Perfmon4j is a suite of performance monitoring tools that are intended to be used to diagnose performance bottlenecks and monitor throughput and response time in production Java applications. Its main features include servlet response time monitoring, detailed thread trace sampling, Java instrumentation that enables Package, Class, and Method monitoring without code modification, snapshot monitoring of system metrics including Garbage Collection, Memory Pools, etc., an API for applying additional monitoring points via method annotations or in-line timers, and support for dynamically enabling monitors in running applications.
Niocchi is a Java crawler library implementing synchronous I/O multiplexing. This specific type of implementation allows crawling tens of thousands of hosts in parallel on a single low end server. Niocchi has been designed for big search engines that need to crawl massive amount of data, but can also be used to write no-frills crawlers.
GNU WebSocket4J is a WebSocket protocol implementation in Java. It allows you to build Web applications that interact with applications running in a JVM. GNU WebSocket4J implements both the server and client side of the protocol, so it can be used to build both WebSocket servers and clients.
InfinityDB is an all-Java B+Tree database engine that is embeddable in the smallest to the largest applications that run on hand held devices, workstations, servers, or in distributed systems. InfinityDB provides a data integrity guarantee through all non-media failures, provides a simple API with only a few basic methods, and requires no administrative support. Version 2 offers full ACID transactionality without a log and with fine-grained locks. Programmers can easily superimpose their own data model or employ the Entity-Attribute-Value model by direct low-level access. The basic engine provides multi-valued or set attributes, all primitive Java types, unlimited Large Objects, heterogenous values, composite keys (Entities) and values, and unlimited sparse attributes, all extensible in-place with no schema changes.
VectorGraphics2D can export Java painting operations to Encapsulated PostScript (EPS), Scalable Vector Graphics (SVG), or Portable Document Format (PDF) files. It supports the rendering of all geometric shapes provided by the Java language. More advanced features like transparency or clipping paths can be used as well. It has a very small footprint and can be easily used as a replacement for Java's java.awt.Graphics2D class.
SDMetrics Core is a Java library to calculate metrics of structural design properties such as coupling, size, and complexity for UML designs. It also checks design rules to automatically detect incomplete or incorrect design, and adherence to style guidelines such as circular dependencies or naming conventions. The library provides an XMI parser for import of XMI 1.x files with UML1.3/1.4 models, and XMI 2.0/2.1 files with UML 2.x models. Design metrics, rules, and XMI import are highly customizable.
jRapidRPC is a Java RPC library that allows you to create client-server applications that talk in objects. It is small, fast, and extensible. Its smallness helps you learn how to use the library quickly. jRapidRPC is fast due to its compact size and lack of complexity. Also, it uses the ProtoStuff serializer by default. jRapidRPC's extensibility allows you to can write a new client-server or a new serializer.