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Optimizing Database Queries in a Java Application

StrategicallyuseindexesonfrequentlyqueriedcolumnsinWHERE,JOIN,andORDERBYclauses,includingcompositeindexesformulti-columnfilters,whileavoidingover-indexingtopreventwriteperformancedegradation;2.OptimizeJPA/HibernatebyresolvingtheN 1queryproblemwithJOI

Jul 27, 2025 am 02:15 AM

Optimizing Database Queries in a Java Persistence Layer

1. To solve the N 1 query problem, you need to use JOINFETCH or @EntityGraph; 2. Restrict the result set size through paging and cursor paging; 3. Reasonably configure entity mapping and lazy loading to avoid loading too much associated data; 4. Use DTO projection to query only the required fields; 5. Enable Level 2 cache and reasonably configure the cache strategy; 6. Turn on SQL logs and use tools to analyze the generated SQL performance; 7. Use native SQL to improve efficiency through complex operations; 8. Create database indexes for common query conditions and use execution plan analysis; the core of optimization is to reduce database round trips, reduce data transmission, and select appropriate acquisition strategies based on the scenario, and ultimately continuously improve performance through monitoring.

Jul 27, 2025 am 02:04 AM

A Deep Dive into the Java Virtual Machine (JVM) Internals

TheJVMenablesJava’s"writeonce,runanywhere"capabilitybymanagingcodeexecutionthroughkeyinternalcomponents.1)Classloaders(Bootstrap,Extension,Application)load.classfilesinadelegationhierarchy,storingclassmetadataintheMethodArea.2)Runtimedataar

Jul 27, 2025 am 01:55 AM

How to Secure a Java Web Application from OWASP Top 10 Vulnerabilities

UsePreparedStatementandparameterizedqueriestopreventinjection;2.ImplementSpringSecuritywithstrongpasswordhashingandMFAforsecureauthentication;3.EnforceRBACwith@PreAuthorizeanddeny-by-defaultaccesscontrol;4.EncryptdataintransitwithTLS1.2 andatrestusin

Jul 27, 2025 am 01:54 AM

GraalVM Native Image: Compiling Your Java Application Ahead-of-Time

GraalVMNativeImage converts Java applications into native executable files through AOT compilation, solving the problems of slow startup and high memory usage in the traditional JVM mode. 1. The startup speed is milliseconds, suitable for Serverless and microservices; 2. The memory usage is reduced by 30% to 70%; 3. The deployment package is smaller, and there is no need to carry JVM; 4. The security is improved and the attack surface is reduced. Note when using: 1. Reflection, dynamic proxy, etc. need to be explicitly configured; 2. Resource files need to be included through resource-config.json; 3. Dynamic class loading is limited; 4. Some libraries that rely on ASM or dynamically generate bytecode are incompatible. Mainstream frameworks such as SpringBoot3 and Quarkus

Jul 27, 2025 am 01:53 AM

java compile

Migrating Legacy Java Applications to Modern Architectures

The core of migrating old Java applications is to understand business logic and technical debt, rather than rewriting code. 1. Evaluate the status of the existing system and identify hard-coded, module coupling and database design; 2. Clean up core functions and explicitly ensure modules that are retained, replaced or cut off; 3. Identify technical debts, such as old versions of Spring or abandoned libraries, and list module dependencies and maintenance costs; 4. Architecture selection prioritizes modularization, and then gradually transition to microservices; 5. Data migration is first used to map tables, gradually migrate and avoid changing code and database at the same time; 6. Complete automated testing and CI pipelines to ensure stable functions after modification. The entire process needs to be modified and verified to prevent the omission of details from causing problems.

Jul 27, 2025 am 01:52 AM

Optimizing Java Application Performance on Kubernetes

SetKubernetesmemorylimitsanduse-XX:MaxRAMPercentage=75.0toensureJVMheapstayswithincontainerlimits,leaving20–25%headroomfornativememory.2.UseG1GCforlatency-sensitiveapps(-XX: UseG1GC-XX:MaxGCPauseMillis=200)orZGC/ShenandoahinJava11 forlowpausetimes,wh

Jul 27, 2025 am 01:45 AM

The Evolution of Java: What's New in Java 21

Java21,anLTSrelease,introducesmajorenhancementsthatmodernizetheplatform.1.VirtualThreadsarenowfinal,enablingefficient,lightweightconcurrencyidealforI/O-boundtasks,allowingsimplesynchronouscodetoscale.2.StructuredConcurrency(preview)improveserrorhandl

