Package javassist

Class ClassPool

java.lang.Object

javassist.ClassPool

public class ClassPool
extends Object

A container of CtClass objects. A CtClass object must be obtained from this object. If get() is called on this object, it searches various sources represented by ClassPath to find a class file and then it creates a CtClass object representing that class file. The created object is returned to the caller.

Memory consumption memo:

ClassPool objects hold all the CtClasses that have been created so that the consistency among modified classes can be guaranteed. Thus if a large number of CtClasses are processed, the ClassPool will consume a huge amount of memory. To avoid this, a ClassPool object should be recreated, for example, every hundred classes processed. Note that getDefault() is a singleton factory. Otherwise, detach() in CtClass should be used to avoid huge memory consumption.

ClassPool hierarchy:

ClassPools can make a parent-child hierarchy as java.lang.ClassLoaders. If a ClassPool has a parent pool, get() first asks the parent pool to find a class file. Only if the parent could not find the class file, get() searches the ClassPaths of the child ClassPool. This search order is reversed if ClassPath.childFirstLookup is true.

See Also:

• CtClass
• ClassPath

Field Summary

Fields

Modifier and Type	Field	Description
static boolean	cacheOpenedJarFile	If true, the contents of a jar file are cached after the jar file is opened.
boolean	childFirstLookup	Determines the search order.
static boolean	doPruning	Turning the automatic pruning on/off.
static boolean	releaseUnmodifiedClassFile	If true, unmodified and not-recently-used class files are periodically released for saving memory.

Constructor Summary

Constructors

Constructor	Description
ClassPool()	Creates a root class pool.
ClassPool(boolean useDefaultPath)	Creates a root class pool.
ClassPool(ClassPool parent)	Creates a class pool.

Method Summary

Modifier and Type	Method	Description
ClassPath	appendClassPath(String pathname)	Appends a directory or a jar (or zip) file to the end of the search path.
ClassPath	appendClassPath(ClassPath cp)	Appends a ClassPath object to the end of the search path.
void	appendPathList(String pathlist)	Appends directories and jar files for search.
ClassPath	appendSystemPath()	Appends the system search path to the end of the search path.
void	clearImportedPackages()	Clear all the package names recorded by importPackage().
URL	find(String classname)	Searches the class path to obtain the URL of the class file specified by classname.
CtClass	get(String classname)	Reads a class file from the source and returns a reference to the CtClass object representing that class file.
CtClass[]	get(String[] classnames)	Reads class files from the source and returns an array of CtClass objects representing those class files.
CtClass	getAndRename(String orgName, String newName)	Reads a class file and constructs a CtClass object with a new name.
ClassLoader	getClassLoader()	Get the classloader for toClass(), getAnnotations() in CtClass, etc.
CtClass	getCtClass(String classname)	Returns a CtClass object with the given name.
static ClassPool	getDefault()	Returns the default class pool.
Iterator<String>	getImportedPackages()	Returns all the package names recorded by importPackage().
CtMethod	getMethod(String classname, String methodname)	Reads a class file and obtains a compile-time method.
CtClass	getOrNull(String classname)	Reads a class file from the source and returns a reference to the CtClass object representing that class file.
void	importPackage(String packageName)	Record a package name so that the Javassist compiler searches the package to resolve a class name.
ClassPath	insertClassPath(String pathname)	Inserts a directory or a jar (or zip) file at the head of the search path.
ClassPath	insertClassPath(ClassPath cp)	Insert a ClassPath object at the head of the search path.
Object[]	lookupCflow(String name)	Undocumented method.
CtClass	makeAnnotation(String name)	Creates a new annotation.
CtClass	makeClass(InputStream classfile)	Creates a new class (or interface) from the given class file.
CtClass	makeClass(InputStream classfile, boolean ifNotFrozen)	Creates a new class (or interface) from the given class file.
CtClass	makeClass(String classname)	Creates a new public class.
CtClass	makeClass(String classname, CtClass superclass)	Creates a new public class.
CtClass	makeClass(ClassFile classfile)	Creates a new class (or interface) from the given class file.
CtClass	makeClass(ClassFile classfile, boolean ifNotFrozen)	Creates a new class (or interface) from the given class file.
CtClass	makeClassIfNew(InputStream classfile)	Creates a new class (or interface) from the given class file.
CtClass	makeInterface(String name)	Creates a new public interface.
CtClass	makeInterface(String name, CtClass superclass)	Creates a new public interface.
void	makePackage(ClassLoader loader, String name)	Deprecated.
void	recordInvalidClassName(String name)	Deprecated.
void	removeClassPath(ClassPath cp)	Detatches the ClassPath object from the search path.
Class	toClass(CtClass clazz)	Converts the given class to a java.lang.Class object.
Class<?>	toClass(CtClass ct, Class<?> neighbor)	Converts the class to a java.lang.Class object.
Class	toClass(CtClass ct, Class<?> neighbor, ClassLoader loader, ProtectionDomain domain)	Converts the class to a java.lang.Class object.
Class	toClass(CtClass ct, ClassLoader loader)	Deprecated. Replaced by toClass(CtClass,Class,ClassLoader,ProtectionDomain).
Class	toClass(CtClass ct, ClassLoader loader, ProtectionDomain domain)	Deprecated. Replaced by toClass(CtClass,Class,ClassLoader,ProtectionDomain).
Class<?>	toClass(CtClass ct, MethodHandles.Lookup lookup)	Converts the class to a java.lang.Class object.
String	toString()	Returns the class search path.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

