Posts Tagged ‘Oracle’
[DevoxxUK2024] Project Leyden: Capturing Lightning in a Bottle by Per Minborg
Per Minborg, a seasoned member of Oracle’s Core Library team, delivered an insightful session at DevoxxUK2024, unveiling the ambitions of Project Leyden, a transformative initiative to enhance Java application performance. Focused on slashing startup time, accelerating warmup, and reducing memory footprint, Per’s talk explores how Java can evolve to meet modern demands while preserving its dynamic nature. By strategically shifting computations to optimize execution, Project Leyden introduces innovative techniques like condensers and enhanced Class Data Sharing (CDS). This session provides a roadmap for developers seeking to harness Java’s potential in high-performance environments, balancing flexibility with efficiency.
The Vision of Project Leyden
Per begins by outlining the core objectives of Project Leyden: improving startup time, warmup time, and memory footprint. Startup time, the duration from launching an application to its first meaningful output (e.g., a “Hello World” or serving a web request), is critical for user experience. Warmup time, the period until an application reaches peak performance through JIT compilation, can hinder responsiveness in dynamic systems. Footprint, encompassing memory and storage use, impacts scalability, especially in cloud environments. Per emphasizes that the best approach is to eliminate unnecessary computations, but when that’s not feasible, shifting them temporally—either earlier to compile time or later to runtime—can yield significant gains. This philosophy underpins Leyden’s strategy to refine Java’s execution model.
Shifting Computations for Efficiency
A cornerstone of Project Leyden is the concept of temporal computation shifting. Per explains that Java’s dynamic nature—encompassing dynamic class loading, JIT compilation, and runtime optimizations—enables expressive programming but can inflate startup and warmup times. By moving computations to build time, such as through constant folding or ahead-of-time (AOT) compilation, Leyden reduces runtime overhead. Alternatively, lazy evaluation postpones non-critical tasks, streamlining startup. Per introduces condensers, a novel mechanism that transforms program representations by shifting computations earlier, adding metadata, or imposing constraints on dynamism. Condensers are composable, meaning-preserving, and selectable, allowing developers to tailor optimizations based on application needs. For instance, a condenser might precompile lambda expressions into bytecode at build time, slashing runtime costs.
Enhancing Class Data Sharing (CDS)
Per delves into Class Data Sharing (CDS), a long-standing Java feature that Project Leyden enhances to achieve dramatic performance boosts. CDS allows pre-initialized JDK classes to be stored in a file, bypassing costly class loading during startup. With CDS++, Leyden extends this to include application classes, compiled code, and resolved constant pool references. Per shares compelling benchmarks: a test compiling 100 small Java files achieved a 2x startup improvement, while an XML parsing workload saw an 8x boost. For the Spring Pet Clinic benchmark, Leyden’s optimizations, including early class loading and cached compiled code, yielded up to 4x faster startup. These gains stem from a training run approach, where a representative execution gathers profiling data to inform optimizations, ensuring compatibility across platforms.
Balancing Dynamism and Performance
Java’s dynamism—encompassing dynamic typing, class loading, and reflection—empowers developers but complicates optimization. Per proposes selective constraints to balance this trade-off. For example, developers can restrict dynamic class loading for specific modules, enabling aggressive optimizations without sacrificing Java’s flexibility. The stable value feature, initially part of Leyden but now a standalone JEP, allows delayed initialization of final fields while maintaining performance akin to compile-time constants. Per illustrates this with a Fibonacci computation example, where memoization using stable values drastically reduces recursive overhead. By offering a “mixer board” of concessions, Leyden empowers developers to fine-tune performance, ensuring compatibility and preserving program semantics across diverse use cases.
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[DevoxxBE2023] Moving Java Forward Together: Community Power
Sharat Chander, Oracle’s Senior Director of Java Developer Engagement, delivered a compelling session at DevoxxBE2023, emphasizing the Java community’s pivotal role in driving the language’s evolution. With over 25 years in the IT industry, Sharat’s passion for Java and community engagement shone through as he outlined how developers can contribute to Java’s future, ensuring its relevance for decades to come.
