org.apache.commons.jexl3

## Interface JexlContext

- All Known Subinterfaces:
    JexlContext.ThreadLocal
  All Known Implementing Classes:
    MapContext, ObjectContext

      public interface 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".

  The interpreter variable resolution algorithm will try the different sequences of identifiers till it finds one that exists in the context; if "x" is an object known in the context (JexlContext.has("x") returns true), "x.y" will not be looked up in the context but will most likely refer to "x.getY()".

  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.

  Since:
    1.0

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Interface and Description
    --- | ---
    `static interface` | `JexlContext.NamespaceFunctor` Namespace type that allows creating an instance to delegate namespace methods calls to.
    `static interface` | `JexlContext.NamespaceResolver` This interface declares how to resolve a namespace from its name; it is used by the interpreter during evalutation.
    `static interface` | `JexlContext.ThreadLocal` A marker interface that indicates the interpreter to put this context in the JexlEngine thread local context instance during evaluation.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Object` | `get(String name)` Gets the value of a variable.
    `boolean` | `has(String name)` Checks whether a variable is defined in this context.
    `void` | `set(String name, Object value)` Sets the value of a variable.

- - ### Method Detail

    - #### get

          Object get(String name)

      Gets the value of a variable.
      Parameters:
        `name` - the variable's name
      Returns:
        the value

    - #### set

          void set(String name,
                 Object value)

      Sets the value of a variable.
      Parameters:
        `name` - the variable's name
        `value` - the variable's value

    - #### has

          boolean has(String name)

      Checks whether a variable is defined in this context.

      A variable may be defined with a null value; this method checks whether the value is null or if the variable is undefined.

      Parameters:
        `name` - the variable's name
      Returns:
        true if it exists, false otherwise

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