Compass – A java search engine framework build on Lucene

Compass is a first class open source Java Search Engine Framework, enabling the power of Search Engine semantics to your application stack decoratively. Built on top of the amazing Lucene Search Engine, Compass integrates seamlessly to popular development frameworks like Hibernate and Spring. It provides search capability to your application data model and synchronizes changes with the datasource. With Compass: write less code, find data quicker.

As of version 0.8, Compass also provides a Lucene Jdbc Directory implementation, allowing storing Lucene index within a database for both pure Lucene applications and Compass enabled applications. Note, when using Compass, using a database as the index storage requires only updating configuration settings.

Technorati tags: Compass, Hibernate, Lucene, Spring Framework

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Lucene : Integrate advanced search functionalities into your apps

Lucene is a powerful and widely used open source full-text search engine written in Java. Lucene is well known for its full-text indexing and searching, but some of its more advanced features, such as multi-criteria searching and filtering, and sorting, are less well known.

As a full-text search engine, Lucene needs little introduction. Lucene, an open source project hosted by Apache, aims to produce high-performance full-text indexing and search software. The Java Lucene product itself is a high-performance, high capacity, full-text search tool used by many popular Websites such as the Wikipedia online encyclopedia and TheServerSide.com, as well as in many, many Java applications. It is a fast, reliable tool that has proved its value in countless demanding production environments.

Although Lucene is well known for its full-text indexing, many developers are less aware that it can also provide powerful complementary searching, filtering, and sorting functionalities. Indeed, many searches involve combining full-text searches with filters on different fields or criteria. For example, you may want to search a database of books or articles using a full-text search, but with the possibility to limit the results to certain types of books. Traditionally, this type of criteria-based searching is in the realm of the relational database. However, Lucene offers numerous powerful features that let you efficiently combine full-text searches with criteria-based searches and sorts.

Reference: http://www.javaworld.com/javaworld/jw-09-2006/jw-0925-lucene.html?lsrc=jwrss

Technorati tags: Lucene

Log4j levels

Using Log4J (http://logging.apache.org/log4j/docs/), which is generally accepted as the benchmark for all Java applications. This provides the following logging levels.

  • FATAL
  • ERROR
  • WARN
  • INFO
  • DEBUG
  • TRACE – from 1.2.12, latest is 1.2.13

A description for what handling should occur per logging level.

FATAL. As the name suggests, all processing should stop. Should logging include a FATAL, the process is a Failure.

ERROR. An error has occured, and this requires attention, and action. Generally processing should stop, however additional post processing, or an alternative path could occur. Should logging include an ERROR, the process is a Failure.

WARN. Something that is unexpected occured, however it doesn’t affect the general processing from succeeding successfully. If a process includes WARN and not FATAL/ERROR it should be considered successful.

INFO. Information Only. On high volume systems, this level of logging may even be turned off. This generally indicates key information values or steps, and can assist when enabled in longer running processes to identify where a process is. You don’t log errors at INFO.

DEBUG. For Debugging Purposes only.

Ok, well that sounds like common sense. Here is what I observed on a client site.

  • Code logs a FATAL, but continues processing
  • A FATAL is logged, yet the calling process reports success
  • An ERROR is logged, yet the calling process reports success.
  • A lot of WARN are logged, and this is misleading, as it appears more information regarding XML elements not processed (We are talking 20+ Warnings per batch process). From what I’ve observed, these don’t require futher action, and should be changed in INFO.
  • Errors are being logged as INFO. A NullPointer RunTime Exception is logged as INFO. If an error provides an Exception argument where a stack trace is printed, it ain’t an INFO message.

Reference: http://blog.arabx.com.au/?cat=12

Technorati tags: Log4j

Spring Season in IT

Introduction

Officially the spring season might be over but spring still seems to be lingering around. If you did not get the smell of the Spring Framework this summer then you might be missing something. You might be having your fingers crossed skeptically about another run of the mill Framework system that we have been seeing for the last couple of years. Hundreds of open source and propriety frameworks have sprung all over the place making it difficult to identify what each framework does, so the skepticism is understandable, but before we write off spring like one of those others it might be worth briefly peeking through it. Spring proposes a new paradigm, a pluggable, non-intrusive and robust framework.

Summary

Unlike other frameworks and APIs, spring does not impose itself wholly on to the design of a project. Spring is modular and has been divided logically into independent packages, which can function independently. The architects of an application have the flexibility to implement just a few spring packages and leave out most of the packages in spring. The “Spring Framework” would not feel bad with this attitude and on the contrary encourages users to introduce Spring into existing applications in a phased manner. So no matter what kind of framework you are using now Spring will co-exist with it without causing you
nightmares and further more Spring will allow you to choose specific packages in Spring.

The “Struts” framework is no doubt a good framework to enhance the ability of the web tier, but the biggest drawback is the fact that it caters only to the web tier and leaves most of the Enterprise tier or middle tier to the fancy of the application architects. The Application architects need to provide an additional framework to deal with the enterprise tier and make sure that the new framework integrates well with the Struts framework. Spring tries to alleviate this problem by providing a comprehensive framework, which includes an MVC framework, an AOP integration framework, a JDBC integration framework, and an EJB integration framework. It also provides integration modules for major O/R mapping tools like Hibernate and JDO. Spring provides all these in a modular fashion without imposing any layer on to the user. Spring is not a take-it-or- leave-it kind of framework. It tries to seamlessly blend into the existing framework users have without hindrances. Spring also provides transaction management support using Java classes,
email support packages using framework classes, web services support through proxies and many more features like the above. As mentioned earlier all these packages are optional and spring does not make any of them mandatory. Spring can seamlessly integrate with existing applications and provide specific functionality that you intend to provide with minimal demands for customization. A user can continue to use Struts for the web tier and toplink O/R for the database and meanwhile hook spring to provide e-mail services and web services support. Spring is based on the Inversion of Control/Dependency Injection pattern that has been making rounds in message boards all over the Internet.
Reference :
http://javaboutique.internet.com/tutorials/spring_frame/article.html