Building Microservices with Spring Boot and Apache Thrift. Part 2. Swifty services

http://bsideup.blogspot.com/2015/04/spring-boot-thrift-part2.html

In previous article I showed you how to use pure Apache Thrift to create protocols for your services. This time I will explain how to use Facebook Swift (not the best name for project BTW :)) to get rid of Thrift IDL files for server code.

Few words about Swift. Swift - Java annotation-based generator for Apache Thrift. It's priceless when you develop your APIs in Java and want to expose them to the other world using Apache Thrift.

Protocol

Lets recreate our previous example ( https://github.com/bsideup/spring-boot-thrift ) with it. Start with simple build.gradle file:

	apply plugin: 'java'
	apply plugin: 'spring-boot'
	buildscript {
	repositories {
	jcenter()
	}
	dependencies {
	classpath("org.springframework.boot:spring-boot-gradle-plugin:1.2.1.RELEASE")
	}
	}
	repositories {
	jcenter()
	}
	sourceCompatibility = 1.8
	targetCompatibility = 1.8
	dependencies {
	compile "org.projectlombok:lombok:1.16.2"
	compile("org.springframework.boot:spring-boot-starter-web")
	compile 'com.facebook.swift:swift-annotations:0.14.1'
	compile 'com.facebook.swift:swift-service:0.14.1'
	compile 'com.facebook.swift:swift-codec:0.14.1'
	compile 'com.facebook.nifty:nifty-core:0.14.1'
	compile 'org.apache.thrift:libthrift:0.9.1'
	testCompile "org.springframework.boot:spring-boot-starter-test"
	}

view rawbuild.gradle hosted with ❤ by GitHub

Nothing special, Spring Boot with few Facebook Swift libraries.

Next we need to add Swift protocol classes:

	package com.example.calculator.protocol;
	import com.facebook.swift.service.ThriftMethod;
	import com.facebook.swift.service.ThriftService;
	import com.google.common.util.concurrent.ListenableFuture;
	@ThriftService
	public interface TCalculatorService {
	@ThriftMethod
	int calculate(int num1, int num2, TOperation op) throws TDivisionByZeroException;
	}

view rawTCalculatorService.java hosted with ❤ by GitHub

Exception is simple Swift struct which extend Exception (See Ma no TException)

	package com.example.calculator.protocol;
	import com.facebook.swift.codec.ThriftStruct;
	@ThriftStruct
	public final class TDivisionByZeroException extends Exception {
	}

view rawTDivisionByZeroException.java hosted with ❤ by GitHub

Enums are handled with Swift, so we don't need to annotate them (but we can)

	package com.example.calculator.protocol;
	public enum TOperation {
	ADD,
	SUBTRACT,
	MULTIPLY,
	DIVIDE
	}

view rawTOperation.java hosted with ❤ by GitHub

Next - application main class for Spring Boot:

	package com.example.calculator;
	import com.example.calculator.protocol.TCalculatorService;
	import com.facebook.nifty.processor.NiftyProcessorAdapters;
	import com.facebook.swift.codec.ThriftCodecManager;
	import com.facebook.swift.service.ThriftEventHandler;
	import com.facebook.swift.service.ThriftServiceProcessor;
	import org.apache.thrift.protocol.*;
	import org.apache.thrift.server.TServlet;
	import org.springframework.boot.SpringApplication;
	import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
	import org.springframework.context.annotation.*;
	import javax.servlet.Servlet;
	import java.util.Arrays;
	@Configuration
	@EnableAutoConfiguration
	@ComponentScan
	public class CalculatorApplication {
	public static void main(String[] args) {
	SpringApplication.run(CalculatorApplication.class, args);
	}
	@Bean
	TProtocolFactory tProtocolFactory() {
	return new TBinaryProtocol.Factory();
	}
	@Bean
	ThriftCodecManager thriftCodecManager() {
	return new ThriftCodecManager();
	}
	@Bean
	Servlet thrift(ThriftCodecManager thriftCodecManager, TProtocolFactory protocolFactory, TCalculatorService exampleService) {
	ThriftServiceProcessor processor = new ThriftServiceProcessor(thriftCodecManager, Arrays.<ThriftEventHandler>asList(), exampleService);
	return new TServlet(
	NiftyProcessorAdapters.processorToTProcessor(processor),
	protocolFactory,
	protocolFactory
	);
	}
	}

view rawCalculatorApplication.java hosted with ❤ by GitHub

Test

Now we're ready to write some tests:

