Package org.springframework.expression.spel

Class CodeFlow

java.lang.Object
org.springframework.expression.spel.CodeFlow
All Implemented Interfaces:
Opcodes
public class CodeFlow extends Object implements Opcodes
Manages the class being generated by the compilation process.

Records intermediate compilation state as the bytecode is generated.

Also includes various bytecode generation helper functions.

Since:
4.1
Author:
Andy Clement, Juergen Hoeller, Sam Brannen

  • Constructor Details

    • CodeFlow

      public CodeFlow(String className, ClassWriter classWriter)
      Construct a new CodeFlow for the given class.
      Parameters:
      className - the name of the class
      classWriter - the corresponding ASM ClassWriter

  • Method Details

    • loadTarget

      public void loadTarget(MethodVisitor mv)
      Push the byte code to load the target (i.e. what was passed as the first argument to CompiledExpression.getValue(target, context))
      Parameters:
      mv - the method visitor into which the load instruction should be inserted

    • loadEvaluationContext

      public void loadEvaluationContext(MethodVisitor mv)
      Push the bytecode to load the EvaluationContext (the second parameter passed to the compiled expression method).
      Parameters:
      mv - the method visitor into which the load instruction should be inserted
      Since:
      4.3.4

    • pushDescriptor

      public void pushDescriptor(@Nullable String descriptor)
      Record the descriptor for the most recently evaluated expression element.
      Parameters:
      descriptor - type descriptor for most recently evaluated element

    • enterCompilationScope

      public void enterCompilationScope()
      Enter a new compilation scope, usually due to nested expression evaluation. For example when the arguments for a method invocation expression are being evaluated, each argument will be evaluated in a new scope.

    • exitCompilationScope

      public void exitCompilationScope()
      Exit a compilation scope, usually after a nested expression has been evaluated. For example after an argument for a method invocation has been evaluated this method returns us to the previous (outer) scope.

    • lastDescriptor

      @Nullable public String lastDescriptor()
      Return the descriptor for the item currently on top of the stack (in the current scope).

    • unboxBooleanIfNecessary

      public void unboxBooleanIfNecessary(MethodVisitor mv)
      If the codeflow shows the last expression evaluated to java.lang.Boolean then insert the necessary instructions to unbox that to a boolean primitive.
      Parameters:
      mv - the method visitor into which new instructions should be inserted

    • finish

      public void finish()
      Called after the main expression evaluation method has been generated, this method will call back any registered FieldAdders or ClinitAdders to add any extra information to the class representing the compiled expression.

    • registerNewField

      public void registerNewField(CodeFlow.FieldAdder fieldAdder)
      Register a FieldAdder which will add a new field to the generated class to support the code produced by an AST node's primary generateCode() method.

    • registerNewClinit

      public void registerNewClinit(CodeFlow.ClinitAdder clinitAdder)
      Register a ClinitAdder which will add code to the static initializer in the generated class to support the code produced by an AST node's primary generateCode() method.

    • nextFieldId

      public int nextFieldId()

    • nextFreeVariableId

      public int nextFreeVariableId()

    • getClassName

      public String getClassName()

    • generateCodeForArgument

      public void generateCodeForArgument(MethodVisitor methodVisitor, SpelNode argument, Class<?> requiredType)
      Generate bytecode that loads the supplied argument onto the stack.

      Delegates to generateCodeForArgument(MethodVisitor, SpelNode, String) with the descriptor for the supplied requiredType.

      This method also performs any boxing, unboxing, or check-casting necessary to ensure that the type of the argument on the stack matches the supplied requiredType.

      Use this method when a node in the AST will be used as an argument for a constructor or method invocation. For example, if you wish to invoke a method with an indexNode that must be of type int for the actual method invocation within bytecode, you would call codeFlow.generateCodeForArgument(methodVisitor, indexNode, int.class).