childFirstLookup

public boolean childFirstLookup

Determines the search order.

If this field is true, get() first searches the class path associated to this ClassPool and then the class path associated with the parent ClassPool. Otherwise, the class path associated with the parent is searched first.

The default value is false.

doPruning

public static boolean doPruning

Turning the automatic pruning on/off.

If this field is true, CtClass objects are automatically pruned by default when toBytecode() etc. are called. The automatic pruning can be turned on/off individually for each CtClass object.

The initial value is false.

See Also:

• CtClass.prune()
• CtClass.stopPruning(boolean)
• CtClass.detach()

releaseUnmodifiedClassFile

public static boolean releaseUnmodifiedClassFile

If true, unmodified and not-recently-used class files are periodically released for saving memory.

The initial value is true.

cacheOpenedJarFile

public static boolean cacheOpenedJarFile

If true, the contents of a jar file are cached after the jar file is opened.

The initial value is true.

Constructor Details

ClassPool

public ClassPool()

Creates a root class pool. No parent class pool is specified.

ClassPool

public ClassPool(boolean useDefaultPath)

Creates a root class pool. If useDefaultPath is true, appendSystemPath() is called. Otherwise, this constructor is equivalent to the constructor taking no parameter.

Parameters:

useDefaultPath - true if the system search path is appended.

ClassPool

public ClassPool(ClassPool parent)

Creates a class pool.

Parameters:

parent - the parent of this class pool. If this is a root class pool, this parameter must be null.

See Also:

• getDefault()

Method Details

getDefault

public static ClassPool getDefault()

Returns the default class pool. The returned object is always identical since this method is a singleton factory.

The default class pool searches the system search path, which usually includes the platform library, extension libraries, and the search path specified by the -classpath option or the CLASSPATH environment variable.

When this method is called for the first time, the default class pool is created with the following code snippet:

ClassPool cp = new ClassPool();
 cp.appendSystemPath();
 

If the default class pool cannot find any class files, try ClassClassPath, ModuleClassPath, or LoaderClassPath.

See Also:

• ClassClassPath
• LoaderClassPath

toString

public String toString()

Returns the class search path.

Overrides:

toString in class Object

importPackage

public void importPackage(String packageName)

Record a package name so that the Javassist compiler searches the package to resolve a class name. Don't record the java.lang package, which has been implicitly recorded by default.

