public class ClassWriter extends ClassVisitor
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.Modifier and Type | Field and Description |
---|---|
static int |
COMPUTE_FRAMES
Flag to automatically compute the stack map frames of methods from
scratch.
|
static int |
COMPUTE_MAXS
Flag to automatically compute the maximum stack size and the maximum
number of local variables of methods.
|
api, cv
Constructor and Description |
---|
ClassWriter(ClassReader classReader,
int flags)
Constructs a new
ClassWriter object and enables optimizations for
"mostly add" bytecode transformations. |
ClassWriter(int flags)
Constructs a new
ClassWriter object. |
Modifier and Type | Method and Description |
---|---|
protected java.lang.String |
getCommonSuperClass(java.lang.String type1,
java.lang.String type2)
Returns the common super type of the two given types.
|
int |
newClass(java.lang.String value)
Adds a class reference to the constant pool of the class being build.
|
int |
newConst(java.lang.Object cst)
Adds a number or string constant to the constant pool of the class being
build.
|
int |
newField(java.lang.String owner,
java.lang.String name,
java.lang.String desc)
Adds a field reference to the constant pool of the class being build.
|
int |
newHandle(int tag,
java.lang.String owner,
java.lang.String name,
java.lang.String desc)
Adds a handle to the constant pool of the class being build.
|
int |
newInvokeDynamic(java.lang.String name,
java.lang.String desc,
Handle bsm,
java.lang.Object... bsmArgs)
Adds an invokedynamic reference to the constant pool of the class being
build.
|
int |
newMethod(java.lang.String owner,
java.lang.String name,
java.lang.String desc,
boolean itf)
Adds a method reference to the constant pool of the class being build.
|
int |
newMethodType(java.lang.String methodDesc)
Adds a method type reference to the constant pool of the class being
build.
|
int |
newNameType(java.lang.String name,
java.lang.String desc)
Adds a name and type to the constant pool of the class being build.
|
int |
newUTF8(java.lang.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,
java.lang.String name,
java.lang.String signature,
java.lang.String superName,
java.lang.String[] interfaces)
Visits the header of the class.
|
AnnotationVisitor |
visitAnnotation(java.lang.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,
java.lang.String name,
java.lang.String desc,
java.lang.String signature,
java.lang.Object value)
Visits a field of the class.
|
void |
visitInnerClass(java.lang.String name,
java.lang.String outerName,
java.lang.String innerName,
int access)
Visits information about an inner class.
|
MethodVisitor |
visitMethod(int access,
java.lang.String name,
java.lang.String desc,
java.lang.String signature,
java.lang.String[] exceptions)
Visits a method of the class.
|
void |
visitOuterClass(java.lang.String owner,
java.lang.String name,
java.lang.String desc)
Visits the enclosing class of the class.
|
void |
visitSource(java.lang.String file,
java.lang.String debug)
Visits the source of the class.
|
AnnotationVisitor |
visitTypeAnnotation(int typeRef,
TypePath typePath,
java.lang.String desc,
boolean visible)
Visits an annotation on a type in the class signature.
|
public static final int COMPUTE_MAXS
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(int)
,
Constant Field Valuespublic static final int COMPUTE_FRAMES
MethodVisitor.visitFrame(int, int, java.lang.Object[], int, java.lang.Object[])
method are ignored, and the stack map
frames are recomputed from the methods bytecode. The arguments of the
visitMaxs
method are also ignored and
recomputed from the bytecode. In other words, computeFrames implies
computeMaxs.ClassWriter(int)
,
Constant Field Valuespublic ClassWriter(int flags)
ClassWriter
object.flags
- option flags that can be used to modify the default behavior
of this class. See COMPUTE_MAXS
,
COMPUTE_FRAMES
.public ClassWriter(ClassReader classReader, int flags)
ClassWriter
object and enables optimizations for
"mostly add" bytecode transformations. These optimizations are the
following:
ClassReader
receives MethodVisitor
objects that come from
a ClassWriter
(and not from any other ClassVisitor
instance).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.flags
- option flags that can be used to modify the default behavior
of this class. These option flags do not affect methods
that are copied as is in the new class. This means that the
maximum stack size nor the stack frames will be computed for
these methods. See COMPUTE_MAXS
,
COMPUTE_FRAMES
.public final void visit(int version, int access, java.lang.String name, java.lang.String signature, java.lang.String superName, java.lang.String[] interfaces)
ClassVisitor
visit
in class ClassVisitor
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.public final void visitSource(java.lang.String file, java.lang.String debug)
ClassVisitor