The Legacy and Longevity of Java
Sharat began by reflecting on Java’s 28-year journey, a testament to its enduring impact on software development. He engaged the audience with a poll, revealing the diverse experience levels among attendees, from those using Java for five years to veterans with over 25 years of expertise. This diversity underscores Java’s broad adoption across industries, from small startups to large enterprises.
Java’s success, Sharat argued, stems from its thoughtful innovation strategy. Unlike the “move fast and break things” mantra, the Java team prioritizes stability and backward compatibility, ensuring that applications built on older versions remain functional. Projects like Amber, Panama, and the recent introduction of virtual threads in Java 21 exemplify this incremental yet impactful approach to innovation.
Balancing Stability and Progress
Sharat addressed the tension between rapid innovation and maintaining stability, a challenge given Java’s extensive history. He highlighted the six-month release cadence introduced to reduce latency to innovation, allowing developers to adopt new features without waiting for major releases. This approach, likened to a train arriving every three minutes, minimizes disruption and enhances accessibility.
The Java team’s commitment to trust, innovation, and predictability guides its development process. Sharat emphasized that Java’s design principles—established 28 years ago—continue to shape its evolution, ensuring it meets the needs of diverse applications, from AI and big data to emerging fields like quantum computing.
Community as the Heart of Java
The core of Sharat’s message was the community’s role in Java’s vitality. He debunked the “build it and they will come” myth, stressing that Java’s success relies on active community participation. Programs like the OpenJDK project invite developers to engage with mailing lists, review code check-ins, and contribute to technical decisions, fostering transparency and collaboration.
Sharat also highlighted foundational programs like the Java Community Process (JCP) and Java Champions, who advocate for Java independently, providing critical feedback to the Java team. He encouraged attendees to join Java User Groups (JUGs), noting the nearly 400 groups worldwide as vital hubs for knowledge sharing and networking.
Digital Engagement and Future Initiatives
Recognizing the digital era’s impact, Sharat discussed Oracle’s efforts to reach Java’s 10 million developers through platforms like dev.java. This portal aggregates learning resources, community content, and programs like JEEP Cafe and Sip of Java, which offer digestible insights into Java’s features. The recently launched Java Playground provides a browser-based environment for experimenting with code snippets, accelerating feature adoption.
Sharat also announced the community contributions initiative on dev.java, featuring content from Java Champions like Venkat Subramaniam and Hannes Kutz. This platform aims to showcase community expertise, encouraging developers to submit their best practices via GitHub pull requests.
Nurturing Diversity and Inclusion
A poignant moment in Sharat’s talk was his call for greater gender diversity in the Java community. He acknowledged the industry’s shortcomings in achieving balanced representation and urged collective action to expand the community’s mindshare. Programs like JDuchess aim to create inclusive spaces, ensuring Java’s evolution benefits from diverse perspectives.
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[DevoxxBE2023] The Panama Dojo: Black Belt Programming with Java 21 and the FFM API by Per Minborg
In an engaging session at Devoxx Belgium 2023, Per Minborg, a Java Core Library team member at Oracle and an OpenJDK contributor, guided attendees through the intricacies of the Foreign Function and Memory (FFM) API, a pivotal component of Project Panama. With a blend of theoretical insights and live coding, Per demonstrated how this API, in its third preview in Java 21, enables seamless interaction with native memory and functions using pure Java code. His talk, dubbed the “Panama Dojo,” showcased the API’s potential to enhance performance and safety, culminating in a hands-on demo of a lightweight microservice framework built with memory segments, arenas, and memory layouts.
Unveiling the FFM API’s Capabilities
Per introduced the FFM API as a solution to the limitations of Java Native Interface (JNI) and direct buffers. Unlike JNI, which requires cumbersome C stubs and inefficient data passing, the FFM API allows direct native memory access and function calls. Per illustrated this with a Point struct example, where a memory segment models a contiguous memory region with 64-bit addressing, supporting both heap and native segments. This eliminates the 2GB limit of direct buffers, offering greater flexibility and efficiency.
The API introduces memory segments with constraints like size, lifetime, and thread confinement, preventing out-of-bounds access and use-after-free errors. Per highlighted the importance of deterministic deallocation, contrasting Java’s automatic memory management with C’s manual approach. The FFM API’s arenas, such as confined and shared arenas, manage segment lifecycles, ensuring resources are freed explicitly, as demonstrated in a try-with-resources block that deterministically deallocates a segment.