Since version 3.14, packageName can be a fully-qualified class name.

Note that get() in ClassPool does not search the recorded package. Only the compiler searches it.

Parameters:

packageName - the package name. It must not include the last '.' (dot). For example, "java.util" is valid but "java.util." is wrong.

Since:

3.1

clearImportedPackages

public void clearImportedPackages()

Clear all the package names recorded by importPackage(). The java.lang package is not removed.

Since:

3.1

See Also:

• importPackage(String)

getImportedPackages

public Iterator<String> getImportedPackages()

Returns all the package names recorded by importPackage().

Since:

3.1

See Also:

• importPackage(String)

recordInvalidClassName

public void recordInvalidClassName(String name)

Deprecated.

Records a class name that never exists. For example, a package name can be recorded by this method. This would improve execution performance since get() quickly throw an exception without searching the class path at all if the given name is an invalid name recorded by this method. Note that searching the class path takes relatively long time.

The current implementation of this method performs nothing.

Parameters:

name - an invalid class name (separeted by dots).

lookupCflow

public Object[] lookupCflow(String name)

Undocumented method. Do not use; internal-use only.

Parameters:

name - the name of $cflow variable

getAndRename

public CtClass getAndRename(String orgName,
 String newName)
                     throws NotFoundException

Reads a class file and constructs a CtClass object with a new name. This method is useful if you want to generate a new class as a copy of another class (except the class name). For example,

 getAndRename("Point", "Pair")
 

returns a CtClass object representing Pair class. The definition of Pair is the same as that of Point class except the class name since Pair is defined by reading Point.class.

Parameters:

orgName - the original (fully-qualified) class name

newName - the new class name

Throws:

NotFoundException

get

public CtClass get(String classname)
            throws NotFoundException

Reads a class file from the source and returns a reference to the CtClass object representing that class file. If that class file has been already read, this method returns a reference to the CtClass created when that class file was read at the first time.

If classname ends with "[]", then this method returns a CtClass object for that array type.

To obtain an inner class, use "$" instead of "." for separating the enclosing class name and the inner class name.

Parameters:

classname - a fully-qualified class name.

Throws:

NotFoundException

getOrNull

public CtClass getOrNull(String classname)

Reads a class file from the source and returns a reference to the CtClass object representing that class file. This method is equivalent to get except that it returns null when a class file is not found and it never throws an exception.

Parameters:

classname - a fully-qualified class name.

Returns:

a CtClass object or null.

Since:

3.13

See Also:

• get(String)
• find(String)

getCtClass

public CtClass getCtClass(String classname)
                   throws NotFoundException

Returns a CtClass object with the given name. This is almost equivalent to get(String) except that classname can be an array-type "descriptor" (an encoded type name) such as [Ljava/lang/Object;.

Using this method is not recommended; this method should be used only to obtain the CtClass object with a name returned from getClassInfo in javassist.bytecode.ClassPool. getClassInfo returns a fully-qualified class name but, if the class is an array type, it returns a descriptor.

Parameters:

classname - a fully-qualified class name or a descriptor representing an array type.

Throws:

NotFoundException

Since:

3.8.1

See Also:

• get(String)
• ConstPool.getClassInfo(int)
• Descriptor.toCtClass(String, ClassPool)

find

public URL find(String classname)

Searches the class path to obtain the URL of the class file specified by classname. It is also used to determine whether the class file exists.

Parameters:

classname - a fully-qualified class name.

Returns:

null if the class file could not be found.

See Also:

• CtClass.getURL()

get

public CtClass[] get(String[] classnames)
              throws NotFoundException

Reads class files from the source and returns an array of CtClass objects representing those class files.

If an element of classnames ends with "[]", then this method returns a CtClass object for that array type.

Parameters:

classnames - an array of fully-qualified class name.

