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2.4. API Bundle
Overview
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This section explains how to set up a Maven project for a typical API bundle.
The
hello-paris bundle exemplifies an API bundle, which contains only public Java interfaces. Hence, the API bundle should export all of its own packages and associate a version number with the exported packages.
Directory structure
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The
hello-paris bundle has the following directory structure:
hello-paris/
|
\--src/
|
\--main/
| |
| \--java/
| |
| \--org/fusesource/example/hello/paris/
| |
| \-HelloParis.java
|
\--test/
The Java source code is located under the
src/main/java sub-directory. The org.fusesource.example.hello.paris package is public and all of its classes and interfaces can be exported from the bundle.
There are no blueprint resources associated with this bundle.
Sample API
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The
hello-paris bundle is a pure API, which means it contains only Java interfaces. In this example, there is a single interface, HelloParis, which returns a localized greeting and a Clock object that tells the local time. The HelloParis interface is defined as follows:
// Java
package org.fusesource.example.hello.paris;
import org.fusesource.example.time.Clock;
public interface HelloParis {
public String getGreeting();
public Clock getLocalTime();
}Maven dependencies
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In the Maven POM file, the
hello-paris bundle defines dependencies on the following Maven artifact:
time-util
Import and export rules
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The following import and export rules apply to the
hello-paris bundle:
- Exporting own packages—the
org.fusesource.example.hello.parispackage is public, and must be exported. - Importing own packages—none of the bundle's own packages should be imported.
- Importing dependent packages—any external package dependencies must be imported.
Maven bundle plug-in settings
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The Maven bundle plug-in is configured to export the API package,
org.fusesource.example.hello.paris (coded as ${project.groupId}.hello.paris*). The Export-Package instruction also contains entries to block the export of any packages containing .impl or .internal. In this case, the bundle plug-in instructions are as follows:
<instructions>
<Bundle-SymbolicName>${project.groupId}.${project.artifactId}</Bundle-SymbolicName>
<Import-Package>*</Import-Package>
<Export-Package>
!${project.groupId}*.impl*,
!${project.groupId}*.internal*,
${project.groupId}.hello.paris*;version=${project.version}
</Export-Package>
</instructions>Generated MANIFEST.MF file
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When you build the bundle using Maven, the Maven bundle plug-in automatically generates the following
MANIFEST.MF file:
Manifest-Version: 1.0
Bundle-Name: hello-paris
Built-By: JBLOGGS
Build-Jdk: 1.5.0_08
Created-By: Apache Maven Bundle Plugin
Import-Package: org.fusesource.example.time;version="[1.0,2)"
Bundle-ManifestVersion: 2
Bundle-SymbolicName: org.fusesource.example.hello-paris
Tool: Bnd-1.15.0
Bnd-LastModified: 1296826928285
Export-Package: org.fusesource.example.hello.paris;uses:="org.fusesour
ce.example.time";version="1.0"
Bundle-Version: 1.0.0
The
Import-Package header lists one external package dependency, org.fusesource.example.time. None of the bundle's own packages are imported.
The
Export-Package header is used to export the API package, org.fusesource.example.hello.paris, while the uses clause declares a transitive dependency on the org.fusesource.example.time package.
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