Class MethodGen

java.lang.Object
org.apache.bcel.classfile.AccessFlags
org.apache.bcel.generic.FieldGenOrMethodGen
org.apache.bcel.generic.MethodGen
All Implemented Interfaces:
Cloneable, NamedAndTyped
public class MethodGen extends FieldGenOrMethodGen
Template class for building up a method. This is done by defining exception handlers, adding thrown exceptions, local variables and attributes, whereas the 'LocalVariableTable' and 'LineNumberTable' attributes will be set automatically for the code. Use stripAttributes() if you don't like this. While generating code it may be necessary to insert NOP operations. You can use the 'removeNOPs' method to get rid off them. The resulting method object can be obtained via the 'getMethod()' method.
See Also:

  • Constructor Details

    • MethodGen

      public MethodGen(int accessFlags, Type returnType, Type[] argTypes, String[] argNames, String methodName, String className, InstructionList il, ConstantPoolGen cp)
      Declare method. If the method is non-static the constructor automatically declares a local variable '$this' in slot 0. The actual code is contained in the 'il' parameter, which may further manipulated by the user. But they must take care not to remove any instruction (handles) that are still referenced from this object. For example one may not add a local variable and later remove the instructions it refers to without causing havoc. It is safe however if you remove that local variable, too.
      Parameters:
      accessFlags - access qualifiers.
      returnType - method type.
      argTypes - argument types.
      argNames - argument names (if this is null, default names will be provided for them).
      methodName - name of method.
      className - class name containing this method (may be null, if you don't care).
      il - instruction list associated with this method, may be null only for abstract or native methods.
      cp - constant pool.

    • MethodGen

      public MethodGen(Method method, String className, ConstantPoolGen cp)
      Instantiate from existing method.
      Parameters:
      method - method.
      className - class name containing this method.
      cp - constant pool.

  • Method Details

    • getComparator

      public static BCELComparator<FieldGenOrMethodGen> getComparator()
      Gets the comparison strategy object.
      Returns:
      Comparison strategy object.

    • getMaxStack

      public static int getMaxStack(ConstantPoolGen cp, InstructionList il, CodeExceptionGen[] et)
      Gets the maximum stack depth of an instruction list by performing control flow analysis.
      Parameters:
      cp - The constant pool generator.
      il - The instruction list.
      et - The exception handlers.
      Returns:
      maximum stack depth used by method.

    • setComparator

      public static void setComparator(BCELComparator<FieldGenOrMethodGen> comparator)
      Sets the comparison strategy object.
      Parameters:
      comparator - Comparison strategy object.

    • addAnnotationsAsAttribute

      public void addAnnotationsAsAttribute(ConstantPoolGen cp)
      Adds annotations as an attribute.
      Parameters:
      cp - The constant pool generator.
      Since:
      6.0

    • addCodeAttribute

      public void addCodeAttribute(Attribute a)
      Add an attribute to the code. Currently, the JVM knows about the LineNumberTable, LocalVariableTable and StackMap attributes, where the former two will be generated automatically and the latter is used for the MIDP only. Other attributes will be ignored by the JVM but do no harm.
      Parameters:
      a - attribute to be added.

    • addException

      public void addException(String className)
      Add an exception possibly thrown by this method.
      Parameters:
      className - (fully qualified) name of exception.

    • addExceptionHandler

      public CodeExceptionGen addExceptionHandler(InstructionHandle startPc, InstructionHandle endPc, InstructionHandle handlerPc, ObjectType catchType)
      Add an exception handler, that is, specify region where a handler is active and an instruction where the actual handling is done.
      Parameters:
      startPc - Start of region (inclusive).
      endPc - End of region (inclusive).
      handlerPc - Where handling is done.
      catchType - class type of handled exception or null if any exception is handled.
      Returns:
      new exception handler object.

