Developing Functions in Java (Using Eclipse)

Function Syntax

The following is the syntax for creating a handler function in Java:

Scope Return parameter Function name (User-defined parameter, Context)

• Scope: It must be defined as public for the function that FunctionGraph invokes to execute your code.
• Return parameter: user-defined output, which is converted into a character string and returned as an HTTP response. The HTTP response is a JSON string.
• Function name: user-defined function name.
• User-defined parameter: FunctionGraph supports only one user-defined parameter. For complex parameters, define them as an object and provide data through JSON strings. When invoking a function, FunctionGraph parses the JSON strings as an object.
• Context: runtime information provided for executing the function. For details, see SDK APIs.

When creating a function in Java, define a handler in the format of [Package name].[Class name].[Function name].

Java Initializer

FunctionGraph supports the following Java runtime:

• Java 8
• Java 11

Initializer syntax:

[Package name].[Class name].[Execution function name]

For example, if the initializer is named com.huawei.Demo.my_initializer, FunctionGraph loads the my_initializer function defined in the com.huawei file.

To use Java to build initialization logic, define a Java function as the initializer. The following is a simple initializer:

public void my_initializer(Context context)
{
RuntimeLogger log = context.getLogger();
log.log(String.format("ak:%s", context.getAccessKey()));
}

• Function Name

  The function name my_initializer must be the initializer function name specified for a function.

  For example, if the initializer is named com.huawei.Demo.my_initializer, FunctionGraph loads the my_initializer function defined in the com.huawei file.

• context

  The context parameter contains the runtime information about a function. For example, request ID, temporary AK, and function metadata.

SDK APIs

The Java SDK (verification file: fss-java-sdk-2.0.5.sha256) provides context, event, and logging APIs.

• Event APIs

  Event structure definitions are added to the Java SDK. Currently, DMS, DIS, SMN, timer, APIG, and Kafka triggers are supported. The definitions make coding much simpler when triggers are required.

  1. APIG trigger
     1. APIGTriggerEvent methods

        Table 1 APIGTriggerEvent methods

        Method	Description
        isBase64Encoded()	Checks whether the body of an event is encoded using Base64.
        getHttpMethod()	Obtains the HTTP request method.
        getPath()	Obtains the HTTP request path.
        getBody()	Obtains the HTTP request body.
        getPathParameters()	Obtains all path parameters.
        getRequestContext()	Obtains API Gateway configurations (returned as an APIGRequestContext object).
        getHeaders()	Obtains the HTTP request header.
        getQueryStringParameters()	Obtains query parameters. NOTE: The value of a query parameter cannot be an array. To support an array, customize the corresponding event structure.
        getRawBody()	Obtains the content before Base64 encoding.
        getUserData()	Obtains the user data set in the APIG custom authorizer.

        Table 2 APIGRequestContext methods

        Method	Description
        getApiId()	Obtains the API ID.
        getRequestId()	Obtains the request ID of an API request.
        getStage()	Obtains the name of the environment in which an API has been published.
        getSourceIp()	Obtains the source IP address in the APIG custom authorizer.

     2. APIGTriggerResponse methods

        Table 3 APIGTriggerResponse construction methods

        Method	Description
        APIGTriggerResponse()	Set the following parameters: headers: null statusCode: 200 body: "" isBase64Encoded: false
        APIGTriggerResponse(statusCode, headers, body)	Set the value of isBase64Encoded to false, and use the input values of other parameters.
        APIGTriggerResponse(statusCode, headers, isBase64Encoded, body)	Set the parameters in sequence.

        Table 4 APIGTriggerResponse methods

        Method	Description
        setBody(String body)	Sets the message body.
        setHeaders(Map<String,String> headers)	Sets the HTTP response header to be returned.
        setStatusCode(int statusCode)	Sets the HTTP status code.
        setBase64Encoded(boolean isBase64Encoded)	Configures Base64 encoding for the response body.
        setBase64EncodedBody(String body)	Encodes the input with Base64 and configures it in the body.
        addHeader(String key, String value)	Adds a group of HTTP headers.
        removeHeader(String key)	Removes the specified header.
        addHeaders(Map<String,String> headers)	Adds multiple headers.

        

        APIGTriggerResponse methods have the headers attribute, which can be initialized using the setHeaders method or a constructor function with the headers parameter.

  2. DIS trigger

     Table 5 DISTriggerEvent methods

     Method	Description
     getShardID()	Obtains the partition ID.
     getMessage()	Obtains the DIS message body (DISMessage structure).
     getTag()	Obtains the version of a function.
     getStreamName()	Obtains the stream name.

