Package org.apache.velocity.tools

Class ClassUtils

java.lang.Object

org.apache.velocity.tools.ClassUtils

public class ClassUtils
extends java.lang.Object

Repository for common class and reflection methods.

Version:

$Id: ClassUtils.java 511959 2007-02-26 19:24:39Z nbubna $

Author:

Nathan Bubna

Method Summary

Modifier and Type	Method	Description
static java.lang.reflect.Method	findDeclaredMethod(java.lang.Class clazz, java.lang.String name, java.lang.Class... params)	Find a declared method in a class.
static java.lang.reflect.Method	findFactoryMethod(java.lang.Class factory, java.lang.Class target)	Given a factory class and a target class, search for the following methods:
static java.lang.reflect.Method	findGetter(java.lang.String getterName, java.lang.Class clazz)
static java.lang.reflect.Method	findGetter(java.lang.String getterName, java.lang.Class clazz, boolean mandatory)
static java.lang.reflect.Method	findMethod(java.lang.Class clazz, java.lang.String name, java.lang.Class... params)	Find a callable method in a class
static java.lang.reflect.Method	findSetter(java.lang.String setterName, java.lang.Class clazz)
static java.lang.reflect.Method	findSetter(java.lang.String setterName, java.lang.Class clazz, java.util.function.Predicate<java.lang.Class> argumentClassFilter)
static java.lang.reflect.Method	findSetter(java.lang.String setterName, java.lang.Class clazz, java.util.function.Predicate<java.lang.Class> argumentClassFilter, boolean mandatory)
static java.lang.Class	getClass(java.lang.String name)	Load a class with a given name.
static java.lang.Object	getFieldValue(java.lang.Class clazz, java.lang.String fieldname)	Given a class and a static field name, get the field value.
static java.lang.Object	getFieldValue(java.lang.String fieldPath)	Given a static field path, aka classname.field, get the field value.
static java.lang.Object	getInstance(java.lang.String classname)	Get an instance of a named class.
static java.util.Iterator	getIterator(java.lang.Object obj)	Retrieves an Iterator from or creates and Iterator for the specified object.
static java.net.URL	getResource(java.lang.String name, java.lang.Object caller)	Load a given resource.
static java.io.InputStream	getResourceAsStream(java.lang.String name, java.lang.Object caller)	This is a convenience method to load a resource as a stream.
static java.util.List<java.net.URL>	getResources(java.lang.String name, java.lang.Object caller)	Load all resources with the specified name.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getClass

public static java.lang.Class getClass(java.lang.String name)
                                throws java.lang.ClassNotFoundException

Load a class with a given name. It will try to load the class in the following order:

• From Thread.currentThread().getContextClassLoader()
• Using the basic Class.forName(java.lang.String)
• From ClassUtils.class.getClassLoader()

Parameters:

name - Fully qualified class name to be loaded

Returns:

Class object

Throws:

java.lang.ClassNotFoundException - if the class cannot be found

getInstance

public static java.lang.Object getInstance(java.lang.String classname)
                                    throws java.lang.ClassNotFoundException,
                                           java.lang.IllegalAccessException,
                                           java.lang.InstantiationException

Get an instance of a named class.

Parameters:

classname - class name

Returns:

new class instance

Throws:

java.lang.ClassNotFoundException - if class is not found

java.lang.IllegalAccessException - if not granted

java.lang.InstantiationException - if instance creation throwed

getResources

public static java.util.List<java.net.URL> getResources(java.lang.String name,
                                                        java.lang.Object caller)

Load all resources with the specified name. If none are found, we prepend the name with '/' and try again. This will attempt to load the resources from the following methods (in order):

• Thread.currentThread().getContextClassLoader().getResources(name)
• ClassUtils.class.getClassLoader().getResources(name)
• ClassUtils.class.getResource(name)
• getCallerLoader(Object caller).getResources(name)
• caller.getClass().getResource(name)

Parameters:

name - The name of the resources to load

caller - The instance or Class calling this method

Returns:

the list of found resources

getResource

public static java.net.URL getResource(java.lang.String name,
                                       java.lang.Object caller)

Load a given resource. This method will try to load the resource using the following methods (in order):

• Thread.currentThread().getContextClassLoader().getResource(name)
• ClassUtils.class.getClassLoader().getResource(name)
• ClassUtils.class.getResource(name)
• caller.getClass().getResource(name) or, if caller is a Class, caller.getResource(name)

Parameters:

name - The name of the resource to load

caller - The instance or Class calling this method

Returns:

the found URL, or null if not found

getResourceAsStream

public static java.io.InputStream getResourceAsStream(java.lang.String name,
                                                      java.lang.Object caller)

