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bcel API: Class MethodGen
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org.apache.bcel.generic
Class MethodGen

java.lang.Object
  |
  +--org.apache.bcel.classfile.AccessFlags
        |
        +--org.apache.bcel.generic.FieldGenOrMethodGen
              |
              +--org.apache.bcel.generic.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.

Version:
$Id: MethodGen.java,v 1.1.1.1 2001/10/29 20:00:24 jvanzyl Exp $
Author:
M. Dahm, Patrick C. Beard
See Also:
InstructionList, Method

Fields inherited from class org.apache.bcel.generic.FieldGenOrMethodGen
cp, name, type
 
Fields inherited from class org.apache.bcel.classfile.AccessFlags
access_flags
 
Constructor Summary
MethodGen(int access_flags, Type return_type, Type[] arg_types, java.lang.String[] arg_names, java.lang.String method_name, java.lang.String class_name, InstructionList il, ConstantPoolGen cp)
          Declare method.
MethodGen(Method m, java.lang.String class_name, ConstantPoolGen cp)
          Instantiate from existing method.
 
Method Summary
 void addCodeAttribute(Attribute a)
          Add an attribute to the code.
 void addException(java.lang.String class_name)
          Add an exception possibly thrown by this method.
 CodeExceptionGen addExceptionHandler(InstructionHandle start_pc, InstructionHandle end_pc, InstructionHandle handler_pc, ObjectType catch_type)
          Add an exception handler, i.e., specify region where a handler is active and an instruction where the actual handling is done.
 LineNumberGen addLineNumber(InstructionHandle ih, int src_line)
          Give an instruction a line number corresponding to the source code line.
 LocalVariableGen addLocalVariable(java.lang.String name, Type type, InstructionHandle start, InstructionHandle end)
          Adds a local variable to this method and assigns an index automatically.
 LocalVariableGen addLocalVariable(java.lang.String name, Type type, int slot, InstructionHandle start, InstructionHandle end)
          Adds a local variable to this method.
 void addObserver(MethodObserver o)
          Add observer for this object.
 MethodGen copy(java.lang.String class_name, ConstantPoolGen cp)
           
 java.lang.String getArgumentName(int i)
           
 java.lang.String[] getArgumentNames()
           
 Type getArgumentType(int i)
           
 Type[] getArgumentTypes()
           
 java.lang.String getClassName()
           
 Attribute[] getCodeAttributes()
           
 CodeExceptionGen[] getExceptionHandlers()
           
 java.lang.String[] getExceptions()
           
 InstructionList getInstructionList()
           
 LineNumberGen[] getLineNumbers()
           
 LineNumberTable getLineNumberTable(ConstantPoolGen cp)
           
 LocalVariableGen[] getLocalVariables()
           
 LocalVariableTable getLocalVariableTable(ConstantPoolGen cp)
           
 int getMaxLocals()
           
 int getMaxStack()
           
static int getMaxStack(ConstantPoolGen cp, InstructionList il, CodeExceptionGen[] et)
          Computes stack usage of an instruction list by performing control flow analysis.
 Method getMethod()
          Get method object.
 Type getReturnType()
           
 java.lang.String getSignature()
           
 void removeCodeAttribute(Attribute a)
          Remove a code attribute.
 void removeCodeAttributes()
          Remove all code attributes.
 void removeException(java.lang.String c)
          Remove an exception.
 void removeExceptionHandler(CodeExceptionGen c)
          Remove an exception handler.
 void removeExceptionHandlers()
          Remove all line numbers.
 void removeExceptions()
          Remove all exceptions.
 void removeLineNumber(LineNumberGen l)
          Remove a line number.
 void removeLineNumbers()
          Remove all line numbers.
 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.
 void removeLocalVariables()
          Remove all local variables.
 void removeNOPs()
          Remove all NOPs from the instruction list (if possible) and update every object refering to them, i.e., branch instructions, local variables and exception handlers.
 void removeObserver(MethodObserver o)
          Remove observer for this object.
 void setArgumentName(int i, java.lang.String name)
           
 void setArgumentNames(java.lang.String[] arg_names)
           
 void setArgumentType(int i, Type type)
           
 void setArgumentTypes(Type[] arg_types)
           
 void setClassName(java.lang.String class_name)
           
 void setInstructionList(InstructionList il)
           
 void setMaxLocals()
          Compute maximum number of local variables.
 void setMaxLocals(int m)
          Set maximum number of local variables.
 void setMaxStack()
          Computes max.
 void setMaxStack(int m)
          Set maximum stack size for this method.
 void setReturnType(Type return_type)
           
 void stripAttributes(boolean flag)
          Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O
 java.lang.String toString()
          Return string representation close to declaration format, `public static void main(String[]) throws IOException', e.g.
 void update()
          Call notify() method on all observers.
 
