java.lang.Object
- org.apache.sling.launchpad.base.impl.Sling

```
public class Sling
extends Object
```
The Sling serves as the starting point for Sling.
- The Sling(Notifiable, Logger, LaunchpadContentProvider, Map) method launches Apache Felix as the OSGi framework implementation we use.
Launch Configuration
The Apache Felix framework requires configuration parameters to be specified for startup. This servlet builds the list of parameters from three locations:
1. The sling.properties file is read from the servlet class path. This properties file contains default settings.
2. Extensions of this servlet may provide additional properties to be loaded overwriting the loadPropertiesOverride(Map) method.
3. Finally, web application init parameters are added to the properties and may overwrite existing properties of the same name(s).
After loading all properties, variable substitution takes place on the property values. A variable is indicated as ${<prop-name>} where <prop-name> is the name of a system or configuration property (configuration properties override system properties). Variables may be nested and are resolved from inner-most to outer-most. For example, the property value ${outer-${inner}} is resolved by first resolving ${inner} and then resolving the property whose name is the catenation of outer- and the result of resolving ${inner}.

Field Summary

Fields
Modifier and Type	Field	Description
`static String`	`CONFIG_PROPERTIES`	The name of the default launcher properties file to setup the environment for the `Felix` framework (value is "sling.properties").
`static String`	`JCR_REPO_CONFIG_FILE_URL`	The name of the configuration property defining the URL of an existing repository config file (repository.xml).
`static String`	`JCR_REPO_HOME`	The name of the configuration property defining the JCR home directory (value is "sling.repository.home").
`protected org.apache.felix.framework.Logger`	`logger`	The simple logger to log messages during startup and shutdown to
`static String`	`OSGI_FRAMEWORK_BUNDLES`	The name of the configuration property defining a properties file defining a list of bundles, which are installed into the framework when it has been launched (value is "org.apache.osgi.bundles").
`static String`	`PROP_EXTRA_CAPS`
`static String`	`PROP_SYSTEM_PACKAGES`
`static String`	`SLING_HOME_URL`	The name of the configuration property defining the Sling home directory as an URL (value is "sling.home.url").
`static String`	`SLING_IGNORE_SYSTEM_PROPERTIES`	The property to be set to ignore the system properties when building the Felix framework properties (value is "sling.ignoreSystemProperties").

Constructor Summary

Constructors
Constructor	Description
`Sling(Notifiable notifiable, org.apache.felix.framework.Logger logger, org.apache.sling.launchpad.api.LaunchpadContentProvider resourceProvider, Map<String,String> propOverwrite)`	Initializes this servlet by loading the framework configuration properties, starting the OSGi framework (Apache Felix) and exposing the system bundle context and the `Felix` instance as servlet context attributes.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`destroy()`	Destroys this servlet by shutting down the OSGi framework and hence the delegatee servlet if one is set at all.
`org.osgi.framework.BundleContext`	`getBundleContext()`	Returns the `BundleContext` of the system bundle of the OSGi framework launched by this servlet.
`protected void`	`loadPropertiesOverride(Map<String,String> properties)`	Loads additional properties into the `properties` object.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - SLING_HOME_URL
```
public static final String SLING_HOME_URL
```
    The name of the configuration property defining the Sling home directory as an URL (value is "sling.home.url").
    The value of this property is assigned the value of new File(${sling.home}).toURI().toString() before resolving the property variables.
    
    See Also:
    
    SharedConstants.SLING_HOME, Constant Field Values
  - JCR_REPO_HOME
```
public static final String JCR_REPO_HOME
```
    The name of the configuration property defining the JCR home directory (value is "sling.repository.home").
    The value of this property could be set as a system property, init-param in web.xml or property in sling.properties.
    Default value to #SLING_HOME/repository_name
    
    See Also:
    
    Constant Field Values
  - JCR_REPO_CONFIG_FILE_URL
```
public static final String JCR_REPO_CONFIG_FILE_URL
```
    The name of the configuration property defining the URL of an existing repository config file (repository.xml).
    The value of this property could be set as a system property, init-param in web.xml or property in sling.properties.
    Default value to #SLING_HOME/repository_name/repository.xml
    
    See Also:
    
    Constant Field Values
  - OSGI_FRAMEWORK_BUNDLES
```
public static final String OSGI_FRAMEWORK_BUNDLES
```
    The name of the configuration property defining a properties file defining a list of bundles, which are installed into the framework when it has been launched (value is "org.apache.osgi.bundles").
    This configuration property is generally set in the web application configuration and may be referenced in all property files (default, user supplied and web application parameters) used to build the framework configuration.
    