Structuring Memory with Layouts and Arenas
Memory layouts, a key FFM API feature, provide a declarative way to define memory structures, reducing manual offset computations. Per showed how a Point layout with x and y doubles uses var handles to access fields safely, leveraging JIT optimizations for atomic operations. This approach minimizes bugs in complex structs, as var handles inherently account for offsets, unlike manual calculations.
Arenas further enhance safety by grouping segments with shared lifetimes. Per demonstrated a confined arena, restricting access to a single thread, and a shared arena, allowing multi-threaded access with thread-local handshakes for safe closure. These constructs bridge the gap between C’s flexibility and Rust’s safety, offering a balanced model for Java developers. In his live demo, Per used an arena to allocate a MarketInfo segment, showcasing deterministic deallocation and thread safety.
Building a Persistent Queue with Memory Mapping
The heart of Per’s session was a live coding demo constructing a persistent queue using memory mapping and atomic operations. He defined a MarketInfo record for stock exchange data, including timestamp, symbol, and price fields. Using a record mapper, Per serialized and deserialized records to and from memory segments, demonstrating immutability and thread safety. The mapper, a potential future JDK feature, simplifies data transfer between Java objects and native memory.
Per then implemented a memory-mapped queue, where a file-backed segment stores headers and payloads. Headers use atomic operations to manage mutual exclusion across threads and JVMs, ensuring safe concurrent access. In the demo, a producer appended MarketInfo records to the queue, while two consumers read them asynchronously, showcasing low-latency, high-performance data sharing. Per’s use of sparse files allowed a 1MB queue to scale virtually, highlighting the API’s efficiency.
Crafting a Microservice Framework
The session culminated in assembling these components into a microservice framework. Per’s queue, inspired by Chronicle Queue, supports persistent, high-performance data exchange across JVMs. The framework leverages memory mapping for durability, atomic operations for concurrency, and record mappers for clean data modeling. Per demonstrated its practical application by persisting a queue to a file and reading it in a separate JVM, underscoring its robustness for distributed systems.
He emphasized the reusability of these patterns across domains like machine learning and graphics processing, where native libraries are prevalent. Tools like jextract, briefly mentioned, further unlock native libraries like TensorFlow, enabling Java developers to integrate them effortlessly. Per’s framework, though minimal, illustrates how the FFM API can transform Java’s interaction with native code, offering a safer, faster alternative to JNI.
Performance and Safety in Harmony
Throughout, Per stressed the FFM API’s dual focus on performance and safety. Native function calls, faster than JNI, and memory segments with strict constraints outperform direct buffers while preventing common errors. The API’s integration with existing JDK features, like var handles, ensures compatibility and optimization. Per’s live coding, despite its complexity, flowed seamlessly, reinforcing the API’s practicality for real-world applications.
Conclusion: Embracing the Panama Dojo
Per’s session was a masterclass in leveraging the FFM API to push Java’s boundaries. By combining memory segments, layouts, arenas, and atomic operations, he crafted a framework that exemplifies the API’s potential. His call to action—experiment with the FFM API in Java 21—invites developers to explore this transformative tool, promising enhanced performance and safety for native interactions. The Panama Dojo left attendees inspired to break new ground in Java development.
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[DevoxxBE2023] Java Language Update by Brian Goetz
At Devoxx Belgium 2023, Brian Goetz, Oracle’s Java Language Architect, delivered an insightful session on the evolution of Java, weaving together a narrative of recent advancements, current features in preview, and a vision for the language’s future. With his deep expertise, Brian illuminated how Java balances innovation with compatibility, ensuring it remains a cornerstone of modern software development. His talk explored the introduction of records, sealed classes, pattern matching, and emerging features like string templates and simplified program structures, all designed to enhance Java’s expressiveness and accessibility. Through a blend of technical depth and practical examples, Brian showcased Java’s commitment to readable, maintainable code while addressing contemporary programming challenges.