      Parameters:
      methodVisitor - the ASM MethodVisitor into which code should be generated
      argument - a SpelNode that represents an argument to a method or constructor
      requiredType - the required type for the argument when invoking the corresponding constructor or method
      Since:
      6.2
      See Also:

    • generateCodeForArgument

      public void generateCodeForArgument(MethodVisitor methodVisitor, SpelNode argument, String requiredTypeDesc)
      Generate bytecode that loads the supplied argument onto the stack.

      This method also performs any boxing, unboxing, or check-casting necessary to ensure that the type of the argument on the stack matches the supplied requiredTypeDesc.

      Use this method when a node in the AST will be used as an argument for a constructor or method invocation. For example, if you wish to invoke a method with an indexNode that must be of type int for the actual method invocation within bytecode, you would call codeFlow.generateCodeForArgument(methodVisitor, indexNode, "I").

      Parameters:
      methodVisitor - the ASM MethodVisitor into which code should be generated
      argument - a SpelNode that represents an argument to a method or constructor
      requiredTypeDesc - a descriptor for the required type for the argument when invoking the corresponding constructor or method
      Since:
      6.2
      See Also:

    • insertUnboxInsns

      public static void insertUnboxInsns(MethodVisitor mv, char ch, @Nullable String stackDescriptor)
      Insert any necessary cast and value call to convert from a boxed type to a primitive value.
      Parameters:
      mv - the method visitor into which instructions should be inserted
      ch - the primitive type desired as output
      stackDescriptor - the descriptor of the type on top of the stack

    • insertUnboxNumberInsns

      public static void insertUnboxNumberInsns(MethodVisitor mv, char targetDescriptor, @Nullable String stackDescriptor)
      For numbers, use the appropriate method on the number to convert it to the primitive type requested.
      Parameters:
      mv - the method visitor into which instructions should be inserted
      targetDescriptor - the primitive type desired as output
      stackDescriptor - the descriptor of the type on top of the stack

    • insertAnyNecessaryTypeConversionBytecodes

      public static void insertAnyNecessaryTypeConversionBytecodes(MethodVisitor mv, char targetDescriptor, String stackDescriptor)
      Insert any necessary numeric conversion bytecodes based upon what is on the stack and the desired target type.
      Parameters:
      mv - the method visitor into which instructions should be placed
      targetDescriptor - the (primitive) descriptor of the target type
      stackDescriptor - the descriptor of the operand on top of the stack

    • findPublicDeclaringClass

      @Nullable public static Class<?> findPublicDeclaringClass(Method method)
      Find the first public class or interface in the method's class hierarchy that declares the supplied method.

      Sometimes the reflective method discovery logic finds a suitable method that can easily be called via reflection but cannot be called from generated code when compiling the expression because of visibility restrictions. For example, if a non-public class overrides toString(), this method will traverse up the type hierarchy to find the first public type that declares the method (if there is one). For toString(), it may traverse as far as Object.

      Parameters:
      method - the method to process
      Returns:
      the public class or interface that declares the method, or null if no such public type could be found
      Since:
      6.2

    • createSignatureDescriptor

      public static String createSignatureDescriptor(Method method)
      Create the JVM signature descriptor for a method. This consists of the descriptors for the method parameters surrounded with parentheses, followed by the descriptor for the return type. Note the descriptors here are JVM descriptors, unlike the other descriptor forms the compiler is using which do not include the trailing semicolon.
      Parameters:
      method - the method
      Returns:
      a String signature descriptor (e.g. "(ILjava/lang/String;)V")

    • createSignatureDescriptor

      public static String createSignatureDescriptor(Constructor<?> ctor)
      Create the JVM signature descriptor for a constructor. This consists of the descriptors for the constructor parameters surrounded with parentheses, followed by the descriptor for the return type, which is always "V". Note the descriptors here are JVM descriptors, unlike the other descriptor forms the compiler is using which do not include the trailing semicolon.
      Parameters:
      ctor - the constructor
      Returns:
      a String signature descriptor (e.g. "(ILjava/lang/String;)V")

