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Java Performance Profiling with JFR and VisualVM

JFR and VisualVM are an efficient combination of Java performance analysis. JFR is responsible for low overhead to collect JVM running data, and VisualVM is used for visual analysis. 1. Enable JFR to enable it by adding the -XX: FlightRecorder parameter at startup or using the jcmd command during operation. It is recommended to use the profile template to obtain more detailed events. 2. Use the jcmd command to set parameters such as duration and filename for timed recording, or you can accurately control the acquisition event through custom .jfc files. 3. VisualVM needs to install the community enhancement version and add the JFR plug-in. After loading the .jfr file, you can use Overview and Telemet.

Jul 29, 2025 am 01:32 AM

java performance

Mastering Unit and Integration Testing in Java with JUnit 5 and Mockito

TomasterJavatestingwithJUnit5andMockito,useunittestsforisolatedcodewithmockeddependenciesandintegrationtestsforrealcomponentinteractions.1.Unittestsfocusonsinglemethodsorclassesusing@Mockand@InjectMockstoisolatelogic.2.Integrationtestsvalidatefullwor

Jul 29, 2025 am 01:24 AM

Unit Testing and Mocking in Java with JUnit 5 and Mockito

Use JUnit5 and Mockito to effectively isolate dependencies for unit testing. 1. Create a mock object through @Mock, @InjectMocks inject the tested instance, @ExtendWith enables Mockito extension; 2. Use when().thenReturn() to define the simulation behavior, verify() to verify the number of method calls and parameters; 3. Can simulate exception scenarios and verify error handling; 4. Recommend constructor injection, avoid over-simulation, and maintain test atomicity; 5. Use assertAll() to merge assertions, and @Nested organizes the test scenarios to improve test maintainability and reliability.

Jul 29, 2025 am 01:20 AM

java unit test

The Foreign Function & Memory API in Java 21

Java21 introduces Foreign Function & MemoryAPI to solve the complexity, poor security, and large performance overhead of JNI; 2. Core components include MemorySegment (memory abstraction), ValueLayout/MemoryLayout (memory layout), SymbolLookup (function symbol search), FunctionDescriptor and MethodHandle (function call definition), Arena (memory life cycle management); 3. Pure Java code can safely and efficiently call local functions and operate off-heap memory, without writing C code or manually managing memory; 4. Compared with JN

Jul 29, 2025 am 01:16 AM

java api

Serverless Java with AWS Lambda

Using Java to implement a serverless architecture on AWSLambda is feasible and efficient, and the key is reasonable optimization. 1. Use Java17 (Corretto) for best performance and language features; 2. Reduce cold start time by up to 90% by enabling SnapStart (for Java11 and 17); 3. Use ProvisionedConcurrency to warm up instances to deal with traffic fluctuations; 4. Use MavenShade or GradleShadow plug-in to streamline deployment packages to avoid the introduction of redundant dependencies; 5. Use lightweight frameworks such as Quarkus and Micronaut, or use GraalVM to generate native images to accelerate startup; 6.

Jul 29, 2025 am 01:10 AM

java programming

Securing Java Web Applications with Spring Security

Authenticationverifiesuseridentity,whileauthorizationdeterminesaccessrights.2.Addspring-boot-starter-securitydependencyandconfigureSecurityConfigwithcustomSecurityFilterChainandUserDetailsServiceusingBCryptPasswordEncoderinproduction.3.ForRESTAPIs,di

Jul 29, 2025 am 01:03 AM

High-Performance Java Messaging with RabbitMQ

Toachievehigh-performanceRabbitMQmessaginginJava,youmustoptimizebothclientandbrokerconfigurations.1.UseconnectionandchannelpoolingviaCachingConnectionFactorywithacachedchannelpooltoreduceoverhead.2.Enablepublisherconfirmsasynchronouslyandusebatchconf

