@Controller 类中的 Spring @Value 注释不评估属性文件中的值
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Spring @Value annotation in @Controller class not evaluating to value inside properties file
提问by Chris
I am new to Spring and trying to inject a string with a value using the @Value("${loginpage.message}")annotation inside of a controller annotated with the @Controllerannotation and the value of my string is being evaluated as the string "${loginpage.message}"and not what is inside my properties file.
我是 Spring 的新手，并尝试使用带有@Value("${loginpage.message}")注释的控制器内部的注释注入一个带有值的字符串，@Controller并且我的字符串的值被评估为字符串，"${loginpage.message}"而不是我的属性文件中的内容。
Below is my controller with the string 'message' that I want to inject.
下面是我的控制器，其中包含我要注入的字符串“消息”。
@Controller
public class LoginController extends BaseController {
@Value("${loginpage.message}")
private String message;
@RequestMapping("/")
public String goToLoginPage(Model model) {
model.addAttribute("message", message);
return "/login";
}
}
My application context looks like this:
我的应用程序上下文如下所示：
<context:property-placeholder location="classpath:properties/application.properties" />
<context:annotation-config />
<context:component-scan base-package="com.me.application" />
My properties file has the line:
我的属性文件有一行：
loginpage.message=this is a test message
Spring must be picking up the value at some point because whenever I change @Value("${loginpage.message}")to a value not in the properties file like @Value("${notInPropertiesFile}"), I get an exception.
Spring 必须在某个时候获取该值，因为每当我更改@Value("${loginpage.message}")为不在属性文件中的值时，例如@Value("${notInPropertiesFile}")，我都会收到异常。
回答by Boris Treukhov
It seems that the question has been already asked Spring 3.0.5 doesn't evaluate @Value annotation from properties
似乎已经问过这个问题Spring 3.0.5 没有从属性中评估 @Value 注释
The difference between web app root and servlet application contexts is one of the top sources of confusion in Spring, see Difference between applicationContext.xml and spring-servlet.xml in Spring Framework
Web 应用程序根和 servlet 应用程序上下文之间的差异是 Spring 中最容易混淆的来源之一，请参阅 Spring Framework 中 applicationContext.xml 和 spring-servlet.xml 之间的差异
From @Valuejavadoc :
从@Valuejavadoc ：
Note that actual processing of the @Value annotation is performed by a BeanPostProcessor
注意@Value注解的实际处理是由一个BeanPostProcessor执行的
BeanPostProcessor interfaces are scoped per-container. This is only relevant if you are using container hierarchies. If you define a BeanPostProcessor in one container, it will only do its work on the beans in that container. Beans that are defined in one container are not post-processed by a BeanPostProcessor in another container, even if both containers are part of the same hierarchy.
BeanPostProcessor 接口的范围是每个容器的。这仅在您使用容器层次结构时才相关。如果你在一个容器中定义了一个 BeanPostProcessor，它只会在那个容器中的 bean 上工作。在一个容器中定义的 Bean 不会由另一个容器中的 BeanPostProcessor 进行后处理，即使两个容器都是同一层次结构的一部分。
回答by tn.stackoverflow
Yea I am having same issue with Spring 3. It doesn't seem to work inside Controllers. To fix the issue I created a another bean with @Service and injected that into the controller. It did work for me. Hope this would be helpful to someone as I spent all day to figure it out.
是的，我在 Spring 3 中遇到了同样的问题。它似乎在控制器中不起作用。为了解决这个问题，我用@Service 创建了另一个 bean 并将其注入控制器。它确实对我有用。希望这会对某人有所帮助，因为我花了一整天的时间来弄清楚。
回答by jediz
You can @Autowire Environmentand then environment.getProperty("name").
