com.tangosol.io.pof
Class ConfigurablePofContext

java.lang.Object
  com.tangosol.io.pof.ConfigurablePofContext

All Implemented Interfaces:

ClassLoaderAware, PofContext, Serializer, XmlConfigurable

Direct Known Subclasses:

SafeConfigurablePofContext

public class ConfigurablePofContext
extends Object
implements PofContext, XmlConfigurable

This class implements the PofContext interface using information provided in a configuration file (or in a passed XML configuration).

For each user type supported by this POF context, it must be provided with:

• A valid user type ID that is unique within this POF context;
• A Java class name that identifies a Java class or interface that all values of the user type are type-assignable to (and that no values of other user types are type-assignable to); in other words, all values of the user type (and no values of other user types) are instances of the specified class, instances of a sub-class of the specified class, or (if it is an interface) instances of a class that implements the specified interface;
• A Java class name that identifies a non-abstract implementation of the PofSerializer interface.

The format of the configuration XML is as follows:

 <pof-config>
   <user-type-list>
     ..
     <user-type>
       <type-id>53</type-id>
       <class-name>com.mycompany.data.Trade</class-name>
       <serializer>
         <class-name>com.tangosol.io.pof.PortableObjectSerializer</class-name>
         <init-params>
           <init-param>
             <param-type>int</param-type>
             <param-value>{type-id}</param-value>
           </init-param>
         </init-params>
       </serializer>
     </user-type>

     <user-type>
       <type-id>54</type-id>
       <class-name>com.mycompany.data.Position</class-name>
     </user-type>

     ..
     <include>file:/my-pof-config.xml</include>

     ..
   </user-type-list>

   <allow-interfaces>false</allow-interfaces>
   <allow-subclasses>false</allow-subclasses>
 </pof-config>
 

For each user type, a user-type element must exist inside the user-type-list element. The user-type-list element contains up to three elements, in the following order:

• The user-type element should contain a type-id element whose value specifies the unique integer type ID; if none of the user-type elements contains a type-id element, then the type IDs for the user types will be based on the order in which they appear in the configuration, with the first user type being assigned the type ID 0, the second user type being assigned the type ID 1, and so on. (It is strongly recommended that user types IDs always be specified, in order to support schema versioning and evolution.)
• The class-name element is required, and specifies the fully qualified name of the Java class or interface that all values of the user type are type-assignable to.
• The serializer element is used to specify an implementation of PofSerializer to use to serialize and deserialize user type values to and from a POF stream. Within the serializer element, the class-name element is required, and zero or more constructor parameters can be defined within an init-params block. If no serializer is specified, then the user type is assumed to implement the PortableObject interface, and the PortableObjectSerializer implementation is used.

The optional include element allows user-type elements defined in another configuration XML to be added to the user type list. The value of this element is a locator string (either a valid path or URL) that specifies the location of the target PofContext configuration file. The user-type elements of the target file are imported verbatum; therefore, if the included elements contain explicit type identifiers, each identifier must be unique with respect to the the user type identifiers (either explicit or generated) defined within the including file. If the included user types do not contain explicit type identifiers, then the type identifiers will be based on the order in which the user types appear in the composite configuration file. Multiple include elements may be used within a single user-type-list element.

The ConfigurablePofContext is truly ClassLoader-aware. It is conceivable that the ConfigurablePofContext is loaded by the system ClassLoader (or some other relatively global ClassLoader), while the objects deserialized by the PofContext are loaded by an application-specific ClassLoader, such as is typical within an application server. The ConfigurablePofContext is designed to load the configuration, the POF-able object classes and the PofSerializer classes from within a specified ClassLoader context, and to pass the ClassLoader information on to the PofSerializer instances, just in case they are not loaded from within the application's ClassLoader context. In other words, the ConfigurablePofContext, its configuration, the PofSerializer classes and the POF-able classes can all be loaded by the same ClassLoader, or they can all be loaded by different ClassLoaders, so long as the configuration, the POF-able classes and the PofSerializer classes can be loaded by either the specified ClassLoader or by the ClassLoader that loaded the ConfigurablePofContext itself.

