我想到了许多内部解决方案。就像在数据库中拥有属性并每N秒轮询一次。然后还要检查.properties文件的时间戳修改并重新加载。
但是我一直在寻找Java EE标准和Spring Boot文档，但似乎找不到最佳的方法。
我需要我的应用程序读取属性文件（或环境变量或数据库参数），然后能够重新读取它们。生产中使用的最佳实践是什么？
正确的答案至少可以解决一种情况（Spring Boot或Java EE），并提供有关如何使其在另一种情况下工作的概念性提示用于Spring和Java EE的抽象类不是干净代码的最佳示例。但是它易于使用，并且确实满足了以下基本初始要求：
- 除Java 8类外，不使用任何外部库。
- 仅一个文件即可解决问题（Java EE版本约为160行）。
- 文件系统中提供的标准Java属性UTF-8编码文件的使用。
- 支持加密的属性。
For Spring Boot
此代码有助于在不使用Spring Cloud Config服务器的情况下热重载application.properties文件（在某些情况下可能会过分使用）
你可以只复制并粘贴此抽象类（SO goodies：D），这是从该SO答案派生的代码
// imports from java/spring/lombokpublic abstract class ReloadableProperties { @Autowired protected StandardEnvironment environment; private long lastModTime = 0L; private Path configPath = null; private PropertySource<?> appConfigPropertySource = null; @PostConstruct private void stopIfProblemsCreatingContext() { System.out.println("reloading"); MutablePropertySources propertySources = environment.getPropertySources(); Optional<PropertySource<?>> appConfigPsOp = StreamSupport.stream(propertySources.spliterator(), false) .filter(ps -> ps.getName().matches("^.*applicationConfig.*file:.*$")) .findFirst(); if (!appConfigPsOp.isPresent()) { // this will stop context initialization // (i.e. kill the spring boot program before it initializes) throw new RuntimeException("Unable to find property Source as file"); } appConfigPropertySource = appConfigPsOp.get(); String filename = appConfigPropertySource.getName(); filename = filename .replace("applicationConfig: [file:", "") .replaceAll("\]$", ""); configPath = Paths.get(filename); } @Scheduled(fixedRate=2000) private void reload() throws IOException { System.out.println("reloading..."); long currentModTs = Files.getLastModifiedTime(configPath).toMillis(); if (currentModTs > lastModTime) { lastModTime = currentModTs; Properties properties = new Properties(); @Cleanup InputStream inputStream = Files.newInputStream(configPath); properties.load(inputStream); environment.getPropertySources() .replace( appConfigPropertySource.getName(), new PropertiesPropertySource( appConfigPropertySource.getName(), properties ) ); System.out.println("Reloaded."); propertiesReloaded(); } } protected abstract void propertiesReloaded();}然后，创建一个bean类，该类允许从使用抽象类的applicatoin.properties中检索属性值
@Componentpublic class AppProperties extends ReloadableProperties { public String dynamicProperty() { return environment.getProperty("dynamic.prop"); } public String anotherDynamicProperty() { return environment.getProperty("another.dynamic.prop"); } @Override protected void propertiesReloaded() { // do something after a change in property values was done }}确保将@EnableScheduling添加到你的@SpringBootApplication中
@SpringBootApplication@EnableSchedulingpublic class MainApp { public static void main(String[] args) { SpringApplication.run(MainApp.class, args); }}现在，你可以在需要的地方自动装配AppProperties Bean。只需确保始终调用其中的方法，而不是将其值保存在变量中即可。并确保重新配置任何使用可能具有不同属性值初始化的资源或bean。
目前，我仅使用外部默认找到的
./config/application.properties文件对此进行了测试。
对于Java EE
我做了一个普通的Java SE抽象类来完成这项工作。
你可以复制并粘贴以下内容：
// imports from java.* and javax.crypto.*public abstract class ReloadableProperties { private volatile Properties properties = null; private volatile String propertiesPassword = null; private volatile long lastModTimeOfFile = 0L; private volatile long lastTimeChecked = 0L; private volatile Path propertyFileAddress; abstract protected void propertiesUpdated(); public class DynProp { private final String propertyName; public DynProp(String propertyName) { this.propertyName = propertyName; } public String val() { try { return ReloadableProperties.this.getString(propertyName); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } } } protected void init(Path path) { this.propertyFileAddress = path; initOrReloadIfNeeded(); } private synchronized void initOrReloadIfNeeded() { boolean firstTime = lastModTimeOfFile == 0L; long currentTs = System.currentTimeMillis(); if ((lastTimeChecked + 3000) > currentTs) return; try { File fa = propertyFileAddress.toFile(); long currModTime = fa.lastModified(); if (currModTime > lastModTimeOfFile) { lastModTimeOfFile = currModTime; InputStreamReader isr = new InputStreamReader(new FileInputStream(fa), StandardCharsets.UTF_8); Properties prop = new Properties(); prop.load(isr); properties = prop; isr.close(); File passwordFiles = new File(fa.getAbsolutePath() + ".key"); if (passwordFiles.exists()) { byte[] bytes = Files.readAllBytes(passwordFiles.toPath()); propertiesPassword = new String(bytes,StandardCharsets.US_ASCII); propertiesPassword = propertiesPassword.trim(); propertiesPassword = propertiesPassword.replaceAll("(\r|\n)", ""); } } updateProperties(); if (!firstTime) propertiesUpdated(); } catch (Exception e) { e.printStackTrace(); } } private void updateProperties() { List<DynProp> dynProps = Arrays.asList(this.getClass().getDeclaredFields()) .stream() .filter(f -> f.getType().isAssignableFrom(DynProp.class)) .map(f-> fromField(f)) .collect(Collectors.toList()); for (DynProp dp :dynProps) { if (!properties.containsKey(dp.propertyName)) { System.out.println("propertyName: "+ dp.propertyName + " does not exist in property file"); } } for (Object key : properties.keySet()) { if (!dynProps.stream().anyMatch(dp->dp.propertyName.equals(key.toString()))) { System.out.println("property in file is not used in application: "+ key); } } } private DynProp fromField(Field f) { try { return (DynProp) f.get(this); } catch (IllegalAccessException e) { e.printStackTrace(); } return null; } protected String getString(String param) throws Exception { initOrReloadIfNeeded(); String value = properties.getProperty(param); if (value.startsWith("ENC(")) { String cipheredText = value .replace("ENC(", "") .replaceAll("\)$", ""); value = decrypt(cipheredText, propertiesPassword); } return value; } public static String encrypt(String plainText, String key) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, InvalidKeySpecException { SecureRandom secureRandom = new SecureRandom(); byte[] keyBytes = key.getBytes(StandardCharsets.US_ASCII); SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256"); KeySpec spec = new PBEKeySpec(key.toCharArray(), new byte[]{0,1,2,3,4,5,6,7}, 65536, 128); SecretKey tmp = factory.generateSecret(spec); SecretKey secretKey = new SecretKeySpec(tmp.getEnpred(), "AES"); byte[] iv = new byte[12]; secureRandom.nextBytes(iv); final Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding"); GCMParameterSpec parameterSpec = new GCMParameterSpec(128, iv); //128 bit auth tag length cipher.init(Cipher.ENCRYPT_MODE, secretKey, parameterSpec); byte[] cipherText = cipher.doFinal(plainText.getBytes(StandardCharsets.UTF_8)); ByteBuffer byteBuffer = ByteBuffer.allocate(4 + iv.length + cipherText.length); byteBuffer.putInt(iv.length); byteBuffer.put(iv); byteBuffer.put(cipherText); byte[] cipherMessage = byteBuffer.array(); String cyphertext = base64.getEnprer().enpreToString(cipherMessage); return cyphertext; } public static String decrypt(String cypherText, String key) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, InvalidKeySpecException { byte[] cipherMessage = base64.getDeprer().depre(cypherText); ByteBuffer byteBuffer = ByteBuffer.wrap(cipherMessage); int ivLength = byteBuffer.getInt(); if(ivLength < 12 || ivLength >= 16) { // check input parameter throw new IllegalArgumentException("invalid iv length"); } byte[] iv = new byte[ivLength]; byteBuffer.get(iv); byte[] cipherText = new byte[byteBuffer.remaining()]; byteBuffer.get(cipherText); byte[] keyBytes = key.getBytes(StandardCharsets.US_ASCII); final Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding"); SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256"); KeySpec spec = new PBEKeySpec(key.toCharArray(), new byte[]{0,1,2,3,4,5,6,7}, 65536, 128); SecretKey tmp = factory.generateSecret(spec); SecretKey secretKey = new SecretKeySpec(tmp.getEnpred(), "AES"); cipher.init(Cipher.DECRYPT_MODE, secretKey, new GCMParameterSpec(128, iv)); byte[] plainText= cipher.doFinal(cipherText); String plain = new String(plainText, StandardCharsets.UTF_8); return plain; }}然后，你可以通过以下方式使用它：
public class AppProperties extends ReloadableProperties { public static final AppProperties INSTANCE; static { INSTANCE = new AppProperties(); INSTANCE.init(Paths.get("application.properties")); } @Override protected void propertiesUpdated() { // run pre every time a property is updated } public final DynProp wsUrl = new DynProp("ws.url"); public final DynProp hiddenText = new DynProp("hidden.text");}如果要使用编码的属性，可以将其值括在ENC（）中，然后将在属性文件的相同路径和名称中搜索解密密码，并添加.key扩展名。在此示例中，它将在application.properties.key文件中查找密码。
application.properties->
ws.url=http://some websidehidden.text=ENC(AAAADCzaasd9g61MI4l5sbCXrFNaQfQrgkxygNmFa3UuB9Y+YzRuBGYj+A==)
aplication.properties.key->
password aca
对于Java EE解决方案的属性值的加密，我查阅了Patrick Favre-Bulle的出色文章，内容涉及Java和Android中的AES对称加密。然后在关于AES / GCM / NoPadding的 SO问题中检查了密码，块模式和填充。最后，我使AES位元从@erickson的密码中获得了一个很好的答案，有关SO 密码的加密。关于Spring中的值属性加密，我认为它们与Java简化加密集成在一起
是否可以将此视为最佳做法，否则可能不在范围之内。该答案显示了如何在Spring Boot和Java EE中具有可重载的属性。