     Table 6 DISMessage methods

     Method	Description
     getNextPatitionCursor()	Obtains the next partition cursor.
     getRecords()	Obtains message records (DISRecord structure).
     getMillisBehindLatest()	Reserved (Currently, 0 is returned.)

     Table 7 DISRecord methods

     Method	Description
     getPartitionKey()	Obtains the data partition.
     getData()	Obtains data.
     getRawData()	Obtains UTF-8 data strings decoded using Base64.
     getSequenceNumber()	Obtains the sequence number (ID of each record).

  3. DMS trigger

     Table 8 DMSTriggerEvent methods

     Method	Description
     getQueueId()	Obtains the queue ID.
     getRegion()	Obtains the region name.
     getEventType()	Obtains the event type (MessageCreated is returned).
     getConsumerGroupId()	Obtains the consumer group ID.
     getMessages()	Obtains the DMS message (DMSMessage structure).

     Table 9 DMSMessage methods

     Method	Description
     getBody()	Obtains the message body.
     getAttributes()	Obtains the message attribute set.

  4. SMN trigger

     Table 10 SMNTriggerEvent method

     Method	Description
     getRecord()	Obtains message records (SMNRecord structure).

     Table 11 SMNRecord methods

     Method	Description
     getEventVersion()	Obtains the event version. (Currently, the version is 1.0.)
     getEventSubscriptionUrn()	Obtains the subscription Uniform Resource Name (URN).
     getEventSource()	Obtains the event source.
     getSmn()	Obtains the message body (SMNBody structure).

     Table 12 SMNBody methods

     Method	Description
     getTopicUrn()	Obtains the topic URN.
     getTimeStamp()	Obtains the timestamp of a message.
     getMessageAtrributes()	Obtains the message attribute set.
     getMessage()	Obtains the message body.
     getType()	Obtains the message type.
     getMessageId()	Obtains the message ID.
     getSubject()	Obtains the message topic.

  5. Timer trigger

     Table 13 TimerTriggerEvent methods

     Method	Description
     getVersion()	Obtains the version. (Currently, the version is v1.0.)
     getTime()	Obtains the current time.
     getTriggerType()	Obtains the trigger type (Timer).
     getTriggerName()	Obtains the trigger name.
     getUserEvent()	Obtains the additional information of the trigger.

  6. Kafka trigger

     Table 14 Kafka trigger

     Method	Description
     getEventVersion	Obtains event version.
     getRegion	Obtains region information.
     getEventTime	Obtains event time.
     getTriggerType	Obtains trigger type.
     getInstanceId	Obtains instance ID.
     getRecords	Obtains record.

  

  1. When using an APIG trigger, set the first parameter of the handler function (for example, handler) to handler(APIGTriggerEvent event, Context context).
  2. The preceding TriggerEvent methods have corresponding set methods, which are recommended for local debugging. DIS and LTS triggers have getRawData() methods, but do not have setRawData() methods.
• Context APIs

  The context APIs are used to obtain the context, such as agency AK/SK, current request ID, allocated memory space, and number of CPUs, required for executing a function.

  Table 15 describes the context APIs provided by FunctionGraph.

  Table 15 Context methods

  Method	Description
  getRequestID( )	Obtains a request ID.
  getRemainingTimeInMilliSeconds ( )	Obtains the remaining running time of a function.
  getAccessKey( )	Obtains the AK (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function. NOTE: FunctionGraph has stopped maintaining the getAccessKey API in the Runtime SDK. You cannot use this API to obtain a temporary AK.
  getSecretKey( )	Obtains the SK (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function. NOTE: FunctionGraph has stopped maintaining the getSecretKey API in the Runtime SDK. You cannot use this API to obtain a temporary SK.
  getSecurityAccessKey( )	Obtains the SecurityAccessKey (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function.
  getSecuritySecretKey( )	Obtains the SecuritySecretKey (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function.
  getSecurityToken( )	Obtains the SecurityToken (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function.
  getUserData(string key)	Uses keys to obtain the values passed by environment variables.
  getFunctionName( )	Obtains the name of a function.
  getRunningTimeInSeconds ( )	Obtains the timeout of a function.
  getVersion( )	Obtains the version of a function.
  getMemorySize( )	Obtains the allocated memory.
  getCPUNumber( )	CPU usage of a function.
  getPackage( )	Obtains a function group, that is, an app.
  getToken( )	Obtains the token (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function.
  getLogger( )	Obtains the logger method provided by the context. By default, information such as the time and request ID is output.
  getAlias	Obtains function alias.

