com.sleepycat.asm
Class ClassWriter

java.lang.Object
  extended by com.sleepycat.asm.ClassWriter
All Implemented Interfaces:
ClassVisitor

public class ClassWriter
extends Object
implements ClassVisitor

A ClassVisitor that generates classes in bytecode form. More precisely this visitor generates a byte array conforming to the Java class file format. It can be used alone, to generate a Java class "from scratch", or with one or more ClassReader and adapter class visitor to generate a modified class from one or more existing Java classes.

Author:
Eric Bruneton

Field Summary
(package private) static int CLASS
          The type of CONSTANT_Class constant pool items.
(package private)  ClassReader cr
          The class reader from which this class writer was constructed, if any.
(package private) static int DOUBLE
          The type of CONSTANT_Double constant pool items.
(package private) static int FIELD
          The type of CONSTANT_Fieldref constant pool items.
(package private) static int FIELDORMETH_INSN
          The type of field and method invocations instructions.
(package private)  FieldWriter firstField
          The fields of this class.
(package private)  MethodWriter firstMethod
          The methods of this class.
(package private) static int FLOAT
          The type of CONSTANT_Float constant pool items.
(package private) static int IINC_INSN
          The type of the IINC instruction.
(package private) static int IMETH
          The type of CONSTANT_InterfaceMethodref constant pool items.
(package private) static int IMPLVAR_INSN
          The type of instructions with an implicit local variable index argument.
(package private)  int index
          Index of the next item to be added in the constant pool.
(package private) static int INT
          The type of CONSTANT_Integer constant pool items.
(package private)  Item[] items
          The constant pool's hash table data.
(package private) static int ITFMETH_INSN
          The type of the INVOKEINTERFACE instruction.
(package private)  Item key
          A reusable key used to look for items in the hash items.
(package private)  Item key2
          A reusable key used to look for items in the hash items.
(package private)  Item key3
          A reusable key used to look for items in the hash items.
(package private) static int LABEL_INSN
          The type of instructions with a 2 bytes bytecode offset label.
(package private) static int LABELW_INSN
          The type of instructions with a 4 bytes bytecode offset label.
(package private)  FieldWriter lastField
          The fields of this class.
(package private)  MethodWriter lastMethod
          The methods of this class.
(package private) static int LDC_INSN
          The type of the LDC instruction.
(package private) static int LDCW_INSN
          The type of the LDC_W and LDC2_W instructions.
(package private) static int LONG
          The type of CONSTANT_Long constant pool items.
(package private) static int LOOK_INSN
          The type of the LOOKUPSWITCH instruction.
(package private) static int MANA_INSN
          The type of the MULTIANEWARRAY instruction.
(package private) static int METH
          The type of CONSTANT_Methodref constant pool items.
(package private) static int NAME_TYPE
          The type of CONSTANT_NameAndType constant pool items.
(package private) static int NOARG_INSN
          The type of instructions without any argument.
(package private)  ByteVector pool
          The constant pool of this class.
(package private) static int SBYTE_INSN
          The type of instructions with an signed byte argument.
(package private) static int SHORT_INSN
          The type of instructions with an signed short argument.
(package private) static int STR
          The type of CONSTANT_String constant pool items.
(package private) static int TABL_INSN
          The type of the TABLESWITCH instruction.
(package private)  int threshold
          The threshold of the constant pool's hash table.
(package private) static byte[] TYPE
          The instruction types of all JVM opcodes.
(package private) static int TYPE_INSN
          The type of instructions with a type descriptor argument.
(package private) static int UTF8
          The type of CONSTANT_Utf8 constant pool items.
(package private) static int VAR_INSN
          The type of instructions with a local variable index argument.
(package private)  int version
          Minor and major version numbers of the class to be generated.
(package private) static int WIDE_INSN
          The type of the WIDE instruction.
 
