Lucene

Since Camel 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>

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&…​

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:

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

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

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-lucene-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 11 options, which are listed below.

Name Description Default Type

camel.component.lucene.config.analyzer

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

camel.component.lucene.config.authority

String

camel.component.lucene.config.host

The URL to the lucene server

String

camel.component.lucene.config.index-directory

A file system directory in which index files are created upon analysis of the document by the specified analyzer

File

camel.component.lucene.config.lucene-version

Version

camel.component.lucene.config.max-hits

An integer value that limits the result set of the search operation

Integer

camel.component.lucene.config.operation

Operation to do such as insert or query.

LuceneOperation

camel.component.lucene.config.source-directory

An optional directory containing files to be used to be analyzed and added to the index at producer startup.

File

camel.component.lucene.config.uri

URI

camel.component.lucene.enabled

Enable lucene component

true

Boolean

camel.component.lucene.resolve-property-placeholders

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

Boolean

Sending/Receiving Messages to/from the cache

Message Headers

Header Description

QUERY

The Lucene Query to performed on the index. The query may include wildcards and phrases

RETURN_LUCENE_DOCS

Camel 2.15: Set this header to true to include the actual Lucene documentation when returning hit information.

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

Lucene Processor

There is a processor called LuceneQueryProcessor available to perform queries against lucene without the need to create a producer.

Lucene Usage Samples

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");
    }
};

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());

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");
   }
};

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");
   }
};
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