Methods inherited from class org.apache.bcel.generic.FieldGenOrMethodGen
addAttribute, clone, getAttributes, getConstantPool, getName, getType, removeAttribute, removeAttributes, setConstantPool, setName, setType
 
Methods inherited from class org.apache.bcel.classfile.AccessFlags
getAccessFlags, isAbstract, isAbstract, isFinal, isFinal, isInterface, isInterface, isNative, isNative, isPrivate, isPrivate, isProtected, isProtected, isPublic, isPublic, isStatic, isStatic, isStrictfp, isStrictfp, isSynchronized, isSynchronized, isTransient, isTransient, isVolatile, isVolatile, setAccessFlags
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

MethodGen

public MethodGen(int access_flags,
                 Type return_type,
                 Type[] arg_types,
                 java.lang.String[] arg_names,
                 java.lang.String method_name,
                 java.lang.String class_name,
                 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 he 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:
access_flags - access qualifiers
return_type - method type
arg_types - argument types
arg_names - argument names (if this is null, default names will be provided for them)
method_name - name of method
class_name - 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 m,
                 java.lang.String class_name,
                 ConstantPoolGen cp)
Instantiate from existing method.
Parameters:
m - method
class_name - class name containing this method
cp - constant pool
Method Detail

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,
                                         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

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.

removeLocalVariables

public void removeLocalVariables()
Remove all local variables.

getLocalVariables

public LocalVariableGen[] getLocalVariables()

getLocalVariableTable

public LocalVariableTable getLocalVariableTable(ConstantPoolGen cp)
Returns:
`LocalVariableTable' attribute of all the local variables of this method.

addLineNumber

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

removeLineNumber

public void removeLineNumber(LineNumberGen l)
Remove a line number.

removeLineNumbers

public void removeLineNumbers()
Remove all line numbers.

getLineNumbers

public LineNumberGen[] getLineNumbers()

getLineNumberTable

public LineNumberTable getLineNumberTable(ConstantPoolGen cp)
Returns:
`LineNumberTable' attribute of all the local variables of this method.

addExceptionHandler

public CodeExceptionGen addExceptionHandler(InstructionHandle start_pc,
                                            InstructionHandle end_pc,
                                            InstructionHandle handler_pc,
                                            ObjectType catch_type)
Add an exception handler, i.e., specify region where a handler is active and an instruction where the actual handling is done.
Parameters:
start_pc - Start of region (inclusive)
end_pc - End of region (inclusive)
handler_pc - Where handling is done
catch_type - fully qualified class name of handled exception or null if any exception is handled
Returns:
new exception handler object

removeExceptionHandler

public void removeExceptionHandler(CodeExceptionGen c)
Remove an exception handler.

removeExceptionHandlers

public void removeExceptionHandlers()
Remove all line numbers.

getExceptionHandlers

public CodeExceptionGen[] getExceptionHandlers()

addException

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

removeException

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

removeExceptions

public void removeExceptions()
Remove all exceptions.

getExceptions

public java.lang.String[] getExceptions()

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

removeCodeAttribute

public void removeCodeAttribute(Attribute a)
Remove a code attribute.

removeCodeAttributes

public void removeCodeAttributes()
Remove all code attributes.

getCodeAttributes

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

getMethod

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

removeNOPs

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

setMaxLocals

public void setMaxLocals(int m)
Set maximum number of local variables.

getMaxLocals

public int getMaxLocals()

setMaxStack

public void setMaxStack(int m)
Set maximum stack size for this method.

getMaxStack

public int getMaxStack()

getClassName

public java.lang.String getClassName()
Returns:
class that contains this method

setClassName

public void setClassName(java.lang.String class_name)

setReturnType

public void setReturnType(Type return_type)

getReturnType

public Type getReturnType()

setArgumentTypes

public void setArgumentTypes(Type[] arg_types)

getArgumentTypes

public Type[] getArgumentTypes()

setArgumentType

public void setArgumentType(int i,
                            Type type)

getArgumentType

public Type getArgumentType(int i)

setArgumentNames

public void setArgumentNames(java.lang.String[] arg_names)

getArgumentNames

public java.lang.String[] getArgumentNames()

setArgumentName

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

getArgumentName

public java.lang.String getArgumentName(int i)

getInstructionList

public InstructionList getInstructionList()

setInstructionList

public void setInstructionList(InstructionList il)

getSignature

public java.lang.String getSignature()
Overrides:
getSignature in class FieldGenOrMethodGen
Following copied from class: org.apache.bcel.generic.FieldGenOrMethodGen
Returns:
signature of method/field.

setMaxStack

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

setMaxLocals

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

stripAttributes

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

getMaxStack

public static int getMaxStack(ConstantPoolGen cp,
                              InstructionList il,
                              CodeExceptionGen[] et)
Computes stack usage of an instruction list by performing control flow analysis.
Returns:
maximum stack depth used by method

addObserver

public void addObserver(MethodObserver o)
Add observer for this object.

removeObserver

public void removeObserver(MethodObserver o)
Remove observer for this object.

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 he has finished editing the object.

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.

copy

public MethodGen copy(java.lang.String class_name,
                      ConstantPoolGen cp)
Returns:
deep copy of this method
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