javassist

Class CtClass

public abstract class CtClass extends Object

An instance of CtClass represents a class. It is obtained from ClassPool.

See Also: get

Field Summary
static CtClassbooleanType
The CtClass object representing the boolean type.
static CtClassbyteType
The CtClass object representing the byte type.
static CtClasscharType
The CtClass object representing the char type.
static CtClassdoubleType
The CtClass object representing the double type.
static CtClassfloatType
The CtClass object representing the float type.
static CtClassintType
The CtClass object representing the int type.
static CtClasslongType
The CtClass object representing the long type.
static CtClassshortType
The CtClass object representing the short type.
static Stringversion
The version number of this release.
static CtClassvoidType
The CtClass object representing the void type.
Method Summary
voidaddConstructor(CtConstructor c)
Adds a constructor.
voidaddField(CtField f)
Adds a field.
voidaddField(CtField f, String init)
Adds a field with an initial value.
voidaddField(CtField f, CtField.Initializer init)
Adds a field with an initial value.
voidaddInterface(CtClass anInterface)
Adds an interface.
voidaddMethod(CtMethod m)
Adds a method.
voiddebugWriteFile()
Writes a class file as writeFile() does although this method does not prune or freeze the class after writing the class file.
voiddefrost()
Defrosts the class so that the class can be modified again.
voiddetach()
Removes this CtClass object from the ClassPool.
AccessorMakergetAccessorMaker()
Undocumented method.
Object[]getAnnotations()
Returns the annotations associated with this class.
byte[]getAttribute(String name)
Obtains an attribute with the given name.
Object[]getAvailableAnnotations()
Returns the annotations associated with this class.
ClassFilegetClassFile()
Returns a class file for this class.
ClassFilegetClassFile2()
Returns a class file for this class (read only).
CtConstructorgetClassInitializer()
Gets the class initializer (static constructor) declared in the class.
ClassPoolgetClassPool()
Returns a ClassPool for this class.
CtClassgetComponentType()
If this object represents an array, this method returns the component type of the array.
CtConstructorgetConstructor(String desc)
Returns the constructor with the given signature, which is represented by a character string called method descriptor.
CtConstructor[]getConstructors()
Returns an array containing CtConstructor objects representing all the non-private constructors of the class.
CtBehavior[]getDeclaredBehaviors()
Gets all the constructors and methods declared in the class.
CtConstructorgetDeclaredConstructor(CtClass[] params)
Returns a constructor receiving the specified parameters.
CtConstructor[]getDeclaredConstructors()
Gets all the constructors declared in the class.
CtFieldgetDeclaredField(String name)
Retrieves the field with the specified name among the fields declared in the class.
CtField[]getDeclaredFields()
Gets all the fields declared in the class.
CtMethodgetDeclaredMethod(String name, CtClass[] params)
Retrieves the method with the specified name and parameter types among the methods declared in the class.
CtMethodgetDeclaredMethod(String name)
Retrieves the method with the specified name among the methods declared in the class.
CtMethod[]getDeclaredMethods()
Gets all methods declared in the class.
CtClassgetDeclaringClass()
If this class is a member class or interface of another class, then the class enclosing this class is returned.
CtMethodgetEnclosingMethod()
Returns the immediately enclosing method of this class.
CtFieldgetField(String name)
Returns the field with the specified name.
CtField[]getFields()
Returns an array containing CtField objects representing all the non-private fields of the class.
CtClass[]getInterfaces()
Obtains the class objects representing the interfaces implemented by the class or, if this object represents an interface, the interfaces extended by that interface.
