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• Spring focuses around providing a way to manage your business objects. (DSpace currently lacks this capability).
• Spring is both comprehensive and modular. Spring has a layered architecture, you can choose to use just about any part of it in isolation.
• It is easy to introduce Spring incrementally into existing projects. (The Latest DSpace WebMVC, REST and XMLUI development efforts already leverage Spring WebMVC in the application tier).
• Spring is designed from the ground up to help you write code that's easy to test. Spring is an ideal framework for test driven projects. (DSpace has only just introduced a JUnit Test Suite, which does not leverage Spring in its solution. However, the DSpace Service Manager already delivers a testing suite leverages Spring to support testing configuration).
• Spring is an increasingly important integration technology, its role recognized by several large vendors. By utilizing Spring, DSpace will be able to incrementally improve its architecture to be more robust, and more "enterprise grade".

The Service Manager

The ServiceManager provides the DSpace Application with the above Spring ApplicationContext so that the developer  does not need to be responsible for its creation when developing against DSpace. Thus, to extend the pervious example, the DSpace class and its underlying Service Manager can be utilized to get at any object that has been instantiated as a service bean by core or addon application code.Example example = new DSpace().getSingletonService("my-example", Example.class);
/* Go on to do something interesting with the service */

The DSpace Service Manager implementation manages the entire lifecycle of a running DSpace application and provides access to services by Applications that may be executing external to this "kernel" of DSpace Services. Via Spring and loading of individual dspace.cfg properties the ServiceManager manages the configuration of those services, (either through providing those properties to the Spring Application Context where they can be injected in Spring definition xml files and/or "annotations" or by exposing those properties via the injection of the DSpace ConfigurationService.

DSpace ConfigurationService

The ServiceManagerSystem abstraction allows the DSpace ServiceManager to use different systems to manage its services. The current implementation is Spring Framework based. The original design intent of the Service Manager was to support more than one IoC/DI Solution, however, as work has progressed with DSpace, it has become clear that there are trade offs to consider in its usage.

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public interface Session extends HttpSession {

    /**
     * @return the session identifier.  This is not the {@link #getId()}
     * from HttpSession unless no session id was specified when the
     * session was bound.
     */
    public String getSessionId();

    /**
     * Return the internal user ID for this session.
     *
     * @return internal user ID for the user using this session.
     * This is null if the session is anonymous.
     */
    public String getUserId();

    /**
     * Get the external/enterprise user ID for this session.
     *
     * @return the external/enterprise user id of the user associated with this session
     */
    public String getUserEID();

    /**
     * @return true if this session is active OR false if the session has timed out or been invalidated
     */
    public boolean isActive();

    /**
     * @return id of the server with which this session is associated.
     */
    public String getServerId();

    /**
     * @return the IP Address from which this session originated
     */
    public String getOriginatingHostIP();

    /**
     * @return the hostname from which this session originated
     */
    public String getOriginatingHostName();

    /**
     * Get an attribute from the session if one exists.
     * @param key  the key for the attribute
     * @return the value if one exists OR null if none
     */
    public String getAttribute(String key);

    /**
     * Set an attribute on a session.
     *
     * @param key for the attribute
     * @param value (if this is null then the attribute is removed)
     */
    public void setAttribute(String key, String value);

    /**
     * Get all attributes of this session.
     * @return a copy of the attributes in this session.
     * Modifying it has no effect on the session attributes.
     */
    public Map<String, String> getAttributes();

    /**
     * Purges all data from this session and effectively resets it to an
     * anonymous session.  Does not invalidate the session, though.
     */
    public void clear();

Behind APIs

 can be reimplemented without affecting developers who are using the services. 

Most of the services have plugin/provider points so that customizations can be added into the system without touching the core services code.

Example, specialized authentication system and wants to manage the authentication calls which come into the system. The implementor can simply implement an AuthenticationProvider and then register it with the DS2 kernel's ServiceManager. This can be done at any time and does not have to be done during Kernel startup. This allows providers to be swapped out at runtime without disrupting the DS2 service if desired. It can also speed up development by allowing quick hot redeploys of code during development.

Configuration Service

The ConfigurationService controls the external and internal configuration of DSpace 2. It reads Properties files when the kernel starts up and merges them with any dynamic configuration data which is available from the services. This service allows settings to be updated as the system is running, and also defines listeners which allow services to know when their configuration settings have changed and take action if desired. It is the central point to access and manage all the configuration settings in DSpace.

Manages the configuration of the DSpace 2 system. Can be used to manage configuration for providers and plugins also.

