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Java API Development with the Spring Framework

StartbysettingupaSpringBootprojectusingSpringInitializrwithdependencieslikeSpringWeb,SpringDataJPA,andLombokforstreamlineddevelopment.2.CreateaRESTcontrollerwith@RestControlleranduseannotationslike@GetMapping,@PostMapping,@PathVariable,and@RequestBod

Jul 26, 2025 am 07:26 AM

how to connect to mysql database in java with jdbc

The most common method to connect to MySQL databases in Java is to use JDBC. The specific steps are as follows: 1. Add MySQLJDBC driver dependency. The Maven project can add mysql-connector-java dependency in pom.xml. Non-Maven projects can manually introduce jar packages; 2. Load the driver class and establish a connection. Load the driver through Class.forName("com.mysql.cj.jdbc.Driver"), and use the DriverManager.getConnection() method to pass in the URL, username and password of the format jdbc:mysql://

Jul 26, 2025 am 07:24 AM

Testing Java Applications with JUnit 5 and Mockito

First, you need to correctly configure JUnit5 and Mockito dependencies in your project, and then write test cases using JUnit5 and mock dependencies in combination with Mockito. 1. Add test dependencies of JUnit5 and Mockito in Maven or Gradle; 2. Write unit tests using JUnit5 annotation and assertion methods such as @Test and assertEquals; 3. Create mock objects with @Mock, @InjectMocks inject the tested object, @ExtendWith(MockitoExtension.class) to enable Mockito support, and define mocks through when().thenReturn()

Jul 26, 2025 am 07:21 AM

what is public static void main string args in java

publicstaticvoidmain(String[]args) is the entry point of a Java program and must be declared in a fixed format to ensure that Java can be correctly recognized and executed. Its components respectively indicate: public allows external access, static can be called without instantiation, void means no return value, main is the method name, and String[]args is used to receive command line parameters. Common errors include spelling errors, parameter type errors, missing static keywords, or adding extra parameters. A correct understanding of the functions of each part can help avoid errors and implement parameterized running programs.

Jul 26, 2025 am 07:04 AM

Object-Oriented Design Principles in a Modern Java Context

Object-orienteddesignprinciplesremainessentialinmodernJavadevelopment,evolvingalongsidenewlanguagefeaturesandarchitecturalpatterns.1.SOLIDprinciplesaremorerelevantthanever:SRPensuressingle-purposeclasses,especiallyinlayeredframeworkslikeSpring;OCPpro

Jul 26, 2025 am 07:00 AM

Using Project Loom for Lightweight Concurrency in Java

ProjectLoomintroducesvirtualthreadstosolveJava’sconcurrencylimitationsbyenablinglightweight,scalablethreading.1.VirtualthreadsareJVM-managed,low-footprintthreadsthatallowmillionsofconcurrentthreadswithminimalOSresources.2.Theysimplifyhigh-concurrency

Jul 26, 2025 am 06:41 AM

java concurrent

Building Resilient Java Microservices with Resilience4j

Resilience4j improves the flexibility of Java microservices through circuit breakers, current limiting, retry and other mechanisms. 1. Use circuit breakers to prevent cascade failures and prevent requests from being sent when services fail frequently; 2. Use current limit control to control concurrent access to avoid sudden traffic overwhelming downstream services; 3. Respond to temporary errors through retry mechanisms, but avoid invalid retry and resource waste; 4. Multiple strategies can be used in combination to enhance the overall resilience of the system, but attention should be paid to the mutual influence between policies. Properly configuring these functions can significantly improve the stability and fault tolerance of distributed systems.

Jul 26, 2025 am 06:36 AM

java microservices

How to add an element to an array in Java?