In order to be used by the ConfigurablePofContext, a PofSerializer implementation must provide a public constructor that accepts the parameters detailed by the init-params element. The parameter values, as specified by the param-value element, can specify one of the following substitutable values:

• {type-id} - replaced with the Type ID of the User Type;
• {class-name} - replaced with the name of the class for the User Type;
• {class} - replaced with the Class for the User Type;
• {class-loader} - replaced with the ConfigurablePofContext's ContextClassLoader.

If the init-params element is not present, then the ConfigurablePofContext attempts to construct the PofSerializer by searching for one of the following constructors in the same order as they appear here:

• (int nTypeId, Class clz, ClassLoader loader)
• (int nTypeId, Class clz)
• (int nTypeId)
• ()

Once constructed, if the PofSerializer implements the XmlConfigurable interface, the setConfig method is invoked, and it is passed the parameter XML information, transposed as described by transformInitParams, and as described in the pof-config.dtd file.

Finally, if the PofSerializer implements the ClassLoaderAware interface and a ClassLoader has been specified, then the setContextClassLoader method is invoked with the reference to the specified ClassLoader.

Conceptually, the identity of a ConfigurablePofContext is a combination of a configuration locator and a ClassLoader. The ClassLoader is used to resolve and load the configuration details whose location is specified by the configuration locator, and to load all of the classes specified by the configuration. To achieve acceptable performance, and to limit the redundant use of resources, the ConfigurablePofContext maintains a WeakHashMap keyed by ClassLoader, whose corresponding values are each a WeakHashMap keyed by configuration locator, whose corresponding values contain the data necessary to efficiently perform the operations prescribed by the PofContext interface.

Note: The configuration for the default constructor can be specified using the tangosol.pof.config system property.

Since:

Coherence 3.2

Author:

jh/cp 2006.07.24

Nested Class Summary

protected static class

ConfigurablePofContext.PofConfig The information related to the configuration of a particular PofContext for a specific URI and ClassLoader.

Field Summary

static String	DEFAULT_RESOURCE The name of the application resource that contains the default set of wire-format-to-object bindings.
static String	PROPERTY_CONFIG The name of the system property ("tangosol.pof.config") that can be used to override the location of the default POF configuration file.

Constructor Summary

ConfigurablePofContext()
Default constructor.

ConfigurablePofContext(String sLocator)
Create a ConfigurablePofContext that will load configuration information from the specified locator.

ConfigurablePofContext(XmlElement xml)
Create a ConfigurablePofContext that will use the passed configuration information.

