弹簧引导应用程序.属性值未填充

java spring spring-boot

2022-08-31 09:26:51

我有一个非常简单的Spring Boot应用程序，我正在尝试使用一些外部化配置。我试图遵循弹簧启动文档上的信息，但是我遇到了一个障碍。

当我在应用程序下面的外部配置下运行应用程序时，属性文件不会填充到bean中的变量中。我确信我正在做一些愚蠢的事情，谢谢你的任何建议。

MyBean.java（位于 /src/main/java/foo/bar/）

package foo.bar;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
public class MyBean {

    @Value("${some.prop}")
    private String prop;

    public MyBean() {
        System.out.println("================== " + prop + "================== ");
    }
}

Application.java（位于 /src/main/java/foo/）

package foo;

import foo.bar.MyBean;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.SpringApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan
@EnableAutoConfiguration
public class Application {

    @Autowired
    private MyBean myBean;

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

application.properties（位于 /src/main/resources/中）

some.prop=aabbcc

执行Spring Boot应用程序时的日志输出：

grb-macbook-pro:properties-test-app grahamrb$ java -jar ./build/libs/properties-test-app-0.1.0.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.1.5.RELEASE)

2014-09-10 21:28:42.149  INFO 16554 --- [           main] foo.Application                          : Starting Application on grb-macbook-pro.local with PID 16554 (/Users/grahamrb/Dropbox/dev-projects/spring-apps/properties-test-app/build/libs/properties-test-app-0.1.0.jar started by grahamrb in /Users/grahamrb/Dropbox/dev-projects/spring-apps/properties-test-app)
2014-09-10 21:28:42.196  INFO 16554 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@67e38ec8: startup date [Wed Sep 10 21:28:42 EST 2014]; root of context hierarchy
2014-09-10 21:28:42.828  INFO 16554 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Overriding bean definition for bean 'beanNameViewResolver': replacing [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration.class]] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter.class]]
2014-09-10 21:28:43.592  INFO 16554 --- [           main] .t.TomcatEmbeddedServletContainerFactory : Server initialized with port: 8080
2014-09-10 21:28:43.784  INFO 16554 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2014-09-10 21:28:43.785  INFO 16554 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/7.0.54
2014-09-10 21:28:43.889  INFO 16554 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2014-09-10 21:28:43.889  INFO 16554 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1695 ms
2014-09-10 21:28:44.391  INFO 16554 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2014-09-10 21:28:44.393  INFO 16554 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
================== null==================
2014-09-10 21:28:44.606  INFO 16554 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-09-10 21:28:44.679  INFO 16554 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2014-09-10 21:28:44.679  INFO 16554 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[text/html],custom=[]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest)
2014-09-10 21:28:44.716  INFO 16554 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-09-10 21:28:44.716  INFO 16554 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-09-10 21:28:44.902  INFO 16554 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2014-09-10 21:28:44.963  INFO 16554 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080/http
2014-09-10 21:28:44.965  INFO 16554 --- [           main] foo.Application                          : Started Application in 3.316 seconds (JVM running for 3.822)
^C2014-09-10 21:28:54.223  INFO 16554 --- [       Thread-2] ationConfigEmbeddedWebApplicationContext : Closing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@67e38ec8: startup date [Wed Sep 10 21:28:42 EST 2014]; root of context hierarchy
2014-09-10 21:28:54.225  INFO 16554 --- [       Thread-2] o.s.j.e.a.AnnotationMBeanExporter        : Unregistering JMX-exposed beans on shutdown

答案 1

执行属性注入的方式将不起作用，因为注入是在调用构造函数后完成的。

您需要执行下列操作之一：

更好的解决方案

@Component
public class MyBean {

    private final String prop;

    @Autowired
    public MyBean(@Value("${some.prop}") String prop) {
        this.prop = prop;
        System.out.println("================== " + prop + "================== ");
    }
}

解决方案将有效，但可测试性较差且可读性稍差

@Component
public class MyBean {

    @Value("${some.prop}")
    private String prop;

    public MyBean() {

    }

    @PostConstruct
    public void init() {
        System.out.println("================== " + prop + "================== ");
    }
}

另请注意，它不是特定于Spring Boot的，而是适用于任何Spring应用程序

答案 2

用户“geoand”在这里指出原因并给出解决方案是正确的。但更好的方法是将配置封装到一个单独的类中，比如 SystemContiguration java 类，然后将该类注入到你想要使用这些字段的任何服务中。

您当前将配置值直接读取到服务中的方式（@grahamrb）容易出错，如果更改配置设置名称，则会导致重构问题。