springboot?serviceImpl初始化注入對象實現(xiàn)方式

更新時間：2023年05月26日 15:32:48 作者：奔跑的閑魚碼農(nóng)

這篇文章主要介紹了springboot?serviceImpl初始化注入對象實現(xiàn)方式，具有很好的參考價值，希望對大家有所幫助。如有錯誤或未考慮完全的地方，望不吝賜教

springboot初始化serviceImpl注入對象

遇到個需求是：公司是煉鋼相關(guān)的項目，點位數(shù)據(jù)上來后放入kafka中，kafka要對數(shù)據(jù)進行處理，根據(jù)配置的點位值判斷點位是否正常。

經(jīng)歷

看到這個需求，開始是這樣實現(xiàn)的(然后每次修改了配置，就置空一下這個map)

public static Map<String, EnergyInstrumentLogDTO> monitorConfigMap = null
//消費方法
private void consumerMsg(Object msg){
?? ?if(monitorConfigMap == null){
?? ??? ?//初始化加載
?? ?}
?? ?//消費消息
}

有個同事看了我寫的，覺得會發(fā)生線程安全問題。仔細一想是覺得有點不對勁，于是乎就修改成了下面這樣

private static Map<String, EnergyInstrumentLogDTO> monitorConfigMap = new HashMap<>();
@Autowired
private LogConfigMapper logConfigMapper;
private ConsumerPointDataMsg(){
?? ?initMonitorConfig();
}
public void refreshMonitorMap() {
?? ??? ?//此處會調(diào)用數(shù)據(jù)庫日志配置logConfigMapper
? ? ? ? initMonitorConfig();
?}

這樣就有一個問題了，類構(gòu)造器中初始化時要調(diào)用logConfigMapper,此刻這個mapper的實體是null的。以上就是問題產(chǎn)生的前因，下面繼續(xù)講述后果，直接上干貨。

解決方案

使用構(gòu)造器注入方式(可能會引發(fā)A啟動要依賴B，B啟動要依賴A導(dǎo)致報錯–懶加載避免)
使用ApplicationContext的bean管理
實現(xiàn)InitializingBean接口，重寫afterPropertiesSet方法。該方法是設(shè)置屬性后執(zhí)行
構(gòu)造方法注入

1.構(gòu)造器注入

@Component
public class PostConstructTest1 {
? ? @Autowired
? ? PostConstructTest2 postConstructTest2;
? ? public PostConstructTest1() {
?? ??? ?//postConstructTest2.test();
? ? }
? ? @PostConstruct
? ? public void init() {
? ? ? ? // todo sth
? ? }
}

Bean初始化時的執(zhí)行順序：構(gòu)造方法 -> @Autowired -> @PostConstruct

2.ApplicationContext

@Component
public class ApplicationContextProvider implements ApplicationContextAware {
? ? private static ApplicationContext applicationContext;
? ? @Override
? ? public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
? ? ? ? this.applicationContext = applicationContext;
? ? }
? ? public static ApplicationContext getApplicationContext() {
? ? ? ? return applicationContext;
? ? }
? ? public static Object getBean(String name) {
? ? ? ? return getApplicationContext().getBean(name);
? ? }
? ? public static <T> T getBean(Class<T> clazz) {
? ? ? ? return getApplicationContext().getBean(clazz);
? ? }
? ? public static <T> T getBean(String name, Class<T> clazz) {
? ? ? ? return getApplicationContext().getBean(name, clazz);
? ? }
}
//使用時
private void initMonitorConfig(){
?? ?LogConfigMapper mapper = ApplicationContextProvider.getBean(LogConfigMapper.class);
}

此種方案不太建議使用，因為有點開掛的感覺，直接到spring容器中去獲取bean

3.重寫afterPropertiesSet

@Component
@Slf4j
public class ConsumerPointDataMsg implements InitializingBean {
?? ?private static Map<String, EnergyInstrumentLogDTO> monitorConfigMap = new HashMap<>();
?? ?@Autowired
?? ?private LogConfigMapper logConfigMapper;
?? ? @Override
? ? public void afterPropertiesSet() throws Exception {
? ? ? ? initMonitorConfig();
? ? }
}

4. 構(gòu)造方法注入

@Configuration
public class XxlJobConfig {
?? ?private final AddressServiceImpl addressService;
?? ?public XxlJobConfig(AddressServiceImpl addressService) {
?? ? ? ? ? ?this.addressService = addressService;
?? ?}
?? ?//直接調(diào)用
?? ?addressService.serviceUrl("XXL-JOB-ADMIN")
}

springboot無法自動注入bean問題

Description:

Field demoService in com.spring.web.DemoApplication required a bean of type 'com.spring.service.DemoService' that could not be found.

