Chapter 14. URL Handlers

A file URL has the syntax, file:PathName, where PathName is the relative or absolute pathname of a file that is available on the Classpath. The provided PathName is parsed by Java’s built-in file URL handler. Hence, the PathName syntax is subject to the usual conventions of a Java pathname: in particular, on Windows, each backslash must either be escaped by another backslash or replaced by a forward slash.

For example, consider the pathname, C:\Projects\camel-bundle\target\foo-1.0-SNAPSHOT.jar, on Windows. The following example shows the correct alternatives for the file URL on Windows:

file:C:/Projects/camel-bundle/target/foo-1.0-SNAPSHOT.jar
file:C:\\Projects\\camel-bundle\\target\\foo-1.0-SNAPSHOT.jar

The following example shows some incorrect alternatives for the file URL on Windows:

file:C:\Projects\camel-bundle\target\foo-1.0-SNAPSHOT.jar        // WRONG!
file://C:/Projects/camel-bundle/target/foo-1.0-SNAPSHOT.jar      // WRONG!
file://C:\\Projects\\camel-bundle\\target\\foo-1.0-SNAPSHOT.jar  // WRONG!

A HTTP URL has the standard syntax, http:Host[:Port]/[Path][#AnchorName][?Query]. You can also specify a secure HTTP URL using the https scheme. The provided HTTP URL is parsed by Java’s built-in HTTP URL handler, so the HTTP URL behaves in the normal way for a Java application.

If you use Maven to build your bundles or if you know that a particular bundle is available from a Maven repository, you can use the Mvn handler scheme to locate the bundle.

An Mvn URL has the following syntax:

mvn:[repositoryUrl!]groupId/artifactId[/[version][/[packaging][/[classifier]]]]

Where repositoryUrl optionally specifies the URL of a Maven repository. The groupId, artifactId, version, packaging, and classifier are the standard Maven coordinates for locating Maven artifacts.

When specifying an Mvn URL, only the groupId and the artifactId coordinates are required. The following examples reference a Maven bundle with the groupId, org.fusesource.example, and with the artifactId, bundle-demo:

mvn:org.fusesource.example/bundle-demo
mvn:org.fusesource.example/bundle-demo/1.1

When the version is omitted, as in the first example, it defaults to LATEST, which resolves to the latest version based on the available Maven metadata.

In order to specify a classifier value without specifying a packaging or a version value, it is permissible to leave gaps in the Mvn URL. Likewise, if you want to specify a packaging value without a version value. For example:

mvn:groupId/artifactId///classifier
mvn:groupId/artifactId/version//classifier
mvn:groupId/artifactId//packaging/classifier
mvn:groupId/artifactId//packaging

When specifying the version value in an Mvn URL, you can specify a version range (using standard Maven version range syntax) in place of a simple version number. You use square brackets—[ and ]—to denote inclusive ranges and parentheses—( and )—to denote exclusive ranges. For example, the range, [1.0.4,2.0), matches any version, v, that satisfies 1.0.4 ⇐ v < 2.0. You can use this version range in an Mvn URL as follows:

mvn:org.fusesource.example/bundle-demo/[1.0.4,2.0)

Before using Mvn URLs for the first time, you might need to customize the Mvn URL handler settings, as follows:

The Mvn URL handler resolves a reference to a local Maven repository and maintains a list of remote Maven repositories. When resolving an Mvn URL, the handler searches first the local repository and then the remote repositories in order to locate the specified Maven artifiact. If there is a problem with resolving an Mvn URL, the first thing you should do is to check the handler settings to see which local repository and remote repositories it is using to resolve URLs.

To check the Mvn URL settings, enter the following commands at the console:

JBossFuse:karaf@root> config:edit org.ops4j.pax.url.mvn
JBossFuse:karaf@root> config:proplist

The config:edit command switches the focus of the config utility to the properties belonging to the org.ops4j.pax.url.mvn persistent ID. The config:proplist command outputs all of the property settings for the current persistent ID. With the focus on org.ops4j.pax.url.mvn, you should see a listing similar to the following:

   org.ops4j.pax.url.mvn.defaultRepositories = file:/path/to/JBossFuse/jboss-fuse-7.4.0.fuse-740028-redhat-00001/system@snapshots@id=karaf.system,file:/home/userid/.m2/repository@snapshots@id=local,file:/path/to/JBossFuse/jboss-fuse-7.4.0.fuse-740028-redhat-00001/local-repo@snapshots@id=karaf.local-repo,file:/path/to/JBossFuse/jboss-fuse-7.4.0.fuse-740028-redhat-00001/system@snapshots@id=child.karaf.system
   org.ops4j.pax.url.mvn.globalChecksumPolicy = warn
   org.ops4j.pax.url.mvn.globalUpdatePolicy = daily
   org.ops4j.pax.url.mvn.localRepository = /path/to/JBossFuse/jboss-fuse-7.4.0.fuse-740028-redhat-00001/data/repository
   org.ops4j.pax.url.mvn.repositories = http://repo1.maven.org/maven2@id=maven.central.repo, https://maven.repository.redhat.com/ga@id=redhat.ga.repo, https://maven.repository.redhat.com/earlyaccess/all@id=redhat.ea.repo, https://repository.jboss.org/nexus/content/groups/ea@id=fuseearlyaccess
   org.ops4j.pax.url.mvn.settings = /path/to/jboss-fuse-7.4.0.fuse-740028-redhat-00001/etc/maven-settings.xml
   org.ops4j.pax.url.mvn.useFallbackRepositories = false
   service.pid = org.ops4j.pax.url.mvn

Where the localRepository setting shows the local repository location currently used by the handler and the repositories setting shows the remote repository list currently used by the handler.

