springboot and retry hello world example

Introduction

This post would demo springboot and retry hello world example, which would use the default retry policy.

Environments

• SpringBoot 1.5.12
• Java 1.8

The SpringBoot version in pom.xml

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>1.5.12.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

The dependencies for spring retry with springboot starters in pom.xml

We must add the following dependencies to make the retry example work:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.retry</groupId>
    <artifactId>spring-retry</artifactId>
    <version>1.1.5.RELEASE</version>
</dependency>

The entry class @SpringBootApplication

@SpringBootApplication
@EnableRetry
public class MainApp {
    public static void main(String[] args) {
        SpringApplication.run(MainApp.class, args);
    }
}

You can add @EnableRetry to any @Configuration class.

The mayFailMethod in the service

@Component
public class RetryService {
    private static Log log = LogFactory.getLog(RetryService.class);
    private int retryTimes = 0; //line 0

    @Retryable //line 1
    public boolean mayFailMethod() throws Exception {
        retryTimes++; //line 2
        log.info("do mailFailMethod "+retryTimes);
        try {
            Thread.sleep(1000); //line 3
        }catch (InterruptedException ex) {
            ex.printStackTrace();
        }
        if(retryTimes<3) { //line 4
            throw new Exception("failed");
        }else {
            log.info("mailFailMethod success");
            return true; //line 5
        }
    }
}

The code explantion:

• line 0
  • we define a variable retryTimes to record the real retry times by spring retry module
• line 1
  • this line use the annotation @Retryable to enable the retry policy on method mayFailMethod
• line 2
  • In order to know how many times this method is retried, I increment the retryTimes every time the method is called
• line 3
  • Sleep for a while to mimic the network latency of a long running method
• line 4
  • Because the default retry policy is 3, so ,when retry before 3 times, this method would always fail by throw an Exception
• line 5
  • if retry after 3 times, this method would return true.

The test code

If you don’t know how to do unit testing with springboot , you can reference the post: How to do unit testing with springboot hello world example

@RunWith(SpringRunner.class) //line 0
@SpringBootTest             // line 0
public class TestRetryService {
    @Autowired  //line 1
    private RetryService retryService;

    @Test //line2
    public void testRetryHelloWorld() {
        try {
            boolean result = retryService.mayFailMethod(); //line 2
            assertTrue(result);//line 3
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The code explanation:

• line 0:
  • SpringBoot testcase must use the @RunWith(SpringRunner.class) and @SpringBootTest
• line 1:
  • We autowired the class under test: RetryService
• line 2:
  • We call the mayFailMethod only one time,and make sure that the result is true(assume retry is done successfully)

Run the test code

Let’s run the test code:

2018-05-01 21:08:58.558  INFO 38693 --- [           main] java8.learn.retry.RetryService           : do mayFailMethod 1
2018-05-01 21:09:00.568  INFO 38693 --- [           main] java8.learn.retry.RetryService           : do mayFailMethod 2
2018-05-01 21:09:02.576  INFO 38693 --- [           main] java8.learn.retry.RetryService           : do mayFailMethod 3
2018-05-01 21:09:03.577  INFO 38693 --- [           main] java8.learn.retry.RetryService           : mayFailMethod success

Process finished with exit code 0

As we can see from the console output, the retryService.mayFailMethod() is retried automatically by spring retry, and has retried 3 times. At last, the retry end successfully by return a true value.

It’s so easy, do you think so? You can find the complete code in the github repository bswen github

You can find detail documents about the springboot and unit testing here:

• springboot
• spring retry