  

  Results returned by using the getToken(), getAccessKey(), and getSecretKey() methods contain sensitive information. Exercise caution when using these methods.

• Logging API

  Table 16 describes the logging API provided in the Java SDK.

  Table 16 Logging API

  Method	Description
  RuntimeLogger()	Records user input logs using the method log(String string).

Developing a Java Function

Perform the following procedure to develop a Java function:

1. Create a function project.
   1. Configure Eclipse and create a Java project named JavaTest, as shown in Figure 1.
      Figure 1 Creating a project
      
   2. Add a dependency to the project.

      Download the Java SDK to a local development environment, and decompress the SDK package, as shown in Figure 2.

      Figure 2 Decompressing the downloaded SDK
      
   3. Configure the dependency.

      Create a folder named lib in the project directory, copy the Runtime-2.0.5.jar file in the SDK package to the lib folder, and add the JAR file as a dependency of the project, as shown in Figure 3.

      Figure 3 Configuring the dependency
      

2. Create a function.
   1. Create a package named com.huawei.demo, and then create a class named TriggerTests under the package, as shown in Figure 4.
      Figure 4 Creating a package named com.huawei.demo
      
   2. Define the function handler in TriggerTests.java, as shown in Figure 5.

      1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

      package com.huawei.demo; import java.io.UnsupportedEncodingException; import java.util.HashMap; import java.util.Map; import com.huawei.services.runtime.Context; import com.huawei.services.runtime.entity.apig.APIGTriggerEvent; import com.huawei.services.runtime.entity.apig.APIGTriggerResponse; import com.huawei.services.runtime.entity.dis.DISTriggerEvent; import com.huawei.services.runtime.entity.dms.DMSTriggerEvent; import com.huawei.services.runtime.entity.smn.SMNTriggerEvent; import com.huawei.services.runtime.entity.timer.TimerTriggerEvent; public class TriggerTests { public APIGTriggerResponse apigTest(APIGTriggerEvent event, Context context){ System.out.println(event); Map<String, String> headers = new HashMap<String, String>(); headers.put("Content-Type", "application/json"); return new APIGTriggerResponse(200, headers, event.toString()); } public String smnTest(SMNTriggerEvent event, Context context){ System.out.println(event); return "ok"; } public String dmsTest(DMSTriggerEvent event, Context context){ System.out.println(event); return "ok"; } public String timerTest(TimerTriggerEvent event, Context context){ System.out.println(event); return "ok"; } public String disTest(DISTriggerEvent event, Context context) throws UnsupportedEncodingException{ System.out.println(event); System.out.println(event.getMessage().getRecords()[0].getRawData()); return "ok"; } }

      Figure 5 Defining the function handler
      
      

      For details about the constraints for the APIG event source, see Base64 Decoding and Response Structure.

3. Package the project files.
   1. Right-click the JavaTest project and choose Export, as shown in Figure 6.
      Figure 6 Packaging the project files
      
   2. Export the project to a directory as a JAR file, as shown in Figure 7 and Figure 8.
      Figure 7 Selecting a format
      
      Figure 8 Specifying the destination path
      

4. Log in to the FunctionGraph console, create a Java function, and upload the code package.
5. Test the function.
   1. Create a test event.

      Select apig-event-template and click Create.

   2. Click Test.

      The function execution result consists of three parts: function output (returned by callback), summary, and logs (output by using the console.log or getLogger() method).

   3. Create an APIG trigger.
   4. Access the API URL, as shown in Figure 9.
      Figure 9 Accessing the API URL
      

      Change the handler to com.huawei.demo.TriggerTests.smnTest and change the event template to smn-event-template.

6. Use a user-defined parameter in the Java code.
   Create a Person class in the project, as shown in Figure 10.

   Figure 10 Creating a Person class
   
   Create a class named PersonTest.java, and add a handler function to the class, as shown in Figure 11.

   Figure 11 Creating a class named PersonTest.java
   

   Upload the exported JAR file on the function details page, change the handler to com.huawei.demo.PersonTest.personTest, and save the change.

   Figure 12 Uploading a JAR file
   

   In the Configure Test Event dialog box, select blank-template, and enter a test event.

   Click Create, and then click Test.

Execution Result

The execution result consists of the function output, summary, and log output.

{
  "errorMessage": "",
  "stackTrace": []
}