See https://stackoverflow.com/a/15562319/632293
你可以@Autowire Environment然后environment.getProperty("name")。见https://stackoverflow.com/a/15562319/632293
回答by AbdusSalam
You need to use PropertySourcePlaceHolder if you are using @Value annotation because it can extract the value from a properties file. If you are using java config base you need to create a bean like this
如果您使用 @Value 注释，则需要使用 PropertySourcePlaceHolder，因为它可以从属性文件中提取值。如果您使用的是 java config base，则需要像这样创建一个 bean
@Bean
public static PropertySourcesPlaceholderConfigurer propertyConfigInDev() {
return new PropertySourcesPlaceholderConfigurer();
}
Or if you are using xml based then declare the bean accordingly.
或者，如果您使用的是基于 xml 的，则相应地声明 bean。
回答by Stefano Scarpanti
I had similar issue in my spring project, but specifically spring BATCH one. I built initially my config as below
我在 spring 项目中遇到了类似的问题，但特别是 spring BATCH one。我最初构建我的配置如下
@Configuration
public class BatchConfig
{
@Bean
public Job job(@Autowired Step stepMulti, @Autowired Step stepMultiDiff, @Autowired Step stepMultiPolling
){
Job job = jobBuilders.get("job")
.start(init0())
.on("POLLING").to(stepMultiPolling)
.from(init0()).on("*").to(stepMulti).next(stepMultiDiff).end()
.build();
return job;
}
@Bean
public Step init0(){
return stepBuilders.get("init0")
.tasklet(new MyDecider())
.build();
}
...
}
with MyDecider shortly as below
与 MyDecider 简单如下
public class MyDecider implements StepExecutionListener , Tasklet{
@Autowired ThreadPoolTaskScheduler taskScheduler;
@Value("${read.chunk.size}") private Integer pagesize;
@Override
public RepeatStatus execute(StepContribution stepContribution, ChunkContext chunkContext) throws Exception {
return RepeatStatus.FINISHED;
}
@Override
public ExitStatus afterStep(StepExecution exe) {
String type = exe.getJobParameters().getString("mode");
log.info("SPRING BATCH props:");
log.info(" READ chunk size: {}", pagesize);
if (StringUtils.equals(type, "send")) {
log.info("MODE batch SENDING...");
if (taskScheduler !=null) taskScheduler.shutdown();
else log.info(" Not able to stop scheduler (is null)");
return new ExitStatus("SEND");
} else {
log.info("MODE batch POLLING...");
return new ExitStatus("POLLING");
}
}
But in this way neither taskScheduler was wired nor pagesize was injected; both null. Thanks to Boris answer, after some try, I changed BatchConfig as below perfectly working
但是这样既没有连接 taskScheduler 也没有注入 pagesize；都为空。感谢鲍里斯的回答，经过一些尝试，我将 BatchConfig 更改为如下完美工作
...
@Bean
public Step init0(){
return stepBuilders.get("init0")
.tasklet(decider())
.build();
}
@Bean
public Tasklet decider() {
return new MyDecider();
}
...
Reason: having MyDecider construction closer to a Bean annotation in BatchConfig (the one of decider()), make spring understand that MyDecider has to be injected properly, with values found in application.property values, and wired with TaskScheduler used (because I tried also to have SpringScheduler activation, but I wanted to swith it off if jar starting option was 'send').
原因：让 MyDecider 构造更接近 BatchConfig 中的 Bean 注释（decider() 之一），让 spring 明白必须正确注入 MyDecider，在 application.property 值中找到值，并使用 TaskScheduler 连接（因为我试过也有 SpringScheduler 激活，但如果 jar 启动选项是“发送”，我想关闭它）。
NOTE: with option mode="send" spring batch job takes the way towards stepMulti and not stepMultiPolling, because MyDecider exit status was SEND and not POLLING; but that is just an explanation out of this topic, so I skip further details.
注意：使用选项 mode="send" spring 批处理作业采用 stepMulti 而不是 stepMultiPolling，因为 MyDecider 退出状态是 SEND 而不是 POLLING；但这只是本主题的一个解释，所以我跳过更多细节。
Hope this spring batch case can be helpful for someone!
希望这个春季批次案例可以对某人有所帮助！