visitSource
in class ClassVisitor
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.public final void visitOuterClass(java.lang.String owner, java.lang.String name, java.lang.String desc)
ClassVisitor
visitOuterClass
in class ClassVisitor
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.public final AnnotationVisitor visitAnnotation(java.lang.String desc, boolean visible)
ClassVisitor
visitAnnotation
in class ClassVisitor
desc
- the class descriptor of the annotation class.visible
- true if the annotation is visible at runtime.public final AnnotationVisitor visitTypeAnnotation(int typeRef, TypePath typePath, java.lang.String desc, boolean visible)
ClassVisitor
visitTypeAnnotation
in class ClassVisitor
typeRef
- a reference to the annotated type. The sort of this type
reference must be CLASS_TYPE_PARAMETER
,
CLASS_TYPE_PARAMETER_BOUND
or
CLASS_EXTENDS
. See
TypeReference
.typePath
- the path to the annotated type argument, wildcard bound, array
element type, or static inner type within 'typeRef'. May be
null if the annotation targets 'typeRef' as a whole.desc
- the class descriptor of the annotation class.visible
- true if the annotation is visible at runtime.public final void visitAttribute(Attribute attr)
ClassVisitor
visitAttribute
in class ClassVisitor
attr
- an attribute.public final void visitInnerClass(java.lang.String name, java.lang.String outerName, java.lang.String innerName, int access)
ClassVisitor
visitInnerClass
in class ClassVisitor
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 for not member classes.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.public final FieldVisitor visitField(int access, java.lang.String name, java.lang.String desc, java.lang.String signature, java.lang.Object value)
ClassVisitor
visitField
in class ClassVisitor
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.public final MethodVisitor visitMethod(int access, java.lang.String name, java.lang.String desc, java.lang.String signature, java.lang.String[] exceptions)
ClassVisitor
MethodVisitor
instance (or null) each time it is called,
i.e., it should not return a previously returned visitor.visitMethod
in class ClassVisitor
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.public final void visitEnd()
ClassVisitor
visitEnd
in class ClassVisitor
public byte[] toByteArray()
public int newConst(java.lang.Object cst)
Attribute
sub classes, and is
normally not needed by class generators or adapters.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
.public int newUTF8(java.lang.String value)
Attribute
sub classes, and is normally not
needed by class generators or adapters.value
- the String value.public int newClass(java.lang.String value)
Attribute
sub classes, and is
normally not needed by class generators or adapters.value
- the internal name of the class.public int newMethodType(java.lang.String methodDesc)
Attribute
sub classes, and is
normally not needed by class generators or adapters.methodDesc
- method descriptor of the method type.public int newHandle(int tag, java.lang.String owner, java.lang.String name, java.lang.String desc)
Attribute
sub classes, and is normally not needed by
class generators or adapters.tag
- the kind of this handle. Must be Opcodes.H_GETFIELD
,
Opcodes.H_GETSTATIC
, Opcodes.H_PUTFIELD
,
Opcodes.H_PUTSTATIC
, Opcodes.H_INVOKEVIRTUAL
,
Opcodes.H_INVOKESTATIC
,
Opcodes.H_INVOKESPECIAL
,
Opcodes.H_NEWINVOKESPECIAL
or
Opcodes.H_INVOKEINTERFACE
.owner
- the internal name of the field or method owner class.name
- the name of the field or method.desc
- the descriptor of the field or method.public int newInvokeDynamic(java.lang.String name, java.lang.String desc, Handle bsm, java.lang.Object... bsmArgs)
Attribute
sub classes, and is
normally not needed by class generators or adapters.name
- name of the invoked method.desc
- descriptor of the invoke method.bsm
- the bootstrap method.bsmArgs
- the bootstrap method constant arguments.public int newField(java.lang.String owner, java.lang.String name, java.lang.String desc)
Attribute
sub classes, and is
normally not needed by class generators or adapters.owner
- the internal name of the field's owner class.name
- the field's name.desc
- the field's descriptor.public int newMethod(java.lang.String owner, java.lang.String name, java.lang.String desc, boolean itf)
Attribute
sub classes, and is
normally not needed by class generators or adapters.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.public int newNameType(java.lang.String name, java.lang.String desc)
Attribute
sub classes, and is normally not
needed by class generators or adapters.name
- a name.desc
- a type descriptor.protected java.lang.String getCommonSuperClass(java.lang.String type1, java.lang.String type2)
type1
- the internal name of a class.type2
- the internal name of another class.Copyright © 2016 Oracle Corporation. All Rights Reserved.