org.objectweb.asm
Class ClassReader
A Java class parser to make a
ClassVisitor
visit an existing class.
This class parses a byte array conforming to the Java class file format and
calls the appropriate visit methods of a given class visitor for each field,
method and bytecode instruction encountered.
- Eric Bruneton
- Eugene Kuleshov
static int | EXPAND_FRAMES - Flag to expand the stack map frames.
|
static int | SKIP_CODE - Flag to skip method code.
|
static int | SKIP_DEBUG - Flag to skip the debug information in the class.
|
static int | SKIP_FRAMES - Flag to skip the stack map frames in the class.
|
byte[] | b - The class to be parsed.
|
int | header - Start index of the class header information (access, name...) in
b .
|
EXPAND_FRAMES
public static final int EXPAND_FRAMES
Flag to expand the stack map frames. By default stack map frames are
visited in their original format (i.e. "expanded" for classes whose
version is less than V1_6, and "compressed" for the other classes). If
this flag is set, stack map frames are always visited in expanded format
(this option adds a decompression/recompression step in ClassReader and
ClassWriter which degrades performances quite a lot).
SKIP_CODE
public static final int SKIP_CODE
Flag to skip method code. If this class is set CODE
attribute won't be visited. This can be used, for example, to retrieve
annotations for methods and method parameters.
SKIP_DEBUG
public static final int SKIP_DEBUG
Flag to skip the debug information in the class. If this flag is set the
debug information of the class is not visited, i.e. the
visitLocalVariable
and
visitLineNumber
methods will not be
called.
SKIP_FRAMES
public static final int SKIP_FRAMES
Flag to skip the stack map frames in the class. If this flag is set the
stack map frames of the class is not visited, i.e. the
visitFrame
method will not be called.
This flag is useful when the
ClassWriter.COMPUTE_FRAMES
option is
used: it avoids visiting frames that will be ignored and recomputed from
scratch in the class writer.
b
public final byte[] b
The class to be parsed.
The content of this array must not be
modified. This field is intended for Attribute
sub classes, and
is normally not needed by class generators or adapters.
header
public final int header
Start index of the class header information (access, name...) in
b
.
ClassReader
public ClassReader(InputStream is)
throws IOException
is
- an input stream from which to read the class.
ClassReader
public ClassReader(String name)
throws IOException
name
- the fully qualified name of the class to be read.
ClassReader
public ClassReader(byte[] b)
b
- the bytecode of the class to be read.
ClassReader
public ClassReader(byte[] b,
int off,
int len)
b
- the bytecode of the class to be read.off
- the start offset of the class data.len
- the length of the class data.
accept
public void accept(ClassVisitor classVisitor,
int flags)
Makes the given visitor visit the Java class of this
ClassReader
.
This class is the one specified in the constructor (see
ClassReader
).
classVisitor
- the visitor that must visit this class.flags
- option flags that can be used to modify the default behavior
of this class. See SKIP_DEBUG
, EXPAND_FRAMES
.
accept
public void accept(ClassVisitor classVisitor,
Attribute[] attrs,
int flags)
Makes the given visitor visit the Java class of this
ClassReader
.
This class is the one specified in the constructor (see
ClassReader
).
classVisitor
- the visitor that must visit this class.attrs
- prototypes of the attributes that must be parsed during the
visit of the class. Any attribute whose type is not equal to the
type of one the prototypes will not be parsed: its byte array
value will be passed unchanged to the ClassWriter. This may
corrupt it if this value contains references to the constant pool,
or has syntactic or semantic links with a class element that has
been transformed by a class adapter between the reader and the
writer.flags
- option flags that can be used to modify the default behavior
of this class. See SKIP_DEBUG
, EXPAND_FRAMES
.
getAccess
public int getAccess()
Returns the class's access flags (see
Opcodes
). This value may
not reflect Deprecated and Synthetic flags when bytecode is before 1.5
and those flags are represented by attributes.
getClassName
public String getClassName()
getInterfaces
public String[] getInterfaces()
Returns the internal names of the class's interfaces (see
getInternalName
).
- the array of internal names for all implemented interfaces or
null.
getItem
public int getItem(int item)
Returns the start index of the constant pool item in
b
, plus
one.
This method is intended for Attribute
sub classes, and is
normally not needed by class generators or adapters.
item
- the index a constant pool item.
- the start index of the constant pool item in
b
, plus
one.
getSuperName
public String getSuperName()
Returns the internal of name of the super class (see
getInternalName
). For interfaces, the
super class is
Object
.
- the internal name of super class, or null for
Object
class.
readByte
public int readByte(int index)
Reads a byte value in
b
.
This method is intended for
Attribute
sub classes, and is normally not needed by class
generators or adapters.
index
- the start index of the value to be read in b
.
readClass
public String readClass(int index,
char[] buf)
Reads a class constant pool item in
b
.
This method is
intended for Attribute
sub classes, and is normally not needed by
class generators or adapters.
index
- the start index of an unsigned short value in b
,
whose value is the index of a class constant pool item.buf
- buffer to be used to read the item. This buffer must be
sufficiently large. It is not automatically resized.
- the String corresponding to the specified class item.
readConst
public Object readConst(int item,
char[] buf)
Reads a numeric or string constant pool item in
b
.
This
method is intended for Attribute
sub classes, and is normally not
needed by class generators or adapters.
item
- the index of a constant pool item.buf
- buffer to be used to read the item. This buffer must be
sufficiently large. It is not automatically resized.
- the
Integer
, Float
, Long
,
Double
, String
or Type
corresponding to
the given constant pool item.
readInt
public int readInt(int index)
Reads a signed int value in
b
.
This method is intended for
Attribute
sub classes, and is normally not needed by class
generators or adapters.
index
- the start index of the value to be read in b
.
readLabel
protected Label readLabel(int offset,
Label[] labels)
Returns the label corresponding to the given offset. The default
implementation of this method creates a label for the given offset if it
has not been already created.
offset
- a bytecode offset in a method.labels
- the already created labels, indexed by their offset. If a
label already exists for offset this method must not create a new
one. Otherwise it must store the new label in this array.
- a non null Label, which must be equal to labels[offset].
readLong
public long readLong(int index)
Reads a signed long value in
b
.
This method is intended
for Attribute
sub classes, and is normally not needed by class
generators or adapters.
index
- the start index of the value to be read in b
.
readShort
public short readShort(int index)
Reads a signed short value in
b
.
This method is intended
for Attribute
sub classes, and is normally not needed by class
generators or adapters.
index
- the start index of the value to be read in b
.
readUTF8
public String readUTF8(int index,
char[] buf)
Reads an UTF8 string constant pool item in
b
.
This method
is intended for Attribute
sub classes, and is normally not needed
by class generators or adapters.
index
- the start index of an unsigned short value in b
,
whose value is the index of an UTF8 constant pool item.buf
- buffer to be used to read the item. This buffer must be
sufficiently large. It is not automatically resized.
- the String corresponding to the specified UTF8 item.
readUnsignedShort
public int readUnsignedShort(int index)
Reads an unsigned short value in
b
.
This method is
intended for Attribute
sub classes, and is normally not needed by
class generators or adapters.
index
- the start index of the value to be read in b
.