Reflecting on Java’s Recent Evolution
Brian began by recapping Java’s significant strides since his last Devoxx appearance, highlighting features like records, sealed classes, and pattern matching. Records, introduced as nominal tuples, provide a concise way to model data with named components, enhancing readability over structural tuples. For instance, a Point record with x and y coordinates is more intuitive than an anonymous tuple of integers. By deriving constructors, accessors, and equality methods from a state declaration, records eliminate boilerplate while making a clear semantic statement about data immutability. Brian emphasized that this semantic focus, rather than mere syntax reduction, distinguishes Java’s approach from alternatives like Lombok.
Sealed classes, another recent addition, allow developers to restrict class hierarchies, specifying permitted subtypes explicitly. This enables libraries to expose abstract types while controlling implementations, as seen in the JDK’s use of method handles. Sealed classes also enhance exhaustiveness checking in switch statements, reducing runtime errors by ensuring all cases are covered. Brian illustrated this with a Shape hierarchy, where a sealed interface permits only Circle and Rectangle, allowing the compiler to verify switch completeness without a default clause.
Advancing Data Modeling with Pattern Matching
Pattern matching, a cornerstone of Java’s recent enhancements, fuses type testing, casting, and binding into a single operation, reducing errors from manual casts. Brian demonstrated how type patterns, like if (obj instanceof String s), streamline code by eliminating redundant casts. Record patterns extend this by deconstructing objects into components, enabling recursive matching for nested structures. For example, a Circle record with a Point center can be matched to extract x and y coordinates in one expression, enhancing both concision and safety.
The revamped switch construct, now an expression supporting patterns and guards, further leverages these capabilities. Brian highlighted its exhaustiveness checking, which uses sealing information to ensure all cases are handled, as in a Color interface sealed to Red, Yellow, and Green. This eliminates the need for default clauses, catching errors at compile time if the hierarchy evolves. By combining records, sealed classes, and pattern matching, Java now supports algebraic data types, offering a powerful framework for modeling complex domains like expressions, where a sealed Expression type can be traversed elegantly with pattern-based recursion.
Introducing String Templates for Safe Aggregation
Looking to the future, Brian introduced string templates, a preview feature addressing the perils of string interpolation. Unlike traditional concatenation or formatting methods, string templates use a template processor to safely combine text fragments and expressions. A syntax like STR.FMT."Hello, \{name\}!" invokes a processor to validate inputs, preventing issues like SQL injection. Brian envisioned a SQL template processor that balances quotes and produces a result set directly, bypassing string intermediaries for efficiency and security. Similarly, a JSON processor could streamline API development by constructing objects from raw fragments, enhancing performance.
This approach reframes interpolation as a broader aggregation problem, allowing developers to define custom processors for domain-specific needs. Brian’s emphasis on safety and flexibility underscores Java’s commitment to robust APIs, drawing inspiration from JavaScript’s tagged functions and Scala’s string interpolators, but tailored to Java’s ecosystem.
Simplifying Java’s On-Ramp and Beyond
To make Java for new developers, Brian discussed preview features like unnamed classes and patterns, which reduce boilerplate for simple programs. A minimal program might omit public static void main, allowing beginners to focus on core logic rather than complex object-oriented constructs. This aligns Java with languages like Python, where incremental learning is prioritized, easing the educational burden on instructors and students alike.
Future enhancements include reconstruction patterns for immutable objects, enabling concise updates like p.with(x: 0) to derive new records from existing ones. Brian also proposed deconstructor patterns for regular classes, mirroring constructors to enable pattern decomposition, enhancing API symmetry. These features aim to make aggregation and decomposition reversible, reducing error-prone asymmetries in object manipulation. For instance, a Person class could declare a deconstructor to extract first and last names, mirroring its constructor, streamlining data handling across Java’s object model.
Conclusion: Java’s Balanced Path Forward
Brian’s session underscored Java’s deliberate evolution, balancing innovation with compatibility. By prioritizing readable, maintainable code, Java addresses modern challenges like loosely coupled services and untyped data, positioning itself as a versatile language for data modeling. Features like string templates and simplified program structures promise greater accessibility, while pattern matching and deconstruction patterns enhance expressiveness. As Java continues to refine its features, it remains a testament to thoughtful design, ensuring developers can build robust, future-ready applications.
