/*
* Copyright 2002-2008 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.core;
import java.io.Externalizable;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
/**
* Provides methods to support various naming and other conventions used
* throughout the framework. Mainly for internal use within the framework.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
public abstract class Conventions {
/**
* Suffix added to names when using arrays.
*/
private static final String PLURAL_SUFFIX = "List";
/**
* Set of interfaces that are supposed to be ignored
* when searching for the 'primary' interface of a proxy.
*/
private static final Set ignoredInterfaces = new HashSet();
static {
ignoredInterfaces.add(Serializable.class);
ignoredInterfaces.add(Externalizable.class);
ignoredInterfaces.add(Cloneable.class);
ignoredInterfaces.add(Comparable.class);
}
/**
* Determine the conventional variable name for the supplied
* <code>Object</code> based on its concrete type. The convention
* used is to return the uncapitalized short name of the <code>Class</code>,
* according to JavaBeans property naming rules: So,
* <code>com.myapp.Product</code> becomes <code>product</code>;
* <code>com.myapp.MyProduct</code> becomes <code>myProduct</code>;
* <code>com.myapp.UKProduct</code> becomes <code>UKProduct</code>.
* <p>For arrays, we use the pluralized version of the array component type.
* For <code>Collection</code>s we attempt to 'peek ahead' in the
* <code>Collection</code> to determine the component type and
* return the pluralized version of that component type.
* @param value the value to generate a variable name for
* @return the generated variable name
*/
public static String getVariableName(Object value) {
Assert.notNull(value, "Value must not be null");
Class valueClass = null;
boolean pluralize = false;
if (value.getClass().isArray()) {
valueClass = value.getClass().getComponentType();
pluralize = true;
}
else if (value instanceof Collection) {
Collection collection = (Collection) value;
if (collection.isEmpty()) {
throw new IllegalArgumentException("Cannot generate variable name for an empty Collection");
}
Object valueToCheck = peekAhead(collection);
valueClass = getClassForValue(valueToCheck);
pluralize = true;
}
else {
valueClass = getClassForValue(value);
}
String name = ClassUtils.getShortNameAsProperty(valueClass);
return (pluralize ? pluralize(name) : name);
}
/**
* Determine the conventional variable name for the supplied parameter,
* taking the generic collection type (if any) into account.
* @param parameter the method or constructor parameter to generate a variable name for
* @return the generated variable name
*/
public static String getVariableNameForParameter(MethodParameter parameter) {
Assert.notNull(parameter, "MethodParameter must not be null");
Class valueClass = null;
boolean pluralize = false;
if (parameter.getParameterType().isArray()) {
valueClass = parameter.getParameterType().getComponentType();
pluralize = true;
}
else if (Collection.class.isAssignableFrom(parameter.getParameterType())) {
if (JdkVersion.isAtLeastJava15()) {
valueClass = GenericCollectionTypeResolver.getCollectionParameterType(parameter);
}
if (valueClass == null) {
throw new IllegalArgumentException("Cannot generate variable name for non-typed Collection parameter type");
}
pluralize = true;
}
else {
valueClass = parameter.getParameterType();
}
String name = ClassUtils.getShortNameAsProperty(valueClass);
return (pluralize ? pluralize(name) : name);
}
/**
* Determine the conventional variable name for the return type of the supplied method,
* taking the generic collection type (if any) into account.
* @param method the method to generate a variable name for
* @return the generated variable name
*/
public static String getVariableNameForReturnType(Method method) {
return getVariableNameForReturnType(method, method.getReturnType(), null);
}
/**
* Determine the conventional variable name for the return type of the supplied method,
* taking the generic collection type (if any) into account, falling back to the
* given return value if the method declaration is not specific enough (i.e. in case of
* the return type being declared as <code>Object</code> or as untyped collection).
* @param method the method to generate a variable name for
* @param value the return value (may be <code>null</code> if not available)
* @return the generated variable name
*/
public static String getVariableNameForReturnType(Method method, Object value) {
return getVariableNameForReturnType(method, method.getReturnType(), value);
}
/**
* Determine the conventional variable name for the return type of the supplied method,
* taking the generic collection type (if any) into account, falling back to the
* given return value if the method declaration is not specific enough (i.e. in case of
* the return type being declared as <code>Object</code> or as untyped collection).