Method Summary

protected void	checkNotInitialized() Verify that the ConfigurablePofContext has not already been initialized.
protected ConfigurablePofContext.PofConfig	createPofConfig() Create a PofConfig object based on a configuration that was either provided as XML, or can be loaded from the specified (or default) URI using the provided ClassLoader.
Object	deserialize(ReadBuffer.BufferInput in) Deserialize an object from a ReadBuffer by reading its state using the specified BufferInput object.
protected void	ensureInitialized() Fully initialize the ConfigurablePofContext if it has not already been initialized.
Class	getClass(int nTypeId) Determine the class associated with the given user type identifier.
String	getClassName(int nTypeId) Determine the name of the class associated with the given user type identifier.
XmlElement	getConfig() Determine the current configuration of the object.
protected String	getConfigLocation() Obtain the location of the configuration that the ConfigurablePofContext used to configure itself.
ClassLoader	getContextClassLoader() Retrieve the context ClassLoader for this object.
protected ConfigurablePofContext.PofConfig	getPofConfig() Obtain the PofConfig that represents the initialized state of the ConfigurablePofContext.
PofSerializer	getPofSerializer(int nTypeId) Return a PofSerializer that can be used to serialize and deserialize an object of the specified user type to and from a POF stream.
int	getUserTypeIdentifier(Class clz) Determine the user type identifier associated with the given class.
int	getUserTypeIdentifier(Object o) Determine the user type identifier associated with the given object.
int	getUserTypeIdentifier(String sClass) Determine the user type identifier associated with the given class name.
protected int	getUserTypeIdentifierInternal(Class clz) Determine the user type identifier associated with the given class.
protected int	getUserTypeIdentifierInternal(String sClass) Determine the user type identifier associated with the given class name.
protected void	initialize() Bind the ConfigurablePofContext to a ClassLoader, resolving all class names, etc.
protected boolean	isInitialized() Determine if the ConfigurablePofContext has completed its initialization.
protected boolean	isInterfaceAllowed() Determine if the ConfigurablePofContext supports the configuration of user types by specifying an interface (instead of a class) for the Java type.
protected boolean	isSubclassAllowed() Determine if the ConfigurablePofContext supports the serialization of an object that is an instance of a sub-class of a configured type, but not actually an instance of a class of a configured type.
boolean	isUserType(Class clz) Determine if the given class is a user type known to this PofContext.
boolean	isUserType(Object o) Determine if the given object is of a user type known to this PofContext.
boolean	isUserType(String sClass) Determine if the class with the given name is a user type known to this PofContext.
protected Class	loadClass(String sClass) Find the specified class, return a Java Class object for it.
protected URL	loadResource(String sURI) Find the specified resource, returning a URL for it.
protected RuntimeException	report(String sURI, int nTypeId, String sClass, Throwable e, String sText) Assemble and throw an informative exception based on the passed details.
void	serialize(WriteBuffer.BufferOutput out, Object o) Serialize an object to a WriteBuffer by writing its state using the specified BufferOutput object.
void	setConfig(XmlElement xml) Specify the configuration for the object.
void	setContextClassLoader(ClassLoader loader) Specify the context ClassLoader for this object.

Field Detail

PROPERTY_CONFIG

public static final String PROPERTY_CONFIG

The name of the system property ("tangosol.pof.config") that can be used to override the location of the default POF configuration file.

The value of this property must be the name of a resource that contains an XML document with the structure defined in /pof-config.dtd (deployed in coherence.jar). An example configuration is provided in the example-pof-config.xml file (found in the same location as the DTD), and includes a list of many of the POF-capable Coherence classes.

The default value for the "tangosol.pof.config" system property is "coherence-pof-config.xml".

See Also:

Constant Field Values

DEFAULT_RESOURCE

public static final String DEFAULT_RESOURCE

The name of the application resource that contains the default set of wire-format-to-object bindings.

The default value for the resource name is "coherence-pof-config.xml". The default can be overriden by specifying a value for the tangosol.pof.config system property.

Constructor Detail

ConfigurablePofContext

public ConfigurablePofContext()

Default constructor.

Create a default ConfigurablePofContext that will load configuration information from the locator specified in DEFAULT_RESOURCE.

ConfigurablePofContext

public ConfigurablePofContext(String sLocator)

Create a ConfigurablePofContext that will load configuration information from the specified locator.

Parameters:

sLocator - the locator that specifies the location of the PofContext configuration file; the locator is either a valid path or a URL

ConfigurablePofContext

public ConfigurablePofContext(XmlElement xml)

Create a ConfigurablePofContext that will use the passed configuration information.

Parameters:

xml - an XmlElement containing information in the format of a configuration file used by ConfigurablePofContext

Method Detail

getConfig

public XmlElement getConfig()

Determine the current configuration of the object.

Note that the configuration will not be available unless the ConfigurablePofContext was constructed with the configuration, the configuration was specified using the XmlConfigurable interface, or the ConfigurablePofContext has fully initialized itself (which does not occur until a ClassLoader is provided, or an attempt is made through the ConfigurablePofContext to serialize or deserialize a POF object, whichever comes first.)

Specified by:

getConfig in interface XmlConfigurable

Returns:

the XML configuration or null

setConfig

public void setConfig(XmlElement xml)

Specify the configuration for the object.