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[DevoxxUS2017] Java EE 8: Adapting to Cloud and Microservices
At DevoxxUS2017, Linda De Michiel, a pivotal figure in the Java EE architecture team and Specification Lead for the Java EE Platform at Oracle, delivered a comprehensive overview of Java EE 8’s development. With her extensive experience since 1997, Linda highlighted the platform’s evolution to embrace cloud computing and microservices, aligning with modern industry trends. Her presentation detailed updates to existing Java Specification Requests (JSRs) and introduced new ones, while also previewing plans for Java EE 9. This post explores the key themes of Linda’s talk, emphasizing Java EE 8’s role in modern enterprise development.
Evolution from Java EE 7
Linda began by reflecting on Java EE 7, which focused on HTML5 support, modernized web-tier APIs, and simplified development through Context and Dependency Injection (CDI). Building on this foundation, Java EE 8 shifts toward cloud-native and microservices architectures. Linda noted that emerging trends, such as containerized deployments and distributed systems, influenced the platform’s direction. By enhancing CDI and introducing new APIs, Java EE 8 aims to streamline development for scalable, cloud-based applications, ensuring developers can build robust systems that meet contemporary demands.
Enhancements to Core JSRs
A significant portion of Linda’s talk focused on updates to existing JSRs, including CDI 2.0, JSON Binding (JSON-B), JSON Processing (JSON-P), and JAX-RS. She announced that CDI 2.0 had unanimously passed its public review ballot, a milestone for the expert group. JSON-B and JSON-P, crucial for data interchange in modern applications, have reached proposed final draft stages, while JAX-RS enhances RESTful services with reactive programming support. Linda highlighted the open-source nature of these implementations, such as GlassFish and Jersey, encouraging community contributions to refine these APIs for enterprise use.
New APIs for Modern Challenges
Java EE 8 introduces new JSRs to address cloud and microservices requirements, notably the Security API. Linda discussed its early draft review, which aims to standardize authentication and authorization across distributed systems. Servlet and JSF updates are also progressing, with JSF nearing final release. These APIs enable developers to build secure, scalable applications suited for microservices architectures. Linda emphasized the platform’s aggressive timeline for a summer release, underscoring the community’s commitment to delivering production-ready solutions that align with industry shifts toward cloud and container technologies.
Community Engagement and Future Directions
Linda stressed the importance of community feedback, directing developers to the Java EE specification project on java.net for JSR details and user groups. She highlighted the Adopt-a-JSR program, led by advocates like Heather VanCura, as a channel for aggregating feedback to expert groups. Looking ahead, Linda briefly outlined Java EE 9’s focus on further cloud integration and modularity. By inviting contributions through open-source platforms like GlassFish, Linda encouraged developers to shape the platform’s future, ensuring Java EE remains relevant in a rapidly evolving technological landscape.
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[DevoxxUS2017] Lessons Learned from Building Hyper-Scale Cloud Services Using Docker by Boris Scholl
At DevoxxUS2017, Boris Scholl, Vice President of Development for Microservices at Oracle, shared valuable lessons from building hyper-scale cloud services using Docker. With a background in Microsoft’s Service Fabric and Container Service, Boris discussed Oracle’s adoption of Docker, Mesos/Marathon, and Kubernetes for resource-efficient, multi-tenant services. His session offered insights into architecture choices and DevOps best practices, providing a roadmap for scalable cloud development. This post examines the key themes of Boris’s presentation, highlighting practical strategies for modern cloud services.
Adopting Docker for Scalability
Boris Scholl began by outlining Oracle’s shift toward cloud services, leveraging Docker to build scalable, multi-tenant applications. He explained how Docker containers optimize resource consumption, enabling rapid service deployment. Drawing from his experience at Oracle, Boris highlighted the pros of containerization, such as portability, and cons, like the need for robust orchestration, setting the stage for discussing advanced DevOps practices.
Orchestration with Mesos and Kubernetes
Delving into orchestration, Boris discussed Oracle’s use of Mesos/Marathon and Kubernetes to manage containerized services. He shared lessons learned, such as the importance of abstracting container management to avoid platform lock-in. Boris’s examples illustrated how orchestration tools ensure resilience and scalability, enabling Oracle to handle hyper-scale workloads while maintaining service reliability.
