Package org.springframework.expression.spel.ast

Class SpelNodeImpl

java.lang.Object
org.springframework.expression.spel.ast.SpelNodeImpl
All Implemented Interfaces:
Opcodes, SpelNode
Direct Known Subclasses:
Assign, BeanReference, CompoundExpression, ConstructorReference, Elvis, FunctionReference, Identifier, Indexer, InlineList, InlineMap, Literal, MethodReference, Operator, OperatorNot, Projection, PropertyOrFieldReference, QualifiedIdentifier, Selection, Ternary, TypeReference, VariableReference
public abstract class SpelNodeImpl extends Object implements SpelNode, Opcodes
The common supertype of all AST nodes in a parsed Spring Expression Language format expression.
Since:
3.0
Author:
Andy Clement, Juergen Hoeller

  • Field Details

    • children

      protected SpelNodeImpl[] children

    • exitTypeDescriptor

      @Nullable protected volatile String exitTypeDescriptor
      Indicates the type descriptor for the result of this expression node. This is set as soon as it is known. For a literal node it is known immediately. For a property access or method invocation it is known after one evaluation of that node.

      The descriptor is like the bytecode form but is slightly easier to work with. It does not include the trailing semicolon (for non array reference types). Some examples: Ljava/lang/String, I, [I

  • Constructor Details

    • SpelNodeImpl

      public SpelNodeImpl(int startPos, int endPos, SpelNodeImpl... operands)

  • Method Details

    • nextChildIs

      protected boolean nextChildIs(Class<?>... classes)
      Return true if the next child is one of the specified classes.

    • getValue

      @Nullable public final Object getValue(ExpressionState expressionState) throws EvaluationException
      Description copied from interface: SpelNode
      Evaluate the expression node in the context of the supplied expression state and return the value.
      Specified by:
      getValue in interface SpelNode
      Parameters:
      expressionState - the current expression state (includes the context)
      Returns:
      the value of this node evaluated against the specified state
      Throws:
      EvaluationException

    • getTypedValue

      public final TypedValue getTypedValue(ExpressionState expressionState) throws EvaluationException
      Description copied from interface: SpelNode
      Evaluate the expression node in the context of the supplied expression state and return the typed value.
      Specified by:
      getTypedValue in interface SpelNode
      Parameters:
      expressionState - the current expression state (includes the context)
      Returns:
      the type value of this node evaluated against the specified state
      Throws:
      EvaluationException

    • isWritable

      public boolean isWritable(ExpressionState expressionState) throws EvaluationException
      Description copied from interface: SpelNode
      Determine if this expression node will support a setValue() call.
      Specified by:
      isWritable in interface SpelNode
      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

      public void setValue(ExpressionState expressionState, @Nullable 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
      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

    • getChild

      public SpelNode getChild(int index)
      Description copied from interface: SpelNode
      Helper method that returns a SpelNode rather than an Antlr Tree node.
      Specified by:
      getChild in interface SpelNode
      Returns:
      the child node cast to a SpelNode

    • getChildCount

      public int getChildCount()
      Description copied from interface: SpelNode
      Return the number of children under this node.
      Specified by:
      getChildCount in interface SpelNode
      Returns:
      the child count

    • getObjectClass

      @Nullable public Class<?> getObjectClass(@Nullable Object obj)
      Description copied from interface: SpelNode
      Determine the class of the object passed in, unless it is already a class object.
      Specified by:
      getObjectClass in interface SpelNode
      Parameters:
      obj - 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

      public int getStartPosition()
      Description copied from interface: SpelNode
      Return the start position of this AST node in the expression string.
      Specified by:
      getStartPosition in interface SpelNode
      Returns:
      the start position

    • getEndPosition

      public int getEndPosition()
      Description copied from interface: SpelNode
      Return the end position of this AST node in the expression string.
      Specified by:
      getEndPosition in interface SpelNode
      Returns:
      the end position

    • isCompilable

      public boolean isCompilable()
      Check whether a node can be compiled to bytecode. The reasoning in each node may be different but will typically involve checking whether the exit type descriptor of the node is known and any relevant child nodes are compilable.
      Returns:
      true if this node can be compiled to bytecode

    • generateCode

      public void generateCode(MethodVisitor mv, CodeFlow cf)
      Generate the bytecode for this node into the supplied visitor. Context info about the current expression being compiled is available in the codeflow object, e.g. including information about the type of the object currently on the stack.
      Parameters:
      mv - the ASM MethodVisitor into which code should be generated
      cf - a context object with info about what is on the stack

    • getExitDescriptor

      @Nullable public String getExitDescriptor()

    • getValue

      @Nullable protected final <T> T getValue(ExpressionState state, Class<T> desiredReturnType) throws EvaluationException
      Throws:
      EvaluationException

    • getValueRef

      protected ValueRef getValueRef(ExpressionState state) throws EvaluationException
      Throws:
      EvaluationException

    • getValueInternal

      public abstract TypedValue getValueInternal(ExpressionState expressionState) throws EvaluationException
      Throws:
      EvaluationException

    • generateCodeForArguments

      protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Member member, SpelNodeImpl[] arguments)
      Generate code that handles building the argument values for the specified method. This method will take account of whether the invoked method is a varargs method and if it is then the argument values will be appropriately packaged into an array.
      Parameters:
      mv - the method visitor where code should be generated
      cf - the current codeflow
      member - the method or constructor for which arguments are being setup
      arguments - the expression nodes for the expression supplied argument values

    • generateCodeForArgument

      protected static void generateCodeForArgument(MethodVisitor mv, CodeFlow cf, SpelNodeImpl argument, String paramDesc)
      Ask an argument to generate its bytecode and then follow it up with any boxing/unboxing/checkcasting to ensure it matches the expected parameter descriptor.