Adding elements to an array in Java requires a workaround to implement because the array length is fixed. 1. Use the Arrays.copyOf method: import the Arrays tool class, define the original array and new elements, create a new array of length 1 and copy the content, and finally add new elements; 2. Create a new array and copy the content: create a new array of length 1, copy the original array content through a loop, and add new elements at the last position; 3. Use ArrayList: Use a dynamic array structure, use the .add() method to directly add elements, which is suitable for frequent modification of data; the above methods are essentially the process of "create new array, copy content, and add new values". When frequent operations, use ArrayLis should be given priority.

Jul 26, 2025 am 06:32 AM

A Deep Dive into Java's HashMap and ConcurrentHashMap

HashMapisnotthread-safeandshouldonlybeusedinsingle-threadedenvironmentsorwithexternalsynchronization,whileConcurrentHashMapisthread-safeanddesignedforconcurrentaccess.2.HashMapallowsnullkeysandvalues,whereasConcurrentHashMapthrowsNullPointerException

Jul 26, 2025 am 06:10 AM

How the Java Platform Module System (JPMS) Works

JPMSintroducesmodulesviamodule-info.javatodefinedependencies,exports,andservices.2.Itenforcesstrongencapsulationbyrestrictingaccesstonon-exportedpackages,evenifclassesarepublic.3.Themodulepathreplacestheclasspath,enablingexplicitdependencyresolutiona

Jul 26, 2025 am 05:51 AM

JPMS Java模塊

The SOLID Principles Explained for Java Developers

The single responsibility principle (SRP) requires a class to be responsible for only one function, such as separating the saving and mail sending in order processing; 2. The opening and closing principle (OCP) requires opening and closing for extensions and closing for modifications, such as adding new graphics without modifying the calculator; 3. The Richter replacement principle (LSP) requires that subclasses can replace the parent class without destroying the program, such as using independent classes to avoid behavior abnormalities caused by square inheritance rectangles; 4. The interface isolation principle (ISP) requires that clients should not rely on unwanted interfaces, such as splitting the multi-function device interface to independent printing, scanning, and fax interfaces; 5. The dependency inversion principle (DIP) requires that high-level modules do not rely on low-level modules, and both rely on abstraction, such as OrderService depends on Data

Jul 26, 2025 am 05:16 AM

java SOLID Principle

Java Persistence with JPA and Hibernate: A Complete Tutorial

JPA is the abbreviation of JavaPersistenceAPI, a standard specification for mapping Java objects to database tables, and Hibernate is one of its most popular implementations, providing object-relational mapping (ORM) functionality that can simplify database operations. 1. JPA defines standards for entity mapping and CRUD operations, allowing developers to operate databases in an object-oriented way and avoid writing a large amount of JDBC code. 2. Hibernate, as an implementation of JPA, not only supports JPA specifications, but also provides advanced features such as caching, lazy loading, and transaction management. 3. Use Maven to add hibernate-core and database driver (such as H2) dependencies and in src

Jul 26, 2025 am 05:13 AM

java

Java Security for LDAP Injection Prevention

The core measures to prevent LDAP injection vulnerabilities include: 1. Avoid direct splicing of user input; 2. Filter or escape special characters; 3. Use security library to build queries. Directly splicing user input into LDAP query statements is the main reason for the injection problem. Attackers can bypass the authentication mechanism by constructing malicious input, such as input admin)(|(password=* to manipulate query logic. Therefore, user input must be processed, and special characters such as *, (,), \, NUL can be replaced by character filtering or escape functions. In addition, it is recommended to use encapsulated classes such as ApacheCommonsLDAP, SpringSecurity, or UnboundIDLDAPSDK.

Jul 26, 2025 am 05:03 AM

Creating a Custom Java Annotation Processor

Define a custom annotation, such as @LogMethod, use @Target(ElementType.METHOD) and @Retention(RetentionPolicy.SOURCE) to ensure that it is only used on methods at compile time; 2. Create annotation processor LogMethodProcessor, inherit the AbstractProcessor, rewrite the process method to process methods marked by @LogMethod, and output the compile-time prompt through Messager; 3. By META-INF/services/javax.annotation.processing.P

Jul 26, 2025 am 04:03 AM