Function Compute:Java handlers

Maven dependency

Add fc-java-core to your pom.xml:

<dependency>
    <groupId>com.aliyun.fc.runtime</groupId>
    <artifactId>fc-java-core</artifactId>
    <version>1.4.1</version>
</dependency>

Check the Maven repository for the latest version.

Before creating a function, package your code and the fc-java-core dependency into a JAR file. See Compile and deploy code packages.

Handler class

// HelloFC.java
package example;

import com.aliyun.fc.runtime.Context;
import com.aliyun.fc.runtime.PojoRequestHandler;

public class HelloFC implements PojoRequestHandler<SimpleRequest, SimpleResponse> {

    @Override
    public SimpleResponse handleRequest(SimpleRequest request, Context context) {
        String message = "Hello, " + request.getFirstName() + " " + request.getLastName();
        return new SimpleResponse(message);
    }
}

Request and response classes

// SimpleRequest.java
package example;

public class SimpleRequest {
    String firstName;
    String lastName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public SimpleRequest() {}
    public SimpleRequest(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
}

// SimpleResponse.java
package example;

public class SimpleResponse {
    String message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public SimpleResponse() {}
    public SimpleResponse(String message) {
        this.message = message;
    }
}

Sample input event

{
  "firstName": "FC",
  "lastName": "aliyun"
}

Prerequisites

Before you begin, ensure that you have:

• A function created in a Java runtime with the sample code below. See Create an event function

• An HTTP trigger configured for the function. See Configure an HTTP trigger

Sample code

The handler implements PojoRequestHandler with HTTPTriggerEvent and HTTPTriggerResponse as the input and output types. For HTTP trigger request and response formats, see Use an HTTP trigger to invoke a function.

App.java - Entry class

package example;

import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

import com.aliyun.fc.runtime.Context;
import com.aliyun.fc.runtime.PojoRequestHandler;

public class App implements PojoRequestHandler<HTTPTriggerEvent, HTTPTriggerResponse> {

    @Override
    public HTTPTriggerResponse handleRequest(HTTPTriggerEvent request, Context context) {
        context.getLogger().info("Receive HTTP Trigger request: " + request.toString());
        String requestBody = request.getBody();
        if (request.isIsBase64Encoded()) {
            requestBody = new String(java.util.Base64.getDecoder().decode(request.getBody()), StandardCharsets.UTF_8);
        }
        String message = "HTTP Trigger request body: " + requestBody;
        context.getLogger().info(message);
        Map<String, String> headers = new HashMap<>();
        headers.put("Content-Type", "text/plain");
        return HTTPTriggerResponse.builder().withStatusCode(200).withHeaders(headers).withBody(request.getBody())
                .withIsBase64Encoded(request.isIsBase64Encoded()).build();
    }
}

HTTPTriggerEvent.java - Request format

package example;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import com.fasterxml.jackson.annotation.JsonProperty;

import java.util.Map;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder(setterPrefix = "with")
public class HTTPTriggerEvent {
    private String version;
    private String rawPath;
    private Map<String, String> headers;
    private Map<String, String> queryParameters;
    private RequestContext requestContext;

    @JsonProperty("isBase64Encoded")
    private boolean IsBase64Encoded;
    private String body;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    @Builder(setterPrefix = "with")
    public static class RequestContext {
        private String accountId;
        private String domainName;
        private String domainPrefix;
        private HttpInfo http;
        private String requestId;
        private String time;
        private String timeEpoch;

        @Data
        @NoArgsConstructor
        @AllArgsConstructor
        @Builder(setterPrefix = "with")
        public static class HttpInfo {
            private String method;
            private String path;
            private String protocol;
            private String sourceIp;
            private String userAgent;
        }
    }

}

HTTPTriggerResponse.java - Response format

package example;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Map;

import com.fasterxml.jackson.annotation.JsonProperty;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder(setterPrefix = "with")
public class HTTPTriggerResponse {
    private int statusCode;
    private Map<String, String> headers;

    @JsonProperty("isBase64Encoded")
    private boolean IsBase64Encoded;
    private String body;
}

Additional Maven dependencies

Add jackson and lombok alongside fc-java-core:

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.16.1</version>
</dependency>
<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <version>1.18.30</version>
</dependency>

Invoke the function

1. Log on to the Function Compute console. In the left-side navigation pane, click Functions.

2. In the top navigation bar, select a region. On the Functions page, click the function to manage.

3. Click the Triggers tab to obtain the public endpoint of the HTTP trigger.

4. Run the following curl command: Replace the URL with your HTTP trigger's public endpoint. Expected response:

      curl -i "https://dev-jav-test-fc-luiqas****.cn-shanghai.fcapp.run" -d 'hello fc3.0'

      HTTP/1.1 200 OK
      Content-Disposition: attachment
      Content-Length: 11
      Content-Type: application/json
      X-Fc-Request-Id: 1-652503f2-afbfd2b1dc4dd0fcb0230959
      Date: Tue, 10 Oct 2023 07:57:38 GMT
   
      hello fc3.0%

Common errors

This handler is designed for HTTP trigger invocations. Invoking it through the Test Function button in the console with a plain string input (such as "Hello, FC!") causes a deserialization error:

{
    "errorType": "com.fasterxml.jackson.databind.exc.MismatchedInputException",
    "errorMessage": "Cannot construct instance of `example.HTTPTriggerEvent` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('Hello, FC!')\n at [Source: (byte[])\"\"Hello, FC!\"\"; line: 1, column: 1]",
    "stackTrace": [
        "com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)",
        "com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1588)",
        "..."
    ]
}

To test this handler, invoke it through the HTTP trigger endpoint or provide a JSON payload that matches the HTTPTriggerEvent structure.