DevOps Best Practices for Resilience
Boris emphasized the critical role of DevOps in running “always-on” services. He advocated for governance to manage diverse team contributions, preventing architectural chaos. His insights included automating CI/CD pipelines and prioritizing diagnostics for monitoring. Boris shared a lesson on avoiding over-reliance on specific orchestrators, suggesting abstraction layers to ease transitions between platforms like Mesos and Kubernetes.
Governance and Future-Proofing
Concluding, Boris stressed the importance of governance in distributed systems, drawing from Oracle’s experience in maintaining component versioning and compatibility. He recommended blogging as a way to share microservices insights, referencing his own posts. His practical advice inspired developers to adopt disciplined DevOps practices, ensuring cloud services remain scalable, resilient, and adaptable to future needs.
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(long tweet) How to display / modify Oracle XDB port?
Oracle XDB port runs by default on port 8080… which is quite an issue for Java web developpers, because of the collision with default port used by servlet engines such as Tomcat and Jetty.
To display Oracle XDB port, run:
[sql]select DBMS_XDB.GETHTTPPORT from dual;[/sql]
To change it (for instance to set it on port 9090), run
[sql]exec DBMS_XDB.SETHTTPPORT(9090);[/sql]
[DevoxxBE2013] Lambda: A Peek Under the Hood
Brian Goetz, Java Language Architect at Oracle, offers an illuminating dissection of lambda expressions in Java SE 8, transcending syntactic sugar to reveal the sophisticated machinery powering this evolution. Renowned for Java Concurrency in Practice and leadership in JSR 335, Brian demystifies lambdas’ implementation atop invokedynamic from Java SE 7. His session, eschewing introductory fare, probes the VM’s strategies for efficiency, contrasting naive inner-class approaches with optimized bootstrapping and serialization.
Lambdas, Brian asserts, unlock expressive potential for applications and libraries, but their true prowess lies in performance rivaling or surpassing inner classes—without the bloat. Through benchmarks and code dives, he showcases flexibility and future-proofing, underscoring the iterative path to a robust design.
From Syntax to Bytecode: The Bootstrap Process
Brian traces lambdas’ lifecycle: source code desugars to invokedynamic callsites, embedding a “recipe” for instantiation. The bootstrap method, invoked once per callsite, crafts a classfile dynamically, caching for reuse.
This declarative embedding, Brian illustrates, avoids inner classes’ per-instance overhead, yielding leaner bytecode and faster captures—non-capturing lambdas hit 1.5x inner-class speeds in early benchmarks.
Optimization Strategies and Capture Semantics
Capturing lambdas, Brian explains, leverage local variable slots via synthetic fields, minimizing allocations. He contrasts “eager” (immediate class creation) with “lazy” (deferred) strategies, favoring the latter for reduced startup.
Invokedynamic’s dynamic binding enables profile-guided refinements, promising ongoing gains. Brian’s throughput metrics affirm lambdas’ edge, even in capturing scenarios.
Serialization and Bridge Methods
Serializing lambdas invokes writeReplace to a serialized form, preserving semantics without runtime overhead. Brian demos bridge methods for functional interfaces, ensuring compatibility.
Default methods, he notes, extend interfaces safely, avoiding binary breakage—crucial for library evolution.
Lessons from Language Evolution
Brian reflects on Lambda’s odyssey: discarded ideas like inner-class syntactic variants paved the way for invokedynamic’s elegance. This resilience, he posits, exemplifies evolving languages amid obvious-but-flawed intuitions.
Project Lambda’s resources—OpenJDK docs, JCP reviews—invite deeper exploration, with binary builds for experimentation.
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[DevoxxBE2012] On the Road to JDK 8: Lambda, Parallel Libraries, and More
Joseph Darcy, a key figure in Oracle’s JDK engineering team, presented an insightful overview of JDK 8 developments. With extensive experience in language evolution, including leading Project Coin for JDK 7, Joseph outlined the platform’s future directions, balancing innovation with compatibility.
He began by contextualizing JDK 8’s major features, particularly lambda expressions and default methods, set for release in September 2013. Joseph polled the audience on JDK usage, noting the impending end of public updates for JDK 6 and urging transitions to newer versions.
