做网站项目主要技术,wordpress微信防红插件,辽宁建设工程信息网中标通知,手机版制作app软件spring 构造函数注入欢迎使用Spring构造函数依赖注入示例指南。 基于构造器的依赖注入是Spring 依赖注入的一种 。 依赖注入的另一种类型是Setter注入和字段注入。 有关Spring依赖注入的更多信息#xff1a; Spring二传手注射的例子 Spring田间注入 依赖注入–构造函数与现… spring 构造函数注入 欢迎使用Spring构造函数依赖注入示例指南。 基于构造器的依赖注入是Spring 依赖注入的一种 。 依赖注入的另一种类型是Setter注入和字段注入。 有关Spring依赖注入的更多信息 Spring二传手注射的例子 Spring田间注入 依赖注入–构造函数与现场注入 依赖注入和控制反转 基于构造函数的依赖注入 它是Spring Dependency Injection的一种 其中对象的构造函数用于注入依赖项。 这种注入方式比较安全因为如果不存在依赖项或无法解决依赖项则不会创建对象。 要理解 基于构造函数的依赖注入在Spring中是如何工作的-显然-我们需要一个Spring应用程序。 考虑一下我们有一个非常简单的Spring应用程序称为DogsService 这是一个虚拟服务。 不知道如何编写Spring Boot Rest Service 阅读 Spring Boot Rest Service 想更多地了解Spring Framework 读这个 Spring框架介绍 Spring框架架构 Spring Bean–单例与原型 Spring自动布线 狗狗 DAO类没有任何依赖关系。 我们在print语句中添加了无参数构造函数。 import com.amitph.spring.dogs.repo.Dog; import org.springframework.stereotype.Component; import java.util.List; Component public class DogsDao { public DogsDao(){ System.out.println( DogsDao no-arg constructor called ); } public ListDog getAllDogs() { System.out.println( DogsDao.getAllDogs called ); return null ; } } 狗服务 服务HAS-A DogsDao 。 服务类具有setter方法 无参数构造函数和带有相应打印语句的参数化构造函数 。 注意参数化的构造函数以Autowrired注释。 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 { private DogsDao dao; public ListDog 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 ); } Autowired public DogsService(DogsDao dao) { System.out.println( DogsService arg constructor called ); this .dao dao; } } 狗的控制器 控制器HAS-A DogsService 。 控制器类还具有一个设置程序一个无参数构造函数和一个带有各自打印语句的参数化构造函数。 注意参数化的构造函数以Autowrired注释。 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 { private DogsService service; GetMapping public ListDog 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 ); } Autowired public DogsController(DogsService service) { System.out.println( DogsController arg constructor called ); this .service service; } } 运行应用程序 启动应用程序时我们应该在控制台上看到以下日志。 2019 - 02 - 04 19 : 56 : 46.812 INFO 68906 --- [ main] com.amitph.spring.dogs.Application : Starting Application on Amitsofficemac.gateway with PID 68906 (/Users/aphaltankar/Workspace/personal/dog-service-jpa/out/production/classes started by aphaltankar in /Users/aphaltankar/Workspace/personal/dog-service-jpa) 2019 - 02 - 04 19 : 56 : 46.815 INFO 68906 --- [ main] com.amitph.spring.dogs.Application : No active profile set, falling back to default profiles: default 2019 - 02 - 04 19 : 56 : 47.379 INFO 68906 --- [ main] .sdrcRepositoryConfigurationDelegate : Bootstrapping Spring Data repositories in DEFAULT mode. 2019 - 02 - 04 19 : 56 : 47.428 INFO 68906 --- [ main] .sdrcRepositoryConfigurationDelegate : Finished Spring Data repository scanning in 45ms. Found --- [ main] .sdrcRepositoryConfigurationDelegate : Finished Spring Data repository scanning in 45ms. Found 1 repository interfaces. 2019 - 02 - 04 19 : 56 : 47.682 INFO 68906 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration of type [org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration$EnhancerBySpringCGLIB$86296a04] is not eligible for getting processed by all BeanPostProcessors ( for example: not eligible for auto-proxying) 2019 - 02 - 04 19 : 56 : 47.931 INFO 68906 --- [ main] osbwembedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2019 - 02 - 04 19 : 56 : 47.944 INFO 68906 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2019 - 02 - 04 19 : 56 : 47.944 INFO 68906 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/ 9.0 . 