albert's blog: March 2019

2019/03/31

[Travel] 貓纜、樟湖步道

2019/03/30

[Travel] 201903 雲端山城太平雲梯、老街

2019/03/15

[Spring boot] A simple spring-retry example

Scenario

How-To
Add spring-retry in your pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>test</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.retry</groupId>
            <artifactId>spring-retry</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Create email service

package com.example.service;

import com.example.rest.EmailResource;
import lombok.extern.slf4j.Slf4j;
import org.springframework.retry.annotation.Backoff;
import org.springframework.retry.annotation.Recover;
import org.springframework.retry.annotation.Retryable;
import org.springframework.stereotype.Service;

@Slf4j
@Service
public class EmailService {

    private int counter = 0;

    /**
     * 最多 retry 5 次，每次 retry 間隔 5 秒鐘
     *
     * @param param
     */
    @Retryable(maxAttempts = 5, backoff = @Backoff(delay = 5000))
    public void sendMailWithRetry(EmailResource.EmailParam param) {
        counter++;
        log.debug("Failed to send mail. Retried " + counter + " times");
        throw new IllegalArgumentException("some error happened");
    }

    /**
     * 當 retry 5 次全部失敗，則到 recover method，印出錯誤訊息
     *
     * @param throwable
     * @param param
     */
    @Recover
    public void recover(Throwable throwable, EmailResource.EmailParam param) {
        String errorMsg = "fail to retry 5 times, param = %s, error message : %s";
        throw new IllegalArgumentException(String.format(errorMsg, param, throwable.getMessage()));
    }

}

Create email resource class

package com.example.rest;

import com.example.service.EmailService;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@Slf4j
@RestController
@RequestMapping(value = "/email")
public class EmailResource {

    @Autowired
    private EmailService emailService;


    @PostMapping(value = "/send")
    public void sendMail(@RequestBody EmailParam param) {
        emailService.sendMailWithRetry(param);
    }

    @Data
    public static class EmailParam {
        private String to;
        private String subject;
        private String content;
    }

}

Enable spring retry function

package com.example.test;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.retry.annotation.EnableRetry;

// add @EnableRetry annotation to enable spring retry function
@EnableRetry
@SpringBootApplication
@ComponentScan(basePackages = "com.example")
public class TestApplication {

    public static void main(String[] args) {
        SpringApplication.run(TestApplication.class, args);
    }

}

Do test and check result

2018-11-28 09:55:32.135 DEBUG 9804 --- [nio-8080-exec-1] com.example.service.EmailService         : Failed to send mail. Retried 1 times
2018-11-28 09:55:37.136 DEBUG 9804 --- [nio-8080-exec-1] com.example.service.EmailService         : Failed to send mail. Retried 2 times
2018-11-28 09:55:42.138 DEBUG 9804 --- [nio-8080-exec-1] com.example.service.EmailService         : Failed to send mail. Retried 3 times
2018-11-28 09:55:47.138 DEBUG 9804 --- [nio-8080-exec-1] com.example.service.EmailService         : Failed to send mail. Retried 4 times
2018-11-28 09:55:52.139 DEBUG 9804 --- [nio-8080-exec-1] com.example.service.EmailService         : Failed to send mail. Retried 5 times
2018-11-28 09:55:52.215 ERROR 9804 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: fail to retry 5 times, param = EmailResource.EmailParam(to=junyuo@gmail.com, subject=email subject, content=email content), error message : some error happened] with root cause

java.lang.IllegalArgumentException: fail to retry 5 times, param = EmailResource.EmailParam(to=junyuo@gmail.com, subject=email subject, content=email content), error message : some error happened
 at com.example.service.EmailService.recover(EmailService.java:37) ~[classes/:na]
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_151]
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_151]
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_151]

2019/03/14

[Spring Boot] java.lang.NoClassDefFoundError: org/aspectj/lang/annotation/Pointcut

Problem
When I add @EnableRetry annotation:

package com.example.test;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.retry.annotation.EnableRetry;

@EnableRetry
@SpringBootApplication
@ComponentScan(basePackages = "com.example")
public class TestApplication {

    public static void main(String[] args) {
        SpringApplication.run(TestApplication.class, args);
    }

}

Then startup my spring boot project, I got the following exception

Caused by: java.lang.NoClassDefFoundError: org/aspectj/lang/annotation/Pointcut
 at org.springframework.aop.aspectj.annotation.AbstractAspectJAdvisorFactory.<clinit>(AbstractAspectJAdvisorFactory.java:62) ~[spring-aop-5.1.2.RELEASE.jar:5.1.2.RELEASE]
 at org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator.initBeanFactory(AnnotationAwareAspectJAutoProxyCreator.java:82) ~[spring-aop-5.1.2.RELEASE.jar:5.1.2.RELEASE]
 at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.setBeanFactory(AbstractAdvisorAutoProxyCreator.java:63) ~[spring-aop-5.1.2.RELEASE.jar:5.1.2.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeAwareMethods(AbstractAutowireCapableBeanFactory.java:1767) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1732) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:576) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
 ... 15 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.aspectj.lang.annotation.Pointcut
 at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_151]
 at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_151]
 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) ~[na:1.8.0_151]
 at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_151]
 ... 21 common frames omitted

How-To
Lacking of spring-boot-starter-aop dependency in pom.xml is root cause. So you need to edit pom.xml as bellows:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>test</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.retry</groupId>
            <artifactId>spring-retry</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

2019/03/13

[Spring boot] org.yaml.snakeyaml.scanner.ScannerException: mapping values are not allowed here

Problem
When I tried to startup my spring boot project, I got this exception:

Caused by: org.yaml.snakeyaml.scanner.ScannerException: mapping values are not allowed here
 in 'reader', line 16, column 17:
        diskdrive: C:
                    ^

 at org.yaml.snakeyaml.scanner.ScannerImpl.fetchValue(ScannerImpl.java:872)
 at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:360)
 at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:226)
 at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingKey.produce(ParserImpl.java:557)
 at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:157)
 at org.yaml.snakeyaml.parser.ParserImpl.checkEvent(ParserImpl.java:147)
 at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:227)
 at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:154)
 at org.yaml.snakeyaml.composer.Composer.composeValueNode(Composer.java:249)
 at org.yaml.snakeyaml.composer.Composer.composeMappingChildren(Composer.java:240)
 at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:228)
 at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:154)
 at org.yaml.snakeyaml.composer.Composer.composeValueNode(Composer.java:249)
 at org.yaml.snakeyaml.composer.Composer.composeMappingChildren(Composer.java:240)
 at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:228)
 at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:154)
 at org.yaml.snakeyaml.composer.Composer.composeDocument(Composer.java:122)
 at org.yaml.snakeyaml.composer.Composer.getNode(Composer.java:84)
 at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:123)
 at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:547)

Here had part of application.yml

opendata:
  file:
    diskdrive: C:
    subdirectory: opendata

How-To
I should add double quote to C: in head and tail. application.yml should modify as bellows:

opendata:
  file:
    diskdrive: "C:"
    subdirectory: opendata

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