Throws:

NotFoundException

getMethod

public CtMethod getMethod(String classname,
 String methodname)
                   throws NotFoundException

Reads a class file and obtains a compile-time method.

Parameters:

classname - the class name

methodname - the method name

Throws:

NotFoundException

See Also:

• CtClass.getDeclaredMethod(String)

makeClass

public CtClass makeClass(InputStream classfile)
                  throws IOException,
RuntimeException

Creates a new class (or interface) from the given class file. If there already exists a class with the same name, the new class overwrites that previous class.

This method is used for creating a CtClass object directly from a class file. The qualified class name is obtained from the class file; you do not have to explicitly give the name.

Parameters:

classfile - class file.

Throws:

RuntimeException - if there is a frozen class with the the same name.

IOException

See Also:

• makeClassIfNew(InputStream)
• ByteArrayClassPath

makeClass

public CtClass makeClass(InputStream classfile,
 boolean ifNotFrozen)
                  throws IOException,
RuntimeException

Creates a new class (or interface) from the given class file. If there already exists a class with the same name, the new class overwrites that previous class.

This method is used for creating a CtClass object directly from a class file. The qualified class name is obtained from the class file; you do not have to explicitly give the name.

Parameters:

classfile - class file.

ifNotFrozen - throws a RuntimeException if this parameter is true and there is a frozen class with the same name.

Throws:

IOException

RuntimeException

See Also:

• ByteArrayClassPath

makeClass

public CtClass makeClass(ClassFile classfile)
                  throws RuntimeException

Creates a new class (or interface) from the given class file. If there already exists a class with the same name, the new class overwrites that previous class.

This method is used for creating a CtClass object directly from a class file. The qualified class name is obtained from the class file; you do not have to explicitly give the name.

Parameters:

classfile - class file.

Throws:

RuntimeException - if there is a frozen class with the the same name.

Since:

3.20

makeClass

public CtClass makeClass(ClassFile classfile,
 boolean ifNotFrozen)
                  throws RuntimeException

Creates a new class (or interface) from the given class file. If there already exists a class with the same name, the new class overwrites that previous class.

This method is used for creating a CtClass object directly from a class file. The qualified class name is obtained from the class file; you do not have to explicitly give the name.

Parameters:

classfile - class file.

ifNotFrozen - throws a RuntimeException if this parameter is true and there is a frozen class with the same name.

Throws:

RuntimeException

Since:

3.20

makeClassIfNew

public CtClass makeClassIfNew(InputStream classfile)
                       throws IOException,
RuntimeException

Creates a new class (or interface) from the given class file. If there already exists a class with the same name, this method returns the existing class; a new class is never created from the given class file.

This method is used for creating a CtClass object directly from a class file. The qualified class name is obtained from the class file; you do not have to explicitly give the name.

Parameters:

classfile - the class file.

Throws:

IOException

RuntimeException

Since:

3.9

See Also:

• makeClass(InputStream)
• ByteArrayClassPath

makeClass

public CtClass makeClass(String classname)
                  throws RuntimeException

Creates a new public class. If there already exists a class with the same name, the new class overwrites that previous class.

If no constructor is explicitly added to the created new class, Javassist generates constructors and adds it when the class file is generated. It generates a new constructor for each constructor of the super class. The new constructor takes the same set of parameters and invokes the corresponding constructor of the super class. All the received parameters are passed to it.

Parameters:

classname - a fully-qualified class name.

Throws:

RuntimeException - if the existing class is frozen.

makeClass

public CtClass makeClass(String classname,
 CtClass superclass)
                  throws RuntimeException

Creates a new public class. If there already exists a class/interface with the same name, the new class overwrites that previous class.

If no constructor is explicitly added to the created new class, Javassist generates constructors and adds it when the class file is generated. It generates a new constructor for each constructor of the super class. The new constructor takes the same set of parameters and invokes the corresponding constructor of the super class. All the received parameters are passed to it.

