如何在 Java EE 和 Spring Boot 中热重载属性? [英] How to hot-reload properties in Java EE and Spring Boot?
问题描述
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 秒轮询一次一样.然后还要检查 .properties 文件的时间戳修改并重新加载它.
Many in-house solutions come to mind. Like having the properties in a database and poll it every N secs. Then also check the timestamp modification for a .properties file and reload it.
但我一直在查看 Java EE 标准和 Spring Boot 文档，但似乎找不到一些最佳方法.
But I was looking in Java EE standards and spring boot docs and I can't seem to find some best way of doing it.
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)，然后才能重新读取它们.生产中使用的最佳实践是什么?
I need my application to read a properties file(or env. variables or DB parameters), then be able to re-read them. What is the best practice being used in production?
正确的答案至少可以解决一个场景(Spring Boot 或 Java EE)，并提供有关如何使其在另一个场景中工作的概念性线索
A correct answer will at least solve one scenario (Spring Boot or Java EE) and provide a conceptual clue on how to make it work on the other
推荐答案
经过进一步研究，重载属性必须慎重考虑.例如，在 Spring 中，我们可以毫无问题地重新加载属性的当前"值.但.在上下文初始化时根据 application.properties 文件(例如数据源、连接池、队列等)中存在的值初始化资源时必须特别小心.
After further research, reloading properties must be carefully considered. In Spring, for example, we can reload the 'current' values of properties without much problem. But. Special care must be taken when resources were initialized at the context initialization time based on the values that were present in the application.properties file (e.g. Datasources, connection pools, queues, etc.).
注意:
用于 Spring 和 Java EE 的抽象类并不是干净代码的最佳示例.但它易于使用，并且确实满足了这些基本的初始要求:
The abstract classes used for Spring and Java EE are not the best example of clean code. But it is easy to use and it does address this basic initial requirements:
- 不使用 Java 8 类以外的外部库.
- 只需一个文件即可解决问题(Java EE 版本约 160 行).
- 使用文件系统中可用的标准 Java 属性 UTF-8 编码文件.
- 支持加密属性.
对于 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(这对于某些用例来说可能有点矫枉过正)
This code helps with hot-reloading application.properties file without the usage of a Spring Cloud Config server (which may be overkill for some use cases)
这个抽象类你可以复制&粘贴(好东西:D)这是一个 从这个 SO 答案派生的代码
This abstract class you may just copy & paste (SO goodies :D ) It's a code derived from this SO answer
// imports from java/spring/lombok
public 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，允许从使用抽象类的 applicatoin.properties 检索属性值
Then you make a bean class that allows retrieval of property values from applicatoin.properties that uses the abstract class
@Component
public 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 添加到您的@SpringBootApplication
Make sure to add @EnableScheduling to your @SpringBootApplication
@SpringBootApplication
@EnableScheduling
public class MainApp {
public static void main(String[] args) {
SpringApplication.run(MainApp.class, args);
}
}
现在您可以在任何需要的地方自动连接 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.并确保重新配置任何使用可能不同的属性值初始化的资源或 bean.
Now you can auto-wire the AppProperties Bean wherever you need it. Just make sure to always call the methods in it instead of saving it's value in a variable. And make sure to re-configure any resource or bean that was initialized with potentially different property values.
目前，我仅使用外部和默认找到的 ./config/application.properties 文件对此进行了测试.
For now, I have only tested this with an external-and-default-found ./config/application.properties file.
对于 Java EE
我制作了一个通用的 Java SE 抽象类来完成这项工作.
I made a common Java SE abstract class to do the job.
您可以复制&粘贴这个:
You may copy & paste this:
// 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.getEncoded(), "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.getEncoder().encodeToString(cipherMessage);
return cyphertext;
}
public static String decrypt(String cypherText, String key)
throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, InvalidKeySpecException {
byte[] cipherMessage = Base64.getDecoder().decode(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.getEncoded(), "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;
}
}
那么你可以这样使用:
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 code every time a property is updated
}
public final DynProp wsUrl = new DynProp("ws.url");
public final DynProp hiddenText = new DynProp("hidden.text");
}
如果您想使用编码属性，您可以将它的值包含在 ENC() 中，并且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.在本例中，它将在 application.properties.key 文件中查找密码.
In case you want to use encoded properties you may enclose it's value inside ENC() and a password for decryption will be searched for in the same path and name of the property file with an added .key extension. In this example it will look for the password in the application.properties.key file.
application.properties ->
application.properties ->
ws.url=http://some webside
hidden.text=ENC(AAAADCzaasd9g61MI4l5sbCXrFNaQfQrgkxygNmFa3UuB9Y+YzRuBGYj+A==)
aplication.properties.key ->
aplication.properties.key ->
password aca
对于 Java EE 解决方案的属性值加密，我咨询了 Patrick Favre-Bulle 关于 Java 和 Android 中使用 AES 的对称加密.然后在这个关于 AES/GCM/NoPadding.最后，我使 AES 位从@erickson 的密码中派生出来，在 SO 关于 AES 基于密码的加密的优秀答案中.关于 Spring 中值属性的加密，我认为它们与 Java 简化加密
For the encryption of property values for the Java EE solution I consulted Patrick Favre-Bulle excellent article on Symmetric Encryption with AES in Java and Android. Then checked the Cipher, block mode and padding in this SO question about AES/GCM/NoPadding. And finally I made the AES bits be derived from a password from @erickson excellent answer in SO about AES Password Based Encryption. Regarding encryption of value properties in Spring I think they are integrated with Java Simplified Encryption
这是否符合最佳实践可能超出了范围.此答案显示了如何在 Spring Boot 和 Java EE 中拥有可重新加载的属性.
Wether this qualify as a best practice or not may be out of scope. This answer shows how to have reloadable properties in Spring Boot and Java EE.
这篇关于如何在 Java EE 和 Spring Boot 中热重载属性?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
