Class MethodGen

  • All Implemented Interfaces:
    java.lang.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:
    InstructionList, Method
    • Constructor Detail

      • MethodGen

        public MethodGen​(int accessFlags,
                         Type returnType,
                         Type[] argTypes,
                         java.lang.String[] argNames,
                         java.lang.String methodName,
                         java.lang.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,
                         java.lang.String className,
                         ConstantPoolGen cp)
        Instantiate from existing method.
        Parameters:
        method - method
        className - class name containing this method
        cp - constant pool
    • Method Detail

      • 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​(java.lang.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, i.e., 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
      • addLocalVariable

        public LocalVariableGen addLocalVariable​(java.lang.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:
        LocalVariable
      • addLocalVariable

        public LocalVariableGen addLocalVariable​(java.lang.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:
        LocalVariable
      • addLocalVariable

        public LocalVariableGen addLocalVariable​(java.lang.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:
        LocalVariable
      • equals

        public boolean equals​(java.lang.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 java.lang.Object
        See Also:
        Object.equals(Object)
      • getClassName

        public java.lang.String getClassName()
        Returns:
        class that contains this method
      • 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).
        Returns:
        method object
      • 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 java.lang.Object
        See Also:
        Object.hashCode()
      • removeException

        public void removeException​(java.lang.String c)
        Remove an exception.
      • 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.
      • removeNOPs

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

        public void removeRuntimeAttributes​(Attribute[] attrs)
        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.
        Since:
        6.5.0
      • setArgumentName

        public void setArgumentName​(int i,
                                    java.lang.String name)
      • setArgumentNames

        public void setArgumentNames​(java.lang.String[] argNames)
      • setClassName

        public void setClassName​(java.lang.String className)
      • setMaxLocals

        public void setMaxLocals()
        Compute maximum number of local variables.
      • setMaxLocals

        public void setMaxLocals​(int m)
        Sets maximum number of local variables.
      • setMaxStack

        public void setMaxStack()
        Computes max. stack size by performing control flow analysis.
      • setMaxStack

        public void setMaxStack​(int m)
        Sets maximum stack size for this method.
      • stripAttributes

        public void stripAttributes​(boolean flag)
        Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O
      • toString

        public final java.lang.String toString()
        Return string representation close to declaration format, 'public static void main(String[]) throws IOException', e.g.
        Overrides:
        toString in class java.lang.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.