CtMethodgetMethod(String name, String desc)
Returns the method with the given name and signature.
CtMethod[]getMethods()
Returns an array containing CtMethod objects representing all the non-private methods of the class.
intgetModifiers()
Returns the modifiers for this class, encoded in an integer.
StringgetName()
Obtains the fully-qualified name of the class.
CtClass[]getNestedClasses()
Returns an array of nested classes declared in the class.
StringgetPackageName()
Obtains the package name.
CollectiongetRefClasses()
Returns a collection of the names of all the classes referenced in this class.
StringgetSimpleName()
Obtains the not-qualified class name.
CtClassgetSuperclass()
Obtains the class object representing the superclass of the class.
URLgetURL()
Returns the uniform resource locator (URL) of the class file.
voidinstrument(CodeConverter converter)
Applies the given converter to all methods and constructors declared in the class.
voidinstrument(ExprEditor editor)
Modifies the bodies of all methods and constructors declared in the class.
booleanisAnnotation()
Determines whether this object represents an annotation type.
booleanisArray()
Returns true if this object represents an array type.
booleanisEnum()
Determines whether this object represents an enum.
booleanisFrozen()
Returns true if the class has been loaded or written out and thus it cannot be modified any more.
booleanisInterface()
Determines whether this object represents a class or an interface.
booleanisModified()
Returns true if the definition of the class has been modified.
booleanisPrimitive()
Returns true if this object represents a primitive Java type: boolean, byte, char, short, int, long, float, double, or void.
static voidmain(String[] args)
Prints the version number and the copyright notice.
CtConstructormakeClassInitializer()
Makes an empty class initializer (static constructor).
CtClassmakeNestedClass(String name, boolean isStatic)
Makes a new public nested class.
StringmakeUniqueName(String prefix)
Makes a unique member name.
voidprune()
Discards unnecessary attributes, in particuar, CodeAttributes (method bodies) of the class, to minimize the memory footprint.
voidremoveConstructor(CtConstructor c)
Removes a constructor declared in this class.
voidremoveField(CtField f)
Removes a field declared in this class.
voidremoveMethod(CtMethod m)
Removes a method declared in this class.
voidreplaceClassName(String oldName, String newName)
Substitutes newName for all occurrences of a class name oldName in the class file.
voidreplaceClassName(ClassMap map)
Changes class names appearing in the class file according to the given map.
voidsetAttribute(String name, byte[] data)
Adds a named attribute.
voidsetInterfaces(CtClass[] list)
Sets implemented interfaces.
voidsetModifiers(int mod)
Sets the modifiers.
voidsetName(String name)
Sets the class name
voidsetSuperclass(CtClass clazz)
Changes a super class unless this object represents an interface.
booleanstopPruning(boolean stop)
Disallows (or allows) automatically pruning this CtClass object.
booleansubclassOf(CtClass superclass)
Determines whether the class directly or indirectly extends the given class.
booleansubtypeOf(CtClass clazz)
Returns true if this class extends or implements clazz.
byte[]toBytecode()
Converts this class to a class file.
voidtoBytecode(DataOutputStream out)
Converts this class to a class file.
ClasstoClass()
Converts this class to a java.lang.Class object.
ClasstoClass(ClassLoader loader, ProtectionDomain domain)
Converts this class to a java.lang.Class object.
ClasstoClass(ClassLoader loader)
Converts this class to a java.lang.Class object.
StringtoString()
Converts the object to a string.
voidwriteFile()
Writes a class file represented by this CtClass object in the current directory.
voidwriteFile(String directoryName)
Writes a class file represented by this CtClass object on a local disk.

