io.cdap.wrangler.expression

Class ELContext

java.lang.Object

io.cdap.wrangler.expression.ELContext

All Implemented Interfaces:

org.apache.commons.jexl3.JexlContext

public class ELContext
extends Object
implements org.apache.commons.jexl3.JexlContext

Manages variables which can be referenced in a JEXL expression.

JEXL variable names in their simplest form are 'java-like' identifiers. JEXL also considers 'ant' inspired variables expressions as valid. For instance, the expression 'x.y.z' is an 'antish' variable and will be resolved as a whole by the context, i.e. using the key "x.y.z". This proves to be useful to solve "fully qualified class names".

Note that JEXL may use '$jexl' and '$ujexl' variables for internal purpose; setting or getting those variables may lead to unexpected results unless specified otherwise.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ELContext.Context Context object passed to every expression evaluation.

Nested classes/interfaces inherited from interface org.apache.commons.jexl3.JexlContext

org.apache.commons.jexl3.JexlContext.NamespaceFunctor, org.apache.commons.jexl3.JexlContext.NamespaceResolver, org.apache.commons.jexl3.JexlContext.ThreadLocal

Constructor Summary

Constructors

Constructor and Description
ELContext() No-op constructors that does nothing but create a instance of context.
ELContext(ExecutorContext context) Constructor that extracts the ExecutorContext internals and turns them into variables.
ELContext(ExecutorContext context, EL el, Row row) Sets the context for EL, includes the required variables in expression, 'this' and 'ctx'.
ELContext(Map<String,Object> values) This constructor provides the pre-defined values for JEXL expression.
ELContext(String name, Object object) This constructor sets the expression context with a variable.

Method Summary

Modifier and Type	Method and Description
ELContext	add(String name, Object value) d Sets a variable with the value.
Object	get(String name) Returns the object associated with the name if found, else it's null.
boolean	has(String name) Checks if a variable exists in the context.
void	set(String name, Object value) Sets a variable with the value.

Methods inherited from class java.lang.Object

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

Constructor Detail

ELContext

public ELContext()

No-op constructors that does nothing but create a instance of context.

ELContext

public ELContext(ExecutorContext context)

Constructor that extracts the ExecutorContext internals and turns them into variables. This method extracts the transient variables, runtime arguments, environment it's running in and the context in which it is running as identifiers that can be used within JEXL expression.

Parameters:

context - to be examined to be extracted into JEXL expression variables.

ELContext

public ELContext(ExecutorContext context,
                 EL el,
                 Row row)

Sets the context for EL, includes the required variables in expression, 'this' and 'ctx'.

Parameters:

context - to be examined to be extracted into JEXL expression variables.

el - the expression.

row - the row for 'this'.

ELContext

public ELContext(String name,
                 Object object)

This constructor sets the expression context with a variable.

Parameters:

name - of the variable.

object - the object associated with the variable.

ELContext

public ELContext(Map<String,Object> values)

This constructor provides the pre-defined values for JEXL expression.

Parameters:

values - map of values.

Method Detail

get

public Object get(String name)

Returns the object associated with the name if found, else it's null.

Specified by:

get in interface org.apache.commons.jexl3.JexlContext

Parameters:

name - of the variable.

Returns:

value if found, null otherwise.

set

public void set(String name,
                Object value)

Sets a variable with the value.

Specified by:

set in interface org.apache.commons.jexl3.JexlContext

Parameters:

name - of the variable.

value - of the variable.

add

public ELContext add(String name,
                     Object value)

d Sets a variable with the value.

Parameters:

name - of the variable.

value - of the variable.

Returns:

'this' context.

has

public boolean has(String name)

Checks if a variable exists in the context.

Specified by:

has in interface org.apache.commons.jexl3.JexlContext

Parameters:

name - of the variable to be checked.

Returns:

true if found, false otherwise.