Constructor Summary
ClassWriter(boolean computeMaxs)
          Constructs a new ClassWriter object.
ClassWriter(boolean computeMaxs, boolean skipUnknownAttributes)
          Constructs a new ClassWriter object.
ClassWriter(ClassReader classReader, boolean computeMaxs)
          Constructs a new ClassWriter object and enables optimizations for "mostly add" bytecode transformations.
 
Method Summary
 int newClass(String value)
          Adds a class reference to the constant pool of the class being build.
 int newConst(Object cst)
          Adds a number or string constant to the constant pool of the class being build.
(package private)  Item newConstItem(Object cst)
          Adds a number or string constant to the constant pool of the class being build.
(package private)  Item newDouble(double value)
          Adds a double to the constant pool of the class being build.
 int newField(String owner, String name, String desc)
          Adds a field reference to the constant pool of the class being build.
(package private)  Item newFloat(float value)
          Adds a float to the constant pool of the class being build.
(package private)  Item newInteger(int value)
          Adds an integer to the constant pool of the class being build.
(package private)  Item newLong(long value)
          Adds a long to the constant pool of the class being build.
 int newMethod(String owner, String name, String desc, boolean itf)
          Adds a method reference to the constant pool of the class being build.
(package private)  Item newMethodItem(String owner, String name, String desc, boolean itf)
          Adds a method reference to the constant pool of the class being build.
 int newNameType(String name, String desc)
          Adds a name and type to the constant pool of the class being build.
 int newUTF8(String value)
          Adds an UTF8 string to the constant pool of the class being build.
 byte[] toByteArray()
          Returns the bytecode of the class that was build with this class writer.
 void visit(int version, int access, String name, String signature, String superName, String[] interfaces)
          Visits the header of the class.
 AnnotationVisitor visitAnnotation(String desc, boolean visible)
          Visits an annotation of the class.
 void visitAttribute(Attribute attr)
          Visits a non standard attribute of the class.
 void visitEnd()
          Visits the end of the class.
 FieldVisitor visitField(int access, String name, String desc, String signature, Object value)
          Visits a field of the class.
 void visitInnerClass(String name, String outerName, String innerName, int access)
          Visits information about an inner class.
 MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions)
          Visits a method of the class.
 void visitOuterClass(String owner, String name, String desc)
          Visits the enclosing class of the class.
 void visitSource(String file, String debug)
          Visits the source of the class.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

NOARG_INSN

static final int NOARG_INSN
The type of instructions without any argument.

See Also:
Constant Field Values

SBYTE_INSN

static final int SBYTE_INSN
The type of instructions with an signed byte argument.

See Also:
Constant Field Values

SHORT_INSN

static final int SHORT_INSN
The type of instructions with an signed short argument.

See Also:
Constant Field Values

VAR_INSN

static final int VAR_INSN
The type of instructions with a local variable index argument.

See Also:
Constant Field Values

IMPLVAR_INSN

static final int IMPLVAR_INSN
The type of instructions with an implicit local variable index argument.

See Also:
Constant Field Values

TYPE_INSN

static final int TYPE_INSN
The type of instructions with a type descriptor argument.

See Also:
Constant Field Values

FIELDORMETH_INSN

static final int FIELDORMETH_INSN
The type of field and method invocations instructions.

See Also:
Constant Field Values

ITFMETH_INSN

static final int ITFMETH_INSN
The type of the INVOKEINTERFACE instruction.

See Also:
Constant Field Values

LABEL_INSN

static final int LABEL_INSN
The type of instructions with a 2 bytes bytecode offset label.

See Also:
Constant Field Values

LABELW_INSN

static final int LABELW_INSN
The type of instructions with a 4 bytes bytecode offset label.

See Also:
Constant Field Values

LDC_INSN

static final int LDC_INSN
The type of the LDC instruction.

See Also:
Constant Field Values

LDCW_INSN

static final int LDCW_INSN
The type of the LDC_W and LDC2_W instructions.

See Also:
Constant Field Values

IINC_INSN

static final int IINC_INSN
The type of the IINC instruction.

