ClassWriter (DataNucleus Core 5.1.13-SNAPSHOT API)

java.lang.Object
- org.datanucleus.enhancer.asm.ClassVisitor
- - org.datanucleus.enhancer.asm.ClassWriter

```
public class ClassWriter
extends ClassVisitor
```
A ClassVisitor that generates a corresponding ClassFile structure, as defined in the Java Virtual Machine Specification (JVMS). It can be used alone, to generate a Java class "from scratch", or with one or more ClassReader and adapter ClassVisitor to generate a modified class from one or more existing Java classes.

Author:

Eric Bruneton

See Also:

JVMS 4

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`COMPUTE_FRAMES` A flag to automatically compute the stack map frames of methods from scratch.
`static int`	`COMPUTE_MAXS` A flag to automatically compute the maximum stack size and the maximum number of local variables of methods.

Fields inherited from class org.datanucleus.enhancer.asm.ClassVisitor
api, cv

Constructor Summary

Constructors
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.

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`protected String`	`getCommonSuperClass(String type1, String type2)` Returns the common super type of the two given types.
`int`	`newClass(String value)` Adds a class reference to the constant pool of the class being build.
`int`	`newConst(Object value)` Adds a number or string constant to the constant pool of the class being build.
`int`	`newField(String owner, String name, String descriptor)` Adds a field reference to the constant pool of the class being build.
`int`	`newHandle(int tag, String owner, String name, String descriptor)` Deprecated. this method is superseded by `newHandle(int, String, String, String, boolean)`.
`int`	`newHandle(int tag, String owner, String name, String descriptor, boolean isInterface)` Adds a handle to the constant pool of the class being build.
`int`	`newInvokeDynamic(String name, String descriptor, Handle bootstrapMethodHandle, Object... bootstrapMethodArguments)` Adds an invokedynamic reference to the constant pool of the class being build.
`int`	`newMethod(String owner, String name, String descriptor, boolean isInterface)` Adds a method reference to the constant pool of the class being build.
`int`	`newMethodType(String methodDescriptor)` Adds a method type reference to the constant pool of the class being build.
`int`	`newModule(String moduleName)` Adds a module reference to the constant pool of the class being build.
`int`	`newNameType(String name, String descriptor)` Adds a name and type to the constant pool of the class being build.
`int`	`newPackage(String packageName)` Adds a package reference 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 content of the class file that was built by this ClassWriter.
`void`	`visit(int version, int access, String name, String signature, String superName, String[] interfaces)` Visits the header of the class.
`AnnotationVisitor`	`visitAnnotation(String descriptor, boolean visible)` Visits an annotation of the class.
`void`	`visitAttribute(Attribute attribute)` Visits a non standard attribute of the class.
`void`	`visitEnd()` Visits the end of the class.
`FieldVisitor`	`visitField(int access, String name, String descriptor, 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 descriptor, String signature, String[] exceptions)` Visits a method of the class.
`ModuleVisitor`	`visitModule(String name, int access, String version)` Visit the module corresponding to the class.
`void`	`visitOuterClass(String owner, String name, String descriptor)` Visits the enclosing class of the class.
`void`	`visitSource(String file, String debug)` Visits the source of the class.
`AnnotationVisitor`	`visitTypeAnnotation(int typeRef, TypePath typePath, String descriptor, boolean visible)` Visits an annotation on a type in the class signature.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - COMPUTE_MAXS
```
public static final int COMPUTE_MAXS
```
    A flag to automatically compute the maximum stack size and the maximum number of local variables of methods. If this flag is set, then the arguments of the MethodVisitor.visitMaxs(int, int) method of the MethodVisitor returned by the visitMethod(int, java.lang.String, java.lang.String, java.lang.String, java.lang.String[]) method will be ignored, and computed automatically from the signature and the bytecode of each method.
    
    See Also:
    
    ClassWriter(int), Constant Field Values
  - COMPUTE_FRAMES
```
public static final int COMPUTE_FRAMES
```
    A flag to automatically compute the stack map frames of methods from scratch. If this flag is set, then the calls to the 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 MethodVisitor.visitMaxs(int, int) method are also ignored and recomputed from the bytecode. In other words, COMPUTE_FRAMES implies COMPUTE_MAXS.
    
    See Also:
    
    ClassWriter(int), Constant Field Values
- Constructor Detail
  - ClassWriter
```
public ClassWriter(int flags)
```
    Constructs a new ClassWriter object.
    