Field Detail

booleanType

public static CtClass booleanType
The CtClass object representing the boolean type.

byteType

public static CtClass byteType
The CtClass object representing the byte type.

charType

public static CtClass charType
The CtClass object representing the char type.

doubleType

public static CtClass doubleType
The CtClass object representing the double type.

floatType

public static CtClass floatType
The CtClass object representing the float type.

intType

public static CtClass intType
The CtClass object representing the int type.

longType

public static CtClass longType
The CtClass object representing the long type.

shortType

public static CtClass shortType
The CtClass object representing the short type.

version

public static final String version
The version number of this release.

voidType

public static CtClass voidType
The CtClass object representing the void type.

Method Detail

addConstructor

public void addConstructor(CtConstructor c)
Adds a constructor. To add a class initializer (static constructor), call makeClassInitializer().

See Also: makeClassInitializer

addField

public void addField(CtField f)
Adds a field.

The CtField belonging to another CtClass cannot be directly added to this class. Only a field created for this class can be added.

See Also: CtField

addField

public void addField(CtField f, String init)
Adds a field with an initial value.

The CtField belonging to another CtClass cannot be directly added to this class. Only a field created for this class can be added.

The initial value is given as an expression written in Java. Any regular Java expression can be used for specifying the initial value. The followings are examples.

Here, the type of variable cc is CtClass. The type of f is CtField.

Parameters: init an expression for the initial value.

See Also: byExpr CtField

addField

public void addField(CtField f, CtField.Initializer init)
Adds a field with an initial value.

The CtField belonging to another CtClass cannot be directly added to this class. Only a field created for this class can be added.

For example,

This code adds an int field named "i". The initial value of this field is 1.

Parameters: init specifies the initial value of the field.

See Also: CtField

addInterface

public void addInterface(CtClass anInterface)
Adds an interface.

Parameters: anInterface the added interface.

addMethod

public void addMethod(CtMethod m)
Adds a method.

debugWriteFile

public void debugWriteFile()
Writes a class file as writeFile() does although this method does not prune or freeze the class after writing the class file. Note that, once writeFile() or toBytecode() is called, it cannot be called again since the class is pruned and frozen. This method would be useful for debugging.

defrost

public void defrost()
Defrosts the class so that the class can be modified again.

To avoid changes that will be never reflected, the class is frozen to be unmodifiable if it is loaded or written out. This method should be called only in a case that the class will be reloaded or written out later again.

If defrost() will be called later, pruning must be disallowed in advance.

See Also: isFrozen CtClass detach

detach

public void detach()
Removes this CtClass object from the ClassPool. After this method is called, any method cannot be called on the removed CtClass object.

If get() in ClassPool is called with the name of the removed method, the ClassPool will read the class file again and constructs another CtClass object representing the same class.

getAccessorMaker

public AccessorMaker getAccessorMaker()
Undocumented method. Do not use; internal-use only.

getAnnotations

public Object[] getAnnotations()
Returns the annotations associated with this class. For example, if an annotation @Author is associated with this class, the returned array contains an Author object. The member values can be obtained by calling methods on the Author object.

Returns: an array of annotation-type objects.

Since: 3.1

See Also: getAnnotations

getAttribute

public byte[] getAttribute(String name)
Obtains an attribute with the given name. If that attribute is not found in the class file, this method returns null.

This is a convenient method mainly for obtaining a user-defined attribute. For dealing with attributes, see the javassist.bytecode package. For example, the following expression returns all the attributes of a class file.

Parameters: name attribute name

See Also: AttributeInfo

getAvailableAnnotations

public Object[] getAvailableAnnotations()
Returns the annotations associated with this class. This method is equivalent to getAnnotations() except that, if any annotations are not on the classpath, they are not included in the returned array.

Returns: an array of annotation-type objects.

Since: 3.3

See Also: getAnnotations getAvailableAnnotations

getClassFile

public ClassFile getClassFile()
Returns a class file for this class.

This method is not available if isFrozen() is true.

getClassFile2

public ClassFile getClassFile2()
Returns a class file for this class (read only). Normal applications do not need calling this method. Use getClassFile().

The ClassFile object obtained by this method is read only. Changes to this object might not be reflected on a class file generated by toBytecode(), toClass(), etc.

This method is available even if isFrozen() is true. However, if the class is frozen, it might be also pruned.

See Also: getClassFile isFrozen prune

getClassInitializer

public CtConstructor getClassInitializer()
Gets the class initializer (static constructor) declared in the class. This method returns null if no class initializer is not declared.

See Also: makeClassInitializer CtConstructor

getClassPool

public ClassPool getClassPool()
Returns a ClassPool for this class.

getComponentType

public CtClass getComponentType()
If this object represents an array, this method returns the component type of the array. Otherwise, it returns null.

getConstructor

public CtConstructor getConstructor(String desc)
Returns the constructor with the given signature, which is represented by a character string called method descriptor. For details of the method descriptor, see the JVM specification or javassist.bytecode.Descriptor.

Parameters: desc method descriptor

See Also: Descriptor

getConstructors

public CtConstructor[] getConstructors()
Returns an array containing CtConstructor objects representing all the non-private constructors of the class.

getDeclaredBehaviors

public CtBehavior[] getDeclaredBehaviors()
Gets all the constructors and methods declared in the class.

getDeclaredConstructor

public CtConstructor getDeclaredConstructor(CtClass[] params)
Returns a constructor receiving the specified parameters.

