Monday, December 29, 2008

Deploying Web Service in Apache AXIS2

The purpose of this article is to talk about how to write web service and deploy it in Apache AXIS2.

First step is downloading and installing apache axis2. There are two ways to use Apache AXIS2.

1. Install AXIS2 as a standalone server using the Standard Binary Distribution.
2. Deploy axis2.war and deploy it in a servlet container.

We will be using the 2nd method in the article. To check the installation open the url http://localhost:8080/axis2 and you should be able to see the home page of apache axis2.

Please locate the folder axis2\WEB-INF\services in exploded war file of axis2. This is the folder where you will copy the code of your service and it will get deployed in apache axis2.

Lets us take a simple example. Write your service class.

public class HelloWorld
{
public String sayHello(String firstName, String lastName)
{
System.out.println("Hello World Invoked");
MessageContext incomingContext = MessageContext.getCurrentMessageContext();
FileDataSource dataSource = new FileDataSource("c:/YServer.txt");
DataHandler dataHandler = new DataHandler(dataSource);
incomingContext.addAttachment("contentID", dataHandler);

String data = DataProvider.getData();
return "Hello " + firstName + " " + lastName + " " + data;
}
public String getServiceName()
{
return "test service";
}
}

Write a services.xml file.

<service>
<description>
This is my first service, which says hello
</description>
<parameter name="ServiceClass">HelloWorld</parameter>
<operation name="sayHello">
<messageReceiver class="org.apache.axis2.rpc.receivers.RPCMessageReceiver"/>
</operation>
<operation name="getServiceName">
<messageReceiver class="org.apache.axis2.rpc.receivers.RPCMessageReceiver"/>
</operation>
</service>

In case you want to receive the SOAP payload as XML Message in the service you need to specify XML Message receiver instead of RPCMessageReceiver in services.xml file. To specify XML Message receiver put the following line as child of <operation> tag in your services.xml.

<messageReceiver

class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>

Also, since the service will receive XML Message as input parameter you need to change the signature of the method of service.

public OMElement sayHello(OMElement element)

OMElement object contains the XML Message, OMElement Object is provided by AXIOM. AXIOM stands for AXis Object Model (also known as OM - Object Model) and refers to the XML infoset model that was initially developed for Apache Axis2.


Bundle your class file, services.xml in the hierarchy as shown in the figure below. See helloworld folder in image below.



Copy your service into the services folder of axis2 as shown in figure, start web server. Open the URL http://localhost:8080/axis2.

On the displayed page Click on services, you should be able to see the name of service you specified in services.xml in the list of web services.

Tuesday, December 2, 2008

Happy Singh @Big 92.7 FM

Happy Singh is telecasted daily and I hear it mostly when I am driving back to home from office @7 PM, I am a big fan of Happy Singh's sense of humour. Listen it you will surely like it.

Monday, December 1, 2008

Getting Started with Apache Lucene

Apache Lucene is a high-performance, full-featured text search engine library.

The API of lucene is very simple to use. Here is overview of some of the objects required to start using Apache Lucene.

Document and Fields

The class "org.apache.lucene.document.Document" is necessary container for the index. Lucene requires all indexed objects to provide an instance of Document. Each document defines one or several fields ( (org.apache.lucene.document.Field). Fields contain classified information about the document or metadata related to document. A sample classification is for example the creation date of a file, author of the document etc. These fields allow you to search later for a specific information in this classification.


IndexWriter

The class org.apache.lucene.index.IndexWriter creates the index. Via the method addDocument you can add an existing Document to the index. The constructor for IndexWriter expects the directory to store the index, and the analyzer for the content of the files. In addition a boolean flag is handed over which indicates if the index should be created new or if an existing index should be extended.

Analyser

The class org.apache.lucene.analysis.standard.StandardAnalyzer provides a standard analyzer. This part is responsible to analyse the text and to filter out certain fill-words, e.g. "and".

Searcher and Query

The class org.apache.lucene.search.Searcher provides the search functionality. org.apache.lucene.search.IndexSearcher searches over an index. What is to be searched is provided via the query (org.apache.lucene.search.Query) class. The search allows wildcard search, e.g. *, ?, logical operations (AND, OR, NOT) and much more, e.g. fussy.

Here's a simple example how to use Lucene for indexing and searching.

public class TestMyLucene
{
public static void main(String[] args) throws Exception
{
Analyzer analyzer = new StandardAnalyzer();

// Store the index in memory:
Directory directory = new RAMDirectory();

// To store an index on disk, use this instead (note that the
// parameter true will overwrite the index in that directory
// if one exists):
//Directory directory = FSDirectory.getDirectory("/tmp/testindex", true);
IndexWriter iwriter = new IndexWriter(directory, analyzer, true);
iwriter.setMaxFieldLength(25000);

Document doc = new Document();
String text = "This is the text to be indexed.";
doc.add(new Field("fieldname", text, Field.Store.YES, Field.Index.TOKENIZED));
iwriter.addDocument(doc);
iwriter.close();

// Now search the index:
IndexSearcher isearcher = new IndexSearcher(directory);

// Parse a simple query that searches for "text":
Query query = QueryParser.parse("text", "fieldname", analyzer);
Hits hits = isearcher.search(query);
System.out.println(hits.length());

// Iterate through the results:
for (int i = 0; i < hits.length(); i++)
{
Document hitDoc = hits.doc(i);
System.out.println(hitDoc.get("fieldname"));
}

isearcher.close();
directory.close();
}
}

In the above example, hits return the matching documents for the query provided.

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