<h1>Java Weekly: Spring Boot 4 and Jackson 3 Support</h1>
<h2>Introduction</h2>
<p>Spring Boot 4’s launch marks a significant milestone with the introduction of support for Jackson 3, the latest iteration of the prominent JVM JSON processing library. This major update not only modernizes JSON handling but also features a flexible transition path for developers upgrading from previous versions.</p>
<h2>Jackson 3 Integration in Spring</h2>
<p>The integration of Jackson 3 in Spring Boot 4 and Spring Framework 7 brings multiple changes aimed at improved JSON processing. A notable change is the shift from the mutable <code>ObjectMapper</code> to the immutable <code>JsonMapper</code>, along with modifications in package names from <code>com.fasterxml.jackson</code> to <code>tools.jackson</code>. The update also includes new default settings, optimizing performance and security.</p>
<p>Spring Boot 4 facilitates a smooth migration by maintaining dependency management for both Jackson 2 and 3, although Jackson 3 becomes the auto-configured default. Developers can upgrade incrementally, leveraging comprehensive guidance on package updates, default settings adjustments, and new configuration patterns. The Spring development team collaborated closely with Jackson’s maintainers ensuring a robust support system, while also providing prolonged support for Jackson 2 to ease the transition period.</p>
<h2>Utilizing Reactive Context in Spring Applications</h2>
<p>The <code>Context</code> pattern in reactive Spring applications addresses the reliability issues associated with <code>ThreadLocal</code> by ensuring that transaction information is consistently propagated through <code>Mono</code> and <code>Flux</code> streams. This improvement is crucial for developers looking to enhance application scalability and reliability in a reactive programming environment.</p>
<h2>Additional Updates and Changes</h2>
<ul>
<li><strong>Spring AI Updates</strong>: Versions 1.0.3 and 1.1.0-M3 are now available, enhancing AI capabilities within Spring applications.</li>
<li><strong>Spring Cloud Milestones</strong>: The release of Spring Cloud 2025.1.0-M3 introduces new features and improvements relevant for cloud-native app development.</li>
<li><strong>Other Development Tools</strong>: Updates include Mandrel 25 for GraalVM users, WildFly 38 Beta for Java EE, and IntelliJ IDEA 2025.2.3, offering refined coding experiences.</li>
<li><strong>Security and Compliance</strong>: The overview encompasses Spring Cloud Contract 5 deprecation details, ONNX AI inference support in Java, and MCP server security enhancements through OIDC.</li>
</ul>
<p>By incorporating these changes, Java developers are empowered to build more efficient, modern, and secure applications, keeping pace with the evolving technological landscape.</p>


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Spring Boot 4 introduces Jackson 3 support with significant changes including the shift from mutable ObjectMapper to immutable JsonMapper and package name updates. The framework maintains backward compatibility by supporting both Jackson 2 and 3 during migration. Additional updates include reactive context improvements for ThreadLocal reliability, Spring AI versions 1.0.3 and 1.1.0-M3, Spring Cloud 2025.1.0-M3 milestone, and various tooling updates like Mandrel 25 and WildFly 38 Beta.