Parameters:

classname - a fully-qualified class name.

superclass - the super class.

Throws:

RuntimeException - if the existing class is frozen.

makeInterface

public CtClass makeInterface(String name)
                      throws RuntimeException

Creates a new public interface. If there already exists a class/interface with the same name, the new interface overwrites that previous one.

Parameters:

name - a fully-qualified interface name.

Throws:

RuntimeException - if the existing interface is frozen.

makeInterface

public CtClass makeInterface(String name,
 CtClass superclass)
                      throws RuntimeException

Creates a new public interface. If there already exists a class/interface with the same name, the new interface overwrites that previous one.

Parameters:

name - a fully-qualified interface name.

superclass - the super interface.

Throws:

RuntimeException - if the existing interface is frozen.

makeAnnotation

public CtClass makeAnnotation(String name)
                       throws RuntimeException

Creates a new annotation. If there already exists a class/interface with the same name, the new interface overwrites that previous one.

Parameters:

name - a fully-qualified interface name. Or null if the annotation has no super interface.

Throws:

RuntimeException - if the existing interface is frozen.

Since:

3.19

appendSystemPath

public ClassPath appendSystemPath()

Appends the system search path to the end of the search path. The system search path usually includes the platform library, extension libraries, and the search path specified by the -classpath option or the CLASSPATH environment variable.

Returns:

the appended class path.

insertClassPath

public ClassPath insertClassPath(ClassPath cp)

Insert a ClassPath object at the head of the search path.

Returns:

the inserted class path.

See Also:

• ClassPath
• URLClassPath
• ByteArrayClassPath

appendClassPath

public ClassPath appendClassPath(ClassPath cp)

Appends a ClassPath object to the end of the search path.

Returns:

the appended class path.

See Also:

• ClassPath
• URLClassPath
• ByteArrayClassPath

insertClassPath

public ClassPath insertClassPath(String pathname)
                          throws NotFoundException

Inserts a directory or a jar (or zip) file at the head of the search path.

Parameters:

pathname - the path name of the directory or jar file. It must not end with a path separator ("/"). If the path name ends with "/*", then all the jar files matching the path name are inserted.

Returns:

the inserted class path.

Throws:

NotFoundException - if the jar file is not found.

appendClassPath

public ClassPath appendClassPath(String pathname)
                          throws NotFoundException

Appends a directory or a jar (or zip) file to the end of the search path.

Parameters:

pathname - the path name of the directory or jar file. It must not end with a path separator ("/"). If the path name ends with "/*", then all the jar files matching the path name are appended.

Returns:

the appended class path.

Throws:

NotFoundException - if the jar file is not found.

removeClassPath

public void removeClassPath(ClassPath cp)

Detatches the ClassPath object from the search path. The detached ClassPath object cannot be added to the path again.

appendPathList

public void appendPathList(String pathlist)
                    throws NotFoundException

Appends directories and jar files for search.

The elements of the given path list must be separated by colons in Unix or semi-colons in Windows.

Parameters:

pathlist - a (semi)colon-separated list of the path names of directories and jar files. The directory name must not end with a path separator ("/").

Throws:

NotFoundException - if a jar file is not found.

toClass

public Class toClass(CtClass clazz)
              throws CannotCompileException

Converts the given 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. It is obtained by calling getClassLoader().

This behavior can be changed by subclassing the pool and changing the getClassLoader() method. 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.

Warining: This method should not be used in Java 11 or later. Use toClass(CtClass,Class).

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.

Throws:

CannotCompileException

See Also:

• toClass(CtClass,Class)
• toClass(CtClass,Class,java.lang.ClassLoader,ProtectionDomain)
• getClassLoader()

getClassLoader

public ClassLoader getClassLoader()

Get the classloader for toClass(), getAnnotations() in CtClass, etc.

The default is the context class loader.

