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Practice of different data types conversion and mapping between Java service layer and controller

This article discusses how to effectively convert and map when the data type returned by the service layer is inconsistent with the type expected by the controller in Java applications. This highlights the implementation method of custom object mappers and considerations when designing the type level. Through instance code, the strategy of converting irrelevant objects (such as Excel data model) into target response objects (such as Resresource) is explained, and the importance of unified return types at the service layer, avoiding the use of Objects, and clear API contracts is emphasized, aiming to improve the maintainability and robustness of the code.

Aug 25, 2025 am 11:36 AM

Spring Boot Application Configuration Center Client Integration Guide

This article aims to guide developers to configure Spring Boot applications as a configuration center client to enable them to dynamically obtain configuration from a remote configuration server. The article will introduce in detail how to add necessary dependencies, configure client attributes, and solve common problems of configuration failure, helping readers quickly build a reliable configuration management solution.

Aug 25, 2025 am 11:30 AM

Inject static configuration values ??into GWT client code using the Gin module

This article describes how to inject static configuration values ??into GWT client code to avoid problems caused by using Guice directly on the client. By using the Gin module, we can effectively bind configuration values ??into client code, enabling clearer, maintainable GWT applications. This article will provide detailed descriptions on how to use the Gin module and provide sample code to help you understand and apply this approach.

Aug 25, 2025 am 11:24 AM

How to cache introspective requests in Spring Security

This document aims to guide developers how to cache OAuth2 introspective requests in Spring Security to improve the stability and performance of resource servers and reduce dependence on authenticated servers. By customizing the OpaqueTokenIntrospector and utilizing the caching mechanism, it can effectively reduce 401 errors and improve user experience. This article will provide detailed code examples and step instructions to help you easily achieve caching of introspective requests.

Aug 25, 2025 am 11:21 AM

What are design patterns in Java?

DesignpatternsinJavaareprovensolutionstorecurringsoftwaredesignproblems,categorizedintocreational,structural,andbehavioraltypes;theypromoteflexibilityandmaintainabilitythroughtemplates—notdirectcode—usingobject-orientedprincipleslikeinheritanceandpol

Aug 25, 2025 am 11:10 AM

java Design Patterns

Use Java Stream to find elements with maximum values ??in List

This article describes how to use the Java Stream API to find a HashMap with the largest "Length" value from an ArrayList. The article first suggests using a custom object instead of a HashMap to store data, and then shows two ways to find a single largest element and find all sets of elements with maximum values, and provides detailed code examples. Additionally, an alternative to using the three-parameter Stream.collect() method is provided to avoid creating intermediate maps.

Aug 25, 2025 am 10:48 AM

How to work with the Java Memory Model

To effectively use the Java memory model, you must first understand that it ensures the visibility and order of variables through the happens-before relationship; 1. Use volatile to ensure that variable read and write directly interacts with the main memory, ensuring visibility but not the atomicity of composite operations; 2. Create happens-before relationship through synchronized blocks or methods to ensure that the write before lock is released is visible to the threads that acquire the same lock in the subsequent memory; 3. Use Thread.start() and Thread.join() to achieve memory visibility between threads; 4. Use atomic classes, concurrent collections and lock tools in the java.util.concurrent package, which are built-in

Aug 25, 2025 am 10:40 AM

Efficient way to find maximum values ??in List using Java Stream

This article explores how to use the Java Stream API to find a HashMap with the maximum length from a List. The article first emphasizes the advantages of using custom objects instead of HashMap, and then introduces two methods to find a single largest element and find all sets of elements with maximum length, and provides clear code examples and detailed explanations to help readers better understand and apply the Stream API.

Aug 25, 2025 am 10:33 AM

What is the Stream API and its benefits in Java?

Java8's StreamAPI provides powerful and declarative data processing methods. 1. Supports functional programming through method chains to make the code more concise and easy to read; 2. Provides rich intermediate operations (such as filter, map, sorted) and terminal operations (such as forEach, collect, reduce), which facilitates the construction of complex data processing pipelines; 3. Parallel processing can be achieved through parallelStream() or stream().parallel(), automatically manages multi-threaded task division and result merging, and improves the processing performance of large data sets; 4. Improves code maintainability, reduces the use of loops and temporary variables, and clearly expresses the operation intention; 5.

Aug 25, 2025 am 10:26 AM

How to get a substring in Java

To get substrings in Java, you need to use the substring() method of the String class. This method has two overloaded forms: 1.substring(intbeginIndex) returns the substring from the specified index to the end of the string; 2.substring(intbeginIndex,intendIndex) returns the characters from beginIndex to endIndex (not included). The index starts at 0 and endIndex is an exclusive value. If the index goes out of bounds, an IndexOutOfBoundsException will be thrown. When using it, make sure the index is valid or bounds are checked in advance to avoid exceptions.

Aug 25, 2025 am 10:24 AM

Understanding standard output buffering: behavioral differences and control methods for Python, C, Java, and Go

This article explores in-depth differences in standard output (stdout) buffering mechanisms for different programming languages ??(Python, C, Java, Go), especially the different behaviors that appear when the output is connected to a terminal (TTY) or a pipeline. We will parse why Python and C adopt block buffering by default in non-TTY environments, while Java and Go tend to always use line buffering, and provide practical methods to control output immediacy, such as the flush=True parameter in Python.

Aug 25, 2025 am 10:18 AM

A variant that implements the Optional.or() method

This article aims to guide developers how to implement variants of the or() method of the Optional class. This method receives a Supplier that provides an Optional and returns the Optional provided by the Supplier when the original Optional is empty. The article will dig into the issues encountered when accessing private fields and provide a variety of solutions, including using intermediate variables and type conversions, and analyzing their respective pros and cons.

Aug 25, 2025 am 10:06 AM

Advanced Java Generics and Wildcards Explained

WildcardsinJavagenericsincludeunbounded(?),upper-bounded(?extendsT),andlower-bounded(?superT),withthePECSprincipleguidingtheiruse:use?extendsTforproducers(reading)and?superTforconsumers(writing);2.Typeerasureremovesgenerictypeinformationatruntime,pre

Aug 25, 2025 am 10:02 AM

java Generics

Solve Spring JPA foreign key constraint creation error: Correct handling of composite primary keys

This article aims to help developers resolve foreign key constraint creation errors encountered when mapping database tables with composite primary keys using Spring JPA. Through the example code, we explain in detail how to define a composite primary key class and use it correctly in the entity class, and finally successfully create a foreign key relationship, avoiding the number of referencing and referenced columns for foreign key disagree errors.

Aug 25, 2025 am 10:00 AM