    See Also:
    
    Constant Field Values
  - SLING_IGNORE_SYSTEM_PROPERTIES
```
public static final String SLING_IGNORE_SYSTEM_PROPERTIES
```
    The property to be set to ignore the system properties when building the Felix framework properties (value is "sling.ignoreSystemProperties"). If this is property is set to true (case does not matter), the system properties will not be used by loadConfigProperties(Map).
    
    See Also:
    
    Constant Field Values
  - CONFIG_PROPERTIES
```
public static final String CONFIG_PROPERTIES
```
    The name of the default launcher properties file to setup the environment for the Felix framework (value is "sling.properties").
    Extensions of this class may overwrite some or all properties in this file through Web Application parameters or other properties files.
    
    See Also:
    
    Constant Field Values
  - PROP_SYSTEM_PACKAGES
```
public static final String PROP_SYSTEM_PACKAGES
```
    See Also:
    
    Constant Field Values
  - PROP_EXTRA_CAPS
```
public static final String PROP_EXTRA_CAPS
```
    See Also:
    
    Constant Field Values
  - logger
```
protected final org.apache.felix.framework.Logger logger
```
    The simple logger to log messages during startup and shutdown to
- Constructor Detail
  - Sling
```
public Sling(Notifiable notifiable,
             org.apache.felix.framework.Logger logger,
             org.apache.sling.launchpad.api.LaunchpadContentProvider resourceProvider,
             Map<String,String> propOverwrite)
      throws org.osgi.framework.BundleException
```
    Initializes this servlet by loading the framework configuration properties, starting the OSGi framework (Apache Felix) and exposing the system bundle context and the Felix instance as servlet context attributes.
    
    Parameters:
    
    notifiable - The notifiable
    
    logger - The logger
    
    resourceProvider - The resource provider
    
    propOverwrite - The properties to overwrite
    
    Throws:
    
    org.osgi.framework.BundleException - if the framework cannot be initialized.
- Method Detail
  - destroy
```
public final void destroy()
```
    Destroys this servlet by shutting down the OSGi framework and hence the delegatee servlet if one is set at all.
  - loadPropertiesOverride
```
protected void loadPropertiesOverride(Map<String,String> properties)
```
    Loads additional properties into the properties object.
    This implementation does nothing and may be overwritten by extensions requiring additional properties to be set.
    This method is called when the servlet is initialized to prepare the configuration for Felix. Implementations may add properties from implementation specific sources. Properties added here overwrite properties loaded from the default properties file and may be overwritten by parameters set in the web application.
    The properties object has not undergone variable substition and properties added by this method may also contain values refererring to other properties.
    The properties added in this method will not be persisted in the sling.properties file in the sling.home directory.
    
    Parameters:
    
    properties - The Properties object to which custom properties may be added.
  - getBundleContext
```
public final org.osgi.framework.BundleContext getBundleContext()
```
    Returns the BundleContext of the system bundle of the OSGi framework launched by this servlet. This method only returns a non-null object after the system bundle of the framework has been started and before it is being stopped.
    
    Returns:
    
    The BundleContext of the system bundle

Class Sling

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

SLING_HOME_URL

JCR_REPO_HOME

JCR_REPO_CONFIG_FILE_URL

OSGI_FRAMEWORK_BUNDLES

SLING_IGNORE_SYSTEM_PROPERTIES

CONFIG_PROPERTIES

PROP_SYSTEM_PACKAGES

PROP_EXTRA_CAPS

logger

Constructor Detail

Sling

Method Detail

destroy

loadPropertiesOverride

getBundleContext