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Spring Boot

Singleton Inject but need dynamic changing value​

A bug finds in those of tasks where you need change the date by the nature.
Firstly You should inject a prototype bean to spring context, instead of injecting a singleton object; Secondly you need use this way.

@Component
public class SingletonService {

    // Use ObjectFactory (can also use javax.inject.Provider or Spring's Provider)
    @Resource
    private ObjectFactory<PrototypeBean> prototypeBeanFactory;

    public void callTest() {
        PrototypeBean prototypeBean = prototypeBeanFactory.getObject();
        prototypeBean.doSomething();
    }
}

Startup Problems​

Springboot startup error org.springframework.boot does not exist​

Suggest using method 2 to input mvn idea:idea in terminal, method 1 in Spring Boot project, when running other Main method test classes, will restart SpringBoot project, if you still get from ApplicationContext, then you will receive error container already closed. See blog

spring boot source code running SpringApplication error​

Could not find artifact lifecycle-mapping:lifecycle-mapping:jar:sources:1.0.0 See blog Already paid to view! Speechless

gradle spring boot 3.0 import error​

Invalid source release: 17

Ensure gradle version JDK 17 and JDK version are correct.

image-20230728021351697

Startup console log has no color​

Introduce in spring-logback.xml

<include resource="org/springframework/boot/logging/logback/base.xml"/>
<logger name="org.springframework.web" level="INFO"/>
<logger name="org.springboot.sample" level="TRACE"/>

logback modify log print content​

Code: extends ThrowableHandlingConverter impl convert method

logback config

<conversionRule convertionWord="someKeyMsg" convertClass="com.xxx.xxx.Xclass"/>

Packaging Problems​

after run the packaged jar occurs this unable to find main class​

Method 1. Replace plugin

<!--<plugin>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-maven-plugin</artifactId>
	<configuration>
		<mainClass>none</mainClass>
		<classifier>execute</classifier>
	</configuration>
	<executions>
		<execution>
			<goals>
				<goal>repackage</goal>
			</goals>
		</execution>
	</executions>
</plugin>-->
<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-source-plugin</artifactId>
	<version>3.0.1</version>
	<executions>
		<execution>
			<id>attach-sources</id>
			<goals>
				<goal>jar</goal>
			</goals>
		</execution>
	</executions>
</plugin>

Method 2: Remove spring-boot parent, then use spring boot plugin to package

Get Real Class Annotation of AOP Proxy Object​

In Spring Boot, after using AOP technologies like @Aspect, injected Bean is proxy object. Directly through getClass().getAnnotation() often cannot get annotation on original class (especially JDK dynamic proxy).

Core Solution: Use Spring provided AopProxyUtils to penetrate proxy, get final original business class.

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import org.springframework.aop.framework.AopProxyUtils;
// ...
@Component
public class MyAnnotationScanner implements ApplicationRunner {

    private final ApplicationContext context;
    private final Map<String, MyAnnotation> cacheMap = new ConcurrentHashMap<>();

    public MyAnnotationScanner(ApplicationContext context) {
        this.context = context;
    }

    @Override
    public void run(ApplicationArguments args) {
        // 1. Get all Beans with specific annotation
        Map<String, Object> beans = context.getBeansWithAnnotation(MyAnnotation.class);

        beans.forEach((name, bean) -> {
            // 2. Penetrate proxy, get real class (TargetClass)
            Class<?> targetClass = AopProxyUtils.ultimateTargetClass(bean);
            
            // 3. Extract annotation information
            MyAnnotation anno = AnnotationUtils.findAnnotation(targetClass, MyAnnotation.class);
            
            if (anno != null) {
                cacheMap.put(targetClass.getName(), anno);
            }
        });
    }
}
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