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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].

SDK APIs

The Java SDK provides context, event, and logging APIs.

  • Event APIs

    Event structure definitions are added to the Java SDK. Currently, CTS, DMS, DIS, SMN, LTS, Timer, and APIG 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 has been 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 encryption.

        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. LTS trigger
      Table 14 LTSTriggerEvent method

      Method

      Description

      getLts()

      Obtains LTS messages (LTSBody structure).
      Table 15 LTSBody methods

      Method

      Description

      getData()

      Obtains original LTS messages.

      getRawData()

      Obtains UTF-8 messages decoded using Base64.
    7. CTS trigger
      Table 16 CTSTriggerEvent method

      Method

      Description

      getCTS()

      Obtains the CTS message body (CTS structure).
      Table 17 CTS structure methods

      Method

      Description

      getTime()

      Obtains the time when a trace occurred.

      getUser()

      Obtains the information (user structure) about the user who triggered the trace.

      getRequest()

      Obtains the request content of the trace.

      getResponse()

      Obtains the response content of the trace.

      getCode()

      Obtains the response code.

      getServiceType()

      Obtains the name of the service involved in the trace.

      getResourceType()

      Obtains the type of the resource involved in the trace.

      getResourceName()

      Obtains the name of the resource involved in the trace.

      getResourceId()

      Obtains the ID of the resource involved in the trace.

      getTraceName()

      Obtains the trace name.

      getTraceType()

      Obtains the trace type, for example, ConsoleAction.

      getRecordTime()

      Obtains the time when CTS received the trace.

      getTraceId()

      Obtains the trace ID.

      getTraceStatus()

      Obtains the trace status.
      Table 18 User methods

      Method

      Description

      getName()

      Obtains the username (an account can create multiple users).

      getId()

      Obtains the user ID.

      getDomain()

      Obtains the account information.
      Table 19 Domain methods

      Method

      Description

      getName()

      Obtains the account name.

      getId()

      Obtains the account ID.
    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 20 describes the context APIs provided by FunctionGraph.

    Table 20 Context methods

    Method

    Description

    getRequestID( )

    Obtains a request ID.

    getRemainingTimeInMilligetRunningTimeInSecondsSeconds ( )

    Obtains the remaining running time of a function.

    getAccessKey( )

    Obtains the AK (valid for 24 hours) of an agency. If you use this method, you need to configure an agency for the function.

    getSecretKey( )

    Obtains the SK (valid for 24 hours) of 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( )

    Number of CPU millicores used by the function (1 core = 1000 millicores).

    The value of this field is proportional to that of MemorySize. By default, 100 CPU millicores are required for 128 MB memory. The number of CPU millicores is calculated as follows: Memory/128 x 100 + 200 (basic CPU millicores).

    getProjectID( )

    Obtains a project ID.

    getPackage( )

    Obtains a function group, that is, an app.

    getToken( )

    Obtains the token (valid for 24 hours) of 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.

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

  • Logging API

    Table 21 describes the logging API provided in the Java SDK.

    Table 21 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-1.1.3.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. 
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      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.lts.LTSTriggerEvent;
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";
    }

    public String ltsTest(LTSTriggerEvent event, Context context) throws UnsupportedEncodingException {
        System.out.println(event);
        System.out.println("raw data: " + event.getLts().getRawData());
        return "ok";
    }
}
      Figure 5 Defining the function handler

      The example code contains multiple handler functions, which use different types of triggers.

  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, as shown in Figure 9.

    Figure 9 Creating a function

  5. Test the function.

    1. Create a test event.

      Select apig-event-template and click Save.

      Figure 10 Configuring a test event
    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), as shown in Figure 11.

      Figure 11 Execution result
    3. Create an APIG trigger, as shown in Figure 12.
      Figure 12 Creating an APIG trigger
    4. Access the API URL, as shown in Figure 13.
      Figure 13 Accessing the API URL
      Change the handler to com.huawei.demo.TriggerTests.smnTest and change the event template to smn-event-template. Figure 14 shows the execution result.
      Figure 14 Execution result

  6. Use a user-defined parameter in the Java code.

    Create a Person class in the project, as shown in Figure 15.
    Figure 15 Creating a Person class
    Create a class named PersonTest.java, and add a handler function to the class, as shown in Figure 16.
    Figure 16 Creating a class named PersonTest.java
    After exporting the new package, upload it to the function, change the function handler to com.huawei.demo.PersonTest.personTest, and click Save, as shown in Figure 17.
    Figure 17 Uploading the code package
    In the Configure Test Event dialog box, select blank-template, enter a test event, and click Save, as shown in Figure 18.
    Figure 18 Configuring a test event
    Click Test. Figure 19 shows the execution result.
    Figure 19 Execution result

Execution Result

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

Table 22 Description of the execution result

Parameter

Successful Execution

Failed Execution

Function Output

The defined function output information is returned.

A JSON file that contains errorMessage and stackTrace is returned. The format is as follows:

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

errorMessage: Error message returned by the runtime.

stackTrace: Stack error information returned by the runtime.

Summary

Request ID, Memory Configured, Execution Duration, Memory Used, and Billed Duration are displayed.

Request ID, Memory Configured, Execution Duration, Memory Used, and Billed Duration are displayed.

Log Output

Function logs are printed. A maximum of 4 KB logs can be displayed.

Error information is printed. A maximum of 4 KB logs can be displayed.

Example of the function output when a function fails to be executed:

{
  "errorMessage": "Exception: package.index",
  "stackTrace": []
}

Example of the log output when a function fails to be executed:

2020-07-27 15:16:55.819+08:00 Start invoke request '249d3490-d586-447e-92b7-945485126528', version: latest
2020-07-27 15:16:56.011+08:00 {
  "errorMessage": "Exception: package.index",
  "stackTrace": []
}
2020-07-27 15:16:56.114+08:00 Finish invoke request '249d3490-d586-447e-92b7-945485126528', duration: 294.518ms, billing duration: 300ms, memory used: 74.262MB.