	package com.example.calculator;
	import com.example.calculator.protocol.TCalculatorService;
	import com.example.calculator.protocol.TDivisionByZeroException;
	import com.example.calculator.protocol.TOperation;
	import com.facebook.nifty.client.HttpClientConnector;
	import com.facebook.swift.codec.ThriftCodecManager;
	import com.facebook.swift.service.ThriftClientManager;
	import org.apache.thrift.protocol.TProtocolFactory;
	import org.junit.Before;
	import org.junit.Test;
	import org.junit.runner.RunWith;
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.beans.factory.annotation.Value;
	import org.springframework.boot.test.IntegrationTest;
	import org.springframework.boot.test.SpringApplicationConfiguration;
	import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
	import org.springframework.test.context.web.WebAppConfiguration;
	import java.net.URI;
	import static org.junit.Assert.*;
	@RunWith(SpringJUnit4ClassRunner.class)
	@SpringApplicationConfiguration(classes = CalculatorApplication.class)
	@WebAppConfiguration
	@IntegrationTest("server.port:0")
	public class CalculatorApplicationTest {
	@Autowired
	TProtocolFactory protocolFactory;
	@Autowired
	ThriftCodecManager thriftCodecManager;
	@Value("${local.server.port}")
	protected int port;
	protected TCalculatorService client;
	@Before
	public void setUp() throws Exception {
	HttpClientConnector connector = new HttpClientConnector(URI.create("http://localhost:" + port + "/thrift/"));
	ThriftClientManager clientManager = new ThriftClientManager(thriftCodecManager);
	client = clientManager.createClient(connector, TCalculatorService.class).get();
	}
	@Test
	public void testAdd() throws Exception {
	assertEquals(5, client.calculate(2, 3, TOperation.ADD));
	}
	@Test
	public void testSubtract() throws Exception {
	assertEquals(3, client.calculate(5, 2, TOperation.SUBTRACT));
	}
	@Test
	public void testMultiply() throws Exception {
	assertEquals(10, client.calculate(5, 2, TOperation.MULTIPLY));
	}
	@Test
	public void testDivide() throws Exception {
	assertEquals(2, client.calculate(10, 5, TOperation.DIVIDE));
	}
	@Test(expected = TDivisionByZeroException.class)
	public void testDivisionByZero() throws Exception {
	client.calculate(10, 0, TOperation.DIVIDE);
	}
	}

view rawCalculatorApplicationTest.java hosted with ❤ by GitHub

As you can see, only difference here (compared to Thrift version) is setUp method.
Diff with Thrift version

Implementation

We still have no Swift service implementation. Implementation of handler looks almost the same asprevious:

	package com.example.calculator.handler;
	import com.example.calculator.protocol.TCalculatorService;
	import com.example.calculator.protocol.TDivisionByZeroException;
	import com.example.calculator.protocol.TOperation;
	import org.springframework.stereotype.Component;
	import com.example.calculator.service.CalculatorService;
	import org.springframework.beans.factory.annotation.Autowired;
	@Component
	public class CalculatorServiceHandler implements TCalculatorService {
	@Autowired
	CalculatorService calculatorService;
	@Override
	public int calculate(int num1, int num2, TOperation op) throws TDivisionByZeroException {
	switch(op) {
	case ADD:
	return calculatorService.add(num1, num2);
	case SUBTRACT:
	return calculatorService.subtract(num1, num2);
	case MULTIPLY:
	return calculatorService.multiply(num1, num2);
	case DIVIDE:
	try {
	return calculatorService.divide(num1, num2);
	} catch(IllegalArgumentException e) {
	throw new TDivisionByZeroException();
	}
	default:
	throw new IllegalArgumentException("Unknown operation " + op);
	}
	}
	}

view rawCalculatorServiceHandler.java hosted with ❤ by GitHub

Diff with Thrift version

Now if you will run tests you should see all tests green.

Thrift integration

But hey, how about other non-Java consumers of service? Don't worry, Swift comes with a tool for generating *.thrift files from annotated Java classes:https://github.com/facebook/swift/tree/master/swift2thrift-generator-cli

Example output for our service will be:

	namespace java.swift com.example.calculator.protocol
	namespace java com.example.calculator.protocol
	namespace py com.example.calculator.protocol
	namespace as3 com.example.calculator.protocol
	enum TOperation {
	ADD, SUBTRACT, MULTIPLY, DIVIDE
	}
	exception TDivisionByZeroException {
	}
	service TCalculatorService {
	i32 calculate(1: i32 arg0, 2: i32 arg1, 3: TOperation arg2) throws (1: TDivisionByZeroException ex1);
	}

view rawcalculator.thrift hosted with ❤ by GitHub

Conclusion

Full source files for this example can be found at GitHub: https://github.com/bsideup/spring-boot-swift

Next time I will show you how to write Async Thrift services using Swift with minimal changes. Stay tuned!