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spring注入私有字段_Spring字段依赖注入示例

發布時間：2023/12/3 40 豆豆

生活随笔收集整理的這篇文章主要介紹了 spring注入私有字段_Spring字段依赖注入示例小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

spring注入私有字段

了解如何編寫Spring Field Injection示例 。 字段注入是Spring框架 依賴注入的一種 。在本教程中，我們將編寫幾個類，并看一看現場注入工程。

有關Spring依賴注入的更多信息：

Spring Setter依賴注入示例
Spring構造函數依賴注入示例
Spring依賴注入–字段vs設置器vs構造函數注入
Spring依賴注入和控制反轉

基于字段的依賴注入

在這種類型的依賴注入中，Spring將依賴直接分配給字段。它不同于構造函數注入或基于Setter的依賴注入。

有趣的是，即使字段是私有的，Spring也會注入依賴項。 Spring使用Java Reflections來做到這一點。因此，許多專家稱它為不安全。

字段注入可能是依賴注入的最簡單（但有風險）形式。為了更好地理解它，我們假設我們有一個正在運行的Spring Boot Service 。它是一項虛擬服務，旨在了解現場注入。

不知道如何編寫Spring Boot Rest Service？

讀這個： Sprint Boot休息服務

想更多地了解Spring Framework？

讀這個：

Spring框架介紹
Spring建筑
春天@Autowired
Spring中的@Autowired注釋

讓我們先編寫我們的DogsService類

狗服務

此類對DogsDao具有依賴關系。用@Autowired注釋參考變量。有一個setter和兩個構造函數，分別帶有打印消息。

import com.amitph.spring.dogs.dao.DogsDao; import com.amitph.spring.dogs.repo.Dog; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; import java.util.List; @Component public class DogsService { @Autowired private DogsDao dao; public List<Dog> getDogs() { System.out.println( "DogsService.getDogs called" ); return dao.getAllDogs(); } public void setDao(DogsDao dao) { System.out.println( "DogsService setter called" ); this .dao = dao; } public DogsService(){ System.out.println( "DogsService no-arg constructor called" ); } public DogsService(DogsDao dao) { System.out.println( "DogsService arg constructor called" ); this .dao = dao; } }

狗的控制器

控制器對DogsService具有依賴性。與服務類類似，將@Autowired批注添加到參考變量。有帶有打印消息的setter和構造函數。

import com.amitph.spring.dogs.repo.Dog; import com.amitph.spring.dogs.service.DogsService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import java.util.List; @RestController @RequestMapping ( "/dogs" ) public class DogsController { @Autowired private DogsService service; @GetMapping public List<Dog> getDogs() { return service.getDogs(); } public void setService(DogsService service) { System.out.println( "DogsController setter called" ); this .service = service; } public DogsController(){ System.out.println( "DogsController no-arg constructor called" ); } public DogsController(DogsService service) { System.out.println( "DogsController arg constructor called" ); this .service = service; } }

