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Java Security for Broken Access Control

Access control vulnerabilities are common in Java applications, especially in web development, and are mainly caused by poor permission verification. There are four solutions: First, the permission verification is pre-installed, intercepted at the Controller or Filter layer, and unified entry control permissions; second, use SpringSecurity to simplify permission control, and centrally manage interface permissions through annotation or configuration classes; third, prevent IDOR vulnerabilities, do attribution checks when accessing resources, and restrict overprivileges in combination with database query; fourth, avoid hard-coded permission logic, and use the RBAC model to dynamically configure permission rules to improve flexibility and maintainability.

Jul 16, 2025 am 02:51 AM

java Access control

Understanding Java Stack Overflows and Heap Dumps

StackOverflow is an error caused by the depth of the thread call stack exceeding the JVM limit. It is common in infinite recursion or too deep recursion. It can be prevented by avoiding deep recursion and setting a reasonable stack size; HeapDump is a heap memory snapshot generated by the JVM in memory overflow and other situations. It is used to analyze memory leaks and object occupations. It can be triggered by OutOfMemoryError, jmap or JVM parameters. Common tools include EclipseMAT, VisualVM and jhat; although the two are not directly related, StackOverflow may indirectly raise OutOfMemoryError, thereby generating HeapDump. When troubleshooting, you should first check the code logic and then combine it with H.

Jul 16, 2025 am 02:46 AM

Building Low-Latency Java Trading Systems

The construction of a low-latency trading system can be achieved by reducing GC pauses, thread binding, selecting appropriate data structures and communication methods, and fine tuning and monitoring. 1. Reduce GC pauses, enable ZGC, control object life cycle, use off-heap memory and monitor with JFR; 2. Use thread binding and CPU isolation, bind key threads through taskset or thread affinity library, and configure isolcpus in Linux to ensure execution predictability; 3. Choose cache-friendly data structures such as ring buffers to avoid switching to CAS to use lock mechanisms, and use UDP or Disruptor to improve performance in communication; 4. Deploy a real-time monitoring system, and continuously optimize system performance in combination with JMH testing, Netty/Aeron communication and asynchronous logs.

Jul 16, 2025 am 02:42 AM

How does HashMap work internally in Java?

The underlying implementation of HashMap in Java is a combination structure of arrays, linked lists and red and black trees. 1. It calculates the index position through the hash value of the key and uses perturbation processing to reduce hash collisions; 2. When a hash conflict occurs, the linked list uses the linked list to store elements with the same index; 3. When the linked list length exceeds the threshold (default 8), it converts to a red and black tree to improve performance; 4. When the number of elements exceeds the capacity and multiplies the load factor (default 0.75), it triggers capacity expansion, doubles the array size and redistributes elements; 5. When customizing the key, it needs to rewrite the equals() and hashCode() methods to ensure correct access.

Jul 16, 2025 am 02:41 AM

java hashmap

Understanding Java Synchronizers: Semaphores, CountDownLatch

Semaphore is used to control the number of concurrent accesses, suitable for resource pool management and flow-limiting scenarios, and control permissions through acquire and release; CountDownLatch is used to wait for multiple thread operations to complete, suitable for the main thread to coordinate child thread tasks. 1. Semaphore initializes the specified number of licenses, supports fair and non-fair modes, and when used, the release should be placed in the finally block to avoid deadlock; 2. CountDownLatch initializes the count, call countDown to reduce the count, await blocks until the count returns to zero, and cannot be reset; 3. Select according to the requirements: use Semaphore to limit concurrency, wait for all completions to use CountDown

Jul 16, 2025 am 02:40 AM

java

Java Kubernetes Operators for Application Management

The core reason for writing Kubernetes Operator in Java is to reduce the cost of switching technology stacks, especially on the basis of existing Java application stacks, which facilitates debugging, testing and CI/CD integration; 1. JOSDK provides well-encapsulated annotation and callback mechanisms to simplify the development process; 2. Development steps include introducing dependencies, defining CRDs, writing Reconcilers, and starting the main program; 3. Notes include version compatibility, RBAC permission configuration, local debugging difficulties and performance overhead; 4. The deployment process is to build jar packages, create images, configure RBAC, deploy Pods, and continuously maintain logs and version upgrades.

Jul 16, 2025 am 02:38 AM

Optimizing Hibernate Performance in Java Applications

Hibernate performance optimization needs to start from three aspects: lazy loading, caching, and batch processing. 1. Use lazy loading reasonably, set @OneToOne and @ManyToOne to FetchType.LAZY, and use JOINFETCH to avoid N 1 queries when needed; 2. Enable secondary caching and query caching, add dependencies and configure @Cacheable, suitable for scenarios where data changes less; 3. Set the batch size during batch processing and flush and clear regularly. A large amount of data can be considered for JDBC or StatelessSession to reduce memory consumption.