This is a convenience method to load a resource as a stream. The algorithm used to find the resource is given in getResource()

Parameters:

name - The name of the resource to load

caller - The instance or Class calling this method

Returns:

the resource input stream or null if not found

findMethod

public static java.lang.reflect.Method findMethod(java.lang.Class clazz,
                                                  java.lang.String name,
                                                  java.lang.Class... params)
                                           throws java.lang.SecurityException

Find a callable method in a class

Parameters:

clazz - target class

name - method name

params - method arguments classes

Returns:

method object

Throws:

java.lang.SecurityException - if not granted

findDeclaredMethod

public static java.lang.reflect.Method findDeclaredMethod(java.lang.Class clazz,
                                                          java.lang.String name,
                                                          java.lang.Class... params)
                                                   throws java.lang.SecurityException

Find a declared method in a class. It will be made accessible if needed and allowed.

Parameters:

clazz - target class

name - method name

params - method arguments classes

Returns:

Throws:

java.lang.SecurityException - if not allowed

getFieldValue

public static java.lang.Object getFieldValue(java.lang.String fieldPath)
                                      throws java.lang.ClassNotFoundException,
                                             java.lang.NoSuchFieldException,
                                             java.lang.SecurityException,
                                             java.lang.IllegalAccessException

Given a static field path, aka classname.field, get the field value.

Parameters:

fieldPath - field path

Returns:

field value

Throws:

java.lang.ClassNotFoundException - if class hasn't been found

java.lang.NoSuchFieldException - if field hasn't been found

java.lang.SecurityException - if not granted

java.lang.IllegalAccessException - if field is not accessible

getFieldValue

public static java.lang.Object getFieldValue(java.lang.Class clazz,
                                             java.lang.String fieldname)
                                      throws java.lang.NoSuchFieldException,
                                             java.lang.SecurityException,
                                             java.lang.IllegalAccessException

Given a class and a static field name, get the field value.

Parameters:

clazz - target class

fieldname - field name

Returns:

field value

Throws:

java.lang.NoSuchFieldException - if field hasn't been found

java.lang.SecurityException - if not granted

java.lang.IllegalAccessException - if field is not accessible

getIterator

public static java.util.Iterator getIterator(java.lang.Object obj)
                                      throws java.lang.NoSuchMethodException,
                                             java.lang.IllegalAccessException,
                                             java.lang.reflect.InvocationTargetException

Retrieves an Iterator from or creates and Iterator for the specified object. This method is almost entirely copied from Engine's UberspectImpl class.

Parameters:

obj - the target obj

Returns:

an iterator over the content of obj, or null if not found

Throws:

java.lang.NoSuchMethodException - if no iterator() method

java.lang.IllegalAccessException - if iterator() method not callable

java.lang.reflect.InvocationTargetException - if iterator() method throwed

findFactoryMethod

public static java.lang.reflect.Method findFactoryMethod(java.lang.Class factory,
                                                         java.lang.Class target)

Given a factory class and a target class, search for the following methods:

• createTargetClassname(),
• newTargetClassname(), or
• getTargetClassname().

Parameters:

factory - factory class

target - target class

Returns:

first factory method found, or null otherwise

findGetter

public static java.lang.reflect.Method findGetter(java.lang.String getterName,
                                                  java.lang.Class clazz)
                                           throws java.lang.NoSuchMethodException

Throws:

java.lang.NoSuchMethodException

findGetter

public static java.lang.reflect.Method findGetter(java.lang.String getterName,
                                                  java.lang.Class clazz,
                                                  boolean mandatory)
                                           throws java.lang.NoSuchMethodException

Throws:

java.lang.NoSuchMethodException

findSetter

public static java.lang.reflect.Method findSetter(java.lang.String setterName,
                                                  java.lang.Class clazz)
                                           throws java.lang.NoSuchMethodException

Throws:

java.lang.NoSuchMethodException

findSetter

public static java.lang.reflect.Method findSetter(java.lang.String setterName,
                                                  java.lang.Class clazz,
                                                  java.util.function.Predicate<java.lang.Class> argumentClassFilter)
                                           throws java.lang.NoSuchMethodException

Throws:

java.lang.NoSuchMethodException

findSetter

public static java.lang.reflect.Method findSetter(java.lang.String setterName,
                                                  java.lang.Class clazz,
                                                  java.util.function.Predicate<java.lang.Class> argumentClassFilter,
                                                  boolean mandatory)
                                           throws java.lang.NoSuchMethodException

Throws:

java.lang.NoSuchMethodException