Benefits over the DSpace ConfigurationManager

Benefits over the Legacy DSpace ConfigurationManager

• Type Casting: Common Configuration Interface supports type casting of configuration values of the type required by the caller.
• Array Parsing: As part of this type casting, the Configuration Service will split comma separated values for you when you request the property as type "Array"

  Code Block

  /* type casting */ int value = configurationService.getPropertyAsType("some-integer",int.class); /* Array Parsing */ String[] values = configurationService.getPropertyAsType("some-array", String[].class); /* Default Values */ int value = configurationService.getPropertyAsType("some-integer",1); /* Default Array Values */ String[] values = configurationService.getPropertyAsType("some-array",new String[]{"my", "own", "array"});

• Type Casting: Common Configuration Interface supports type casting of configuration values of the type required by the caller.
• Array Parsing: As part of this type casting, the Configuration Service will split your comma separated values for you

Recommendations: Why parse values if you do not have to, avoid Parsing Values where-ever possible.

• Use commas for lists of values, use lookups (If you end up thinking you want to create maps in your properties, your doing it in the wrong place look instead at Spring Configuration and objectifying your configuration)
• Objectifying Configuration (Its best to wire your application components with Spring).

Acquiring the Configuration Service

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• thinking you want to create maps in your properties, your doing it in the wrong place look instead at Spring Configuration and objectifying your configuration)
• Objectifying Configuration (Its best to wire your application components with Spring).

 can be reimplemented without affecting developers who are using the services. 

Most of the services have plugin/provider points so that customizations can be added into the system without touching the core services code.

Example, specialized authentication system and wants to manage the authentication calls which come into the system. The implementor can simply implement an AuthenticationProvider and then register it with the DS2 kernel's ServiceManager. This can be done at any time and does not have to be done during Kernel startup. This allows providers to be swapped out at runtime without disrupting the DS2 service if desired. It can also speed up development by allowing quick hot redeploys of code during development.

Configuration Service

The ConfigurationService controls the external and internal configuration of DSpace 2. It reads Properties files when the kernel starts up and merges them with any dynamic configuration data which is available from the services. This service allows settings to be updated as the system is running, and also defines listeners which allow services to know when their configuration settings have changed and take action if desired. It is the central point to access and manage all the configuration settings in DSpace.

Manages the configuration of the DSpace 2 system. Can be used to manage configuration for providers and plugins also.

Acquiring the Configuration Service

/* Instantiate the Utility Class */
DSpace dspace = new DSpace();

/* Access get the Service Manager by convenience method */
ConfigurationService service = dspace.getSingletonService(ConfigurationService.class);

The ConfigurationService API

public interface ConfigurationService {

    /**
     * Get a configuration property (setting) from the system as a
     * specified type.
     *
     * @param <T>
     * @param name the property name
     * @param type the type to return the property as
     * @return the property value OR null if none is found
     * @throws UnsupportedOperationException if the type cannot be converted to the requested type
     */
    public <T> T getPropertyAsType(String name, Class<T> type);

    /**
     * Get a configuration property (setting) from the system, or return
     * a default value if none is found.
     *
     * @param <T>
     * @param name the property name
     * @param defaultValue the value to return if this name is not found
     * @return the property value OR null if none is found
     * @throws IllegalArgumentException if the defaultValue type does not match the type of the property by name
     */
    public <T> T getPropertyAsType(String name, T defaultValue);

    /**
     * Get a configuration property (setting) from the system, or return
     * (and possibly store) a default value if none is found.
     *
     * @param <T>
     * @param name the property name
     * @param defaultValue the value to return if this name is not found
     * @param setDefaultIfNotFound if this is true and the config value
     * is not found then the default value will be set in the
     * configuration store assuming it is not null.  Otherwise the
     * default value is just returned but not set.
     * @return the property value OR null if none is found
     * @throws IllegalArgumentException if the defaultValue type does not match the type of the property by name
     */
    public <T> T getPropertyAsType(String name, T defaultValue, boolean setDefaultIfNotFound);

    /**
     * Get all currently known configuration settings
     *
     * @return all the configuration properties as a map of name -> value
     */
    public Map<String, String> getAllProperties();

    /**
     * Convenience method - get a configuration property (setting) from
     * the system.
     *
     * @param name the property name
     * @return the property value OR null if none is found
     */
    public String getProperty(String name);

    /**
     * Convenience method - get all configuration properties (settings)
     * from the system.
     *
     * @return all the configuration properties in a properties object (name -> value)
     */
    public Properties getProperties();

    /**
     * Set a configuration property (setting) in the system.
     * Type is not important here since conversion happens automatically
     * when properties are requested.
     *
     * @param name the property name
     * @param value the property value (set this to null to clear out the property)
     * @return true if the property is new or changed from the existing value, false if it is the same
     * @throws IllegalArgumentException if the name is null
     * @throws UnsupportedOperationException if the type cannot be converted to something that is understandable by the system as a configuration property value
     */
    public boolean setProperty(String name, Object value);

}

The most important

Legacy Configuration

_\[dspace\]/config/dspace.cfg_

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