org.springframework.util
Class ClassUtils

java.lang.Object
  org.springframework.util.ClassUtils

public abstract class ClassUtils
extends Object

Miscellaneous class utility methods. Mainly for internal use within the framework; consider Jakarta's Commons Lang for a more comprehensive suite of class utilities.

Since:

1.1

Author:

Keith Donald, Rob Harrop, Juergen Hoeller

See Also:

TypeUtils, ReflectionUtils

Field Summary

static String	ARRAY_SUFFIX Suffix for array class names: "[]"
static String	CGLIB_CLASS_SEPARATOR The CGLIB class separator character "$$"
static String	CLASS_FILE_SUFFIX The ".class" file suffix

Constructor Summary

ClassUtils()

Method Summary

static String	addResourcePathToPackagePath(Class clazz, String resourceName) Return a path suitable for use with ClassLoader.getResource (also suitable for use with Class.getResource by prepending a slash ('/') to the return value.
static String	classNamesToString(Class[] classes) Build a String that consists of the names of the classes/interfaces in the given array.
static String	classNamesToString(Collection classes) Build a String that consists of the names of the classes/interfaces in the given collection.
static String	classPackageAsResourcePath(Class clazz) Given an input class object, return a string which consists of the class's package name as a pathname, i.e., all dots ('.') are replaced by slashes ('/').
static Class	createCompositeInterface(Class[] interfaces, ClassLoader classLoader) Create a composite interface Class for the given interfaces, implementing the given interfaces in one single Class.
static Class	forName(String name) Replacement for Class.forName() that also returns Class instances for primitives (like "int") and array class names (like "String[]").
static Class	forName(String name, ClassLoader classLoader) Replacement for Class.forName() that also returns Class instances for primitives (like "int") and array class names (like "String[]").
static Class[]	getAllInterfaces(Object instance) Return all interfaces that the given instance implements as array, including ones implemented by superclasses.
static Set	getAllInterfacesAsSet(Object instance) Return all interfaces that the given instance implements as Set, including ones implemented by superclasses.
static Class[]	getAllInterfacesForClass(Class clazz) Return all interfaces that the given class implements as array, including ones implemented by superclasses.
static Set	getAllInterfacesForClassAsSet(Class clazz) Return all interfaces that the given class implements as Set, including ones implemented by superclasses.
static String	getClassFileName(Class clazz) Determine the name of the class file, relative to the containing package: e.g.
static Constructor	getConstructorIfAvailable(Class clazz, Class[] paramTypes) Determine whether the given class has a constructor with the given signature, and return it if available (else return null).
static ClassLoader	getDefaultClassLoader() Return the default ClassLoader to use: typically the thread context ClassLoader, if available; the ClassLoader that loaded the ClassUtils class will be used as fallback.
static int	getMethodCountForName(Class clazz, String methodName) Return the number of methods with a given name (with any argument types), for the given class and/or its superclasses.
static Method	getMethodIfAvailable(Class clazz, String methodName, Class[] paramTypes) Determine whether the given class has a method with the given signature, and return it if available (else return null).
static Method	getMostSpecificMethod(Method method, Class targetClass) Given a method, which may come from an interface, and a target class used in the current reflective invocation, find the corresponding target method if there is one.
static String	getPackageName(Class clazz) Determine the name of the package of the given class: e.g.
static String	getQualifiedMethodName(Method method) Return the qualified name of the given method, consisting of fully qualified interface/class name + "." + method name.
static String	getQualifiedName(Class clazz) Return the qualified name of the given class: usually simply the class name, but component type class name + "[]" for arrays.
static String	getShortName(Class clazz) Get the class name without the qualified package name.
static String	getShortName(String className) Get the class name without the qualified package name.
static String	getShortNameAsProperty(Class clazz) Return the short string name of a Java class in decapitalized JavaBeans property format.
static Method	getStaticMethod(Class clazz, String methodName, Class[] args) Return a static method of a class.
static Class	getUserClass(Class clazz) Return the user-defined class for the given class: usually simply the given class, but the original class in case of a CGLIB-generated subclass.
static Class	getUserClass(Object instance) Return the user-defined class for the given instance: usually simply the class of the given instance, but the original class in case of a CGLIB-generated subclass.
static boolean	hasAtLeastOneMethodWithName(Class clazz, String methodName) Does the given class and/or its superclasses at least have one or more methods (with any argument types)?
static boolean	hasConstructor(Class clazz, Class[] paramTypes) Determine whether the given class has a constructor with the given signature.
static boolean	hasMethod(Class clazz, String methodName, Class[] paramTypes) Determine whether the given class has a method with the given signature.
static boolean	isAssignable(Class lhsType, Class rhsType) Check if the right-hand side type may be assigned to the left-hand side type, assuming setting by reflection.
static boolean	isAssignableValue(Class type, Object value) Determine if the given type is assignable from the given value, assuming setting by reflection.
static boolean	isPresent(String className) Determine whether the Class identified by the supplied name is present and can be loaded.
static boolean	isPresent(String className, ClassLoader classLoader) Determine whether the Class identified by the supplied name is present and can be loaded.
static boolean	isPrimitiveArray(Class clazz) Check if the given class represents an array of primitives, i.e. boolean, byte, char, short, int, long, float, or double.
static boolean	isPrimitiveOrWrapper(Class clazz) Check if the given class represents a primitive (i.e. boolean, byte, char, short, int, long, float, or double) or a primitive wrapper (i.e.
static boolean	isPrimitiveWrapper(Class clazz) Check if the given class represents a primitive wrapper, i.e.
static boolean	isPrimitiveWrapperArray(Class clazz) Check if the given class represents an array of primitive wrappers, i.e.
static Class	resolveClassName(String className, ClassLoader classLoader) Resolve the given class name into a Class instance.
static Class	resolvePrimitiveClassName(String name) Resolve the given class name as primitive class, if appropriate, according to the JVM's naming rules for primitive classes.

