This is a collection of cookbook-style examples showing how to
add certain types of modifications to a DSpace installation.
It is based on experience with the DSpace 1.5.0 binary release, the first
to use the new module layout and build system.

Please feel free to add your own examples of typical DSpace modifications.

Prerequisites

You must be familiar with installing
and configuring DSpace 1.5.
It may help to review Building+DSpace+From+Source.

See also the presentation
Customizing DSpace 1.5 with Basic Overlays
from Open Repositories O8, by
Tim Donohue and
Graham Triggs.
It provides an excellent overview of the build process and how
overlays work. It was the inspiration for this page.

This page concentrates on examples not covered in that presentation,
such as the common case of just adding some plugin implementations.

Recipe 1: Adding Local Code as a Maven Project

Customizations to DSpace often require the addition of local code, i.e. classes in non-DSpace packages. For example, when you wish to provide your own AuthenticationMethod implmentation. By putting this code into a separate Maven project, and modifying a few DSpace POMs, you can have your local classes added to both the webapps of interest and the DSpace command-line applications.

The trick is to manage dependencies correctly. Your local project will depend explicitly on the

dspace-api

project so it can import DSpace API interfaces and classes. Thus, the

dspace-api

project cannot depend on it. You have to add a dependency on your local project to every POM that generates an executable build product (i.e. the webapps, and the command-line apps). Those projects also depend on

dspace-api

so the API classes will be available.

Example of Local Code Project

Here is a live example of how the DSpace 1.5.2 POMs were modified to add a local package named *

dash-api

*. This project contains several plugin implementations, and it has its own dependencies on some other projects which support that code. All of the classes in

dash-api

are in packages under the

edu.harvard...

hierarchy, so they do not conflict with DSpace.

Note that the POMs are presented in a very simplified form, eliding the elements like repositories that depend on your local environment or can be easily extrapolated. We only show the elements pertinent to this discussion:

First, establish dash-api POM

Create a dash-api subdirectory at the same level as dspace-api, and add this POM:

<project>
   <groupId>edu.harvard.hul.ois.dash</groupId>
   <artifactId>dash-api</artifactId>
   <packaging>jar</packaging>

   <parent>
      <groupId>org.dspace</groupId>
      <artifactId>dspace-parent</artifactId>
      <version>1.5.2-SNAPSHOT</version>
   </parent>

   <dependencies>
      <dependency>
         <groupId>org.dspace</groupId>
         <artifactId>dspace-api</artifactId>
      </dependency>
        ...other dspace dependencies...
      <dependency>
         <groupId>edu.harvard.hul.ois</groupId>
         <artifactId>util</artifactId>
      </dependency>
      <dependency>
         <groupId>commons-httpclient</groupId>
         <artifactId>commons-httpclient</artifactId>
      </dependency>
        ....other external dependencies...
   </dependencies>
</project>

Modify the dspace POM

Add the following sections to the POM of the

dspace

project. This ensures the code gets built, and that it will be available to DSpace command-line utilities.

Add to profiles element

     <profile>
        <id>dash-api</id>
        <activation>
           <file>
              <exists>../dash-api/pom.xml</exists>
           </file>
        </activation>
        <modules>
           <module>../dash-api</module>
        </modules>
     </profile>

Add to dependencies element

    <dependency>
      <groupId>edu.harvard.hul.ois.dash</groupId>
      <artifactId>dash-api</artifactId>
    </dependency>

Modify POM for each relevant Webapp

For each webapp you plan to build, e.g. xmlui, add the following elements to the POM in its subdirectory under dspace/modules/. For example, add to dspace/modules/xmlui/pom.xml this element to its dependencies list:

      <dependency>
        <groupId>edu.harvard.hul.ois.dash</groupId>
        <artifactId>dash-api</artifactId>
      </dependency>

Modify the dspace-parent POM

Finally, you must add a version declaration for dash-api to the dspace-parent POM.
Add this element to the dependencies list:

       <dependency>
          <groupId>edu.harvard.hul.ois.dash</groupId>
          <artifactId>dash-api</artifactId>
          <version>${project.version}</version>
        </dependency>

Other Dependencies

Don't forget to add version declarations for other new dependencies if they are not explicit in e.g. the dash-api POM.

Recipe 2: Adding Customizations to Webapps with Overlays

The excellent presentation
Customizing DSpace 1.5 with Basic Overlays
from Open Repositories O8, by
Tim Donohue and
Graham Triggs shows how to manage your local UI customizations and keep your added code well-segregated from the DSpace codebase so upgrades are simplified.
It also provides an overview of the build process and how maven
overlays work.