See Also:
Constant Field Values

TABL_INSN

static final int TABL_INSN
The type of the TABLESWITCH instruction.

See Also:
Constant Field Values

LOOK_INSN

static final int LOOK_INSN
The type of the LOOKUPSWITCH instruction.

See Also:
Constant Field Values

MANA_INSN

static final int MANA_INSN
The type of the MULTIANEWARRAY instruction.

See Also:
Constant Field Values

WIDE_INSN

static final int WIDE_INSN
The type of the WIDE instruction.

See Also:
Constant Field Values

TYPE

static byte[] TYPE
The instruction types of all JVM opcodes.


CLASS

static final int CLASS
The type of CONSTANT_Class constant pool items.

See Also:
Constant Field Values

FIELD

static final int FIELD
The type of CONSTANT_Fieldref constant pool items.

See Also:
Constant Field Values

METH

static final int METH
The type of CONSTANT_Methodref constant pool items.

See Also:
Constant Field Values

IMETH

static final int IMETH
The type of CONSTANT_InterfaceMethodref constant pool items.

See Also:
Constant Field Values

STR

static final int STR
The type of CONSTANT_String constant pool items.

See Also:
Constant Field Values

INT

static final int INT
The type of CONSTANT_Integer constant pool items.

See Also:
Constant Field Values

FLOAT

static final int FLOAT
The type of CONSTANT_Float constant pool items.

See Also:
Constant Field Values

LONG

static final int LONG
The type of CONSTANT_Long constant pool items.

See Also:
Constant Field Values

DOUBLE

static final int DOUBLE
The type of CONSTANT_Double constant pool items.

See Also:
Constant Field Values

NAME_TYPE

static final int NAME_TYPE
The type of CONSTANT_NameAndType constant pool items.

See Also:
Constant Field Values

UTF8

static final int UTF8
The type of CONSTANT_Utf8 constant pool items.

See Also:
Constant Field Values

cr

ClassReader cr
The class reader from which this class writer was constructed, if any.


version

int version
Minor and major version numbers of the class to be generated.


index

int index
Index of the next item to be added in the constant pool.


pool

ByteVector pool
The constant pool of this class.


items

Item[] items
The constant pool's hash table data.


threshold

int threshold
The threshold of the constant pool's hash table.


key

Item key
A reusable key used to look for items in the hash items.


key2

Item key2
A reusable key used to look for items in the hash items.


key3

Item key3
A reusable key used to look for items in the hash items.


firstField

FieldWriter firstField
The fields of this class. These fields are stored in a linked list of FieldWriter objects, linked to each other by their FieldWriter.next field. This field stores the first element of this list.


lastField

FieldWriter lastField
The fields of this class. These fields are stored in a linked list of FieldWriter objects, linked to each other by their FieldWriter.next field. This field stores the last element of this list.


firstMethod

MethodWriter firstMethod
The methods of this class. These methods are stored in a linked list of MethodWriter objects, linked to each other by their MethodWriter.next field. This field stores the first element of this list.


lastMethod

MethodWriter lastMethod
The methods of this class. These methods are stored in a linked list of MethodWriter objects, linked to each other by their MethodWriter.next field. This field stores the last element of this list.

Constructor Detail

ClassWriter

public ClassWriter(boolean computeMaxs)
Constructs a new ClassWriter object.

Parameters:
computeMaxs - true if the maximum stack size and the maximum number of local variables must be automatically computed. If this flag is true, then the arguments of the visitMaxs method of the MethodVisitor returned by the visitMethod method will be ignored, and computed automatically from the signature and the bytecode of each method.

ClassWriter

public ClassWriter(boolean computeMaxs,
                   boolean skipUnknownAttributes)
Constructs a new ClassWriter object.

Parameters:
computeMaxs - true if the maximum stack size and the maximum number of local variables must be automatically computed. If this flag is true, then the arguments of the visitMaxs method of the MethodVisitor returned by the visitMethod method will be ignored, and computed automatically from the signature and the bytecode of each method.
skipUnknownAttributes - Deprecated. The value of this parameter is ignored.