    • addLineNumber

      public LineNumberGen addLineNumber(InstructionHandle ih, int srcLine)
      Give an instruction a line number corresponding to the source code line.
      Parameters:
      ih - instruction to tag.
      srcLine - The source line number.
      Returns:
      new line number object.
      See Also:

    • addLocalVariable

      public LocalVariableGen addLocalVariable(String name, Type type, InstructionHandle start, InstructionHandle end)
      Adds a local variable to this method and assigns an index automatically.
      Parameters:
      name - variable name.
      type - variable type.
      start - from where the variable is valid, if this is null, it is valid from the start.
      end - until where the variable is valid, if this is null, it is valid to the end.
      Returns:
      new local variable object.
      See Also:

    • addLocalVariable

      public LocalVariableGen addLocalVariable(String name, Type type, int slot, InstructionHandle start, InstructionHandle end)
      Adds a local variable to this method.
      Parameters:
      name - variable name.
      type - variable type.
      slot - The index of the local variable, if type is long or double, the next available index is slot+2.
      start - from where the variable is valid.
      end - until where the variable is valid.
      Returns:
      new local variable object.
      See Also:

    • addLocalVariable

      public LocalVariableGen addLocalVariable(String name, Type type, int slot, InstructionHandle start, InstructionHandle end, int origIndex)
      Adds a local variable to this method.
      Parameters:
      name - variable name.
      type - variable type.
      slot - The index of the local variable, if type is long or double, the next available index is slot+2.
      start - from where the variable is valid.
      end - until where the variable is valid.
      origIndex - The index of the local variable prior to any modifications.
      Returns:
      new local variable object.
      See Also:

    • addObserver

      public void addObserver(MethodObserver o)
      Add observer for this object.
      Parameters:
      o - The observer to add.

    • addParameterAnnotation

      public void addParameterAnnotation(int parameterIndex, AnnotationEntryGen annotation)
      Adds a parameter annotation.
      Parameters:
      parameterIndex - The parameter index.
      annotation - The annotation.

    • addParameterAnnotationsAsAttribute

      public void addParameterAnnotationsAsAttribute(ConstantPoolGen cp)
      Adds parameter annotations as an attribute.
      Parameters:
      cp - The constant pool generator.
      Since:
      6.0

    • copy

      public MethodGen copy(String className, ConstantPoolGen cp)
      Creates a deep copy of this method.
      Parameters:
      className - The class name.
      cp - The constant pool generator.
      Returns:
      deep copy of this method.

    • equals

      public boolean equals(Object obj)
      Return value as defined by given BCELComparator strategy. By default two MethodGen objects are said to be equal when their names and signatures are equal.
      Overrides:
      equals in class Object
      See Also:

    • getAnnotationsOnParameter

      public List<AnnotationEntryGen> getAnnotationsOnParameter(int i)
      Gets a list of AnnotationGen objects representing parameter annotations.
      Parameters:
      i - The parameter index.
      Returns:
      list of AnnotationGen objects.
      Since:
      6.0

    • getArgumentName

      public String getArgumentName(int i)
      Gets the argument name at the specified index.
      Parameters:
      i - The argument index.
      Returns:
      The argument name.

    • getArgumentNames

      public String[] getArgumentNames()
      Gets all argument names.
      Returns:
      array of argument names.

    • getArgumentType

      public Type getArgumentType(int i)
      Gets the argument type at the specified index.
      Parameters:
      i - The argument index.
      Returns:
      The argument type.

    • getArgumentTypes

      public Type[] getArgumentTypes()
      Gets all argument types.
      Returns:
      array of argument types.

    • getClassName

      public String getClassName()
      Gets the class that contains this method.
      Returns:
      class that contains this method.

    • getCodeAttributes

      public Attribute[] getCodeAttributes()
      Gets all attributes of this method.
      Returns:
      all attributes of this method.

    • getExceptionHandlers

      public CodeExceptionGen[] getExceptionHandlers()
      Gets an array of declared exception handlers.
      Returns:
      array of declared exception handlers.

    • getExceptions

      public String[] getExceptions()
      Gets an array of thrown exceptions.
      Returns:
      array of thrown exceptions.