    Parameters:
    
    flags - option flags that can be used to modify the default behavior of this class. Must be zero or more of COMPUTE_MAXS and COMPUTE_FRAMES.
  - ClassWriter
```
public ClassWriter(ClassReader classReader,
                   int flags)
```
    Constructs a new ClassWriter object and enables optimizations for "mostly add" bytecode transformations. These optimizations are the following:
    - The constant pool and bootstrap methods from the original class are copied as is in the new class, which saves time. New constant pool entries and new bootstrap methods will be added at the end if necessary, but unused constant pool entries or bootstrap methods won't be removed.
    - Methods that are not transformed are copied as is in the new class, directly from the original class bytecode (i.e. without emitting visit events for all the method instructions), which saves a lot of time. Untransformed methods are detected by the fact that the ClassReader receives MethodVisitor objects that come from a ClassWriter (and not from any other ClassVisitor instance).
    Parameters:
    
    classReader - the ClassReader used to read the original class. It will be used to copy the entire constant pool and bootstrap methods 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.Must be zero or more of COMPUTE_MAXS and COMPUTE_FRAMES. These option flags do not affect methods that are copied as is in the new class. This means that neither the maximum stack size nor the stack frames will be computed for these methods.
- Method Detail
  - visit
```
public final void visit(int version,
                        int access,
                        String name,
                        String signature,
                        String superName,
                        String[] interfaces)
```
    Description copied from class: ClassVisitor
    
    Visits the header of the class.
    
    Overrides:
    
    visit in class ClassVisitor
    
    Parameters:
    
    version - the class version. The minor version is stored in the 16 most significant bits, and the major version in the 16 least significant bits.
    
    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 Type.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 Type.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 Type.getInternalName()). May be null.
  - visitSource
```
public final void visitSource(String file,
                              String debug)
```
    Description copied from class: ClassVisitor
    
    Visits the source of the class.
    
    Overrides:
    
    visitSource in class 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 correspondence between source and compiled elements of the class. May be null.
  - visitModule
```
public final ModuleVisitor visitModule(String name,
                                       int access,
                                       String version)
```
    Description copied from class: ClassVisitor
    
    Visit the module corresponding to the class.
    
    Overrides:
    
    visitModule in class ClassVisitor
    
    Parameters:
    
    name - the fully qualified name (using dots) of the module.
    
    access - the module access flags, among ACC_OPEN, ACC_SYNTHETIC and ACC_MANDATED.
    
    version - the module version, or null.
    
    Returns:
    
    a visitor to visit the module values, or null if this visitor is not interested in visiting this module.
  - visitOuterClass
```
public final void visitOuterClass(String owner,
                                  String name,
                                  String descriptor)
```
    Description copied from class: ClassVisitor
    
    Visits the enclosing class of the class. This method must be called only if the class has an enclosing class.
    
    Overrides:
    
    visitOuterClass in class 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.
    
    descriptor - 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 final AnnotationVisitor visitAnnotation(String descriptor,
                                               boolean visible)
```
    Description copied from class: ClassVisitor
    
    Visits an annotation of the class.
    
    Overrides:
    
    visitAnnotation in class ClassVisitor
    
    Parameters:
    
    descriptor - the class descriptor of the annotation class.
    
    visible - true if the annotation is visible at runtime.
    
    Returns:
    
    a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.
  - visitTypeAnnotation
```
public final AnnotationVisitor visitTypeAnnotation(int typeRef,
                                                   TypePath typePath,
                                                   String descriptor,
                                                   boolean visible)
```
    Description copied from class: ClassVisitor
    
    Visits an annotation on a type in the class signature.
    
    Overrides:
    
    visitTypeAnnotation in class ClassVisitor
    
    Parameters:
    
    typeRef - a reference to the annotated type. The sort of this type reference must be TypeReference.CLASS_TYPE_PARAMETER, TypeReference.CLASS_TYPE_PARAMETER_BOUND or TypeReference.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.
    
    descriptor - the class descriptor of the annotation class.
    
    visible - true if the annotation is visible at runtime.
    
    Returns:
    
    a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.
  - visitAttribute
```
public final void visitAttribute(Attribute attribute)
```
    Description copied from class: ClassVisitor
    
    Visits a non standard attribute of the class.
    
    Overrides:
    
    visitAttribute in class ClassVisitor
    
    Parameters:
    
    attribute - an attribute.
  - visitInnerClass
```
public final void visitInnerClass(String name,
                                  String outerName,
                                  String innerName,
                                  int access)
```
    Description copied from class: ClassVisitor
    
    Visits information about an inner class. This inner class is not necessarily a member of the class being visited.
    
    Overrides:
    
    visitInnerClass in class ClassVisitor
    
    Parameters:
    
    name - the internal name of an inner class (see Type.getInternalName()).
    
    outerName - the internal name of the class to which the inner class belongs (see Type.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.
  - visitField
```
public final FieldVisitor visitField(int access,
                                     String name,
                                     String descriptor,
                                     String signature,
                                     Object value)
```
    Description copied from class: ClassVisitor
    
    Visits a field of the class.
    
    Overrides:
    
    visitField in class 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.
    
    descriptor - 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 final MethodVisitor visitMethod(int access,
                                       String name,
                                       String descriptor,
                                       String signature,
                                       String[] exceptions)
```
    Description copied from class: 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.
    