* @param method the method to generate a variable name for
* @param resolvedType the resolved return type of the method
* @param value the return value (may be <code>null</code> if not available)
* @return the generated variable name
*/
public static String getVariableNameForReturnType(Method method, Class resolvedType, Object value) {
Assert.notNull(method, "Method must not be null");
if (Object.class.equals(resolvedType)) {
if (value == null) {
throw new IllegalArgumentException("Cannot generate variable name for an Object return type with null value");
}
return getVariableName(value);
}
Class valueClass = null;
boolean pluralize = false;
if (resolvedType.isArray()) {
valueClass = resolvedType.getComponentType();
pluralize = true;
}
else if (Collection.class.isAssignableFrom(resolvedType)) {
if (JdkVersion.isAtLeastJava15()) {
valueClass = GenericCollectionTypeResolver.getCollectionReturnType(method);
}
if (valueClass == null) {
if (!(value instanceof Collection)) {
throw new IllegalArgumentException(
"Cannot generate variable name for non-typed Collection return type and a non-Collection value");
}
Collection collection = (Collection) value;
if (collection.isEmpty()) {
throw new IllegalArgumentException(
"Cannot generate variable name for non-typed Collection return type and an empty Collection value");
}
Object valueToCheck = peekAhead(collection);
valueClass = getClassForValue(valueToCheck);
}
pluralize = true;
}
else {
valueClass = resolvedType;
}
String name = ClassUtils.getShortNameAsProperty(valueClass);
return (pluralize ? pluralize(name) : name);
}
/**
* Convert <code>String</code>s in attribute name format (lowercase, hyphens separating words)
* into property name format (camel-cased). For example, <code>transaction-manager</code> is
* converted into <code>transactionManager</code>.
*/
public static String attributeNameToPropertyName(String attributeName) {
Assert.notNull(attributeName, "'attributeName' must not be null");
if (attributeName.indexOf("-") == -1) {
return attributeName;
}
char[] chars = attributeName.toCharArray();
char[] result = new char[chars.length -1]; // not completely accurate but good guess
int currPos = 0;
boolean upperCaseNext = false;
for (int i = 0; i < chars.length; i++) {
char c = chars[i];
if (c == '-') {
upperCaseNext = true;
}
else if (upperCaseNext) {
result[currPos++] = Character.toUpperCase(c);
upperCaseNext = false;
}
else {
result[currPos++] = c;
}
}
return new String(result, 0, currPos);
}
/**
* Return an attribute name qualified by the supplied enclosing {@link Class}. For example,
* the attribute name '<code>foo</code>' qualified by {@link Class} '<code>com.myapp.SomeClass</code>'
* would be '<code>com.myapp.SomeClass.foo</code>'
*/
public static String getQualifiedAttributeName(Class enclosingClass, String attributeName) {
Assert.notNull(enclosingClass, "'enclosingClass' must not be null");
Assert.notNull(attributeName, "'attributeName' must not be null");
return enclosingClass.getName() + "." + attributeName;
}
/**
* Determines the class to use for naming a variable that contains
* the given value.
* <p>Will return the class of the given value, except when
* encountering a JDK proxy, in which case it will determine
* the 'primary' interface implemented by that proxy.
* @param value the value to check
* @return the class to use for naming a variable
*/
private static Class getClassForValue(Object value) {
Class valueClass = value.getClass();
if (Proxy.isProxyClass(valueClass)) {
Class[] ifcs = valueClass.getInterfaces();
for (int i = 0; i < ifcs.length; i++) {
Class ifc = ifcs[i];
if (!ignoredInterfaces.contains(ifc)) {
return ifc;
}
}
}
else if (valueClass.getName().lastIndexOf('$') != -1 && valueClass.getDeclaringClass() == null) {
// '$' in the class name but no inner class -
// assuming it's a special subclass (e.g. by OpenJPA)
valueClass = valueClass.getSuperclass();
}
return valueClass;
}
/**
* Pluralize the given name.
*/
private static String pluralize(String name) {
return name + PLURAL_SUFFIX;
}
/**
* Retrieves the <code>Class</code> of an element in the <code>Collection</code>.
* The exact element for which the <code>Class</code> is retreived will depend
* on the concrete <code>Collection</code> implementation.
*/
private static Object peekAhead(Collection collection) {
Iterator it = collection.iterator();
if (!it.hasNext()) {
throw new IllegalStateException(
"Unable to peek ahead in non-empty collection - no element found");
}
Object value = it.next();
if (value == null) {
throw new IllegalStateException(
"Unable to peek ahead in non-empty collection - only null element found");
}
return value;
}
}