AdeadlockinJavaoccurswhentwoormorethreadsareblockedforever,eachwaitingforaresourceheldbytheother,typicallyduetocircularwaitcausedbyinconsistentlockordering;thiscanbepreventedbybreakingoneofthefournecessaryconditions—mutualexclusion,holdandwait,nopree

This article discusses the mechanism and common misunderstandings of Spring Boot applications for handling non-UTF-8 request encoding. The core lies in understanding the importance of the charset parameter in the HTTP Content-Type header, as well as the default character set processing flow of Spring Boot. By analyzing the garbled code caused by wrong testing methods, the article guides readers how to correctly simulate and test requests for different encodings, and explains that Spring Boot usually does not require complex configurations to achieve compatibility under the premise that the client correctly declares encoding.

UseOptional.empty(),Optional.of(),andOptional.ofNullable()tocreateOptionalinstancesdependingonwhetherthevalueisabsent,non-null,orpossiblynull.2.CheckforvaluessafelyusingisPresent()orpreferablyifPresent()toavoiddirectnullchecks.3.Providedefaultswithor

Understand JCA core components such as MessageDigest, Cipher, KeyGenerator, SecureRandom, Signature, KeyStore, etc., which implement algorithms through the provider mechanism; 2. Use strong algorithms and parameters such as SHA-256/SHA-512, AES (256-bit key, GCM mode), RSA (2048-bit or above) and SecureRandom; 3. Avoid hard-coded keys, use KeyStore to manage keys, and generate keys through securely derived passwords such as PBKDF2; 4. Disable ECB mode, adopt authentication encryption modes such as GCM, use unique random IVs for each encryption, and clear sensitive ones in time

The Java design pattern is a reusable solution to common software design problems. 1. The Singleton mode ensures that there is only one instance of a class, which is suitable for database connection pooling or configuration management; 2. The Factory mode decouples object creation, and objects such as payment methods are generated through factory classes; 3. The Observer mode automatically notifies dependent objects, suitable for event-driven systems such as weather updates; 4. The dynamic switching algorithm of Strategy mode such as sorting strategies improves code flexibility. These patterns improve code maintainability and scalability but should avoid overuse.

Create a WebSocket server endpoint to define the path using @ServerEndpoint, and handle connections, message reception, closing and errors through @OnOpen, @OnMessage, @OnClose and @OnError; 2. Ensure that javax.websocket-api dependencies are introduced during deployment and automatically registered by the container; 3. The Java client obtains WebSocketContainer through the ContainerProvider, calls connectToServer to connect to the server, and receives messages using @ClientEndpoint annotation class; 4. Use the Session getBasicRe

Optional is a container class introduced by Java 8. It is used to clearly indicate that a value may be empty, thereby avoiding NullPointerException; 2. It simplifies nested null checking by providing map, orElse and other methods, preventing methods from returning null and standardizing collection return values; 3. Best practices include only returning values, avoiding the use of fields or parameters, distinguishing orElse from orElseGet, and not calling get() directly; 4. Optional should not be abused. If non-empty methods do not need to be wrapped, unnecessary Optional operations should be avoided in the stream; correct use of Optional can significantly improve code security and readability, but it requires good programming habits.

PrepareyourapplicationbyusingMavenorGradletobuildaJARorWARfile,externalizingconfiguration.2.Chooseadeploymentenvironment:runonbaremetal/VMwithjava-jarandsystemd,deployWARonTomcat,containerizewithDocker,orusecloudplatformslikeHeroku.3.Optionally,setup