12 2019 - 02 - 04 19 : 56 : 47.949 INFO 68906 --- [ 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 - 04 19 : 56 : 48.021 INFO 68906 --- [ main] oaccC[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2019 - 02 - 04 19 : 56 : 48.021 INFO 68906 --- [ main] osweb.context.ContextLoader : Root WebApplicationContext: initialization completed in 1158 ms 2019 - 02 - 04 19 : 56 : 48.042 INFO 68906 --- [ main] osbwservlet.ServletRegistrationBean : Servlet dispatcherServlet mapped to [/] 2019 - 02 - 04 19 : 56 : 48.045 INFO 68906 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: characterEncodingFilter to: [/*] 2019 - 02 - 04 19 : 56 : 48.046 INFO 68906 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: hiddenHttpMethodFilter to: [/*] 2019 - 02 - 04 19 : 56 : 48.046 INFO 68906 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: formContentFilter to: [/*] 2019 - 02 - 04 19 : 56 : 48.046 INFO 68906 --- [ main] osbwservlet.FilterRegistrationBean : Mapping filter: requestContextFilter to: [/*] 2019 - 02 - 04 19 : 56 : 48.136 INFO 68906 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool- 1 - Starting... 2019 - 02 - 04 19 : 56 : 48.230 INFO 68906 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool- 1 - Start completed. 2019 - 02 - 04 19 : 56 : 48.322 INFO 68906 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [ name: default ...] 2019 - 02 - 04 19 : 56 : 48.366 INFO 68906 --- [ main] org.hibernate.Version : HHH000412: Hibernate Core { 5.3 . 7 .Final} 2019 - 02 - 04 19 : 56 : 48.366 INFO 68906 --- [ main] org.hibernate.cfg.Environment : HHH000206: hibernate.properties not found 2019 - 02 - 04 19 : 56 : 48.461 INFO 68906 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations { 5.0 . 4 .Final} 2019 - 02 - 04 19 : 56 : 48.546 INFO 68906 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.MySQL5InnoDBDialect 2019 - 02 - 04 19 : 56 : 48.960 INFO 68906 --- [ main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit default DogsDao no-arg constructor called DogsService arg constructor called DogsController arg constructor called 2019 - 02 - 04 19 : 56 : 49.304 INFO 68906 --- [ main] ossconcurrent.ThreadPoolTaskExecutor : Initializing ExecutorService applicationTaskExecutor 2019 - 02 - 04 19 : 56 : 49.330 WARN 68906 --- [ 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 - 04 19 : 56 : 49.479 INFO 68906 --- [ main] osbwembedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path 2019 - 02 - 04 19 : 56 : 49.482 INFO 68906 --- [ main] com.amitph.spring.dogs.Application : Started Application in 3.003 seconds (JVM running for 3.521 ) 第27行正如预期的那样调用了DAO的无参数构造函数。 第28行调用了DogsService的参数化构造函数 DogsService在第27行创建了DAO实例。 第29行调用控制器的参数化构造函数并在第28行创建一个服务实例。 请注意Spring 不会调用设置器和无参数构造器 。 依赖项是通过 构造函数 纯粹注入的 。 此方法优于Spring中的Spring Setter注入和Field注入 。 摘要 在这个Spring构造函数依赖注入示例指南中您学习了基于构造函数的依赖注入在Spring应用程序中如何工作。 我们还使用构造函数注入编写了可执行代码。 当构造函数用于在对象上设置实例变量时称为构造函数注入。 在深入使用Spring Framework之前重要的是要了解Setter注入与字段注入与构造函数注入之间的区别 。 快乐编码 翻译自: https://www.javacodegeeks.com/2019/02/spring-constructor-dependency-injection-example.htmlspring 构造函数注入