Methods inherited from class java.lang.Object

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

Field Detail

ARRAY_SUFFIX

public static final String ARRAY_SUFFIX

Suffix for array class names: "[]"

See Also:

Constant Field Values

CGLIB_CLASS_SEPARATOR

public static final String CGLIB_CLASS_SEPARATOR

The CGLIB class separator character "$$"

See Also:

Constant Field Values

CLASS_FILE_SUFFIX

public static final String CLASS_FILE_SUFFIX

The ".class" file suffix

See Also:

Constant Field Values

Constructor Detail

ClassUtils

public ClassUtils()

Method Detail

getDefaultClassLoader

public static ClassLoader getDefaultClassLoader()

Return the default ClassLoader to use: typically the thread context ClassLoader, if available; the ClassLoader that loaded the ClassUtils class will be used as fallback.

Call this method if you intend to use the thread context ClassLoader in a scenario where you absolutely need a non-null ClassLoader reference: for example, for class path resource loading (but not necessarily for Class.forName, which accepts a null ClassLoader reference as well).

Returns:

the default ClassLoader (never null)

See Also:

Thread.getContextClassLoader()

isPresent

public static boolean isPresent(String className)

Determine whether the Class identified by the supplied name is present and can be loaded. Will return false if either the class or one of its dependencies is not present or cannot be loaded.

Parameters:

className - the name of the class to check

Returns:

whether the specified class is present

isPresent

public static boolean isPresent(String className,
                                ClassLoader classLoader)

Determine whether the Class identified by the supplied name is present and can be loaded. Will return false if either the class or one of its dependencies is not present or cannot be loaded.

Parameters:

className - the name of the class to check

classLoader - the class loader to use (may be null, which indicates the default class loader)

Returns:

whether the specified class is present

forName

public static Class forName(String name)
                     throws ClassNotFoundException,
                            LinkageError

Replacement for Class.forName() that also returns Class instances for primitives (like "int") and array class names (like "String[]").

Always uses the default class loader: that is, preferably the thread context class loader, or the ClassLoader that loaded the ClassUtils class as fallback.

Parameters:

name - the name of the Class

Returns:

Class instance for the supplied name

Throws:

ClassNotFoundException - if the class was not found

LinkageError - if the class file could not be loaded

See Also:

Class.forName(String, boolean, ClassLoader), getDefaultClassLoader()

forName

public static Class forName(String name,
                            ClassLoader classLoader)
                     throws ClassNotFoundException,
                            LinkageError

Replacement for Class.forName() that also returns Class instances for primitives (like "int") and array class names (like "String[]").

