org.objectweb.asm
Class ClassWriter

java.lang.Object
  extended by org.objectweb.asm.ClassWriter
All Implemented Interfaces:
ClassVisitor

public class ClassWriter
extends Object
implements ClassVisitor

A ClassVisitor that generates Java class files. 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

Constructor Summary
ClassWriter(boolean computeMaxs)
          Constructs a new ClassWriter object.
ClassWriter(boolean computeMaxs, boolean skipUnknownAttributes)
          Constructs a new ClassWriter object.
 
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.
 int newConstDouble(double d)
           
 int newConstFloat(float f)
           
 int newConstInt(int i)
           
 int newConstLong(long l)
           
 int newField(String owner, String name, String desc)
          Adds a field reference 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.
 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 superName, String[] interfaces, String sourceFile)
          Visits the header of the class.
 void visitAttribute(Attribute attr)
          Visits a non standard attribute of the class.
 void visitEnd()
          Visits the end of the class.
 void visitField(int access, String name, String desc, Object value, Attribute attrs)
          Visits a field of the class.
 void visitInnerClass(String name, String outerName, String innerName, int access)
          Visits information about an inner class.
 CodeVisitor visitMethod(int access, String name, String desc, String[] exceptions, Attribute attrs)
          Visits a method of the class.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

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 CodeVisitor 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 CodeVisitor returned by the visitMethod method will be ignored, and computed automatically from the signature and the bytecode of each method.
skipUnknownAttributes - true to silently ignore unknown attributes, or false to throw an exception if an unknown attribute is found.
Method Detail

visit

public void visit(int version,
                  int access,
                  String name,
                  String superName,
                  String[] interfaces,
                  String sourceFile)
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 Constants). This parameter also indicates if the class is deprecated.
name - the internal name of the class (see getInternalName).
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 java.lang.Object class.
interfaces - the internal names of the class's interfaces (see getInternalName). May be null.
sourceFile - the name of the source file from which this class was compiled. May be null.

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 void visitField(int access,
                       String name,
                       String desc,
                       Object value,
                       Attribute attrs)
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 Constants). This parameter also indicates if the field is synthetic and/or deprecated.
name - the field's name.
desc - the field's descriptor (see Type).
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.
attrs - the non standard method attributes, linked together by their next field. May be null.

visitMethod

public CodeVisitor visitMethod(int access,
                               String name,
                               String desc,
                               String[] exceptions,
                               Attribute attrs)
Description copied from interface: ClassVisitor
Visits a method of the class. This method must return a new CodeVisitor 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 Constants). This parameter also indicates if the method is synthetic and/or deprecated.
name - the method's name.
desc - the method's descriptor (see Type).
exceptions - the internal names of the method's exception classes (see getInternalName). May be null.
attrs - the non standard method attributes, linked together by their next field. 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.

visitAttribute

public void visitAttribute(Attribute attr)
Description copied from interface: ClassVisitor
Visits a non standard attribute of the class. This method must visit only the first attribute in the given attribute list.

Specified by:
visitAttribute in interface ClassVisitor
Parameters:
attr - a non standard class attribute. Must not be null.

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.

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.

newConstInt

public int newConstInt(int i)

newConstLong

public int newConstLong(long l)

newConstFloat

public int newConstFloat(float f)

newConstDouble

public int newConstDouble(double d)

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.

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.

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.