One of the most important principles of the Maven build system is that there are
standard locations for all of the files in the Maven
project. There are several advantages to this principle. One advantage is that Maven
projects normally have an identical directory layout, making it easy to find files
in a project (once you are familiar with the standard layout). Another advantage is
that the various tools integrated with Maven need almost no
initial configuration. For example, the Java compiler knows that it should compile
all of the source files under src/main/java
and put the results into
target/classes
.
Example 2.1 shows the elements of the standard Maven directory layout that are relevant to building OSGi bundle projects. In addition, the standard locations for Spring-DM and Blueprint configuration files (which are not defined by Maven) are also shown.
Example 2.1. Standard Maven Directory Layout
ProjectDir
/
pom.xml
src/
main/
java/
...
resources/
META-INF/
spring/
*.xml
OSGI-INF/
blueprint/
*.xml
test/
java/
resources/
target/
...
![]() | Note |
---|---|
It is, in fact, possible to override the standard directory layout, but this is not a recommended practice in Maven. |
The pom.xml
file is the Project Object Model (POM) for the current
project, which contains a complete description of how to build the current project.
A pom.xml
file can be completely self-contained, but frequently
(particular for more complex Maven projects) it can import settings from a
parent POM file.
The src/
directory contains all of the code and resource files that
you will work on while developing the project.
The target/
directory contains the result of the build (typically a
JAR file), as well as all all of the intermediate files generated during the build.
For example, after performing a build, the target/classes/
directory
will contain a copy of the resource files and the compiled Java classes.
The main/
directory contains all of the code and resources needed for
building the artifact.
The test/
directory contains all of the code and resources for
running unit tests against the compiled artifact.
The java/
directory contains Java source code (*.java
files) with the standard Java directory layout (that is, where the directory
pathnames mirror the Java package names, with /
in place of the
.
character). The src/main/java/
directory contains
the bundle source code and the src/test/java/
directory contains the
unit test source code.
If you have any configuration files, data files, or Java properties to include in
the bundle, these should be placed under the src/main/resources/
directory. The files and directories under src/main/resources/
will be
copied into the root of the JAR file that is generated by the Maven build
process.
The files under src/test/resources/
are used only during the testing
phase and will not be copied into the generated JAR
file.
By default, Fuse ESB installs and activates support for Spring Dynamic Modules (Spring
DM), which integrates Spring with the OSGi container. This means that it
is possible for you to include Spring configuration files,
META-INF/spring/*.xml
, in your bundle. One of the key consequences
of having Spring DM enabled in the OSGi container is that the lifecycle of the
Spring application context is automatically synchronized with the OSGi bundle
lifecycle:
Activation—when a bundle is activated, Spring DM automatically scans the bundle to look for Spring configuration files in the standard location (any
.xml
files found under theMETA-INF/spring/
directory). If any Spring files are found, Spring DM creates an application context for the bundle and creates the beans defined in the Spring configuration files.Stopping—when a bundle is stopped, Spring DM automatically shuts down the bundle's Spring application context, causing any Spring beans to be deleted.
In practice, this means that you can treat your Spring-enabled bundle as if it is being deployed in a Spring container. Using Spring DM, the features of the OSGi container and a Spring container are effectively merged. In addition, Spring DM provides additional features to support the OSGi container environment—some of these features are discussed in Deploying an OSGi Service.
OSGi R4.2 defines a blueprint container, which is effectively a standardized
version of Spring DM. Fuse ESB has built-in support for the blueprint container, which
you can enable simply by including blueprint configuration files,
OSGI-INF/blueprint/*.xml
, in your project. For more details about
the blueprint container, see Deploying an OSGi Service.