    • toJvmDescriptor

      public static String toJvmDescriptor(Class<?> clazz)
      Determine the JVM descriptor for a specified class. Unlike the other descriptors used in the compilation process, this is the one the JVM wants, so this one includes any necessary trailing semicolon (e.g. Ljava/lang/String; rather than Ljava/lang/String)
      Parameters:
      clazz - a class
      Returns:
      the JVM descriptor for the class

    • toDescriptorFromObject

      public static String toDescriptorFromObject(@Nullable Object value)
      Determine the descriptor for an object instance (or null).
      Parameters:
      value - an object (possibly null)
      Returns:
      the type descriptor for the object (descriptor is "Ljava/lang/Object" for null value)

    • isBooleanCompatible

      @Contract("null -> false") public static boolean isBooleanCompatible(@Nullable String descriptor)
      Determine whether the descriptor is for a boolean primitive or boolean reference type.
      Parameters:
      descriptor - type descriptor
      Returns:
      true if the descriptor is boolean compatible

    • isPrimitive

      @Contract("null -> false") public static boolean isPrimitive(@Nullable String descriptor)
      Determine whether the descriptor is for a primitive type or void.
      Parameters:
      descriptor - type descriptor
      Returns:
      true if a primitive type or void

    • isPrimitiveArray

      @Contract("null -> false") public static boolean isPrimitiveArray(@Nullable String descriptor)
      Determine whether the descriptor is for a primitive array (e.g. "[[I").
      Parameters:
      descriptor - the descriptor for a possible primitive array
      Returns:
      true if the descriptor a primitive array

    • areBoxingCompatible

      public static boolean areBoxingCompatible(String desc1, String desc2)
      Determine whether boxing/unboxing can get from one type to the other.

      Assumes at least one of the types is in boxed form (i.e. single char descriptor).

      Returns:
      true if it is possible to get (via boxing) from one descriptor to the other

    • isPrimitiveOrUnboxableSupportedNumberOrBoolean

      @Contract("null -> false") public static boolean isPrimitiveOrUnboxableSupportedNumberOrBoolean(@Nullable String descriptor)
      Determine if the supplied descriptor is for a supported number type or boolean. The compilation process only (currently) supports certain number types. These are double, float, long and int.
      Parameters:
      descriptor - the descriptor for a type
      Returns:
      true if the descriptor is for a supported numeric type or boolean

    • isPrimitiveOrUnboxableSupportedNumber

      @Contract("null -> false") public static boolean isPrimitiveOrUnboxableSupportedNumber(@Nullable String descriptor)
      Determine if the supplied descriptor is for a supported number. The compilation process only (currently) supports certain number types. These are double, float, long and int.
      Parameters:
      descriptor - the descriptor for a type
      Returns:
      true if the descriptor is for a supported numeric type

    • isIntegerForNumericOp

      @Contract("null -> false") public static boolean isIntegerForNumericOp(Number number)
      Determine whether the given number is to be considered as an integer for the purposes of a numeric operation at the bytecode level.
      Parameters:
      number - the number to check
      Returns:
      true if it is an Integer, Short or Byte

    • toPrimitiveTargetDesc

      public static char toPrimitiveTargetDesc(String descriptor)
      Convert a type descriptor to the single character primitive descriptor.
      Parameters:
      descriptor - a descriptor for a type that should have a primitive representation
      Returns:
      the single character descriptor for a primitive input descriptor

    • insertCheckCast

      public static void insertCheckCast(MethodVisitor mv, @Nullable String descriptor)
      Insert the appropriate CHECKCAST instruction for the supplied descriptor.
      Parameters:
      mv - the method visitor into which the instruction should be inserted
      descriptor - the descriptor of the type to cast to