Recipe 3: (Deprecated) Old Quick-and-Dirty Method of Adding Plugins

This is a slightly simpler but less powerful way to add code to a single webapp at a time. It has drawbacks over the local-API method described in the first section.

With the overlay mechanism,
it is easy to add a Crosswalk
or PackagerPlugins plugin to one of the webapps. This technique
does not let you add code to the libraries accessed by the
command-line utilities, such as dspace/bin/packager (more
about that later).

The following notes assume a binary installation of DSpace 1.5.0,
under the directories:
*source is the "source" directory where builds are done.
*dspace is the target runtime directory, e.g. /dspace

Procedure to Add a Plugin

Step 1: Install sources

Add the necessary Java source files to the overlay directory for each
module that you want to have access to the plugin. This is
source/dspace/modules/{MODULE}/src/main/java
for additional Java sources.

Note that adding a plugin to multiple modules requires a separate copy of the source files for each module, which might complicate maintenance when you have to update the sources; use symbolic links to work around this if you are familiar with them.

For this example, I'll show an ingestion/dissemination crosswalk Plugin, and a
package ingester Plugin that are both implemented in the following class
files:

For the example, assume these files reside under a development
directory, {development}.
To add these classes to the LNI module, we install the sources under
source/dspace/modules/lni/src/main/java with the following
commands:

Step 2: Update DSpace Configuration

If you maintain the DSpace configuration file in your source directory
and use the build tools to copy it into the runtime hierarchy, then
update the source copy of dspace.cfg now. (In my development
environment, I just edit the runtime copy in
dspace/config/dspace.cfg.)

Add entries for the crosswalks, e.g. like the bold line here
(other entries elided for clarity):

Step 3: Modify the POM to Add Dependencies

If your code has any new external dependencies (i.e. it needs modules
not already required by DSpace) then you need to add those to the
POM for the overlay module. In this example, we add the bold lines to the
LNI module's POM at source/dspace/modules/lni/pom.xml

NOTE: Of course, this requires that all the libraries your code depends on
are available to Maven. If not, you'll have to add them to the local
Maven repository or convince someone to put them into a networked maven
repository. This example creates an entry in the local repository:

Step 4: Build with Maven and Deploy

First, build the sources:

Assuming that succeeds, run Ant to install the build products.
NOTE: This does NOT install the configuration files, because I don't work that way; perhaps someone who does could add an alternate command here?

Your DSpace instance should now be running with the new plugins in the
LNI application.

Adding The Same Plugins to Other Applications

The procedure to add these same plugins to another DSpace application,
for example the OAI-PMH server ("oai"), is identical.

If you are adding
the plugins to both lni and oai, you may
wish to symbolically link the Java sources to one master copy someplace
else, so that any changes will take effect in both applications.

In the case of OAI-PMH, you'll also need to modify the
oaicat.properties configuration file to add the appropriate
plugins to OAICAT.

Recipe 4: (Deprecated) Use Overlays to Segregate Local Modifications

You can also use the overlay mechanism to implement a local change or bug-fix
to the DSpace codebase. The process is exactly the same as for
adding plugin implementations, only you add the appropriate DSpace
class files to the source directory instead. These will take precedence
over the distributed code in the classloader.

Again, add the sources under
source/dspace/modules/{MODULE}/src/main/java ,
only under the org/dspace/... hierarchy.

For example, to fix a bug in the org.dspace.app.oai.DSpaceOAICatalog
class, you add that file in Step 1 instead of your own source:

The procedure thereafter is exactly the same as the last recipe (deprecated) for adding plugin
implementations.

Recipe 5: (Deprecated) Old, Poor way of Adding Plugins to Command-Line Applications

The build system does not appear to have any way to accomplish this
with a binary DSpace installation.
(Please correct this if I'm wrong.)

As a kludgy workaround, I've simply added a JAR file manually to the
"lib" directory used by all command-line apps.

Using my crosswalk and packager example above, the command to add my
code to the runtime directory is:

Note that the JAR output file pim.jar
is simply what I chose to call it, use any unique name.
The classes are all in packages under edu.mit so the
jar command picks up everything under edu in the overlay module's
class directory.

Of course you also have to manually copy in whatever other
libraries your code depends on, e.g.

Note that the build installation ("ant update") process wipes the
runtime "lib" directory clean each time, so you'll have to
repeat these commands after every new update.