com.atlassian.johnson

Class Johnson

java.lang.Object

com.atlassian.johnson.Johnson

public class Johnson
extends Object

Singleton class for controlling Johnson.

Because Johnson is intended to be a maintenance and application consistency layer around an application, its functionality is exposed statically. This class provides both the mechanisms for initialising and terminating Johnson, as well as for retrieving its configuration and the container of events.

Where possible to avoid synchronisation issues, it is preferable to bind Johnson to the lifecycle for the servlet container, using JohnsonContextListener to initialise and terminate Johnson.

Since:

2.0

Field Summary

Fields

Modifier and Type	Field and Description
static String	ATTR_CONFIG When used in a web environment, the JohnsonConfig will be exposed in the ServletContext under an attribute with this key.
static String	ATTR_EVENT_CONTAINER When used in a web environment, the JohnsonEventContainer will be exposed in the ServletContext under an attribute with this key.
static String	PARAM_CONFIG_LOCATION During initialisation, the ServletContext is examined for an init-param with this name.

Method Summary

Modifier and Type	Method and Description
static JohnsonConfig	getConfig() Retrieves the statically-bound JohnsonConfig.
static JohnsonConfig	getConfig(javax.servlet.ServletContext context) Attempts to retrieve the JohnsonConfig from the provided ServletContext under the key ATTR_CONFIG before falling back on getConfig().
static JohnsonEventContainer	getEventContainer() Retrieves the statically-bound JohnsonEventContainer.
static JohnsonEventContainer	getEventContainer(javax.servlet.ServletContext context) Attempts to retrieve the JohnsonEventContainer from the provided ServletContext under the key ATTR_EVENT_CONTAINER before falling back on the statically-bound instance.
static void	initialize(javax.servlet.ServletContext context) Initialises Johnson, additionally binding the JohnsonConfig and JohnsonEventContainer to the provided ServletContext and performing any ApplicationEventChecks which have been configured.
static void	initialize(String location) Initialises Johnson, loading its configuration from the provided location, and sets the statically-bound instances of JohnsonConfig and JohnsonEventContainer.
static void	terminate() Terminates Johnson, clearing the statically-bound JohnsonConfig and JohnsonEventContainer.
static void	terminate(javax.servlet.ServletContext context) Terminates Johnson, removing Johnson-related attributes from the provided ServletContext and clearing the statically-bound JohnsonConfig and JohnsonEventContainer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ATTR_CONFIG

public static final String ATTR_CONFIG

When used in a web environment, the JohnsonConfig will be exposed in the ServletContext under an attribute with this key.

Since:

3.0

ATTR_EVENT_CONTAINER

public static final String ATTR_EVENT_CONTAINER

When used in a web environment, the JohnsonEventContainer will be exposed in the ServletContext under an attribute with this key.

Since:

3.0

PARAM_CONFIG_LOCATION

public static final String PARAM_CONFIG_LOCATION

During initialisation, the ServletContext is examined for an init-param with this name. If one is found, it controls the location from which the configuration is loaded. Otherwise, XmlJohnsonConfig.DEFAULT_CONFIGURATION_FILE is used as the default.

Since:

3.0

See Also:

Constant Field Values

Method Detail

getConfig

@Nonnull
public static JohnsonConfig getConfig()

Retrieves the statically-bound JohnsonConfig.

Note: If Johnson has not been initialised, this method will not initialise it. Before attempting to use Johnson, it is left to the application developer to ensure it has been correctly initialised.

Returns:

the working configuration

Throws:

IllegalStateException - if initialize(javax.servlet.ServletContext) has not been called

getConfig

@Nonnull
public static JohnsonConfig getConfig(@Nonnull
                                               javax.servlet.ServletContext context)

Attempts to retrieve the JohnsonConfig from the provided ServletContext under the key ATTR_CONFIG before falling back on getConfig().

Note: If Johnson has not been initialised, this method will not initialise it. Before attempting to use Johnson, it is left to the application developer to ensure it has been correctly initialised.

Parameters:

context - the servlet context

Returns:

the working configuration

Throws:

IllegalStateException - if initialize(javax.servlet.ServletContext) has not been called

getEventContainer

@Nonnull
public static JohnsonEventContainer getEventContainer()

Retrieves the statically-bound JohnsonEventContainer.

Note: If Johnson has not been initialised, this method will not initialise it. Before attempting to use Johnson, it is left to the application developer to ensure it has been correctly initialised.

Returns:

the working event container

Throws:

IllegalStateException - if initialize(javax.servlet.ServletContext) has not been called

Since:

3.0

getEventContainer

@Nonnull
public static JohnsonEventContainer getEventContainer(@Nonnull
                                                               javax.servlet.ServletContext context)

Attempts to retrieve the JohnsonEventContainer from the provided ServletContext under the key ATTR_EVENT_CONTAINER before falling back on the statically-bound instance.

Note: If Johnson has not been initialised, this method will not initialise it. Before attempting to use Johnson, it is left to the application developer to ensure it has been correctly initialised.

Parameters:

context - the servlet context

Returns:

the working event container

Throws:

IllegalStateException - if initialize(javax.servlet.ServletContext) has not been called

initialize

public static void initialize(@Nonnull
                              javax.servlet.ServletContext context)

Initialises Johnson, additionally binding the JohnsonConfig and JohnsonEventContainer to the provided ServletContext and performing any ApplicationEventChecks which have been configured.

If the PARAM_CONFIG_LOCATION init-param is set, it is used to determine the location of the Johnson configuration file. Otherwise, XmlJohnsonConfig.DEFAULT_CONFIGURATION_FILE is assumed.

Note: This method is not synchronised and not thread-safe. It is left to the calling code to ensure proper synchronisation. The easiest way to do this is to initialise Johnson by adding the JohnsonContextListener to web.xml.

Parameters:

context - the servlet context

initialize

public static void initialize(@Nullable
                              String location)

Initialises Johnson, loading its configuration from the provided location, and sets the statically-bound instances of JohnsonConfig and JohnsonEventContainer.

If the location provided is null or empty, XmlJohnsonConfig.DEFAULT_CONFIGURATION_FILE is assumed.

Note: If the configuration fails to load, DefaultJohnsonConfig is used to provide defaults. For more information about what those defaults are, see the documentation for that class.

Parameters:

location - the location of the Johnson configuration file

terminate

public static void terminate()

Terminates Johnson, clearing the statically-bound JohnsonConfig and JohnsonEventContainer.

terminate

public static void terminate(@Nonnull
                             javax.servlet.ServletContext context)

Terminates Johnson, removing Johnson-related attributes from the provided ServletContext and clearing the statically-bound JohnsonConfig and JohnsonEventContainer.

Parameters:

context - the servlet context