如何在Java EE和Spring Boot中热重新加载属性？
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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隔N秒轮询它一样.然后还要检查.properties文件的时间戳修改并重新加载它.
但我正在研究Java EE标准和Spring引导文档,我似乎无法找到一些最好的方法.
我需要我的应用程序来读取属性文件(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？
一个正确的答案至少可以解决一个场景(Spring Boot或Java EE)并提供一个关于如何使其在另一个场景上工作的概念线索
解决方法:
经过进一步的研究,reloading properties must be carefully considered.例如,在Spring中,我们可以重新加载属性的“当前”值而没有太多问题.但.在上下文初始化时根据application.properties文件中存在的值(例如,数据源,连接池,队列等)初始化资源时,必须特别小心.
注意：
用于Spring和Java EE的抽象类不是清洁代码的最佳示例.但它易于使用,它确实满足了这个基本的初始要求：
>不使用Java 8 Classes以外的外部库.
>只有一个文件可以解决问题(Java EE版本约为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新加载application.properties文件(对于某些用例可能过度杀毒)
这个抽象类你可以复制&粘贴(SO好吃的东西：D)这是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中检索属性值
@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@SpringBootApplication中
@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.并确保重新配置使用可能不同的属性值初始化的任何资源或bean.
目前,我只使用外部和默认找到的./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&粘贴这个：
// 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;
}
}
然后你可以这样使用它：
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 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,您可以将其值包含在ENC()中,并且将在具有添加的.key扩展名的属性文件的相同路径和名称中搜索用于解密的密码.在此示例中,它将在application.properties.key文件中查找密码.
application.properties – >
ws.url=http://some webside
hidden.text=ENC(AAAADCzaasd9g61MI4l5sbCXrFNaQfQrgkxygNmFa3UuB9Y+YzRuBGYj+A==)
aplication.properties.key – >
password aca
为了加密Java EE解决方案的属性值,我在Symmetric Encryption with AES in Java and Android上查阅了Patrick Favre-Bulle的优秀文章.然后在这个SO问题中检查了密码,块模式和填充,关于AES/GCM/NoPadding.最后我将AES位从密码中导出来自@erickson关于AES Password Based Encryption的优秀答案.关于Spring中值属性的加密,我认为它们与Java Simplified Encryption集成在一起
这个有资格作为最佳实践的资格可能超出范围.这个答案显示了如何在Spring Boot和Java EE中使用可重新加载的属性.
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