Note that the configuration cannot be set after the ConfigurablePofContext is fully initialized.

Specified by:

setConfig in interface XmlConfigurable

Parameters:

xml - the XML configuration for the object

Throws:

IllegalStateException - if the ConfigurablePofContext is already fully initialized

getContextClassLoader

public ClassLoader getContextClassLoader()

Retrieve the context ClassLoader for this object. The context ClassLoader is provided by the creator of the object for use by the object when loading classes and resources.

Specified by:

getContextClassLoader in interface ClassLoaderAware

Returns:

the context ClassLoader for this object

See Also:

Thread.getContextClassLoader()

setContextClassLoader

public void setContextClassLoader(ClassLoader loader)

Specify the context ClassLoader for this object. The context ClassLoader can be set when the object is created, and allows the creator to provide the appropriate class loader to be used by the object when when loading classes and resources.

Note that the ConfigurablePofContext will fully initialize when it is provided a ClassLoader.

Specified by:

setContextClassLoader in interface ClassLoaderAware

Parameters:

loader - the context ClassLoader for this object

Throws:

IllegalStateException - if the ConfigurablePofContext is already fully initialized

serialize

public void serialize(WriteBuffer.BufferOutput out,
                      Object o)
               throws IOException

Serialize an object to a WriteBuffer by writing its state using the specified BufferOutput object.

Specified by:

serialize in interface Serializer

Parameters:

out - the BufferOutput with which to write the object's state

o - the object to serialize

Throws:

IOException - if an I/O error occurs

deserialize

public Object deserialize(ReadBuffer.BufferInput in)
                   throws IOException

Deserialize an object from a ReadBuffer by reading its state using the specified BufferInput object.

Specified by:

deserialize in interface Serializer

Parameters:

in - the BufferInput with which to read the object's state

Returns:

the deserialized user type instance

Throws:

IOException - if an I/O error occurs

getPofSerializer

public PofSerializer getPofSerializer(int nTypeId)

Return a PofSerializer that can be used to serialize and deserialize an object of the specified user type to and from a POF stream.

Specified by:

getPofSerializer in interface PofContext

Parameters:

nTypeId - the type identifier of the user type that can be serialized and deserialized using the returned PofSerializer; must be non-negative

Returns:

a PofSerializer for the specified user type

getUserTypeIdentifier

public int getUserTypeIdentifier(Object o)

Determine the user type identifier associated with the given object.

Specified by:

getUserTypeIdentifier in interface PofContext

Parameters:

o - an instance of a user type; must not be null

Returns:

the type identifier of the user type associated with the given object

getUserTypeIdentifier

public int getUserTypeIdentifier(Class clz)

Determine the user type identifier associated with the given class.

Specified by:

getUserTypeIdentifier in interface PofContext

Parameters:

clz - a user type class; must not be null

Returns:

the type identifier of the user type associated with the given class

getUserTypeIdentifier

public int getUserTypeIdentifier(String sClass)

Determine the user type identifier associated with the given class name.

Specified by:

getUserTypeIdentifier in interface PofContext

Parameters:

sClass - the name of a user type class; must not be null

Returns:

the type identifier of the user type associated with the given class name

getClassName

public String getClassName(int nTypeId)

Determine the name of the class associated with the given user type identifier.

Specified by:

getClassName in interface PofContext

Parameters:

nTypeId - the user type identifier; must be non-negative

Returns:

the name of the class associated with the specified user type identifier

getClass

public Class getClass(int nTypeId)

Determine the class associated with the given user type identifier.

Specified by:

getClass in interface PofContext

Parameters:

nTypeId - the user type identifier; must be non-negative

Returns:

the class associated with the specified user type identifier

isUserType

public boolean isUserType(Object o)

Determine if the given object is of a user type known to this PofContext.

Specified by:

isUserType in interface PofContext

Parameters:

o - the object to test; must not be null

Returns:

true iff the specified object is of a valid user type

isUserType

public boolean isUserType(Class clz)

Determine if the given class is a user type known to this PofContext.

