org.springframework.expression.spel.ast

## Class Indexer

- java.lang.Object
- - org.springframework.expression.spel.ast.SpelNodeImpl
  - - org.springframework.expression.spel.ast.Indexer

- All Implemented Interfaces:
    SpelNode

      public class Indexer
      extends SpelNodeImpl

  An Indexer can index into some proceeding structure to access a particular piece of it. Supported structures are: strings/collections (lists/sets)/arrays
  Since:
    3.0
  Author:
    Andy Clement, Phillip Webb

- - ### Field Summary

    - ### Fields inherited from class org.springframework.expression.spel.ast.SpelNodeImpl

      `children, pos`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `Indexer(int pos, SpelNodeImpl expr)`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `TypedValue` | `getValueInternal(ExpressionState state)`
    `protected ValueRef` | `getValueRef(ExpressionState state)`
    `boolean` | `isWritable(ExpressionState expressionState)` Determine if this expression node will support a setValue() call.
    `void` | `setValue(ExpressionState state, Object newValue)` Evaluate the expression to a node and then set the new value on that node.
    `String` | `toStringAST()`

    - ### Methods inherited from class org.springframework.expression.spel.ast.SpelNodeImpl

      `getChild, getChildCount, getEndPosition, getObjectClass, getPreviousChild, getStartPosition, getTypedValue, getValue, getValue, nextChildIs`

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### Indexer

          public Indexer(int pos,
                 SpelNodeImpl expr)

  - ### Method Detail

    - #### getValueInternal

          public TypedValue getValueInternal(ExpressionState state)
                                      throws EvaluationException

      Specified by:
        `getValueInternal` in class `SpelNodeImpl`
      Throws:
        `EvaluationException`

    - #### setValue

          public void setValue(ExpressionState state,
                      Object newValue)
                        throws EvaluationException

      Description copied from interface: `SpelNode`
      Evaluate the expression to a node and then set the new value on that node. For example, if the expression evaluates to a property reference then the property will be set to the new value.
      Specified by:
        `setValue` in interface `SpelNode`
      Overrides:
        `setValue` in class `SpelNodeImpl`
      Parameters:
        `state` - the current expression state (includes the context)
        `newValue` - the new value
      Throws:
        `EvaluationException` - if any problem occurs evaluating the expression or setting the new value

    - #### isWritable

          public boolean isWritable(ExpressionState expressionState)
                             throws SpelEvaluationException

      Description copied from interface: `SpelNode`
      Determine if this expression node will support a setValue() call.
      Specified by:
        `isWritable` in interface `SpelNode`
      Overrides:
        `isWritable` in class `SpelNodeImpl`
      Parameters:
        `expressionState` - the current expression state (includes the context)
      Returns:
        true if the expression node will allow setValue()
      Throws:
        `SpelEvaluationException`

    - #### getValueRef

          protected ValueRef getValueRef(ExpressionState state)
                                  throws EvaluationException

      Overrides:
        `getValueRef` in class `SpelNodeImpl`
      Throws:
        `EvaluationException`

    - #### toStringAST

          public String toStringAST()

      Specified by:
        `toStringAST` in interface `SpelNode`
      Specified by:
        `toStringAST` in class `SpelNodeImpl`
      Returns:
        the string form of this AST node