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public class ClassReader
A parser to make a ClassVisitor visit a ClassFile structure, as defined in the Java Virtual Machine Specification (JVMS). This class parses the ClassFile content and calls the appropriate visit methods of a given ClassVisitor for each field, method and bytecode instruction encountered.
Fields
public static final int
A flag to expand the stack map frames.
public static final int
A flag to skip the Code attributes.
public static final int
A flag to skip the SourceFile, SourceDebugExtension, LocalVariableTable, LocalVariableTypeTable and LineNumberTable attributes.
public static final int
A flag to skip the StackMap and StackMapTable attributes.
public final byte[]
Use readByte(int) and the other read methods instead. This field will eventually be deleted.
public final int
The offset in bytes of the ClassFile's access_flags field.
Constructors
public
Constructs a new ClassReader object.
public
ClassReader(String className)
Constructs a new ClassReader object.
public
ClassReader(byte[] classFile)
Constructs a new ClassReader object.
public
ClassReader(byte[] classFileBuffer, int classFileOffset, int classFileLength)
Constructs a new ClassReader object.
Methods
public void
accept(ClassVisitor classVisitor, int parsingOptions)
Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this ClassReader.
public void
accept(ClassVisitor classVisitor, Attribute[] attributePrototypes, int parsingOptions)
Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this ClassReader.
public int
Returns the class's access flags (see Opcodes).
public String
Returns the internal name of the class (see Type.getInternalName()).
public String[]
Returns the internal names of the implemented interfaces (see Type.getInternalName()).
public int
getItem(int constantPoolEntryIndex)
Returns the start offset in this ClassReader of a JVMS 'cp_info' structure (i.e.
public int
Returns the number of entries in the class's constant pool table.
public int
Returns a conservative estimate of the maximum length of the strings contained in the class's constant pool table.
public String
Returns the internal of name of the super class (see Type.getInternalName()).
public int
readByte(int offset)
Reads a byte value in this ClassReader.
public String
readClass(int offset, char[] charBuffer)
Reads a CONSTANT_Class constant pool entry in this ClassReader.
public Object
readConst(int constantPoolEntryIndex, char[] charBuffer)
Reads a numeric or string constant pool entry in this ClassReader.
public int
readInt(int offset)
Reads a signed int value in this ClassReader.
protected Label
readLabel(int bytecodeOffset, Label[] labels)
Returns the label corresponding to the given bytecode offset.
public long
readLong(int offset)
Reads a signed long value in this ClassReader.
public String
readModule(int offset, char[] charBuffer)
Reads a CONSTANT_Module constant pool entry in this ClassReader.
public String
readPackage(int offset, char[] charBuffer)
Reads a CONSTANT_Package constant pool entry in this ClassReader.
public short
readShort(int offset)
Reads a signed short value in this ClassReader.
public String
readUTF8(int offset, char[] charBuffer)
Reads a CONSTANT_Utf8 constant pool entry in this ClassReader.
public int
readUnsignedShort(int offset)
Reads an unsigned short value in this ClassReader.
public static final int EXPAND_FRAMES = 8
A 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/compression step in ClassReader and ClassWriter which degrades performance quite a lot).
public static final int SKIP_CODE = 1
A flag to skip the Code attributes. If this flag is set the Code attributes are neither parsed nor visited.
public static final int SKIP_DEBUG = 2
A flag to skip the SourceFile, SourceDebugExtension, LocalVariableTable, LocalVariableTypeTable and LineNumberTable attributes. If this flag is set these attributes are neither parsed nor visited (i.e. ClassVisitor.visitSource(String, String), MethodVisitor.visitLocalVariable(String, String, String, Label, Label, int) and MethodVisitor.visitLineNumber(int, Label) are not called).
public static final int SKIP_FRAMES = 4
A flag to skip the StackMap and StackMapTable attributes. If this flag is set these attributes are neither parsed nor visited (i.e. MethodVisitor.visitFrame(int, int, Object[], int, Object[]) is not 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.
public final byte[] b
Use readByte(int) and the other read methods instead. This field will eventually be deleted.
A byte array containing the JVMS ClassFile structure to be parsed.
public ClassReader(InputStream inputStream) throws IOException
Constructs a new ClassReader object.
inputStreaman input stream of the JVMS ClassFile structure to be read. This input stream must contain nothing more than the ClassFile structure itself. It is read from its current position to its end.
IOExceptionif a problem occurs during reading.
public ClassReader(String className) throws IOException
Constructs a new ClassReader object.
classNamethe fully qualified name of the class to be read. The ClassFile structure is retrieved with the current class loader's ClassLoader.getSystemResourceAsStream(String).