運行代碼

. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | ' _| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2. 1.0 .RELEASE) 2019 - 02 - 05 06 : 34 : 14.956 INFO 69421 --- [ main] com.amitph.spring.dogs.Application : Starting Application on Amits-office-mac.local with PID 69421 (/Users/aphaltankar/Workspace/personal/dog-service-jpa/out/production/classes started by aphaltankar in /Users/aphaltankar/Workspace/personal/dog-service-jpa) 2019 - 02 - 05 06 : 34 : 14.957 INFO 69421 --- [ main] com.amitph.spring.dogs.Application : No active profile set, falling back to default profiles: default 2019 - 02 - 05 06 : 34 : 15.655 INFO 69421 --- [ main] .sdrcRepositoryConfigurationDelegate : Bootstrapping Spring Data repositories in DEFAULT mode. 2019 - 02 - 05 06 : 34 : 15.711 INFO 69421 --- [ main] .sdrcRepositoryConfigurationDelegate : Finished Spring Data repository scanning in 50ms. Found --- [ main] .sdrcRepositoryConfigurationDelegate : Finished Spring Data repository scanning in 50ms. Found 1 repository interfaces. 2019 - 02 - 05 06 : 34 : 16.013 INFO 69421 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration' of type [org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration$EnhancerBySpringCGLIB$1cc57cd7] is not eligible for getting processed by all BeanPostProcessors ( for example: not eligible for auto-proxying) 2019 - 02 - 05 06 : 34 : 16.318 INFO 69421 --- [ main] osbwembedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2019 - 02 - 05 06 : 34 : 16.335 INFO 69421 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2019 - 02 - 05 06 : 34 : 16.335 INFO 69421 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/ 9.0 . 12 2019 - 02 - 05 06 : 34 : 16.342 INFO 69421 --- [ main] oacatalina.core.AprLifecycleListener : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [/Users/aphaltankar/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.] 2019 - 02 - 05 06 : 34 : 16.429 INFO 69421 --- [ main] oaccC[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2019 - 02 - 05 06 : 34 : 16.429 INFO 69421 --- [ main] osweb.context.ContextLoader : Root WebApplicationContext: initialization completed in 1419 ms 2019 - 02 - 05 06 : 34 : 16.454 INFO 69421 --- [ main] osbwservlet.ServletRegistrationBean : Servlet dispatcherServlet mapped to [/] 2019 - 02 - 05 06 : 34 : 16.457 INFO 69421 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*] 2019 - 02 - 05 06 : 34 : 16.458 INFO 69421 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*] 2019 - 02 - 05 06 : 34 : 16.458 INFO 69421 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: 'formContentFilter' to: [/*] 2019 - 02 - 05 06 : 34 : 16.458 INFO 69421 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*] 2019 - 02 - 05 06 : 34 : 16.581 INFO 69421 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool- 1 - Starting... 2019 - 02 - 05 06 : 34 : 16.702 INFO 69421 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool- 1 - Start completed. 2019 - 02 - 05 06 : 34 : 16.830 INFO 69421 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [ name: default ...] 2019 - 02 - 05 06 : 34 : 16.906 INFO 69421 --- [ main] org.hibernate.Version : HHH000412: Hibernate Core { 5.3 . 7 .Final} 2019 - 02 - 05 06 : 34 : 16.907 INFO 69421 --- [ main] org.hibernate.cfg.Environment : HHH000206: hibernate.properties not found 2019 - 02 - 05 06 : 34 : 17.059 INFO 69421 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations { 5.0 . 4 .Final} 2019 - 02 - 05 06 : 34 : 17.188 INFO 69421 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.MySQL5InnoDBDialect 2019 - 02 - 05 06 : 34 : 17.783 INFO 69421 --- [ main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default' DogsDao no-arg constructor called DogsService no-arg constructor called DogsController no-arg constructor called 2019 - 02 - 05 06 : 34 : 18.208 INFO 69421 --- [ main] ossconcurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor' 2019 - 02 - 05 06 : 34 : 18.244 WARN 69421 --- [ main] aWebConfiguration$JpaWebMvcConfiguration : spring.jpa.open-in-view is enabled by default . Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable . Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable . Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning 2019 - 02 - 05 06 : 34 : 18.420 INFO 69421 --- [ main] osbwembedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '' 2019 - 02 - 05 06 : 34 : 18.422 INFO 69421 --- [ main] com.amitph.spring.dogs.Application : Started Application in 3.878 seconds (JVM running for 4.57 )

所有三個無參數的控制器依次調用。沒有調用setter或參數化的構造函數。還有一點要注意的是標記為@Autowired的字段是private 。

春天可以設置

Spring使用反射在對象上設置私有字段。這聽起來很有用，但另一方面卻不安全。現場注射，其安全性和實用性一直備受爭議。 Spring不遵守對象訪問規則。現在，有些人可能會支持這種說法，或者說spring IoC容器管理所有對象，應該獲得對這些對象的最高控制權。

@Component public class MyClass { @Autowired private DogsController controller; @Autowired private DogsService service; @Autowired private DogsDao dao; @Autowired private ApplicationProperties properties; / business methods }

作為開發人員，我一直喜歡使用Field Injection，因為它確實很簡單且可讀性更高。您實際上可以避免編寫setter方法或構造函數，而將精力放在業務方法上。

摘要

您了解了字段注入是Spring Dependency Injection的一種 ，并編寫了幾類來查看它的工作原理。字段注入很簡單，使類更具可讀性。但是，出于安全考慮，許多人討厭它并避免使用它。

在接下來的部分中，我們將看到Setter注入， Field注入和 Constructor注入這三種方法之間的詳細區別。

快樂編碼！

翻譯自: https://www.javacodegeeks.com/2019/02/spring-field-dependency-injection-example.html