Chapter 205. Lucene Component
Available as of Camel version 2.2
The lucene component is based on the Apache Lucene project. Apache Lucene is a powerful high-performance, full-featured text search engine library written entirely in Java. For more details about Lucene, please see the following links
The lucene component in camel facilitates integration and utilization of Lucene endpoints in enterprise integration patterns and scenarios. The lucene component does the following
- builds a searchable index of documents when payloads are sent to the Lucene Endpoint
- facilitates performing of indexed searches in Camel
This component only supports producer endpoints.
Maven users will need to add the following dependency to their pom.xml for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-lucene</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>205.1. URI format
lucene:searcherName:insert[?options] lucene:searcherName:query[?options]
You can append query options to the URI in the following format, ?option=value&option=value&…
205.2. Insert Options
The Lucene component supports 2 options which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| config (advanced) | To use a shared lucene configuration | LuceneConfiguration | |
| resolveProperty Placeholders (advanced) | Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. | true | boolean |
The Lucene endpoint is configured using URI syntax:
lucene:host:operation
with the following path and query parameters:
205.2.1. Path Parameters (2 parameters):
| Name | Description | Default | Type |
|---|---|---|---|
| host | Required The URL to the lucene server | String | |
| operation | Required Operation to do such as insert or query. | LuceneOperation |
205.2.2. Query Parameters (5 parameters):
| Name | Description | Default | Type |
|---|---|---|---|
| analyzer (producer) | An Analyzer builds TokenStreams, which analyze text. It thus represents a policy for extracting index terms from text. The value for analyzer can be any class that extends the abstract class org.apache.lucene.analysis.Analyzer. Lucene also offers a rich set of analyzers out of the box | Analyzer | |
| indexDir (producer) | A file system directory in which index files are created upon analysis of the document by the specified analyzer | File | |
| maxHits (producer) | An integer value that limits the result set of the search operation | int | |
| srcDir (producer) | An optional directory containing files to be used to be analyzed and added to the index at producer startup. | File | |
| synchronous (advanced) | Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). | false | boolean |
205.3. Sending/Receiving Messages to/from the cache
205.3.1. Message Headers
| Header | Description |
|---|---|
|
| The Lucene Query to performed on the index. The query may include wildcards and phrases |
|
| Camel 2.15: Set this header to true to include the actual Lucene documentation when returning hit information. |
205.3.2. Lucene Producers
This component supports 2 producer endpoints.
insert - The insert producer builds a searchable index by analyzing the body in incoming exchanges and associating it with a token ("content"). query - The query producer performs searches on a pre-created index. The query uses the searchable index to perform score & relevance based searches. Queries are sent via the incoming exchange contains a header property name called 'QUERY'. The value of the header property 'QUERY' is a Lucene Query. For more details on how to create Lucene Queries check out http://lucene.apache.org/java/3_0_0/queryparsersyntax.html
205.3.3. Lucene Processor
There is a processor called LuceneQueryProcessor available to perform queries against lucene without the need to create a producer.
205.4. Lucene Usage Samples
205.4.1. Example 1: Creating a Lucene index
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("direct:start").
to("lucene:whitespaceQuotesIndex:insert?
analyzer=#whitespaceAnalyzer&indexDir=#whitespace&srcDir=#load_dir").
to("mock:result");
}
};205.4.2. Example 2: Loading properties into the JNDI registry in the Camel Context
@Override
protected JndiRegistry createRegistry() throws Exception {
JndiRegistry registry =
new JndiRegistry(createJndiContext());
registry.bind("whitespace", new File("./whitespaceIndexDir"));
registry.bind("load_dir",
new File("src/test/resources/sources"));
registry.bind("whitespaceAnalyzer",
new WhitespaceAnalyzer());
return registry;
}
...
CamelContext context = new DefaultCamelContext(createRegistry());205.4.3. Example 2: Performing searches using a Query Producer
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("direct:start").
setHeader("QUERY", constant("Seinfeld")).
to("lucene:searchIndex:query?
analyzer=#whitespaceAnalyzer&indexDir=#whitespace&maxHits=20").
to("direct:next");
from("direct:next").process(new Processor() {
public void process(Exchange exchange) throws Exception {
Hits hits = exchange.getIn().getBody(Hits.class);
printResults(hits);
}
private void printResults(Hits hits) {
LOG.debug("Number of hits: " + hits.getNumberOfHits());
for (int i = 0; i < hits.getNumberOfHits(); i++) {
LOG.debug("Hit " + i + " Index Location:" + hits.getHit().get(i).getHitLocation());
LOG.debug("Hit " + i + " Score:" + hits.getHit().get(i).getScore());
LOG.debug("Hit " + i + " Data:" + hits.getHit().get(i).getData());
}
}
}).to("mock:searchResult");
}
};205.4.4. Example 3: Performing searches using a Query Processor
RouteBuilder builder = new RouteBuilder() {
public void configure() {
try {
from("direct:start").
setHeader("QUERY", constant("Rodney Dangerfield")).
process(new LuceneQueryProcessor("target/stdindexDir", analyzer, null, 20)).
to("direct:next");
} catch (Exception e) {
e.printStackTrace();
}
from("direct:next").process(new Processor() {
public void process(Exchange exchange) throws Exception {
Hits hits = exchange.getIn().getBody(Hits.class);
printResults(hits);
}
private void printResults(Hits hits) {
LOG.debug("Number of hits: " + hits.getNumberOfHits());
for (int i = 0; i < hits.getNumberOfHits(); i++) {
LOG.debug("Hit " + i + " Index Location:" + hits.getHit().get(i).getHitLocation());
LOG.debug("Hit " + i + " Score:" + hits.getHit().get(i).getScore());
LOG.debug("Hit " + i + " Data:" + hits.getHit().get(i).getData());
}
}
}).to("mock:searchResult");
}
};