Jul 27, 2025 am 01:37 AM

Understanding the Java `final` Keyword and Immutability

Final is not equal to object immutable in Java. It only ensures that variable references cannot be reassigned, but does not guarantee that the state of the object pointed to is immutable; 2. For basic types, final ensures that the value remains unchanged; for object types, references are immutable but the object content can still be modified; 3. Really immutable must be met: the class is declared final, all fields are privatefinal, no setter method, constructor initialization and no mutable state is leaked; 4. If the field is a mutable object, external modifications need to be prevented by defensive copying and returning an unmodified view; 5. Final field has the JMM memory model guarantee to ensure that the objects are correctly published under multiple threads; 6. Common misunderstanding is that final automatically brings inability to be unhealthy; 6. The common misunderstanding is that final automatically brings inability; 5. Final field has the guarantee of JMM memory model to ensure that the object is published correctly; 6. Common misunderstanding is that final automatically brings inability;

Jul 27, 2025 am 01:33 AM

Creating a REST Client in Java using `HttpClient`

The built-in HttpClient in Java11 and above provides a simple REST client implementation. 1. Use HttpClient.newBuilder() to configure timeouts, proxying, etc. and create reusable client instances; 2. Set URI, GET/POST/PUT/DELETE methods, request headers and BodyPublisher through HttpRequest.newBuilder() to send synchronous or asynchronous requests; 3. Use HttpResponse.BodyHandlers to process response bodies, supporting strings, files or byte arrays; 4. Asynchronous requests are combined with thenApply through sendAsync() combined with thenApply

Jul 27, 2025 am 01:28 AM

Advanced Error Handling in Java Microservices

Use@ControllerAdviceforglobalexceptionhandlingtocentralizeerrorresponsesandreduceduplication.2.DefineastructuredErrorResponseDTOwithcode,message,timestamp,andpathforconsistentclientcommunication.3.ImplementcircuitbreakersusingResilience4jtopreventcas

Jul 27, 2025 am 01:14 AM

Advanced Java Multithreading: from synchronized to Lock-Free Algorithms

synchronized is the earliest synchronization mechanism in Java. It is simple and easy to use and has good performance after optimization, but lacks flexibility; 2. ReentrantLock provides advanced functions such as interruptibility, reentrant, and support fairness, which is suitable for scenarios that require fine control; 3. The lock-free algorithm implements non-blocking concurrency based on CAS, such as AtomicLong, LongAdder and ConcurrentLinkedQueue, which performs better in a high-competitive environment, but needs to deal with ABA problems and CPU spin overhead; ultimately, appropriate strategies should be selected based on concurrency strength: synchronized for low-competitive competition, ReentrantLock needs to be used for control, and lock-free structure for high-concurrency scenarios, from

Jul 27, 2025 am 01:13 AM

How to Use the Java `sealed` Classes and Interfaces

When using sealed classes or interfaces, the allowed subclasses must be explicitly listed through permits; 2. Each allowed subclass must be marked as final, sealed or non-sealed; 3. All subclasses must be in the same module or package as the parent class and are directly inherited; 4. It cannot be used with anonymous or local classes; 5. Combining records and pattern matching can achieve type safety and exhaustive checks. Java's sealed classes and interfaces make the type hierarchy safer and predictable by restricting inheritance relationships, and are suitable for modeling closed class variants, such as expression types or state machines. The compiler can ensure that switch expressions handle all situations, thereby improving the maintainability and correctness of the code.

Jul 27, 2025 am 12:55 AM

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Hexagonal Architecture for Maintainable Java Enterprise Applications

Hexagonal Architecture is a software architecture model that improves system maintainability, testability and scalability by decoupling core business logic from external dependencies. 1. The core area includes business logic and use cases, which are implemented independently of the framework and technology; 2. Port defines interactive interfaces, divided into primary port (inbound) and secondary port (outbound); 3. Adapter implements ports, responsible for communicating with external systems, such as web controllers or database access components; 4. In Java, dependencies are isolated through interfaces, and the business layer does not introduce framework annotations, and only uses adapters through dependency injection; 5. In practice, excessive layering and direct calls between adapters should be avoided, and the core logic can be verified by unit tests. This architecture

Jul 27, 2025 am 12:44 AM

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