Specified by:

isUserType in interface PofContext

Parameters:

clz - the class to test; must not be null

Returns:

true iff the specified class is a valid user type

isUserType

public boolean isUserType(String sClass)

Determine if the class with the given name is a user type known to this PofContext.

Specified by:

isUserType in interface PofContext

Parameters:

sClass - the name of the class to test; must not be null

Returns:

true iff the class with the specified name is a valid user type

getUserTypeIdentifierInternal

protected int getUserTypeIdentifierInternal(Class clz)

Determine the user type identifier associated with the given class.

Parameters:

clz - a user type class; must not be null

Returns:

the type identifier of the user type associated with the given class or -1 if the user type is unknown to this PofContext

getUserTypeIdentifierInternal

protected int getUserTypeIdentifierInternal(String sClass)

Determine the user type identifier associated with the given class name.

Parameters:

sClass - the name of a user type class; must not be null

Returns:

the type identifier of the user type associated with the given class name or -1 if the user type is unknown to this PofContext

isInitialized

protected boolean isInitialized()

Determine if the ConfigurablePofContext has completed its initialization.

Returns:

true iff the initialization is complete

getConfigLocation

protected String getConfigLocation()

Obtain the location of the configuration that the ConfigurablePofContext used to configure itself.

Returns:

the location information for the configuration for the ConfigurablePofContext, or null if not yet initialized and no location was specified

getPofConfig

protected ConfigurablePofContext.PofConfig getPofConfig()

Obtain the PofConfig that represents the initialized state of the ConfigurablePofContext.

Returns:

the PofConfig for the ConfigurablePofContext, or null if not yet initialized

isInterfaceAllowed

protected boolean isInterfaceAllowed()

Determine if the ConfigurablePofContext supports the configuration of user types by specifying an interface (instead of a class) for the Java type.

Returns:

true iff an interface name is acceptable in the configuration as the class of a user type

isSubclassAllowed

protected boolean isSubclassAllowed()

Determine if the ConfigurablePofContext supports the serialization of an object that is an instance of a sub-class of a configured type, but not actually an instance of a class of a configured type.

Returns:

true iff serialization of sub-classes is explicitly enabled

checkNotInitialized

protected void checkNotInitialized()

Verify that the ConfigurablePofContext has not already been initialized.

Throws:

IllegalStateException - if the ConfigurablePofContext is already fully initialized

ensureInitialized

protected void ensureInitialized()

Fully initialize the ConfigurablePofContext if it has not already been initialized.

initialize

protected void initialize()

Bind the ConfigurablePofContext to a ClassLoader, resolving all class names, etc.

createPofConfig

protected ConfigurablePofContext.PofConfig createPofConfig()

Create a PofConfig object based on a configuration that was either provided as XML, or can be loaded from the specified (or default) URI using the provided ClassLoader.

Returns:

a PofConfig for this ConfigurablePofContext

loadClass

protected Class loadClass(String sClass)

Find the specified class, return a Java Class object for it.

Parameters:

sClass - the fully qualified class name

Returns:

the Class object for the specified class name, never null

Throws:

RuntimeException - a RuntimeException (or a subclass thereof) is thrown if the specified Class could not be loaded

loadResource

protected URL loadResource(String sURI)

Find the specified resource, returning a URL for it.

Parameters:

sURI - the resource identifier to load

Returns:

a URL for the resource, or null if it could not be found

report

protected RuntimeException report(String sURI,
                                  int nTypeId,
                                  String sClass,
                                  Throwable e,
                                  String sText)

Assemble and throw an informative exception based on the passed details.

Parameters:

sURI - the URI of the configuration

nTypeId - the type ID (if applicable and if known)

sClass - the user type class name (if applicable and if known)

e - the underlying exception, if any

sText - the detailed description of the problem

Returns:

this method does not return; it always throws an exception

Throws:

IllegalStateException - always thrown