javassist

Class 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
booleanchildFirstLookup
Determines the search order.
static booleandoPruning
Turning the automatic pruning on/off.
static booleanreleaseUnmodifiedClassFile
If true, unmodified and not-recently-used class files are periodically released for saving memory.
Constructor Summary
ClassPool()
Creates a root class pool.
ClassPool(boolean useDefaultPath)
Creates a root class pool.
ClassPool(ClassPool parent)
Creates a class pool.
Method Summary
ClassPathappendClassPath(ClassPath cp)
Appends a ClassPath object to the end of the search path.
ClassPathappendClassPath(String pathname)
Appends a directory or a jar (or zip) file to the end of the search path.
voidappendPathList(String pathlist)
Appends directories and jar files for search.
ClassPathappendSystemPath()
Appends the system search path to the end of the search path.
voidclearImportedPackages()
Clear all the package names recorded by importPackage().
URLfind(String classname)
Searches the class path to obtain the URL of the class file specified by classname.
CtClassget(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.
CtClassgetAndRename(String orgName, String newName)
Reads a class file and constructs a CtClass object with a new name.
ClassLoadergetClassLoader()
Get the classloader for toClass(), getAnnotations() in CtClass, etc.
static ClassPoolgetDefault()
Returns the default class pool.
IteratorgetImportedPackages()
Returns all the package names recorded by importPackage().
CtMethodgetMethod(String classname, String methodname)
Reads a class file and obtains a compile-time method.
voidimportPackage(String packageName)
Record a package name so that the Javassist compiler searches the package to resolve a class name.
ClassPathinsertClassPath(ClassPath cp)
Insert a ClassPath object at the head of the search path.
ClassPathinsertClassPath(String pathname)
Inserts a directory or a jar (or zip) file at the head of the search path.
Object[]lookupCflow(String name)
Undocumented method.
CtClassmakeClass(InputStream classfile)
Creates a new class (or interface) from the given class file.
CtClassmakeClass(String classname)
Creates a new public class.
CtClassmakeClass(String classname, CtClass superclass)
Creates a new public class.
CtClassmakeInterface(String name)
Creates a new public interface.
CtClassmakeInterface(String name, CtClass superclass)
Creates a new public interface.
voidrecordInvalidClassName(String name)
Records a name that never exists.
voidremoveClassPath(ClassPath cp)
Detatches the ClassPath object from the search path.
ClasstoClass(CtClass clazz)
Converts the given class to a java.lang.Class object.
ClasstoClass(CtClass ct, ClassLoader loader)
Converts the class to a java.lang.Class object.
ClasstoClass(CtClass ct, ClassLoader loader, ProtectionDomain domain)
Converts the class to a java.lang.Class object.
StringtoString()
Returns the class search path.

Field Detail

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 true.

See Also: prune CtClass

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.

Constructor Detail

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 Detail

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

appendClassPath

public ClassPath appendClassPath(String pathname)
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 ("/").

Returns: the appended class path.

Throws: NotFoundException if the jar file is not found.

appendPathList

public void appendPathList(String pathlist)
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.

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.

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

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: getURL

get

public CtClass get(String classname)
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.

get

public CtClass[] get(String[] classnames)
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.

getAndRename

public CtClass getAndRename(String orgName, String newName)
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, 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

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 getAnnotations

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:

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

See Also: ClassClassPath LoaderClassPath

getImportedPackages

public Iterator getImportedPackages()
Returns all the package names recorded by importPackage().

Since: 3.1

See Also: importPackage

getMethod

public CtMethod getMethod(String classname, String methodname)
Reads a class file and obtains a compile-time method.

Parameters: classname the class name methodname the method name

See Also: getDeclaredMethod

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.

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

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

insertClassPath

public ClassPath insertClassPath(String pathname)
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 ("/").

Returns: the inserted class path.

Throws: NotFoundException if the jar file is not found.

lookupCflow

public Object[] lookupCflow(String name)
Undocumented method. Do not use; internal-use only.

Parameters: name the name of $cflow variable

makeClass

public CtClass makeClass(InputStream classfile)
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.

See Also: ByteArrayClassPath

makeClass

public CtClass makeClass(String classname)
Creates a new public class. If there already exists a class with the same name, the new class overwrites that previous class.

Parameters: classname a fully-qualified class name.

Throws: RuntimeException if the existing class is frozen.

makeClass

public CtClass makeClass(String classname, CtClass superclass)
Creates a new public class. If there already exists a class/interface with the same name, the new class overwrites that previous class.

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)
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)
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.

recordInvalidClassName

public void recordInvalidClassName(String name)
Records a name that never exists. For example, a package name can be recorded by this method. This would improve execution performance since get() does not search 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.

Parameters: name a class name (separeted by dot).

removeClassPath

public void removeClassPath(ClassPath cp)
Detatches the ClassPath object from the search path. The detached ClassPath object cannot be added to the pathagain.

toClass

public Class toClass(CtClass clazz)
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: 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: ClassPool getClassLoader

toClass

public Class toClass(CtClass ct, ClassLoader loader)

Deprecated: Replaced by toClass. A subclass of ClassPool that has been overriding this method should be modified. It should override toClass.

Converts the class to a java.lang.Class object. Do not override this method any more at a subclass because toClass(CtClass) 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.

toClass

public Class toClass(CtClass ct, ClassLoader loader, ProtectionDomain domain)
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: 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.

Since: 3.3

See Also: getClassLoader

toString

public String toString()
Returns the class search path.
Javassist, a Java-bytecode translator toolkit.
Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.