ClassWriter

public ClassWriter(ClassReader classReader,
                   boolean computeMaxs)
Constructs a new ClassWriter object and enables optimizations for "mostly add" bytecode transformations. These optimizations are the following:

Parameters:
classReader - the ClassReader used to read the original class. It will be used to copy the entire constant pool from the original class and also to copy other fragments of original bytecode where applicable.
computeMaxs - true if the maximum stack size and the maximum number of local variables must be automatically computed. If this flag is true, then the arguments of the visitMaxs method of the MethodVisitor returned by the visitMethod method will be ignored, and computed automatically from the signature and the bytecode of each method.
Method Detail

visit

public void visit(int version,
                  int access,
                  String name,
                  String signature,
                  String superName,
                  String[] interfaces)
Description copied from interface: ClassVisitor
Visits the header of the class.

Specified by:
visit in interface ClassVisitor
Parameters:
version - the class version.
access - the class's access flags (see Opcodes). This parameter also indicates if the class is deprecated.
name - the internal name of the class (see getInternalName).
signature - the signature of this class. May be null if the class is not a generic one, and does not extend or implement generic classes or interfaces.
superName - the internal of name of the super class (see getInternalName). For interfaces, the super class is Object. May be null, but only for the Object class.
interfaces - the internal names of the class's interfaces (see getInternalName). May be null.

visitSource

public void visitSource(String file,
                        String debug)
Description copied from interface: ClassVisitor
Visits the source of the class.

Specified by:
visitSource in interface ClassVisitor
Parameters:
file - the name of the source file from which the class was compiled. May be null.
debug - additional debug information to compute the correspondance between source and compiled elements of the class. May be null.

visitOuterClass

public void visitOuterClass(String owner,
                            String name,
                            String desc)
Description copied from interface: ClassVisitor
Visits the enclosing class of the class. This method must be called only if the class has an enclosing class.

Specified by:
visitOuterClass in interface ClassVisitor
Parameters:
owner - internal name of the enclosing class of the class.
name - the name of the method that contains the class, or null if the class is not enclosed in a method of its enclosing class.
desc - the descriptor of the method that contains the class, or null if the class is not enclosed in a method of its enclosing class.

visitAnnotation

public AnnotationVisitor visitAnnotation(String desc,
                                         boolean visible)
Description copied from interface: ClassVisitor
Visits an annotation of the class.

Specified by:
visitAnnotation in interface ClassVisitor
Parameters:
desc - the class descriptor of the annotation class.
visible - true if the annotation is visible at runtime.
Returns:
a non null visitor to visit the annotation values.

visitAttribute

public void visitAttribute(Attribute attr)
Description copied from interface: ClassVisitor
Visits a non standard attribute of the class.

Specified by:
visitAttribute in interface ClassVisitor
Parameters:
attr - an attribute.

visitInnerClass

public void visitInnerClass(String name,
                            String outerName,
                            String innerName,
                            int access)
Description copied from interface: ClassVisitor
Visits information about an inner class. This inner class is not necessarily a member of the class being visited.

Specified by:
visitInnerClass in interface ClassVisitor
Parameters:
name - the internal name of an inner class (see getInternalName).
outerName - the internal name of the class to which the inner class belongs (see getInternalName). May be null.
innerName - the (simple) name of the inner class inside its enclosing class. May be null for anonymous inner classes.
access - the access flags of the inner class as originally declared in the enclosing class.

visitField

public FieldVisitor visitField(int access,
                               String name,
                               String desc,
                               String signature,
                               Object value)
Description copied from interface: ClassVisitor
Visits a field of the class.