    Overrides:
    
    visitMethod in class 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.
    
    descriptor - 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 Type.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 final void visitEnd()
```
    Description copied from class: 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.
    
    Overrides:
    
    visitEnd in class ClassVisitor
  - toByteArray
```
public byte[] toByteArray()
```
    Returns the content of the class file that was built by this ClassWriter.
    
    Returns:
    
    the binary content of the JVMS ClassFile structure that was built by this ClassWriter.
  - newConst
```
public int newConst(Object value)
```
    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:
    
    value - 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.
  - newMethodType
```
public int newMethodType(String methodDescriptor)
```
    Adds a method type 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:
    
    methodDescriptor - method descriptor of the method type.
    
    Returns:
    
    the index of a new or already existing method type reference item.
  - newModule
```
public int newModule(String moduleName)
```
    Adds a module 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:
    
    moduleName - name of the module.
    
    Returns:
    
    the index of a new or already existing module reference item.
  - newPackage
```
public int newPackage(String packageName)
```
    Adds a package 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:
    
    packageName - name of the package in its internal form.
    
    Returns:
    
    the index of a new or already existing module reference item.
  - newHandle
```
@Deprecated
public int newHandle(int tag,
                                 String owner,
                                 String name,
                                 String descriptor)
```
    Deprecated. this method is superseded by newHandle(int, String, String, String, boolean).
    
    Adds a handle 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:
    
    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.
    
    descriptor - the descriptor of the field or method.
    
    Returns:
    
    the index of a new or already existing method type reference item.
  - newHandle
```
public int newHandle(int tag,
                     String owner,
                     String name,
                     String descriptor,
                     boolean isInterface)
```
    Adds a handle 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:
    
    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.
    
    descriptor - the descriptor of the field or method.
    
    isInterface - true if the owner is an interface.
    
    Returns:
    
    the index of a new or already existing method type reference item.
  - newInvokeDynamic
```
public int newInvokeDynamic(String name,
                            String descriptor,
                            Handle bootstrapMethodHandle,
                            Object... bootstrapMethodArguments)
```
    Adds an invokedynamic 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:
    
    name - name of the invoked method.
    
    descriptor - descriptor of the invoke method.
    
    bootstrapMethodHandle - the bootstrap method.
    
    bootstrapMethodArguments - the bootstrap method constant arguments.
    
    Returns:
    
    the index of a new or already existing invokedynamic reference item.
  - newField
```
public int newField(String owner,
                    String name,
                    String descriptor)
```
    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.
    
    descriptor - 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 descriptor,
                     boolean isInterface)
```
    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.
    
    descriptor - the method's descriptor.
    
    isInterface - 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 descriptor)
```
    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.
    
    descriptor - a type descriptor.
    
    Returns:
    
    the index of a new or already existing name and type item.
  - getCommonSuperClass
```
protected String getCommonSuperClass(String type1,
                                     String type2)
```
    Returns the common super type of the two given types. The default implementation of this method loads the two given classes and uses the java.lang.Class methods to find the common super class. It can be overridden to compute this common super type in other ways, in particular without actually loading any class, or to take into account the class that is currently being generated by this ClassWriter, which can of course not be loaded since it is under construction.
    
    Parameters:
    
    type1 - the internal name of a class.
    
    type2 - the internal name of another class.
    
    Returns:
    
    the internal name of the common super class of the two given classes.

Class ClassWriter

Field Summary

Fields inherited from class org.datanucleus.enhancer.asm.ClassVisitor

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

COMPUTE_MAXS

COMPUTE_FRAMES

Constructor Detail

ClassWriter

ClassWriter

Method Detail

visit

visitSource

visitModule

visitOuterClass

visitAnnotation

visitTypeAnnotation

visitAttribute

visitInnerClass

visitField

visitMethod

visitEnd

toByteArray

newConst

newUTF8

newClass

newMethodType

newModule

newPackage

newHandle

newHandle

newInvokeDynamic

newField

newMethod

newNameType

getCommonSuperClass