Function Compute:Event handlers

Prerequisites

Before you begin, ensure that you have:

• Added the fc-java-core dependency to your pom.xml

• Packaged your code and its dependencies into a JAR file

Add the fc-java-core dependency

Add the following 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.

StreamRequestHandler

StreamRequestHandler passes the invocation payload as a raw byte stream. Read from inputStream to get the event data, and write your result to outputStream.

package example;

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

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class HelloFC implements StreamRequestHandler {

    @Override
    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
        outputStream.write(new String("hello world").getBytes());
    }
}

Handler string format

When implementing StreamRequestHandler, set the Handler parameter in your function configuration to:

{package}.{ClassName}::handleRequest

For the example above: example.HelloFC::handleRequest

The package name and class name can be customized, but must match the Handler parameter in your function configuration. For details, see Create a function.

Context object

The context parameter provides runtime information for the current invocation, including the request ID and a temporary AccessKey pair. Its type is com.aliyun.fc.runtime.Context. For details, see Context object.

PojoRequestHandler

PojoRequestHandler automatically deserializes the JSON invocation payload into a typed input object and serializes your return value back to JSON. Both the input and output types must be plain old Java objects (POJOs).

The following example reads a firstName and lastName from the event payload and returns a greeting message.

// 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);
    }
}

// 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;
    }
}

Example event payload

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

Deploy your function

Package your code and the fc-java-core dependency into a JAR file before creating the function. For packaging instructions, see Compile and deploy code packages.

What's next

Explore sample programs with complete build and deployment scripts:

• java11-blank-stream-event — stream-based event handler

• java11-blank-pojo-event — POJO-based event handler