Parameters:

name - the name of the Class

classLoader - the class loader to use (may be null, which indicates the default class loader)

Returns:

Class instance for the supplied name

Throws:

ClassNotFoundException - if the class was not found

LinkageError - if the class file could not be loaded

See Also:

Class.forName(String, boolean, ClassLoader)

resolveClassName

public static Class resolveClassName(String className,
                                     ClassLoader classLoader)
                              throws IllegalArgumentException

Resolve the given class name into a Class instance. Supports primitives (like "int") and array class names (like "String[]").

This is effectively equivalent to the forName method with the same arguments, with the only difference being the exceptions thrown in case of class loading failure.

Parameters:

className - the name of the Class

classLoader - the class loader to use (may be null, which indicates the default class loader)

Returns:

Class instance for the supplied name

Throws:

IllegalArgumentException - if the class name was not resolvable (that is, the class could not be found or the class file could not be loaded)

See Also:

forName(String, ClassLoader)

resolvePrimitiveClassName

public static Class resolvePrimitiveClassName(String name)

Resolve the given class name as primitive class, if appropriate, according to the JVM's naming rules for primitive classes.

Also supports the JVM's internal class names for primitive arrays. Does not support the "[]" suffix notation for primitive arrays; this is only supported by forName(java.lang.String).

Parameters:

name - the name of the potentially primitive class

Returns:

the primitive class, or null if the name does not denote a primitive class or primitive array class

getUserClass

public static Class getUserClass(Object instance)

Return the user-defined class for the given instance: usually simply the class of the given instance, but the original class in case of a CGLIB-generated subclass.

Parameters:

instance - the instance to check

Returns:

the user-defined class

getUserClass

public static Class getUserClass(Class clazz)

Return the user-defined class for the given class: usually simply the given class, but the original class in case of a CGLIB-generated subclass.

Parameters:

clazz - the class to check

Returns:

the user-defined class

getShortName

public static String getShortName(String className)

Get the class name without the qualified package name.

Parameters:

className - the className to get the short name for

Returns:

the class name of the class without the package name

Throws:

IllegalArgumentException - if the className is empty

getShortName

public static String getShortName(Class clazz)

Get the class name without the qualified package name.

Parameters:

clazz - the class to get the short name for

Returns:

the class name of the class without the package name

getShortNameAsProperty

public static String getShortNameAsProperty(Class clazz)

Return the short string name of a Java class in decapitalized JavaBeans property format.

Parameters:

clazz - the class

Returns:

the short name rendered in a standard JavaBeans property format

See Also:

Introspector.decapitalize(String)

getClassFileName

public static String getClassFileName(Class clazz)

Determine the name of the class file, relative to the containing package: e.g. "String.class"

Parameters:

clazz - the class

Returns:

the file name of the ".class" file

getPackageName

public static String getPackageName(Class clazz)

Determine the name of the package of the given class: e.g. "java.lang" for the java.lang.String class.

Parameters:

clazz - the class

Returns:

the package name, or the empty String if the class is defined in the default package

getQualifiedName

public static String getQualifiedName(Class clazz)

Return the qualified name of the given class: usually simply the class name, but component type class name + "[]" for arrays.

Parameters:

clazz - the class

Returns:

the qualified name of the class

getQualifiedMethodName

public static String getQualifiedMethodName(Method method)

Return the qualified name of the given method, consisting of fully qualified interface/class name + "." + method name.

Parameters:

method - the method

Returns:

the qualified name of the method

hasConstructor

public static boolean hasConstructor(Class clazz,
                                     Class[] paramTypes)

Determine whether the given class has a constructor with the given signature.

Essentially translates NoSuchMethodException to "false".

Parameters:

clazz - the clazz to analyze

paramTypes - the parameter types of the method

Returns:

whether the class has a corresponding constructor

See Also:

Class.getMethod(java.lang.String, java.lang.Class...)

getConstructorIfAvailable

public static Constructor getConstructorIfAvailable(Class clazz,
                                                    Class[] paramTypes)

Determine whether the given class has a constructor with the given signature, and return it if available (else return null).

Essentially translates NoSuchMethodException to null.

Parameters:

clazz - the clazz to analyze

paramTypes - the parameter types of the method

Returns:

the constructor, or null if not found

See Also:

Class.getConstructor(java.lang.Class...)

hasMethod

public static boolean hasMethod(Class clazz,
                                String methodName,
                                Class[] paramTypes)

Determine whether the given class has a method with the given signature.

