org.apache.commons.betwixt.expression
Class Context

java.lang.Object
  org.apache.commons.betwixt.expression.Context

Direct Known Subclasses:

ReadContext

public class Context
extends java.lang.Object

Context describes the context used to evaluate bean expressions. This is mostly a bean together with a number of context variables. Context variables are named objects. In other words, a context variable associates an object with a string.

Logging during expression evaluation is done through the logging instance held by this class. The object initiating the evaluation should control this logging and so passing a Log instance is enforced by the constructors.

Context is a natural place to include shared evaluation code. One of the problems that you get with object graphs is that they can be cyclic. Xml cannot (directly) include cycles. Therefore betwixt needs to find and deal properly with cycles. The algorithm used is to check the parentage of a new child. If the child is a parent then that operation fails.

Author:

James Strachan

Constructor Summary

Context()
Construct context with default log

Context(Context context)
Construct a cloned context.

Context(java.lang.Object bean, org.apache.commons.logging.Log log)
Deprecated. 0.5 use constructor which takes a BindingConfiguration

Context(java.lang.Object bean, org.apache.commons.logging.Log log, BindingConfiguration bindingConfiguration)
Convenience constructor sets evaluted bean and log.

Context(java.lang.Object bean, java.util.Map variables, org.apache.commons.logging.Log log)
Deprecated. 0.5 use constructor which takes a converter

Context(java.lang.Object bean, java.util.Map variables, org.apache.commons.logging.Log log, BindingConfiguration bindingConfiguration)
Convenience constructor sets evaluted bean, context variables and log.

Method Summary

java.lang.Object	getBean() Gets the current bean.
java.lang.String	getClassNameAttribute() The name of the attribute which can be specified in the XML to override the type of a bean used at a certain point in the schema.
IdStoringStrategy	getIdMappingStrategy() Gets the strategy used to manage storage and retrieval of id's.
java.lang.String	getInheritedOption(java.lang.String name) Gets the value of the first option with this name.
org.apache.commons.logging.Log	getLog() Gets the current log.
boolean	getMapIDs() Should ID's and IDREF attributes be used to cross-reference matching objects?
ObjectStringConverter	getObjectStringConverter() Gets object <-> string converter.
Options	getOptions() Gets the current Options.
ValueSuppressionStrategy	getValueSuppressionStrategy() Gets the ValueSuppressionStrategy.
java.lang.Object	getVariable(java.lang.String name) Gets the value of a particular context variable.
java.util.Map	getVariables() Gets context variables.
Context	newContext(java.lang.Object newBean) Returns a new child context with the given bean but the same log and variables.
void	popOptions() Pops the current options from the stack.
void	pushOptions(Options options) Pushes the given Options onto the stack.
void	setBean(java.lang.Object bean) Set the current bean.
void	setClassNameAttribute(java.lang.String classNameAttribute) Sets the name of the attribute which can be specified in the XML to override the type of a bean used at a certain point in the schema.
void	setLog(org.apache.commons.logging.Log log) Set the log implementation to which this class logs
void	setValueSuppressionStrategy(ValueSuppressionStrategy valueSuppressionStrategy) Sets the ValueSuppressionStrategy.
void	setVariable(java.lang.String name, java.lang.Object value) Sets the value of a particular context variable.
void	setVariables(java.util.Map variables) Sets context variables.

Methods inherited from class java.lang.Object

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

Constructor Detail

Context

public Context()

Construct context with default log

Context

public Context(java.lang.Object bean,
               org.apache.commons.logging.Log log)

Deprecated. 0.5 use constructor which takes a BindingConfiguration

Convenience constructor sets evaluted bean and log.

Parameters:

bean - evaluate expressions against this bean

log - log to this logger

Context

public Context(java.lang.Object bean,
               org.apache.commons.logging.Log log,
               BindingConfiguration bindingConfiguration)

Convenience constructor sets evaluted bean and log.

Parameters:

bean - evaluate expressions against this bean

log - log to this logger

bindingConfiguration - not null

Context

public Context(Context context)

Construct a cloned context. The constructed context should share bean, variables, log and binding configuration.

Parameters:

context - duplicate the attributes of this bean

Context

public Context(java.lang.Object bean,
               java.util.Map variables,
               org.apache.commons.logging.Log log)

Deprecated. 0.5 use constructor which takes a converter

Convenience constructor sets evaluted bean, context variables and log.