Parameters: params parameter types.

getDeclaredConstructors

public CtConstructor[] getDeclaredConstructors()
Gets all the constructors declared in the class.

See Also: CtConstructor

getDeclaredField

public CtField getDeclaredField(String name)
Retrieves the field with the specified name among the fields declared in the class.

Note: this method does not search the superclasses.

getDeclaredFields

public CtField[] getDeclaredFields()
Gets all the fields declared in the class. The inherited fields are not included.

Note: the result does not include inherited fields.

getDeclaredMethod

public CtMethod getDeclaredMethod(String name, CtClass[] params)
Retrieves the method with the specified name and parameter types among the methods declared in the class.

Note: this method does not search the superclasses.

Parameters: name method name params parameter types

See Also: CtMethod

getDeclaredMethod

public CtMethod getDeclaredMethod(String name)
Retrieves the method with the specified name among the methods declared in the class. If there are multiple methods with the specified name, then this method returns one of them.

Note: this method does not search the superclasses.

See Also: CtMethod

getDeclaredMethods

public CtMethod[] getDeclaredMethods()
Gets all methods declared in the class. The inherited methods are not included.

See Also: CtMethod

getDeclaringClass

public CtClass getDeclaringClass()
If this class is a member class or interface of another class, then the class enclosing this class is returned.

Returns: null if this class is a top-level class or an anonymous class.

getEnclosingMethod

public CtMethod getEnclosingMethod()
Returns the immediately enclosing method of this class. This method works only with JDK 1.5 or later.

Returns: null if this class is not a local class or an anonymous class.

getField

public CtField getField(String name)
Returns the field with the specified name. The returned field may be a private field declared in a super class or interface.

getFields

public CtField[] getFields()
Returns an array containing CtField objects representing all the non-private fields of the class. That array includes non-private fields inherited from the superclasses.

getInterfaces

public CtClass[] getInterfaces()
Obtains the class objects representing the interfaces implemented by the class or, if this object represents an interface, the interfaces extended by that interface.

getMethod

public CtMethod getMethod(String name, String desc)
Returns the method with the given name and signature. The returned method may be declared in a super class. The method signature is represented by a character string called method descriptor, which is defined in the JVM specification.

Parameters: name method name desc method descriptor

See Also: getSignature Descriptor

getMethods

public CtMethod[] getMethods()
Returns an array containing CtMethod objects representing all the non-private methods of the class. That array includes pon-private methods inherited from the superclasses.

getModifiers

public int getModifiers()
Returns the modifiers for this class, encoded in an integer. For decoding, use javassist.Modifier.

If the class is a static nested class (a.k.a. static inner class), the returned modifiers include Modifier.STATIC.

See Also: Modifier

getName

public String getName()
Obtains the fully-qualified name of the class.

getNestedClasses

public CtClass[] getNestedClasses()
Returns an array of nested classes declared in the class. Nested classes are inner classes, anonymous classes, local classes, and static nested classes.

Since: 3.2

getPackageName

public final String getPackageName()
Obtains the package name. It may be null.

getRefClasses

public Collection getRefClasses()
Returns a collection of the names of all the classes referenced in this class. That collection includes the name of this class.

This method may return null.

getSimpleName

public final String getSimpleName()
Obtains the not-qualified class name.

getSuperclass

public CtClass getSuperclass()
Obtains the class object representing the superclass of the class. It returns null if this object represents the java.lang.Object class and thus it does not have the super class.

If this object represents an interface, this method always returns the java.lang.Object class. To obtain the super interfaces extended by that interface, call getInterfaces().

getURL

public URL getURL()
Returns the uniform resource locator (URL) of the class file.

instrument

public void instrument(CodeConverter converter)
Applies the given converter to all methods and constructors declared in the class. This method calls instrument() on every CtMethod and CtConstructor object in the class.

Parameters: converter specifies how to modify.

instrument

public void instrument(ExprEditor editor)
Modifies the bodies of all methods and constructors declared in the class. This method calls instrument() on every CtMethod and CtConstructor object in the class.