    • insertBoxIfNecessary

      public static void insertBoxIfNecessary(MethodVisitor mv, @Nullable String descriptor)
      Determine the appropriate boxing instruction for a specific type (if it needs boxing) and insert the instruction into the supplied visitor.
      Parameters:
      mv - the method visitor for the new instructions
      descriptor - the descriptor of a type that may or may not need boxing

    • insertBoxIfNecessary

      public static void insertBoxIfNecessary(MethodVisitor mv, char ch)
      Determine the appropriate boxing instruction for a specific type (if it needs boxing) and insert the instruction into the supplied visitor.
      Parameters:
      mv - the method visitor for the new instructions
      ch - the descriptor of the type that might need boxing

    • toDescriptor

      public static String toDescriptor(Class<?> type)
      Deduce the descriptor for a type. Descriptors are like JVM type names but missing the trailing ';' so for Object the descriptor is "Ljava/lang/Object" for int it is "I".
      Parameters:
      type - the type (may be primitive) for which to determine the descriptor
      Returns:
      the descriptor

    • toParamDescriptors

      public static String[] toParamDescriptors(Method method)
      Create an array of descriptors representing the parameter types for the supplied method. Returns a zero sized array if there are no parameters.
      Parameters:
      method - a Method
      Returns:
      a String array of descriptors, one entry for each method parameter

    • toParamDescriptors

      public static String[] toParamDescriptors(Constructor<?> ctor)
      Create an array of descriptors representing the parameter types for the supplied constructor. Returns a zero sized array if there are no parameters.
      Parameters:
      ctor - a Constructor
      Returns:
      a String array of descriptors, one entry for each constructor parameter

    • toDescriptors

      public static String[] toDescriptors(Class<?>[] types)
      Create an array of descriptors from an array of classes.
      Parameters:
      types - the input array of classes
      Returns:
      an array of descriptors

    • insertOptimalLoad

      public static void insertOptimalLoad(MethodVisitor mv, int value)
      Create the optimal instruction for loading a number on the stack.
      Parameters:
      mv - where to insert the bytecode
      value - the value to be loaded

    • insertArrayStore

      public static void insertArrayStore(MethodVisitor mv, String arrayComponentType)
      Produce appropriate bytecode to store a stack item in an array.

      The instruction to use varies depending on whether the type is a primitive or reference type.

      Parameters:
      mv - where to insert the bytecode
      arrayComponentType - the component type of the array

    • arrayCodeFor

      public static int arrayCodeFor(String arrayType)
      Determine the appropriate T tag to use for the NEWARRAY bytecode.
      Parameters:
      arrayType - the array primitive component type
      Returns:
      the T tag to use for NEWARRAY

    • isReferenceTypeArray

      public static boolean isReferenceTypeArray(String arrayType)
      Return if the supplied array type has a core component reference type.

    • insertNewArrayCode

      public static void insertNewArrayCode(MethodVisitor mv, int size, String arrayType)
      Produce the correct bytecode to build an array. The opcode to use and the signature to pass along with the opcode can vary depending on the signature of the array type.
      Parameters:
      mv - the method visitor into which code should be inserted
      size - the size of the array
      arrayType - the type of the array

    • insertNumericUnboxOrPrimitiveTypeCoercion

      public static void insertNumericUnboxOrPrimitiveTypeCoercion(MethodVisitor mv, @Nullable String stackDescriptor, char targetDescriptor)
      For use in mathematical operators, handles converting from a (possibly boxed) number on the stack to a primitive numeric type.

      For example, from an Integer to a double, just need to call 'Number.doubleValue()' but from an int to a double, need to use the bytecode 'i2d'.

      Parameters:
      mv - the method visitor when instructions should be appended
      stackDescriptor - a descriptor of the operand on the stack
      targetDescriptor - a primitive type descriptor

    • toBoxedDescriptor

      public static String toBoxedDescriptor(String primitiveDescriptor)