Parameters:

bean - evaluate expressions against this bean

variables - context variables

log - log to this logger

Context

public Context(java.lang.Object bean,
               java.util.Map variables,
               org.apache.commons.logging.Log log,
               BindingConfiguration bindingConfiguration)

Convenience constructor sets evaluted bean, context variables and log.

Parameters:

bean - evaluate expressions against this bean

variables - context variables

log - log to this logger

bindingConfiguration - not null

Method Detail

newContext

public Context newContext(java.lang.Object newBean)

Returns a new child context with the given bean but the same log and variables.

Parameters:

newBean - create a child context for this bean

Returns:

new Context with new bean but shared variables

getBean

public java.lang.Object getBean()

Gets the current bean.

Returns:

the bean against which expressions are evaluated

setBean

public void setBean(java.lang.Object bean)

Set the current bean.

Parameters:

bean - the Object against which expressions will be evaluated

getVariables

public java.util.Map getVariables()

Gets context variables.

Returns:

map containing variable values keyed by variable name

setVariables

public void setVariables(java.util.Map variables)

Sets context variables.

Parameters:

variables - map containing variable values indexed by varibable name Strings

getVariable

public java.lang.Object getVariable(java.lang.String name)

Gets the value of a particular context variable.

Parameters:

name - the name of the variable whose value is to be returned

Returns:

the variable value or null if the variable isn't set

setVariable

public void setVariable(java.lang.String name,
                        java.lang.Object value)

Sets the value of a particular context variable.

Parameters:

name - the name of the variable

value - the value of the variable

getLog

public org.apache.commons.logging.Log getLog()

Gets the current log.

Returns:

the implementation to which this class logs

setLog

public void setLog(org.apache.commons.logging.Log log)

Set the log implementation to which this class logs

Parameters:

log - the implemetation that this class should log to

getObjectStringConverter

public ObjectStringConverter getObjectStringConverter()

Gets object <-> string converter.

Returns:

the Converter to be used for conversions, not null

Since:

0.5

getMapIDs

public boolean getMapIDs()

Should ID's and IDREF attributes be used to cross-reference matching objects?

Returns:

true if ID and IDREF attributes should be used to cross-reference instances

Since:

0.5

getClassNameAttribute

public java.lang.String getClassNameAttribute()

The name of the attribute which can be specified in the XML to override the type of a bean used at a certain point in the schema.

The default value is 'className'.

Returns:

The name of the attribute used to overload the class name of a bean

Since:

0.5

setClassNameAttribute

public void setClassNameAttribute(java.lang.String classNameAttribute)

Sets the name of the attribute which can be specified in the XML to override the type of a bean used at a certain point in the schema.

The default value is 'className'.

Parameters:

classNameAttribute - The name of the attribute used to overload the class name of a bean

Since:

0.5

getValueSuppressionStrategy

public ValueSuppressionStrategy getValueSuppressionStrategy()

Gets the ValueSuppressionStrategy. This is used to control the expression of attributes with certain values.

Returns:

ValueSuppressionStrategy, not null

Since:

0.7

setValueSuppressionStrategy

public void setValueSuppressionStrategy(ValueSuppressionStrategy valueSuppressionStrategy)

Sets the ValueSuppressionStrategy. This is used to control the expression of attributes with certain values.

Parameters:

valueSuppressionStrategy - ValueSuppressionStrategy, not null

Since:

0.7

getIdMappingStrategy

public IdStoringStrategy getIdMappingStrategy()

Gets the strategy used to manage storage and retrieval of id's.

Returns:

Returns the idStoringStrategy, not null

Since:

0.7

getOptions

public Options getOptions()

Gets the current Options.

Returns:

Options that currently apply or null if there are no current options.

Since:

0.7

pushOptions

public void pushOptions(Options options)

Pushes the given Options onto the stack.

Note that code calling push should ensure that popOptions() is called once the options are no longer current. This ensures that the previous options are reinstated.

Parameters:

options - newly current Options, not null

Since:

0.7

popOptions

public void popOptions()

Pops the current options from the stack. The previously current options (if any exist) will be reinstated by this method.

Note code calling this method should have previsouly called popOptions().

Since:

0.7

getInheritedOption

public java.lang.String getInheritedOption(java.lang.String name)

Gets the value of the first option with this name. The stack of inherited options is search (starting from the current option) until an option with a non-null value for the named option is found.

Parameters:

name - the name of the option to be found

Returns:

option value or null if this value is never set

Since:

0.8