Essentially translates NoSuchMethodException to "false".

Parameters:

clazz - the clazz to analyze

methodName - the name of the method

paramTypes - the parameter types of the method

Returns:

whether the class has a corresponding method

See Also:

Class.getMethod(java.lang.String, java.lang.Class...)

getMethodIfAvailable

public static Method getMethodIfAvailable(Class clazz,
                                          String methodName,
                                          Class[] paramTypes)

Determine whether the given class has a method with the given signature, and return it if available (else return null).

Essentially translates NoSuchMethodException to null.

Parameters:

clazz - the clazz to analyze

methodName - the name of the method

paramTypes - the parameter types of the method

Returns:

the method, or null if not found

See Also:

Class.getMethod(java.lang.String, java.lang.Class...)

getMethodCountForName

public static int getMethodCountForName(Class clazz,
                                        String methodName)

Return the number of methods with a given name (with any argument types), for the given class and/or its superclasses. Includes non-public methods.

Parameters:

clazz - the clazz to check

methodName - the name of the method

Returns:

the number of methods with the given name

hasAtLeastOneMethodWithName

public static boolean hasAtLeastOneMethodWithName(Class clazz,
                                                  String methodName)

Does the given class and/or its superclasses at least have one or more methods (with any argument types)? Includes non-public methods.

Parameters:

clazz - the clazz to check

methodName - the name of the method

Returns:

whether there is at least one method with the given name

getMostSpecificMethod

public static Method getMostSpecificMethod(Method method,
                                           Class targetClass)

Given a method, which may come from an interface, and a target class used in the current reflective invocation, find the corresponding target method if there is one. E.g. the method may be IFoo.bar() and the target class may be DefaultFoo. In this case, the method may be DefaultFoo.bar(). This enables attributes on that method to be found.

NOTE: In contrast to AopUtils.getMostSpecificMethod(java.lang.reflect.Method, java.lang.Class), this method does not resolve Java 5 bridge methods automatically. Call BridgeMethodResolver.findBridgedMethod(java.lang.reflect.Method) if bridge method resolution is desirable (e.g. for obtaining metadata from the original method definition).

Parameters:

method - the method to be invoked, which may come from an interface

targetClass - the target class for the current invocation. May be null or may not even implement the method.

Returns:

the specific target method, or the original method if the targetClass doesn't implement it or is null

See Also:

AopUtils.getMostSpecificMethod(java.lang.reflect.Method, java.lang.Class)

getStaticMethod

public static Method getStaticMethod(Class clazz,
                                     String methodName,
                                     Class[] args)

Return a static method of a class.

Parameters:

methodName - the static method name

clazz - the class which defines the method

args - the parameter types to the method

Returns:

the static method, or null if no static method was found

Throws:

IllegalArgumentException - if the method name is blank or the clazz is null

isPrimitiveWrapper

public static boolean isPrimitiveWrapper(Class clazz)

Check if the given class represents a primitive wrapper, i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double.

Parameters:

clazz - the class to check

Returns:

whether the given class is a primitive wrapper class

isPrimitiveOrWrapper

public static boolean isPrimitiveOrWrapper(Class clazz)

Check if the given class represents a primitive (i.e. boolean, byte, char, short, int, long, float, or double) or a primitive wrapper (i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double).

Parameters:

clazz - the class to check

Returns:

whether the given class is a primitive or primitive wrapper class

isPrimitiveArray

public static boolean isPrimitiveArray(Class clazz)

Check if the given class represents an array of primitives, i.e. boolean, byte, char, short, int, long, float, or double.

Parameters:

clazz - the class to check

Returns:

whether the given class is a primitive array class

isPrimitiveWrapperArray

public static boolean isPrimitiveWrapperArray(Class clazz)

Check if the given class represents an array of primitive wrappers, i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double.

Parameters:

clazz - the class to check

Returns:

whether the given class is a primitive wrapper array class

isAssignable

public static boolean isAssignable(Class lhsType,
                                   Class rhsType)

Check if the right-hand side type may be assigned to the left-hand side type, assuming setting by reflection. Considers primitive wrapper classes as assignable to the corresponding primitive types.

