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This tutorial walks through six practical techniques—@Qualifier, @Primary, @Profile, collection injection, @Priority, and custom @Conditional—to control which implementation of a Spring Boot interface is autowired, complete with code examples and usage tips.
This guide explains how Spring's @Qualifier annotation eliminates bean injection ambiguities, shows basic usage, custom qualifier creation, generic qualifiers, fully custom annotations, and advanced attribute‑based qualifiers, all illustrated with clear Java code examples for Spring 6.1.2.
This article explains eight practical ways to control which DAO implementation Spring injects, covering @Qualifier, bean naming, custom qualifiers, manual lookup, profile‑based beans, @Primary, and @Priority, with complete code examples for each method.
This article explains typical Spring Boot bean injection failures—such as missing component scanning, multi‑module scanning gaps, incorrect @Qualifier/@Resource names, and injection in filters or listeners—and provides concrete configuration and code examples to resolve each problem.
Spring’s annotation‑based bean registration and dependency injection replace verbose XML by using component scanning with @Component, @Controller, @Service, and @Repository, while @Autowired (or @Qualifier/@Primary) injects beans by type, @Resource supports name‑based injection, and @Value together with @PropertySource loads external configuration, though developers must handle issues such as NoUniqueBeanDefinitionException when multiple candidates exist.