Parameters: editor specifies how to modify.

isAnnotation

public boolean isAnnotation()
Determines whether this object represents an annotation type. It returns true if this object represents an annotation type.

Since: 3.2

isArray

public boolean isArray()
Returns true if this object represents an array type.

isEnum

public boolean isEnum()
Determines whether this object represents an enum. It returns true if this object represents an enum.

Since: 3.2

isFrozen

public boolean isFrozen()
Returns true if the class has been loaded or written out and thus it cannot be modified any more.

See Also: defrost detach

isInterface

public boolean isInterface()
Determines whether this object represents a class or an interface. It returns true if this object represents an interface.

isModified

public boolean isModified()
Returns true if the definition of the class has been modified.

isPrimitive

public boolean isPrimitive()
Returns true if this object represents a primitive Java type: boolean, byte, char, short, int, long, float, double, or void.

main

public static void main(String[] args)
Prints the version number and the copyright notice.

The following command invokes this method:

makeClassInitializer

public CtConstructor makeClassInitializer()
Makes an empty class initializer (static constructor). If the class already includes a class initializer, this method returns it.

See Also: getClassInitializer

makeNestedClass

public CtClass makeNestedClass(String name, boolean isStatic)
Makes a new public nested class. If this method is called, the CtClass, which encloses the nested class, is modified since a class file includes a list of nested classes.

The current implementation only supports a static nested class. isStatic must be true.

Parameters: name the simple name of the nested class. isStatic true if the nested class is static.

makeUniqueName

public String makeUniqueName(String prefix)
Makes a unique member name. This method guarantees that the returned name is not used as a prefix of any methods or fields visible in this class. If the returned name is XYZ, then any method or field names in this class do not start with XYZ.

Parameters: prefix the prefix of the member name.

prune

public void prune()
Discards unnecessary attributes, in particuar, CodeAttributes (method bodies) of the class, to minimize the memory footprint. After calling this method, the class is read only. It cannot be modified any more. Furthermore, toBytecode(), writeFile(), toClass(), or instrument() cannot be called. However, the method names and signatures in the class etc. are still accessible.

toBytecode(), writeFile(), and toClass() internally call this method.

See Also: toBytecode toClass writeFile instrument CtClass

removeConstructor

public void removeConstructor(CtConstructor c)
Removes a constructor declared in this class.

Parameters: c removed constructor.

Throws: NotFoundException if the constructor is not found.

removeField

public void removeField(CtField f)
Removes a field declared in this class.

Parameters: f removed field.

Throws: NotFoundException if the field is not found.

removeMethod

public void removeMethod(CtMethod m)
Removes a method declared in this class.

Parameters: m removed method.

Throws: NotFoundException if the method is not found.

replaceClassName

public void replaceClassName(String oldName, String newName)
Substitutes newName for all occurrences of a class name oldName in the class file.

Parameters: oldName replaced class name newName substituted class name

replaceClassName

public void replaceClassName(ClassMap map)
Changes class names appearing in the class file according to the given map.

All the class names appearing in the class file are tested with map to determine whether each class name is replaced or not. Thus this method can be used for collecting all the class names in the class file. To do that, first define a subclass of ClassMap so that get() records all the given parameters. Then, make an instance of that subclass as an empty hash-table. Finally, pass that instance to this method. After this method finishes, that instance would contain all the class names appearing in the class file.

Parameters: map the hashtable associating replaced class names with substituted names.

setAttribute

public void setAttribute(String name, byte[] data)
Adds a named attribute. An arbitrary data (smaller than 64Kb) can be saved in the class file. Some attribute name are reserved by the JVM. The attributes with the non-reserved names are ignored when a class file is loaded into the JVM. If there is already an attribute with the same name, this method substitutes the new one for it.

This is a convenient method mainly for adding a user-defined attribute. For dealing with attributes, see the javassist.bytecode package. For example, the following expression adds an attribute info to a class file.

Parameters: name attribute name data attribute value

See Also: AttributeInfo

setInterfaces

public void setInterfaces(CtClass[] list)
Sets implemented interfaces. If this object represents an interface, this method sets the interfaces extended by that interface.