To customize the property settings for the Mvn URL handler, edit the following configuration file:

InstallDir/etc/org.ops4j.pax.url.mvn.cfg

The settings in this file enable you to specify explicitly the location of the local Maven repository, remove Maven repositories, Maven proxy server settings, and more. Please see the comments in the configuration file for more details about these settings.

In particular, if your local Maven repository is in a non-default location, you might find it necessary to configure it explicitly in order to access Maven artifacts that you build locally. In your org.ops4j.pax.url.mvn.cfg configuration file, uncomment the org.ops4j.pax.url.mvn.localRepository property and set it to the location of your local Maven repository. For example:

# Path to the local maven repository which is used to avoid downloading
# artifacts when they already exist locally.
# The value of this property will be extracted from the settings.xml file
# above, or defaulted to:
#     System.getProperty( "user.home" ) + "/.m2/repository"
#
org.ops4j.pax.url.mvn.localRepository=file:E:/Data/.m2/repository

For more details about the mvn URL syntax, see the original Pax URL Mvn Protocol documentation.

If you need to reference a JAR file that is not already packaged as a bundle, you can use the Wrap URL handler to convert it dynamically. The implementation of the Wrap URL handler is based on Peter Krien’s open source Bnd utility.

A Wrap URL has the following syntax:

wrap:locationURL[,instructionsURL][$instructions]

The locationURL can be any URL that locates a JAR (where the referenced JAR is not formatted as a bundle). The optional instructionsURL references a Bnd properties file that specifies how the bundle conversion is performed. The optional instructions is an ampersand, &, delimited list of Bnd properties that specify how the bundle conversion is performed.

In most cases, the default Bnd instructions are adequate for wrapping an API JAR file. By default, Wrap adds manifest headers to the JAR’s META-INF/Manifest.mf file as shown in Table 14.1, “Default Instructions for Wrapping a JAR”.

The following Wrap URL locates version 1.1 of the commons-logging JAR in a Maven repository and converts it to an OSGi bundle using the default Bnd properties:

wrap:mvn:commons-logging/commons-logging/1.1

The following Wrap URL uses the Bnd properties from the file, E:\Data\Examples\commons-logging-1.1.bnd:

wrap:mvn:commons-logging/commons-logging/1.1,file:E:/Data/Examples/commons-logging-1.1.bnd

The following Wrap URL specifies the Bundle-SymbolicName property and the Bundle-Version property explicitly:

wrap:mvn:commons-logging/commons-logging/1.1$Bundle-SymbolicName=apache-comm-log&Bundle-Version=1.1

If the preceding URL is used as a command-line argument, it might be necessary to escape the dollar sign, \$, to prevent it from being processed by the command line, as follows:

wrap:mvn:commons-logging/commons-logging/1.1\$Bundle-SymbolicName=apache-comm-log&Bundle-Version=1.1

For more details about the wrap URL handler, see the following references:

If you need to deploy a WAR file in an OSGi container, you can automatically add the requisite manifest headers to the WAR file by prefixing the WAR URL with war:, as described here.

A War URL is specified using either of the following syntaxes:

war:warURL
warref:instructionsURL

The first syntax, using the war scheme, specifies a WAR file that is converted into a bundle using the default instructions. The warURL can be any URL that locates a WAR file.

The second syntax, using the warref scheme, specifies a Bnd properties file, instructionsURL, that contains the conversion instructions (including some instructions that are specific to this handler). In this syntax, the location of the referenced WAR file does not appear explicitly in the URL. The WAR file is specified instead by the (mandatory) WAR-URL property in the properties file.

Some of the properties in the .bnd instructions file are specific to the War URL handler, as follows:

By default, the War URL handler adds manifest headers to the WAR’s META-INF/Manifest.mf file as shown in Table 14.2, “Default Instructions for Wrapping a WAR File”.

The following War URL locates version 1.4.7 of the wicket-examples WAR in a Maven repository and converts it to an OSGi bundle using the default instructions:

war:mvn:org.apache.wicket/wicket-examples/1.4.7/war

The following Wrap URL specifies the Web-ContextPath explicitly:

war:mvn:org.apache.wicket/wicket-examples/1.4.7/war?Web-ContextPath=wicket

The following War URL converts the WAR file referenced by the WAR-URL property in the wicket-examples-1.4.7.bnd file and then converts the WAR into an OSGi bundle using the other instructions in the .bnd file:

warref:file:E:/Data/Examples/wicket-examples-1.4.7.bnd

For more details about the war URL syntax, see the original Pax URL War Protocol documentation.