Returns:

the classloader for the pool

See Also:

• toClass(CtClass)
• CtClass.getAnnotations()

toClass

public Class toClass(CtClass ct,
 ClassLoader loader)
              throws CannotCompileException

Deprecated.

Replaced by toClass(CtClass,Class,ClassLoader,ProtectionDomain). A subclass of ClassPool that has been overriding this method should be modified. It should override toClass(CtClass,Class,ClassLoader,ProtectionDomain).

Converts the class to a java.lang.Class object. Do not override this method any more at a subclass because toClass(CtClass) will never calls this method.

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.

Throws:

CannotCompileException

toClass

public Class toClass(CtClass ct,
 ClassLoader loader,
 ProtectionDomain domain)
              throws CannotCompileException

Deprecated.

Replaced by toClass(CtClass,Class,ClassLoader,ProtectionDomain).

Converts the class to a java.lang.Class object. Once this method is called, further modifications are not allowed any more.

The class file represented by the given 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.

Parameters:

ct - the class converted into java.lang.Class.

loader - the class loader used to load this class. For example, the loader returned by getClassLoader() can be used for this parameter.

domain - the protection domain for the class. If it is null, the default domain created by java.lang.ClassLoader is used.

Throws:

CannotCompileException

Since:

3.3

See Also:

• getClassLoader()

toClass

public Class<?> toClass(CtClass ct,
 Class<?> neighbor)
                 throws CannotCompileException

Converts the class to a java.lang.Class object. Once this method is called, further modifications are not allowed any more.

This method is available in Java 9 or later. It loads the class by using java.lang.invoke.MethodHandles with neighbor.

Parameters:

ct - the class converted into java.lang.Class.

neighbor - a class belonging to the same package that the converted class belongs to.

Throws:

CannotCompileException

Since:

3.24

toClass

public Class<?> toClass(CtClass ct,
 MethodHandles.Lookup lookup)
                 throws CannotCompileException

Converts the class to a java.lang.Class object. Once this method is called, further modifications are not allowed any more.

This method is available in Java 9 or later. It loads the class by using the given java.lang.invoke.MethodHandles.Lookup.

Parameters:

ct - the class converted into java.lang.Class.

Throws:

CannotCompileException

Since:

3.24

toClass

public Class toClass(CtClass ct,
 Class<?> neighbor,
 ClassLoader loader,
 ProtectionDomain domain)
              throws CannotCompileException

Converts the class to a java.lang.Class object. Once this method is called, further modifications are not allowed any more.

When the JVM is Java 11 or later, this method loads the class by using java.lang.invoke.MethodHandles with neighbor. The other arguments loader and domain are not used; so they can be null.

Otherwise, or when neighbor is null, the class file represented by the given 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.

If your program is for only Java 9 or later, don't use this method. Use toClass(CtClass,Class) or toClass(CtClass,java.lang.invoke.MethodHandles.Lookup).

Parameters:

ct - the class converted into java.lang.Class.

neighbor - a class belonging to the same package that the converted class belongs to. It can be null.

loader - the class loader used to load this class. For example, the loader returned by getClassLoader() can be used for this parameter.

domain - the protection domain for the class. If it is null, the default domain created by java.lang.ClassLoader is used.

Throws:

CannotCompileException

Since:

3.24

See Also:

• getClassLoader()

makePackage

public void makePackage(ClassLoader loader,
 String name)
                 throws CannotCompileException

Deprecated.

Defines a new package. If the package is already defined, this method performs nothing.

You do not necessarily need to call this method. If this method is called, then getPackage() on the Class object returned by toClass() will return a non-null object.

The jigsaw module introduced by Java 9 has broken this method.

Parameters:

loader - the class loader passed to toClass() or the default one obtained by getClassLoader().

name - the package name.

Throws:

CannotCompileException

Since:

3.16

See Also:

• getClassLoader()
• toClass(CtClass)
• CtClass.toClass()