| <?xml version="1.0"?> |
| <document> |
| <properties> |
| <author email="acoliver@apache.org">Andrew C. Oliver</author> |
| <title>Jakarta Lucene - Basic Demo Sources Walkthrough</title> |
| </properties> |
| <body> |
| |
| <section name="About the Code"> |
| <p> |
| In this section we walk through the sources behind the basic Lucene Web Application demo. |
| Where to find it, its parts, and their function. This section is intended for Java developers |
| wishing to understand how to use Jakarta Lucene in their applications or for those involved |
| in deploying web applications based on Lucene. |
| </p> |
| </section> |
| |
| |
| <section name="Location of the source (developers/deployers)"> |
| <p> |
| Relative the directory created when you extracted Lucene or retreived it from CVS, you |
| should see a directory called "src" which in turn contains a directory called "jsp". |
| This is the root for all of the Lucene web demo. |
| </p> |
| <p> |
| Within this directory you should see the index.jsp class. Bring this up in vi or your |
| editor of choice. |
| </p> |
| </section> |
| |
| <section name="index.jsp (developers/deployers)"> |
| <p> |
| This jsp page is pretty boring by itself. All it does is include a header, display a form and |
| include a footer. If you look at the form, it has two fields: query (where you enter your |
| search criteria) and maxresults where you specify the number of results per page. If you look |
| at the form tag, you'll notice it uses the get method as opposed to the post. While this is |
| considered deprecated functionality by the latest w3c specs, its unlikely to go away due to the |
| usefulness of being able to bookmark things like searches. By the structure of this JSP it should |
| be easy to customize it without even editing this particular file. You could simply change the |
| header and footer. Let's look at the header.jsp (located in the same directory) next. |
| </p> |
| </section> |
| |
| <section name="header.jsp (developers/deployers)"> |
| <p> |
| The header is also very simple by itself. The only thing it does is include the configuration.jsp |
| (which you looked at in the last section of this guide) and set the title and a brief header. This |
| would be a good place to put your own custom HTML to "pretty" things up a bit. We won't cover the |
| footer because all it does is display the footer and close your tags. Let's look at the results.jsp, |
| the meat of this application next. |
| </p> |
| </section> |
| |
| <section name="results.jsp (developers)"> |
| <p> |
| The results.jsp had a lot more functionality. Much of it is for paging the search results we'll not |
| cover this as its commented well enough. It does not peform any optimizations such as caching results, |
| etc. as that would make this a more complex example. The first thing in this page is the actual imports |
| for the Lucene classes and Lucene demo classes. These classes are loaded from the jars included in the |
| WEB-INF/lib directory in the final war file. |
| </p> |
| <p> |
| You'll notice that this file includes the same header and footer as the "index.jsp". From there the jsp |
| constructs an IndexSearcher with the "indexLocation" that was specified in the "configuration.jsp". If there |
| is an error of any kind in opening the index, it is diplayed ot the user and a boolean flag is set to tell |
| the rest of the sections of the jsp not to continue. |
| </p> |
| <p> |
| From there, this jsp attempts to get the search criteria, the start index (used for paging) and the maximum |
| number of results per page. If the maximum results per page is not set or not valid then it and the |
| start index are set to default values. If only the start index is invalid it is set to a default value. If |
| the criteria isn't provided then a servlet error is thrown (it is assumed that this is the result of url tampering |
| or some form of browser malfunction). |
| </p> |
| <p> |
| The jsp moves on to construct a StandardAnalyzer just as in the simple demo, to analyze the search critieria, it |
| is passed to the QueryParser along with the criteria to construct a Query object. You'll also notice the |
| string literal "contents" included. This is to specify the search should include the the contents and not |
| the title, url or some other field in the indexed documents. If there is any error in constructing a Query |
| object an error is displayed to the user. |
| </p> |
| <p> |
| In the next section of the jsp the IndexSearcher is asked to search given the query object. the results are |
| returned in a collection called "hits". If the length property of the hits collection is 0 then an error |
| is displayed to the user and the error flag is set. |
| </p> |
| <p> |
| Finally the jsp iterates through the hits collection and displayed properties of the "Document" objects we talked |
| about in the first walkthrough. These objects contain "known" fields specific to their indexer (in this case |
| "IndexHTML" constructs a document with "url", "title" and "contents"). You'll notice that these results are paged |
| but the search is repeated every time. This is an area where optimization could improve performance for large |
| result sets. |
| </p> |
| </section> |
| |
| <section name="More sources (developers)"> |
| <p> |
| There are additional sources used by the web app that were not specifically covered by either walkthrough. For |
| example the HTML parser, the IndexHTML class and HTMLDocument class. These are very similar to the classes |
| covered in the first example, however they have properties sepecific to parsing and indexing HTML. This is |
| beyond our scope; however, by now you should feel like you're "getting started" with Lucene. |
| </p> |
| </section> |
| |
| <section name="Where to go from here? (Everyone!)"> |
| <p> |
| There are a number of things this demo doesn't do or doesn't do quite right. For instance, you may |
| have noticed that documents in the root context are unreachable (unless you reconfigure Tomcat to |
| support that context or redirect to it), anywhere where the directory doesn't quite match the context mapping, |
| you'll have a broken link in your results. If you want to index non-local files or have some other |
| needs this isn't supported, plus there may be security issues with running the indexing application from |
| your webapps directory. There are a number of things left for you the implementor or developer to do. |
| </p> |
| <p> |
| In time some of these things may be added to Lucene as features (if you've got a good idea we'd love to hear it!), |
| but for now: this is where you begin and the search engine/indexer ends. Lastly, one would assume you'd |
| want to follow the above advice and customize the application to look a little more fancy than black on |
| white with "Lucene Template" at the top. We'll see you on the Lucene Users' or Developers' mailing lists! |
| </p> |
| </section> |
| |
| <section name="When to contact the Author"> |
| <p> |
| Please resist the urge to contact the authors of this document (without bribes of fame and fortune attached). First |
| contact the <a href="http://jakarta.apache.org/site/mail.html">mailing lists</a>. That being said feedback, |
| and modifications to this document and samples are ever so greatly appreciatedThey are just best sent to the |
| lists so that everyone can share in them. Certainly you'll get the most help there as well. |
| Thanks for understanding. |
| </p> |
| </section> |
| |
| </body> |
| </document> |
| |