在启动之前在SpringBoot中登录@ConfigurationProperties？

Question

我试图找到一种在上下文启动之前记录我的应用程序属性（通过@ConfigurationProperties注入到我的bean中）的方法，以便可以在初始化所有bean之前看到确切的属性。

我试图在ApplicationEnvironmentPreparedEvent上创建一个侦听器，但是没有一种方法可以检索所有定义的属性，除非一次只获取单个属性。

是否有捷径可寻？ 以某种方式首先初始化@ConfigurationProperties并记录其内容，或者在上下文创建之前检索所有应用程序启动属性？

Answer 1

您可以在实现ApplicationListener的自定义类的帮助下简单地查看应用程序属性，并将其定义为spring-factories条目中的startupup类之一，以便它们在应用程序加载之前执行。 步骤如下：

a）在资源类路径中创建一个名为spring.factories的文件，即带有内容的src \\ main \\ resources \\ META-INF \\ spring.factories-

# Application Listeners
org.springframework.context.ApplicationListener=demo.CustomConfigListener

b）在项目中创建一个自定义侦听器类，如下所示：CustomConfigListener

package demo;

import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.env.EnumerablePropertySource;
import org.springframework.core.env.PropertySource;


public class CustomConfigListener implements ApplicationListener<ApplicationEvent> {

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationEnvironmentPreparedEvent) {
            for(PropertySource<?> source : ((ApplicationEnvironmentPreparedEvent) event).getEnvironment().getPropertySources()){
                if(source.getName().equals("applicationConfigurationProperties")){              
                    if (source instanceof EnumerablePropertySource) {
                        for(String name : ((EnumerablePropertySource) source).getPropertyNames()){
                            System.out.println(name+" :: "+ ((EnumerablePropertySource) source).getProperty(name));
                        }
                    }
                }
            }           
        }       
    }

}

c）您的自定义ConfigurationProperties类

package demo;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties(ignoreUnknownFields = false, prefix = "mail")
public class MailProperties {    
    private String host;
    private int port;
    private Smtp smtp;    
    //Getters & Setters

    public static class Smtp {    
        private boolean auth;
        private boolean starttlsEnable;    
        //Getters & Setters
    }
}

d）最后是application.properties

mail.host=localhost
mail.port=25
mail.smtp.auth=false
mail.smtp.starttls-enable=false

Answer 2

作为@Avis回答的后续，我意识到该代码段不包含任何命令行参数等，因此我对其概念进行了一些更新。 我附加了logger类，以防将来对遇到此问题的任何人有价值。

public class ConfigurationLogger implements ApplicationListener<ApplicationEvent> {
    // slf4j logger
    private static final Logger logger = LoggerFactory.getLogger(ConfigurationLogger.class);

    // used to sanitize any password sensitive keys (copied from Spring Boot's Sanitizer() class
    private Sanitizer sanitizer = new Sanitizer();

    // store the config keys in a sorted map
    private Map<String, Object> configurationProperties = new TreeMap<>();


    /**
     * Trigger upon all events during startup.  Both ApplicatoinEnvironmentPrepareEvent and
     * ApplicationPreparedEvent need access to the same configurationProperties object.  Could
     * have done this through separate events, both extending an abstract base class with a static
     * hash map, but not worth the effort.  Instead have the same class listen for all events, and 
     * delegate to the appropriate method.
     */
    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationEnvironmentPreparedEvent) {
            // store the values
            onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
        }else if( event instanceof ApplicationPreparedEvent){
            // display the values
            logConfigurationProperties( (ApplicationPreparedEvent)event);
        }
    }

    /**
     * Store the properties in the hash map for logging once all property sources have been read
     * 
     * @param event
     */
    private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
        for (PropertySource<?> source : event.getEnvironment().getPropertySources()) {
            if (source instanceof EnumerablePropertySource) {
                for (String key : ((EnumerablePropertySource) source).getPropertyNames()) {
                    Object value = ((EnumerablePropertySource) source).getProperty(key);
                    if (!configurationProperties.containsKey(key)) {
                        configurationProperties.put(key, sanitizer.sanitize(key, value));
                    }
                }
            }
        }
    }

    /**
     * Print all the config properties to the logger
     */
    private void logConfigurationProperties( ApplicationPreparedEvent event) {
        logger.debug("Application started with following parameters: ");
        for( Map.Entry<String, Object> entry : configurationProperties.entrySet()){
            logger.debug("{} :: {}", entry.getKey(), entry.getValue());
        }

    }
}

然后在SpringApplication主类中初始化侦听器：

@SpringBootApplication
public class Application{
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(Application.class);
        app.setShowBanner(false);
        // add configuration properties logger
        app.addListeners(new ConfigurationLogger());
        app.run(args);
    }
}