SpringBoot中 使用@Value註解獲取不到配置文件中的值問題

在學習《spring cloud與Docker微服務架構實戰》一書中，編寫一個簡單的服務提供者和服務消費者的小例子。

@RestController
public class MovieController {
	@Autowired 
	RestTemplate restTemplate;
	
	@GetMapping("/user/{id}")
	public User getUserByID(@PathVariable Long id){
		User user = restTemplate.getForObject("http://localhost:8085/"+id, User.class);
		return user;
	}
}

這裏電影服務消費者去調用用戶服務時，這塊兒是硬編碼問題，所以想先提取到配置文件中。

即先在配置文件中配置服務的URL，這個屬於自定義屬性，所以編譯器給出了提示。

 

@RestController
public class MovieController {
	@Autowired 
	RestTemplate restTemplate;
	
	@Value("user.userServiceUrl")
	private	String userServiceUrl;
	
	@GetMapping("/user/{id}")
	public User getUserByID(@PathVariable Long id){
		User user = restTemplate.getForObject(this.userServiceUrl+id, User.class);
		return user;
	}
}

按照書中代碼，這麼運行就會報錯。

java.lang.IllegalArgumentException: URI is not absolute
	at java.net.URI.toURL(Unknown Source) ~[na:1.8.0_172]
	at org.springframework.http.client.SimpleClientHttpRequestFactory.createRequest(SimpleClientHttpRequestFactory.java:137) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.http.client.support.HttpAccessor.createRequest(HttpAccessor.java:77) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:648) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:613) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:287) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at com.microservice.controller.MovieController.getUserByID(MovieController.java:23) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_172]
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_172]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_172]
	at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_172]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:220) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55) ~[spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:105) ~[spring-boot-actuator-1.4.3.RELEASE.jar:1.4.3.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:89) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106) ~[spring-boot-actuator-1.4.3.RELEASE.jar:1.4.3.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1410) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_172]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_172]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.6.jar:8.5.6]
	at java.lang.Thread.run(Unknown Source) [na:1.8.0_172]

然後我就各種找問題，可以明確知道是@Value註解沒有獲取到配置文件中的屬性值問題，導致調用服務時不能發送正確的請求，因爲URL地址不正確。

後來看到別人博客裏的@Value註解內寫法，嘗試了一下，問題終於解決了。

@RestController
public class MovieController {
	@Autowired 
	RestTemplate restTemplate;
	
	@Value("${user.userServiceUrl}")
	private	String userServiceUrl;
	
	@GetMapping("/user/{id}")
	public User getUserByID(@PathVariable Long id){
		System.out.println("讀取到的url爲"+this.userServiceUrl);
		User user = restTemplate.getForObject(this.userServiceUrl+id, User.class);
		return user;
	}
}

    只需要加上${ }即可。