Parameters: list a list of the CtClass objects representing interfaces, or null if the class implements no interfaces.

setModifiers

public void setModifiers(int mod)
Sets the modifiers.

If the class is a nested class, this method also modifies the class declaring that nested class (i.e. the enclosing class is modified).

Parameters: mod modifiers encoded by javassist.Modifier

See Also: Modifier

setName

public void setName(String name)
Sets the class name

Parameters: name fully-qualified name

setSuperclass

public void setSuperclass(CtClass clazz)
Changes a super class unless this object represents an interface. The new super class must be compatible with the old one.

If this object represents an interface, this method is equivalent to addInterface(); it appends clazz to the list of the super interfaces extended by that interface. Note that an interface can extend multiple super interfaces.

stopPruning

public boolean stopPruning(boolean stop)
Disallows (or allows) automatically pruning this CtClass object.

Javassist can automatically prune a CtClass object when toBytecode() (or toClass(), writeFile()) is called. Since a ClassPool holds all instances of CtClass even after toBytecode() (or toClass(), writeFile()) is called, pruning may significantly save memory consumption.

If ClassPool.doPruning is true, the automatic pruning is on by default. Otherwise, it is off.

Parameters: stop disallow pruning if true. Otherwise, allow.

Returns: the previous status of pruning. true if pruning is already stopped.

See Also: detach prune doPruning

subclassOf

public boolean subclassOf(CtClass superclass)
Determines whether the class directly or indirectly extends the given class. If this class extends a class A and the class A extends a class B, then subclassof(B) returns true.

This method returns true if the given class is identical to the class represented by this object.

subtypeOf

public boolean subtypeOf(CtClass clazz)
Returns true if this class extends or implements clazz. It also returns true if this class is the same as clazz.

toBytecode

public byte[] toBytecode()
Converts this class to a class file. Once this method is called, further modifications are not possible any more.

Returns: the contents of the class file.

toBytecode

public void toBytecode(DataOutputStream out)
Converts this class to a class file. Once this method is called, further modifications are not possible any more.

This method dose not close the output stream in the end.

Parameters: out the output stream that a class file is written to.

toClass

public Class toClass()
Converts this class to a java.lang.Class object. Once this method is called, further modifications are not allowed any more. To load the class, this method uses the context class loader of the current thread. If the program is running on some application server, the context class loader might be inappropriate to load the class.

This method is provided for convenience. If you need more complex functionality, you should write your own class loader.

Note: this method calls toClass() in ClassPool.

Warining: A Class object returned by this method may not work with a security manager or a signed jar file because a protection domain is not specified.

See Also: CtClass toClass

toClass

public Class toClass(ClassLoader loader, ProtectionDomain domain)
Converts this class to a java.lang.Class object. Once this method is called, further modifications are not allowed any more.

The class file represented by this CtClass is loaded by the given class loader to construct a java.lang.Class object. Since a private method on the class loader is invoked through the reflection API, the caller must have permissions to do that.

An easy way to obtain ProtectionDomain object is to call getProtectionDomain() in java.lang.Class. It returns the domain that the class belongs to.

This method is provided for convenience. If you need more complex functionality, you should write your own class loader.

Note: this method calls toClass() in ClassPool.

Parameters: loader the class loader used to load this class. If it is null, the class loader returned by getClassLoader is used. domain the protection domain that the class belongs to. If it is null, the default domain created by java.lang.ClassLoader is used.

Since: 3.3

See Also: ClassPool

toClass

public final Class toClass(ClassLoader loader)

Deprecated: Replaced by toClass

Converts this class to a java.lang.Class object.

Warining: A Class object returned by this method may not work with a security manager or a signed jar file because a protection domain is not specified.

toString

public String toString()
Converts the object to a string.

writeFile

public void writeFile()
Writes a class file represented by this CtClass object in the current directory. Once this method is called, further modifications are not possible any more.

writeFile

public void writeFile(String directoryName)
Writes a class file represented by this CtClass object on a local disk. Once this method is called, further modifications are not possible any more.

Parameters: directoryName it must end without a directory separator.

Javassist, a Java-bytecode translator toolkit.
Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.