    • getInstructionList

      public InstructionList getInstructionList()
      Gets the instruction list.
      Returns:
      The instruction list.

    • getLineNumbers

      public LineNumberGen[] getLineNumbers()
      Gets an array of line numbers.
      Returns:
      array of line numbers.

    • getLineNumberTable

      public LineNumberTable getLineNumberTable(ConstantPoolGen cp)
      Gets the 'LineNumberTable' attribute of all the local variables of this method.
      Parameters:
      cp - The constant pool generator.
      Returns:
      'LineNumberTable' attribute of all the local variables of this method.

    • getLocalVariables

      public LocalVariableGen[] getLocalVariables()
      Gets an array of declared local variables sorted by index. If the range of the variable has not been set yet, it will be set to be valid from the start to the end of the instruction list.
      Returns:
      array of declared local variables sorted by index.

    • getLocalVariableTable

      public LocalVariableTable getLocalVariableTable(ConstantPoolGen cp)
      Gets the 'LocalVariableTable' attribute of all the local variables of this method.
      Parameters:
      cp - The constant pool generator.
      Returns:
      'LocalVariableTable' attribute of all the local variables of this method.

    • getLocalVariableTypeTable

      public LocalVariableTypeTable getLocalVariableTypeTable()
      Gets the 'LocalVariableTypeTable' attribute of this method.
      Returns:
      'LocalVariableTypeTable' attribute of this method.

    • getMaxLocals

      public int getMaxLocals()
      Gets the maximum number of local variables.
      Returns:
      The maximum number of local variables.

    • getMaxStack

      public int getMaxStack()
      Gets the maximum stack size.
      Returns:
      The maximum stack size.

    • getMethod

      public Method getMethod()
      Gets method object. Never forget to call setMaxStack() or setMaxStack(max), respectively, before calling this method (the same applies for max locals).

      When initialized from an existing method, the Code header layout is preserved. Use setCompactCodeHeader(boolean) to change it.

      Returns:
      method object.
      Throws:
      ClassFormatException - Thrown if Code values do not fit the selected header layout.

    • getReturnType

      public Type getReturnType()
      Gets the return type.
      Returns:
      The return type.

    • getSignature

      public String getSignature()
      Description copied from class: FieldGenOrMethodGen
      Gets the signature of method or field.
      Specified by:
      getSignature in class FieldGenOrMethodGen
      Returns:
      signature of method/field.

    • hashCode

      public int hashCode()
      Return value as defined by given BCELComparator strategy. By default return the hash code of the method's name XOR signature.
      Overrides:
      hashCode in class Object
      See Also:

    • isCompactCodeHeader

      public boolean isCompactCodeHeader()
      Gets whether generated Code attributes use compact four-byte headers.
      Returns:
      Whether generated Code attributes use compact headers.
      Since:
      6.14.0
      See Also:

    • removeCodeAttribute

      public void removeCodeAttribute(Attribute a)
      Remove a code attribute.
      Parameters:
      a - The attribute to remove.

    • removeCodeAttributes

      public void removeCodeAttributes()
      Remove all code attributes.

    • removeException

      public void removeException(String c)
      Remove an exception.
      Parameters:
      c - The exception to remove.

    • removeExceptionHandler

      public void removeExceptionHandler(CodeExceptionGen c)
      Remove an exception handler.
      Parameters:
      c - The exception handler to remove.

    • removeExceptionHandlers

      public void removeExceptionHandlers()
      Remove all line numbers.

    • removeExceptions

      public void removeExceptions()
      Remove all exceptions.

    • removeLineNumber

      public void removeLineNumber(LineNumberGen l)
      Remove a line number.
      Parameters:
      l - The line number to remove.

    • removeLineNumbers

      public void removeLineNumbers()
      Remove all line numbers.

    • removeLocalVariable

      public void removeLocalVariable(LocalVariableGen l)
      Remove a local variable, its slot will not be reused, if you do not use addLocalVariable with an explicit index argument.
      Parameters:
      l - The local variable to remove.