IOExceptionif an exception occurs during reading.
public ClassReader(byte[] classFile)
Constructs a new ClassReader object.
classFilethe JVMS ClassFile structure to be read.
public ClassReader(byte[] classFileBuffer, int classFileOffset, int classFileLength)
Constructs a new ClassReader object.
classFileBuffera byte array containing the JVMS ClassFile structure to be read.
classFileOffsetthe offset in byteBuffer of the first byte of the ClassFile to be read.
classFileLengththe length in bytes of the ClassFile to be read.
public void accept(ClassVisitor classVisitor, int parsingOptions)
Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this ClassReader.
classVisitorthe visitor that must visit this class.
parsingOptionsthe options to use to parse this class. One or more of SKIP_CODE, SKIP_DEBUG, SKIP_FRAMES or EXPAND_FRAMES.
public void accept(ClassVisitor classVisitor, Attribute[] attributePrototypes, int parsingOptions)
Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this ClassReader.
classVisitorthe visitor that must visit this class.
attributePrototypesprototypes 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.
parsingOptionsthe options to use to parse this class. One or more of SKIP_CODE, SKIP_DEBUG, SKIP_FRAMES or EXPAND_FRAMES.
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.
the class access flags.
Returns the internal name of the class (see Type.getInternalName()).
the internal class name.
Returns the internal names of the implemented interfaces (see Type.getInternalName()).
the internal names of the directly implemented interfaces. Inherited implemented interfaces are not returned.
public int getItem(int constantPoolEntryIndex)
Returns the start offset in this ClassReader of a JVMS 'cp_info' structure (i.e. a constant pool entry), plus one. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
constantPoolEntryIndexthe index a constant pool entry in the class's constant pool table.
the start offset in this ClassReader of the corresponding JVMS 'cp_info' structure, plus one.
public int getItemCount()
Returns the number of entries in the class's constant pool table.
the number of entries in the class's constant pool table.
public int getMaxStringLength()
Returns a conservative estimate of the maximum length of the strings contained in the class's constant pool table.
a conservative estimate of the maximum length of the strings contained in the class's constant pool table.
Returns the internal of name of the super class (see Type.getInternalName()). For interfaces, the super class is Object.
the internal name of the super class, or null for Object class.
public int readByte(int offset)
Reads a byte value in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of the value to be read in this ClassReader.
the read value.
public String readClass(int offset, char[] charBuffer)
Reads a CONSTANT_Class constant pool entry in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of an unsigned short value in this ClassReader, whose value is the index of a CONSTANT_Class entry in class's constant pool table.
charBufferthe 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 CONSTANT_Class entry.
public Object readConst(int constantPoolEntryIndex, char[] charBuffer)
Reads a numeric or string constant pool entry in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
constantPoolEntryIndexthe index of a CONSTANT_Integer, CONSTANT_Float, CONSTANT_Long, CONSTANT_Double, CONSTANT_Class, CONSTANT_String, CONSTANT_MethodType, CONSTANT_MethodHandle or CONSTANT_Dynamic entry in the class's constant pool.
charBufferthe buffer to be used to read strings. This buffer must be sufficiently large. It is not automatically resized.
the Integer, Float, Long, Double, String, Type, Handle or ConstantDynamic corresponding to the specified constant pool entry.
public int readInt(int offset)
Reads a signed int value in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of the value to be read in this ClassReader.
the read value.
protected Label readLabel(int bytecodeOffset, Label[] labels)
Returns the label corresponding to the given bytecode offset. The default implementation of this method creates a label for the given offset if it has not been already created.
bytecodeOffseta bytecode offset in a method.
labelsthe already created labels, indexed by their offset. If a label already exists for bytecodeOffset 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[bytecodeOffset].
public long readLong(int offset)
Reads a signed long value in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of the value to be read in this ClassReader.
the read value.
public String readModule(int offset, char[] charBuffer)
Reads a CONSTANT_Module constant pool entry in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of an unsigned short value in this ClassReader, whose value is the index of a CONSTANT_Module entry in class's constant pool table.
charBufferthe 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 CONSTANT_Module entry.
public String readPackage(int offset, char[] charBuffer)
Reads a CONSTANT_Package constant pool entry in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of an unsigned short value in this ClassReader, whose value is the index of a CONSTANT_Package entry in class's constant pool table.
charBufferthe 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 CONSTANT_Package entry.
public short readShort(int offset)
Reads a signed short value in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of the value to be read in this ClassReader.
the read value.
public String readUTF8(int offset, char[] charBuffer)
Reads a CONSTANT_Utf8 constant pool entry in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start offset of an unsigned short value in this ClassReader, whose value is the index of a CONSTANT_Utf8 entry in the class's constant pool table.
charBufferthe buffer to be used to read the string. This buffer must be sufficiently large. It is not automatically resized.
the String corresponding to the specified CONSTANT_Utf8 entry.
public int readUnsignedShort(int offset)
Reads an unsigned short value in this ClassReader. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
offsetthe start index of the value to be read in this ClassReader.
the read value.