Action:
Consider defining a bean of type 'com.spring.service.DemoService' in your configuration.

谷歌翻譯為：

com.spring.web.DemoApplication中的field demoService需要無法找到類型為“com.spring.service.DemoService”的bean。

我的代碼：

controller：DemoApplication

package com.spring.web;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.spring.service.DemoService;
@RestController
//@EnableAutoConfiguration
@SpringBootApplication()
public class DemoApplication {
	@Autowired
	private DemoService demoService;
	@RequestMapping("/")
	public String helloWorld(){
		String msg =  demoService.demo();
		return msg;
	}
	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}
}

Service:DemoService

package com.spring.service;
public interface DemoService {
	public String demo();
}

ServiceImpl:DemoServiceImpl

package com.spring.service.impl;
import org.springframework.stereotype.Service;
import com.spring.service.DemoService;
@Component
public class DemoServiceImpl implements DemoService {
	@Override
	public String demo() {
		System.out.println("Hello World!");
		return "Hello World!";
	}
}

報錯：

. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v1.5.6.RELEASE)

2017-09-11 16:16:10.367 INFO 14512 --- [ main] com.spring.web.DemoApplication : Starting DemoApplication on PC2014101864 with PID 14512 (E:\workspacedubbo\boot\boot-web\target\classes started by Administrator in E:\workspacedubbo\boot\boot-web)
2017-09-11 16:16:10.369 INFO 14512 --- [ main] com.spring.web.DemoApplication : No active profile set, falling back to default profiles: default
2017-09-11 16:16:10.421 INFO 14512 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@31206beb: startup date [Mon Sep 11 16:16:10 CST 2017]; root of context hierarchy
2017-09-11 16:16:11.710 INFO 14512 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-09-11 16:16:11.721 INFO 14512 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2017-09-11 16:16:11.722 INFO 14512 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.16
2017-09-11 16:16:11.856 INFO 14512 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2017-09-11 16:16:11.856 INFO 14512 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1438 ms
2017-09-11 16:16:11.992 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/]
2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]
2017-09-11 16:16:12.025 WARN 14512 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoApplication': Unsatisfied dependency expressed through field 'demoService'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.spring.service.DemoService' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2017-09-11 16:16:12.026 INFO 14512 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2017-09-11 16:16:12.038 INFO 14512 --- [ main] utoConfigurationReportLoggingInitializer :

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2017-09-11 16:16:12.107 ERROR 14512 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :

***************************
APPLICATION FAILED TO START
***************************

Description:

Field demoService in com.spring.web.DemoApplication required a bean of type 'com.spring.service.DemoService' that could not be found.

Action:

Consider defining a bean of type 'com.spring.service.DemoService' in your configuration.

解決辦法

根據(jù)英文的提示是在配置中找不到一個指定自動注入類型的bean，

網(wǎng)上搜索得知：

SpringBoot項目的Bean裝配默認規(guī)則是根據(jù)Application類所在的包位置從上往下掃描！
“Application類”是指SpringBoot項目入口類。這個類的位置很關(guān)鍵：
如果Application類所在的包為：com.boot.app，則只會掃描com.boot.app包及其所有子包，如果service或dao所在包不在com.boot.app及其子包下，則不會被掃描！
即, 把Application類放到dao、service所在包的上級，com.boot.Application
知道這一點非常關(guān)鍵，不知道Spring文檔里有沒有給出說明，如果不知道還真是無從解決。

經(jīng)過多方排查得出結(jié)論：

正常情況下加上@Component注解的類會自動被Spring掃描到生成Bean注冊到spring容器中，既然他說沒找到，也就是該注解被沒有被spring識別，問題的核心關(guān)鍵就在application類的注解SpringBootApplication上，

這個注解其實相當(dāng)于下面這一堆注解的效果，其中一個注解就是@Component，在默認情況下只能掃描與控制器在同一個包下以及其子包下的@Component注解，以及能將指定注解的類自動注冊為Bean的@Service@Controller和@ Repository，至此明白問題所在，之前我將接口與對應(yīng)實現(xiàn)類放在了與控制器所在包的同一級目錄下，這樣的注解自然是無法被識別的。