    • removeLocalVariables

      public void removeLocalVariables()
      Remove all local variables.

    • removeLocalVariableTypeTable

      public void removeLocalVariableTypeTable()
      Remove the LocalVariableTypeTable

    • removeNOPs

      public void removeNOPs()
      Remove all NOPs from the instruction list (if possible) and update every object referring to them, that is, branch instructions, local variables and exception handlers.

    • removeObserver

      public void removeObserver(MethodObserver o)
      Remove observer for this object.
      Parameters:
      o - The observer to remove.

    • removeRuntimeAttributes

      public void removeRuntimeAttributes(Attribute[] attributes)
      Would prefer to make this private, but need a way to test if client is using BCEL version 6.5.0 or later that contains fix for BCEL-329.
      Parameters:
      attributes - The attributes to remove.
      Since:
      6.5.0

    • setArgumentName

      public void setArgumentName(int i, String name)
      Sets the argument name at the specified index.
      Parameters:
      i - The argument index.
      name - The argument name.

    • setArgumentNames

      public void setArgumentNames(String[] argNames)
      Sets all argument names.
      Parameters:
      argNames - The argument names.

    • setArgumentType

      public void setArgumentType(int i, Type type)
      Sets the argument type at the specified index.
      Parameters:
      i - The argument index.
      type - The argument type.

    • setArgumentTypes

      public void setArgumentTypes(Type[] argTypes)
      Sets all argument types.
      Parameters:
      argTypes - The argument types.

    • setClassName

      public void setClassName(String className)
      Sets the class name.
      Parameters:
      className - The class name.

    • setCompactCodeHeader

      public void setCompactCodeHeader(boolean compactCodeHeader)
      Sets the header layout of generated Code attributes.

      Compact headers encode max_stack, max_locals, and code_length as unsigned one-, one-, and two-byte fields, respectively, totaling 4 bytes instead of the standard 8. This changes only these field widths, not the bytecode or the remaining attribute layout. Compact headers are intended for historical class file versions 45.0 through 45.2.

      Newly created methods use standard headers by default. Methods initialized from an existing method preserve its header layout. getMethod() checks that compact headers have max_stack and max_locals from 0 through 255 and a code length of at most 65535 bytes.

      When dumping the enclosing class, JavaClass.dump(java.io.DataOutputStream) may select a different layout for consistency with the class version and its other methods. This does not change the generated Code attribute's header setting.

      Parameters:
      compactCodeHeader - Whether to generate compact four-byte Code headers (true) or standard eight-byte headers (false).
      Since:
      6.14.0
      See Also:

    • setInstructionList

      public void setInstructionList(InstructionList il)
      Sets the instruction list.
      Parameters:
      il - The instruction list.

    • setMaxLocals

      public void setMaxLocals()
      Sets the maximum number of local variables by examining the method signature, the instructions and the local variable table entries added via addLocalVariable(String, Type, InstructionHandle, InstructionHandle).

    • setMaxLocals

      public void setMaxLocals(int m)
      Sets maximum number of local variables.
      Parameters:
      m - The maximum number of local variables.

    • setMaxStack

      public void setMaxStack()
      Sets the maximum stack size by performing control flow analysis.

    • setMaxStack

      public void setMaxStack(int m)
      Sets maximum stack size for this method.
      Parameters:
      m - The maximum stack size.

    • setReturnType

      public void setReturnType(Type returnType)
      Sets the return type.
      Parameters:
      returnType - The return type.

    • stripAttributes

      public void stripAttributes(boolean flag)
      Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O.
      Parameters:
      flag - whether to strip attributes.

    • toString

      public final String toString()
      Return string representation close to declaration format, 'public static void main(String[]) throws IOException', for example.
      Overrides:
      toString in class Object
      Returns:
      String representation of the method.

    • update

      public void update()
      Call notify() method on all observers. This method is not called automatically whenever the state has changed, but has to be called by the user after they have finished editing the object.