Jul 29, 2025 am 12:47 AM

Event Sourcing and CQRS Patterns in Java

Event traceability and CQRS are suitable for complex business systems. 1. Event traceability provides complete audit and time travel capabilities by saving event sequence reconstruction status, but increases query complexity; 2. CQRS separates read and write models to improve scalability and performance, but introduces final consistency; 3. In Java, AxonFramework can be implemented in combination with SpringBoot, using @Aggregate to process commands, @EventSourcingHandler updates status, and @EventHandler builds read models; 4. Applicable to scenarios that require high auditability and uneven read and write load, and is not suitable for simple CRUD systems; 5. Pay attention to event immutability, version control, final consistency processing and

Jul 29, 2025 am 12:34 AM

java

Optimizing Java Docker Images for Smaller Size and Faster Startup

Use smaller basic images such as eclipse-temurin:17-jre-alpine or -slim to reduce volume; 2. Use multi-stage construction to separate compilation and operation environments to avoid throwing the build tools and source code into the final image; 3. Optimize the JAR package itself, remove useless dependencies, enable compression, and consider SpringBoot layered JAR; 4. Enable Class Data Sharing (CDS) to reduce startup time and memory usage; 5. Adjust JVM containerized parameters such as -XX: UseContainerSupport and -XX:MaxRAMPercentage to adapt to container resource limitations; 6. Use GraalVM native mirrors to select scenarios with extremely high startup speed requirements

Jul 29, 2025 am 12:27 AM

java docker

Advanced Exception Handling Strategies in Java

Usespecificexceptionsinsteadofgenericonestoenablepreciseerrorhandlingandimprovedebugging.2.Createcustomexceptionsfordomain-specificerrorstoenhancereadability,enabletargetedcatchblocks,andclarifyAPIcontracts.3.Usetry-with-resourcesforautomaticmanageme

Jul 29, 2025 am 12:16 AM

Java Interoperability with Kotlin: A Seamless Integration

Kotlin can integrate seamlessly with Java because the two run on the JVM and the bytecode is interoperable. The Kotlin compiler automatically generates compatible code to bridge syntax differences and adapts to Java features through language design. 1. Kotlin and Java are compiled into the same JVM bytecode, and classes can be called directly from each other and share classpath; 2. Kotlin uses @JvmOverloads to generate overloaded methods for the default parameters, and the top-level functions are compiled into Java static methods (the class name can be customized through @file:JvmName); 3. Kotlin treats Java types as platform types (such as String!), and needs to manually handle empty security, and supports SAM conversion to La

Jul 29, 2025 am 12:15 AM

Java Authentication and Authorization with JWT

JWT is an open standard for safe transmission of information. In Java, authentication and authorization can be achieved through the JJWT library. 1. Add JJWT API, Impl and Jackson dependencies; 2. Create JwtUtil tool class to generate, parse and verify tokens; 3. Write JwtFilter intercepts requests and verify BearerTokens in Authorization header; 4. Register Filter in SpringBoot to protect the specified path; 5. Provide a login interface to return JWT after verifying the user; 6. The protected interface obtains user identity and roles through parsing the token for access control, and ultimately realizes a stateless and extensible security mechanism, suitable for distributed systems.

Jul 29, 2025 am 12:07 AM

java programming

Reactive Programming in Java with Project Reactor and Spring WebFlux

Responsive programming implements high concurrency, low latency non-blocking services in Java through ProjectReactor and SpringWebFlux. 1. ProjectReactor provides two core types: Mono and Flux, supports declarative processing of asynchronous data flows, and converts, filters and other operations through operator chains; 2. SpringWebFlux is built on Reactor, supports two programming models: annotation and functional. It runs on non-blocking servers such as Netty, and can efficiently handle a large number of concurrent connections; 3. Using WebFlux Reactor can improve the concurrency capability and resource utilization in I/O-intensive scenarios, and naturally supports SSE and WebSo.

Jul 29, 2025 am 12:04 AM

java Reactive programming

Writing Testable Java Code with JUnit 5 and Mockito

Writetestablecodeusingdependencyinjectiontoenableloosecoupling,asseenbyreplacinghard-codeddependencieswithinjectedones;2.UseJUnit5forstructuredtestingwithfeatureslike@BeforeEach,@Test,andassertThrowstoensureclean,readable,andreliabletests;3.Mockexter

Jul 28, 2025 am 03:24 AM

mockito JUnit 5