Emphasizing a quantitative approach to compatibility, Joseph described experiments analyzing millions of lines of code to inform decisions, such as lambda conversions from inner classes.
Evolving the Language with Compatibility in Mind
Joseph elaborated on the JDK’s evolution policy, prioritizing binary compatibility while allowing measured source and behavioral changes. He illustrated this with diagrams showing compatibility spaces for different release types, from updates to full platforms.
A core challenge, he explained, is evolving interfaces compatibly. Unlike classes, interfaces cannot add methods without breaking implementations. To address this, JDK 8 introduces default methods, enabling API evolution without user burden.
This ties into lambda support, where functional interfaces facilitate closures. Joseph contrasted this with past changes like generics, which preserved migration compatibility through erasure, avoiding VM modifications.
Lambda Expressions and Implementation Techniques
Diving into lambdas, Joseph defined them as anonymous methods capturing enclosing scope values. He traced their long journey into Java, noting their ubiquity in modern languages.
For implementation, Joseph rejected simple inner class translations due to class explosion and performance overhead. Instead, JDK 8 leverages invokedynamic from JDK 7, allowing runtime strategies like class spinning or method handles.
This indirection decouples binary representation from implementation, enabling optimizations. Joseph shared benchmarks showing non-capturing lambdas outperforming inner classes, especially multithreaded.
Serialization posed challenges, resolved via indirection to reconstruct lambdas independently of runtime details.
Parallel Libraries and Bulk Operations
Joseph highlighted how lambdas enable powerful libraries, abstracting behavior as generics abstract types. Streams introduce pipeline operations—filter, map, reduce—with laziness and fork-join parallelism.
Using the Fork/Join Framework from JDK 7, these libraries handle load balancing implicitly, encapsulating complexity. Joseph demonstrated conversions from collections to streams, facilitating scalable concurrent applications.
Broader JDK 8 Features and Future Considerations
Beyond lambdas, Joseph mentioned annotations on types and repeating annotations, enhancing expressiveness. He stressed deferring decisions to avoid constraining future evolutions, like potential method reference enhancements.
In summary, Joseph portrayed JDK 8 as a coordinated update across language, libraries, and VM, inviting community evaluation through available builds.
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Error grabbing Grapes — [unresolved dependency: com.oracle#ojdbc14;10.2.0.4.0: not found]
I have learnt Groovy since the beginning of the week.
I had to import some classes from Oracle JDBC driver. As a newbie, I wrote the following annotation:
[java]@Grab(group = ‘com.oracle’, module = ‘ojdbc14’, version = ‘10.2.0.4.0’)[/java]
I got the following error:
[java]Error grabbing Grapes — [unresolved dependency: com.oracle#ojdbc14;10.2.0.4.0: not found][/java]
To sum up, adding a dependency to Oracle driver raises two issues:
- adding any external dependency
- adding a dependency to any JDBC driver
Indeed, Grab requires a kind of Maven repository, and you can catch the link between the @Grab annotation below and classic Maven 2 <dependency> tag. As I understood, Grab instructions are closer to Ivy than to Maven system. In my situation, having no “Grab repo” (I don’t know how to call that), I had to download the jars from a Maven repo. To fix it, two operations are needed: hint at Maven (or Ivy) repo, and allow Groovy to access the network.
Regarding the second issue, it is answered by added a @GrabConfig annotation.
Therefore, to fix the original issue:
-
replace [java]@Grab(group = ‘com.oracle’, module = ‘ojdbc14’, version = ‘10.2.0.4.0’)[/java]
with[java]@GrabConfig(systemClassLoader=true)
@GrabResolver(name=’nameOfYourMavenRepo, root=’http://url-of-your-maven-repo:port’)
@Grab(group = ‘com.oracle’, module = ‘ojdbc14’, version = ‘10.2.0.4.0’)
[/java] - at first run, if needed, hint at the proxy to allow Grab to download the Jars, eg: [java]groovy -Dhttp.proxyHost=myProxyHost -Dhttp.proxyPort=8080[/java]
You may notice the needed JAR will be written in the $USER_HOME/.groovy/grapes folder.