3f05d190e4e337cdbcdfdfc82a09d79d2ecd25e
   PHP	2cc76bd2ecd48f00899d18b0f76d05ce2623065180f111c3f70ac14ddf0506f3
   C++	2a54c3f2486d562ea6af1384eca40b301918bdc02f98bbf2c114f282dc059c00
   C	4957556c108e0174d55b4b8d720f296967a9367ca54010792b1b3de039b87363
   Android	0fdcc6fd93a68dce5c3e1b8e6370cc9340429cabfb0f268c3f9e5ea05238ae96

Importing a Project

1. Open Eclipse and choose File > Import.

   The Import dialog box is displayed.

2. Choose General > Existing Projects into Workspace and click Next.

   The Import Projects dialog box is displayed.

   Figure 2 Importing a project
   

3. Click Browse and select the directory where the SDK is decompressed.
   Figure 3 Selecting the demo project
   

4. Click Finish.

   The following figure shows the directory structure of the project.

   Figure 4 Directory structure of the imported project
   

   Modify the parameters in sample code Main.java as required. For details about the sample code, see API Calling Example.

Creating a Project

1. Open Eclipse and choose File > New > Java Project.

   The New Java Project dialog box is displayed.

2. Enter a project name, for example, java-sdk-demo, retain the default settings for other parameters, and click Finish.
   Figure 5 Creating a project
   

3. Import the .jar files in the API Gateway Java SDK.
   1. Choose java-sdk-demo, right-click, and choose Build Path > Add External Archives from the shortcut menu.
      Figure 6 Importing the .jar files
      
   2. Select all .jar files in the \libs directory.
      Figure 7 Selecting all .jar files
      

4. Create a package and Main file.
   1. Choose src, right-click, and choose New > Package from the shortcut menu.
      Figure 8 Creating a package
      
   2. Enter com.apig.sdk.demo for Name.
      Figure 9 Setting a package name
      
   3. Click Finish.

      The package is created.

   4. Choose com.apig.sdk.demo, right-click, and choose New > Class from the shortcut menu.
      Figure 10 Creating a class
      
   5. Enter Main for Name and select public static void main(String[] args).
      Figure 11 Configuring the class
      
   6. Click Finish.

      The Main file is created.

5. View the directory structure of the project.
   Figure 12 Directory structure of the new project
   

   Before using Main.java, enter the required code according to API Calling Example.

API Calling Example

• This section demonstrates how to access a published API.
• You need to create and release an API on the DataArts DataService management console. For details about how to create and publish an API, see Creating an API and Publishing an API.
• The backend of this API is a fake HTTP service, which returns response code 200 and message body Congratulations, sdk demo is running.

1. Add the following references to Main.java:

   import com.cloud.apigateway.sdk.utils.Client;
   import com.cloud.apigateway.sdk.utils.Request;
   import org.apache.http.Header;
   import org.apache.http.HttpEntity;
   import org.apache.http.HttpResponse;
   import org.apache.http.client.methods.HttpRequestBase;
   import org.apache.http.impl.client.CloseableHttpClient;
   import org.apache.http.impl.client.HttpClients;
   import org.apache.http.util.EntityUtils;

2. Construct a request by configuring the following parameters:
   • AppKey: Obtain it by referring to Preparation. Coded or plaintext AK and SK in code pose significant security risks. You are advised to encrypt and store them in configuration files or environment variables and decrypt them when needed. This example takes environment variables as an example.
   • AppSecret: Obtain it by referring to Preparation. Coded or plaintext AK and SK in code pose significant security risks. You are advised to encrypt and store them in configuration files or environment variables and decrypt them when needed. This example takes environment variables as an example.
   • Method: Specify a request method. The sample code uses POST.
   • url: Request URL of the API, excluding the QueryString and fragment parts. For the domain name, use your own independent domain name bound to the group to which the API belongs. Use the sample code in http://{apig-endpoint}/java-sdk.
   • queryString: Specify query parameters to be carried in the URL. Characters (0-9a-zA-Z./;[]\-=~#%^&_+:") are allowed. The sample code uses name=value.
   • Header: Request header. Set a request header as required. It cannot contain underscores (_). The sample code uses Content-Type:text/plain.
   • body: Specify the request body. The sample code uses demo.

   The sample code is as follows:

           Request request = new Request();
           try
           {
               // Coded or plaintext AK and SK in code pose significant security risks. You are advised to encrypt and store them in configuration files or environment variables and decrypt them when needed.
               // In this example, the AK and SK stored in the environment variables are used for identity authentication. Before running this example, configure environment variables SDK_AK and SDK_SK in the local environment.
               String ak = System.getenv("SDK_AK");
               String sk = System.getenv("SDK_SK");
   
               request.setKey(ak);
               request.setSecret(sk);
   
               request.setMethod("POST");
               request.setUrl("http://{apig-endpoint}/java-sdk");
                //Obtain the URL when creating an API group.
               request.addQueryStringParam("name", "value");
               request.addHeader("Content-Type", "text/plain");
               //request.addHeader("x-stage", "publish_env_name"); //Specify an environment name before publishing the API in a non-RELEASE environment.
               request.setBody("demo");
           } catch (Exception e)
           {
               e.printStackTrace();
               return;
           }

3. Sign the request, add header x-Authorization, access the API, and print the result.
   The sample code is as follows:

           CloseableHttpClient client = null;
           try
           {
               HttpRequestBase signedRequest = Client.sign(request);
               Header[] authorization = signedRequest.getHeaders("Authorization");
               signedRequest.addHeader("x-Authorization",authorization[0].getValue());
   
               client = HttpClients.custom().build();
               HttpResponse response = client.execute(signedRequest);
               System.out.println(response.getStatusLine().toString());
               Header[] resHeaders = response.getAllHeaders();
               for (Header h : resHeaders)
               {
                   System.out.println(h.getName() + ":" + h.getValue());
               }
               HttpEntity resEntity = response.getEntity();
               if (resEntity != null)
               {
                   System.out.println(System.getProperty("line.separator") + EntityUtils.toString(resEntity, "UTF-8"));
               }
   
           } catch (Exception e)
           {
               e.printStackTrace();
           } finally
           {
               try
               {
                   if (client != null)
                   {
                       client.close();
                   }
               } catch (IOException e)
               {
                   e.printStackTrace();
               }
           }

4. Choose Main.java, right-click, and choose Run As > Java Application to run the project test code.
   Figure 13 Running the project test code
   

5. On the Console tab page, view the running result.
   Figure 14 Response displayed if the calling is successful