Parameters:

lhsType - the target type

rhsType - the value type that should be assigned to the target type

Returns:

if the target type is assignable from the value type

See Also:

TypeUtils.isAssignable(java.lang.reflect.Type, java.lang.reflect.Type)

isAssignableValue

public static boolean isAssignableValue(Class type,
                                        Object value)

Determine if the given type is assignable from the given value, assuming setting by reflection. Considers primitive wrapper classes as assignable to the corresponding primitive types.

Parameters:

type - the target type

value - the value that should be assigned to the type

Returns:

if the type is assignable from the value

addResourcePathToPackagePath

public static String addResourcePathToPackagePath(Class clazz,
                                                  String resourceName)

Return a path suitable for use with ClassLoader.getResource (also suitable for use with Class.getResource by prepending a slash ('/') to the return value. Built by taking the package of the specified class file, converting all dots ('.') to slashes ('/'), adding a trailing slash if necesssary, and concatenating the specified resource name to this.
As such, this function may be used to build a path suitable for loading a resource file that is in the same package as a class file, although ClassPathResource is usually even more convenient.

Parameters:

clazz - the Class whose package will be used as the base

resourceName - the resource name to append. A leading slash is optional.

Returns:

the built-up resource path

See Also:

ClassLoader.getResource(java.lang.String), Class.getResource(java.lang.String)

classPackageAsResourcePath

public static String classPackageAsResourcePath(Class clazz)

Given an input class object, return a string which consists of the class's package name as a pathname, i.e., all dots ('.') are replaced by slashes ('/'). Neither a leading nor trailing slash is added. The result could be concatenated with a slash and the name of a resource, and fed directly to ClassLoader.getResource(). For it to be fed to Class.getResource instead, a leading slash would also have to be prepended to the returned value.

Parameters:

clazz - the input class. A null value or the default (empty) package will result in an empty string ("") being returned.

Returns:

a path which represents the package name

See Also:

ClassLoader.getResource(java.lang.String), Class.getResource(java.lang.String)

classNamesToString

public static String classNamesToString(Class[] classes)

Build a String that consists of the names of the classes/interfaces in the given array.

Basically like AbstractCollection.toString(), but stripping the "class "/"interface " prefix before every class name.

Parameters:

classes - a Collection of Class objects (may be null)

Returns:

a String of form "[com.foo.Bar, com.foo.Baz]"

See Also:

AbstractCollection.toString()

classNamesToString

public static String classNamesToString(Collection classes)

Build a String that consists of the names of the classes/interfaces in the given collection.

Basically like AbstractCollection.toString(), but stripping the "class "/"interface " prefix before every class name.

Parameters:

classes - a Collection of Class objects (may be null)

Returns:

a String of form "[com.foo.Bar, com.foo.Baz]"

See Also:

AbstractCollection.toString()

getAllInterfaces

public static Class[] getAllInterfaces(Object instance)

Return all interfaces that the given instance implements as array, including ones implemented by superclasses.

Parameters:

instance - the instance to analyse for interfaces

Returns:

all interfaces that the given instance implements as array

getAllInterfacesForClass

public static Class[] getAllInterfacesForClass(Class clazz)

Return all interfaces that the given class implements as array, including ones implemented by superclasses.

If the class itself is an interface, it gets returned as sole interface.

Parameters:

clazz - the class to analyse for interfaces

Returns:

all interfaces that the given object implements as array

getAllInterfacesAsSet

public static Set getAllInterfacesAsSet(Object instance)

Return all interfaces that the given instance implements as Set, including ones implemented by superclasses.

Parameters:

instance - the instance to analyse for interfaces

Returns:

all interfaces that the given instance implements as Set

getAllInterfacesForClassAsSet

public static Set getAllInterfacesForClassAsSet(Class clazz)

Return all interfaces that the given class implements as Set, including ones implemented by superclasses.

If the class itself is an interface, it gets returned as sole interface.

Parameters:

clazz - the class to analyse for interfaces

Returns:

all interfaces that the given object implements as Set

createCompositeInterface

public static Class createCompositeInterface(Class[] interfaces,
                                             ClassLoader classLoader)

Create a composite interface Class for the given interfaces, implementing the given interfaces in one single Class.

This implementation builds a JDK proxy class for the given interfaces.

Parameters:

interfaces - the interfaces to merge

classLoader - the ClassLoader to create the composite Class in

Returns:

the merged interface as Class

See Also:

Proxy.getProxyClass(java.lang.ClassLoader, java.lang.Class...)