## org.springframework.expression.spel
Interface SpelNode

All Known Implementing Classes:
  Assign, BeanReference, BooleanLiteral, CompoundExpression, ConstructorReference, Elvis, FloatLiteral, FunctionReference, Identifier, Indexer, InlineList, IntLiteral, Literal, LongLiteral, MethodReference, NullLiteral, OpAnd, OpDivide, OpEQ, Operator, OperatorBetween, OperatorInstanceof, OperatorMatches, OperatorNot, OperatorPower, OpGE, OpGT, OpLE, OpLT, OpMinus, OpModulus, OpMultiply, OpNE, OpOr, OpPlus, Projection, PropertyOrFieldReference, QualifiedIdentifier, RealLiteral, Selection, SpelNodeImpl, StringLiteral, Ternary, TypeReference, VariableReference

    public interface SpelNode

Represents a node in the Ast for a parsed expression.

Since:
  3.0
Author:
  Andy Clement

Method Summary
`SpelNode` `getChild(int index)` Helper method that returns a SpelNode rather than an Antlr Tree node.
`int` `getChildCount()`
`int` `getEndPosition()`
`Class<?>` `getObjectClass(Object obj)` Determine the class of the object passed in, unless it is already a class object.
`int` `getStartPosition()`
`TypedValue` `getTypedValue(ExpressionState expressionState)` Evaluate the expression node in the context of the supplied expression state and return the typed value.
`Object` `getValue(ExpressionState expressionState)` Evaluate the expression node in the context of the supplied expression state and return the value.
`boolean` `isWritable(ExpressionState expressionState)` Determine if this expression node will support a setValue() call.
`void` `setValue(ExpressionState expressionState, Object newValue)` Evaluate the expression to a node and then set the new value on that node.
`String` `toStringAST()`

Method Detail

### getValue

    Object getValue(ExpressionState expressionState)
                    throws EvaluationException

  Evaluate the expression node in the context of the supplied expression state and return the value.

  Parameters:
    `expressionState` - the current expression state (includes the context)
  Returns:
    the value of this node evaluated against the specified state
  Throws:
    `EvaluationException`

### getTypedValue

    TypedValue getTypedValue(ExpressionState expressionState)
                             throws EvaluationException

  Evaluate the expression node in the context of the supplied expression state and return the typed value.

  Parameters:
    `expressionState` - the current expression state (includes the context)
  Returns:
    the type value of this node evaluated against the specified state
  Throws:
    `EvaluationException`

### isWritable

    boolean isWritable(ExpressionState expressionState)
                       throws EvaluationException

  Determine if this expression node will support a setValue() call.

  Parameters:
    `expressionState` - the current expression state (includes the context)
  Returns:
    true if the expression node will allow setValue()
  Throws:
    `EvaluationException` - if something went wrong trying to determine if the node supports writing

### setValue

    void setValue(ExpressionState expressionState,
                  Object newValue)
                  throws EvaluationException

  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.

  Parameters:
    `expressionState` - 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

### toStringAST

    String toStringAST()

  Returns:
    the string form of this AST node

### getChildCount

    int getChildCount()

  Returns:
    the number of children under this node

### getChild

    SpelNode getChild(int index)

  Helper method that returns a SpelNode rather than an Antlr Tree node.

  Returns:
    the child node cast to a SpelNode

### getObjectClass

    Class<?> getObjectClass(Object obj)

  Determine the class of the object passed in, unless it is already a class object.

  Parameters:
    `o` - the object that the caller wants the class of
  Returns:
    the class of the object if it is not already a class object, or null if the object is null

### getStartPosition

    int getStartPosition()

  Returns:
    the start position of this Ast node in the expression string

### getEndPosition

    int getEndPosition()

  Returns:
    the end position of this Ast node in the expression string