基于 运行 Spring 的应用程序时如何解析占位符？

Question

同学们，我有基于java的Spring配置：

@Configuration
@EnableTransactionManagement
@ComponentScan (basePackages = {"com.abc.dirint"})
@PropertySource("classpath:/settings/${env}/dir.properties")
@EnableScheduling
public class DirConfig {

    private static final Logger log = LoggerFactory.getLogger(DirConfig.class);

    @Autowired
    private Environment environment;

     @Bean
        public static PropertySourcesPlaceholderConfigurer propertyConfigInDev() throws IOException {
            PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer = new PropertySourcesPlaceholderConfigurer();
    propertySourcesPlaceholderConfigurer.setIgnoreUnresolvablePlaceholders(true);
            return propertySourcesPlaceholderConfigurer;
        }


        /*Beans follow...*/ 

        }

当我执行 mvn clean package -Denv=dev 时，它 运行 测试并构建项目没有任何错误。

现在我想运行编译jar。 我执行 java -jar dir-integration-1.2-SNAPSHOT.jar -Denv=dev 并且程序失败（这是预期的），下一个堆栈跟踪：

Exception in thread "main" org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [com.abc.dirint.DirConfig]; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'env' in string value "classpath:/settings/${env}/dir.properties"
        at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:180)

Wnen i 运行 $ java -jar dir-integration-1.2-SNAPSHOT.jar --env=dev 结果如下：

Exception in thread "main" org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [com.abc.dirint.DirConfig]; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'env' in string value "classpath:/settings/${env}/dir.properties"
        at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:180)
        at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:308)
        at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:228)
        at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:270)
        at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:93)
        at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:686)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:524)
        at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
        at com.abc.dirint.AdApp.main(AdApp.java:19) Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'env' in string value "classpath:/settings/${env}/dir.properties"
        at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174)
        at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126)
        at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:236)
        at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210)
        at org.springframework.core.env.AbstractEnvironment.resolveRequiredPlaceholders(AbstractEnvironment.java:571)
        at org.springframework.context.annotation.ConfigurationClassParser.processPropertySource(ConfigurationClassParser.java:379)
        at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:

我应该怎么做才能在应用 运行ning 期间从指定的属性文件接收属性？

Answer 1

来自 java -h

Usage: java [-options] class [args...]
           (to execute a class)
   or  java [-options] -jar jarfile [args...]
           (to execute a jar file)
where options include:
...
    -D<name>=<value>
                  set a system property

因此，运行 系统 属性 提供的 jar 的正确命令应该是 java -Denv=dev -jar dir-integration-1.2-SNAPSHOT.jar 而不是

---

而且，您应该知道，使用 mvn ... -Denv=dev 和 java -Denv=dev ... 是完全不同的两件事。

对于 mvn，占位符替换发生在 编译时间，这意味着最终的 jar 将包含 @PropertySource("classpath:/settings/dev/dir.properties")

但是，您的第二种方法是将占位符保留在已编译的 class 中，并依靠 Spring 在 运行time[=30] 中执行替换=]