Jul 16, 2025 am 02:26 AM

Java Memory Leaks Detection and Resolution Strategies

The method to judge Java memory leaks includes observing the continuous growth of heap memory, frequent FullGC and poor recycling effect, and an OutOfMemoryError exception, and can be analyzed by jstat and jmap. 2. Common reasons include cache not being cleaned, listener not being logged out, ThreadLocal not being cleaned, and static collection abuse. The response methods are to use weak references or regular cleaning, timely anti-registration, call remove(), and reasonably design static collection cleaning logic. 3. In terms of tools, it is recommended to assist in positioning leakage points such as VisualVM, EclipseMAT, YourKit, etc., and you can observe the growth trend of the object by comparing heapdump. 4. After repair, you need to simulate the load in the test environment and do it

Jul 16, 2025 am 02:19 AM

Java Performance Bottlenecks Identification

When the CPU usage rate is too high, first use top-H and jstack to analyze the thread stack, and combine JProfiler or asyncProfiler to locate hot spots; 2. Frequent GC can detect memory leaks through log analysis and MAT, paying attention to static collections, cache and other references; 3. I/O and database problems can be positioned through APM tools or logs, and the optimization methods include cache addition, asynchronous processing and database indexing; 4. Unreasonable thread pool configuration may lead to blockage, so the number of threads, queues and rejection policies should be set reasonably, and the running status should be monitored. Mastering these directions and tools can effectively identify Java performance bottlenecks.

Jul 16, 2025 am 02:13 AM

Building High-Throughput Java Microservices

To build a high-throughput Java microservice, we need to start from architecture design, technology selection and performance tuning, and the core lies in "balancing" response speed, stability and scalability. 1. Use lightweight frameworks such as SpringWebFlux or Micronaut to improve processing efficiency, especially suitable for I/O-intensive tasks; 2. Optimize database access, and use asynchronous drivers, caches, library and tables and batch query strategies to reduce bottlenecks; 3. Proper thread pools and concurrent controls to distinguish CPU and I/O-intensive tasks, and choose high-performance IO frameworks to improve underlying efficiency; 4. Use Prometheus, Micrometer, ELKStack and other tools to continuously monitor and tune, pay attention to GC logs to optimize

Jul 16, 2025 am 02:12 AM

java

Java API Versioning Strategies

There are four common ways to control Java API version: 1. The URL path contains the version number, such as /api/v1/users, which is simple and intuitive; 2. Control the version through HTTP request header, such as Accept header field, keep the URL clean but inconvenient to debug; 3. The query parameter control version, such as version=1, is suitable for temporary solutions but is not recommended for long-term use; 4. The client SDK package plus back-end multi-version support is suitable for long-term maintenance of SaaS products and complex systems. The selection should be based on project size, user group and compatibility needs.

Jul 16, 2025 am 02:01 AM

Advanced Java Security Manager Configuration

The core goal of Java Security Manager configuration is to control code permissions, prevent overprivileged operations, and ensure normal function operation. The specific steps are as follows: 1. Modify the security.manager settings in the java.security file and use -Djava.security.policy to enable the security manager; 2. When writing the policy file, you should clarify the CodeBase and SignedBy properties, and accurately set the permissions such as FilePermission, SocketPermission, etc. to avoid security risks; 3. Common problems: If the class loading fails, you need to add defineClass permission, and the reflection is restricted, you need to reflect.

Jul 16, 2025 am 01:59 AM

java programming

Java Virtual Threads Scheduling and Execution Model

VirtualThreads is a lightweight thread managed by JVM, with low creation and destruction costs, making Java applications easy to run hundreds of thousands of concurrent tasks. 1. They are scheduled through ForkJoinPool, submitted to the shared pool by default, and bound to OS threads to execute; 2. Automatically release the underlying threads when blocking to improve resource utilization; 3. Use collaborative scheduling and actively hand over CPU control when encountering I/O, sleep and other operations; 4. It is not supported to custom scheduling strategies, developers do not need to manage underlying details such as thread pool size; 5. It is recommended to avoid long-term CPU-intensive tasks, and it is recommended to be used in high-concurrency I/O scenarios such as web servers.

Jul 16, 2025 am 01:56 AM

Advanced Java Reflection for Code Analysis

ReflectioninJavaenablesruntimeinspectionofclasses,methods,andfieldswithoutpriorcompile-timeknowledge.2.ItallowsaccesstoprivatemembersviasetAccessible(true),usefulintestingandmockingframeworks.3.Youcananalyzecustomannotationstoextractmetadata,crucialf

Jul 16, 2025 am 01:53 AM

java reflection