Specified by:
visitField in interface ClassVisitor
Parameters:
access - the field's access flags (see Opcodes). This parameter also indicates if the field is synthetic and/or deprecated.
name - the field's name.
desc - the field's descriptor (see Type).
signature - the field's signature. May be null if the field's type does not use generic types.
value - the field's initial value. This parameter, which may be null if the field does not have an initial value, must be an Integer, a Float, a Long, a Double or a String (for int, float, long or String fields respectively). This parameter is only used for static fields. Its value is ignored for non static fields, which must be initialized through bytecode instructions in constructors or methods.
Returns:
a visitor to visit field annotations and attributes, or null if this class visitor is not interested in visiting these annotations and attributes.

visitMethod

public MethodVisitor visitMethod(int access,
                                 String name,
                                 String desc,
                                 String signature,
                                 String[] exceptions)
Description copied from interface: ClassVisitor
Visits a method of the class. This method must return a new MethodVisitor instance (or null) each time it is called, i.e., it should not return a previously returned visitor.

Specified by:
visitMethod in interface ClassVisitor
Parameters:
access - the method's access flags (see Opcodes). This parameter also indicates if the method is synthetic and/or deprecated.
name - the method's name.
desc - the method's descriptor (see Type).
signature - the method's signature. May be null if the method parameters, return type and exceptions do not use generic types.
exceptions - the internal names of the method's exception classes (see getInternalName). May be null.
Returns:
an object to visit the byte code of the method, or null if this class visitor is not interested in visiting the code of this method.

visitEnd

public void visitEnd()
Description copied from interface: ClassVisitor
Visits the end of the class. This method, which is the last one to be called, is used to inform the visitor that all the fields and methods of the class have been visited.

Specified by:
visitEnd in interface ClassVisitor

toByteArray

public byte[] toByteArray()
Returns the bytecode of the class that was build with this class writer.

Returns:
the bytecode of the class that was build with this class writer.

newConstItem

Item newConstItem(Object cst)
Adds a number or string constant to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:
cst - the value of the constant to be added to the constant pool. This parameter must be an Integer, a Float, a Long, a Double, a String or a Type.
Returns:
a new or already existing constant item with the given value.

newConst

public int newConst(Object cst)
Adds a number or string constant to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
cst - the value of the constant to be added to the constant pool. This parameter must be an Integer, a Float, a Long, a Double or a String.
Returns:
the index of a new or already existing constant item with the given value.

newUTF8

public int newUTF8(String value)
Adds an UTF8 string to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
value - the String value.
Returns:
the index of a new or already existing UTF8 item.

newClass

public int newClass(String value)
Adds a class reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
value - the internal name of the class.
Returns:
the index of a new or already existing class reference item.

newField

public int newField(String owner,
                    String name,
                    String desc)
Adds a field reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
owner - the internal name of the field's owner class.
name - the field's name.
desc - the field's descriptor.
Returns:
the index of a new or already existing field reference item.

newMethodItem

Item newMethodItem(String owner,
                   String name,
                   String desc,
                   boolean itf)
Adds a method reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:
owner - the internal name of the method's owner class.
name - the method's name.
desc - the method's descriptor.
itf - true if owner is an interface.
Returns:
a new or already existing method reference item.

newMethod

public int newMethod(String owner,
                     String name,
                     String desc,
                     boolean itf)
Adds a method reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
owner - the internal name of the method's owner class.
name - the method's name.
desc - the method's descriptor.
itf - true if owner is an interface.
Returns:
the index of a new or already existing method reference item.

newInteger

Item newInteger(int value)
Adds an integer to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:
value - the int value.
Returns:
a new or already existing int item.

newFloat

Item newFloat(float value)
Adds a float to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:
value - the float value.
Returns:
a new or already existing float item.

newLong

Item newLong(long value)
Adds a long to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:
value - the long value.
Returns:
a new or already existing long item.

newDouble

Item newDouble(double value)
Adds a double to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:
value - the double value.
Returns:
a new or already existing double item.

newNameType

public int newNameType(String name,
                       String desc)
Adds a name and type to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
name - a name.
desc - a type descriptor.
Returns:
the index of a new or already existing name and type item.


Copyright 2004-2006 Sleepycat, Inc. All Rights Reserved.