io.katharsis.utils.ClassUtils Maven / Gradle / Ivy
package io.katharsis.utils;
import io.katharsis.resource.annotations.JsonApiResource;
import io.katharsis.resource.exception.ResourceException;
import io.katharsis.utils.java.Optional;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
/**
* Provides reflection methods for parsing information about a class.
*/
public class ClassUtils {
private static final ClassUtils INSTANCE = new ClassUtils();
private ClassUtils() {
}
/**
* Returns a list of class fields. Supports inheritance and doesn't return synthetic fields.
*
* @param beanClass class to be searched for
* @return a list of found fields
*/
public static List getClassFields(Class beanClass) {
Map result = new HashMap<>();
Class currentClass = beanClass;
while (currentClass != null && currentClass != Object.class) {
for (Field field : currentClass.getDeclaredFields()) {
if (!field.isSynthetic()) {
Field v = result.get(field.getName());
if (v == null) {
result.put(field.getName(), field);
}
}
}
currentClass = currentClass.getSuperclass();
}
return new LinkedList<>(result.values());
}
/**
* Returns an instance of bean's annotation
*
* @param beanClass class to be searched for
* @param annotationClass type of an annotation
* @param type of an annotation
* @return an instance of an annotation
*/
public static Optional getAnnotation(Class beanClass, Class annotationClass) {
Class currentClass = beanClass;
while (currentClass != null && currentClass != Object.class) {
if (currentClass.isAnnotationPresent(annotationClass)) {
return Optional.of(currentClass.getAnnotation(annotationClass));
}
currentClass = currentClass.getSuperclass();
}
return Optional.empty();
}
/**
* Tries to find a class fields. Supports inheritance and doesn't return synthetic fields.
*
* @param beanClass class to be searched for
* @param fieldName field name
* @return a list of found fields
*/
public static Field findClassField(Class beanClass, String fieldName) {
Class currentClass = beanClass;
while (currentClass != null && currentClass != Object.class) {
for (Field field : currentClass.getDeclaredFields()) {
if (field.isSynthetic()) {
continue;
}
if (field.getName().equals(fieldName)) {
return field;
}
}
currentClass = currentClass.getSuperclass();
}
return null;
}
/**
*
* Return a list of class getters. Supports inheritance and overriding, that is when a method is found on the
* lowest level of inheritance chain, no other method can override it.
*
* A getter:
*
* - Starts with an is if returns boolean or {@link Boolean} value
* - Starts with a get if returns non-boolean value
*
*
* @param beanClass class to be searched for
* @return a list of found getters
*/
public static List getClassGetters(Class beanClass) {
Map result = new HashMap<>();
Class currentClass = beanClass;
while (currentClass != null && currentClass != Object.class) {
for (Method method : currentClass.getDeclaredMethods()) {
if (INSTANCE.isGetter(method)) {
Method v = result.get(method.getName());
if (v == null) {
result.put(method.getName(), method);
}
}
}
currentClass = currentClass.getSuperclass();
}
return new LinkedList<>(result.values());
}
/**
* Return a list of class setters. Supports inheritance and overriding, that is when a method is found on the
* lowest level of inheritance chain, no other method can override it.
*
* @param beanClass class to be searched for
* @return a list of found getters
*/
public static List getClassSetters(Class beanClass) {
Map result = new HashMap<>();
Class currentClass = beanClass;
while (currentClass != null && currentClass != Object.class) {
for (Method method : currentClass.getDeclaredMethods()) {
if (INSTANCE.isSetter(method)) {
Method v = result.get(method.getName());
if (v == null) {
result.put(method.getName(), method);
}
}
}
currentClass = currentClass.getSuperclass();
}
return new LinkedList<>(result.values());
}
/**
* Return a first occurrence of a method annotated with specified annotation
*
* @param searchClass class to be searched
* @param annotationClass annotation class
* @return annotated method or null
*/
public static Method findMethodWith(Class searchClass, Class annotationClass) {
Method foundMethod = null;
methodFinder:
while (searchClass != null && searchClass != Object.class) {
for (Method method : searchClass.getDeclaredMethods()) {
if (method.isAnnotationPresent(annotationClass)) {
foundMethod = method;
break methodFinder;
}
}
searchClass = searchClass.getSuperclass();
}
return foundMethod;
}
/**
* Returns the first clazz in the ancestor hierarchy with the JsonApiResource annotation
*
* @param data instance
* @param instance type
* @return class or null
*/
public static Class getJsonApiResourceClass(final T data) {
return getJsonApiResourceClass((Class) data.getClass());
}
public static Class getJsonApiResourceClass(final Class candidateClass) {
Class currentClass = candidateClass;
while (currentClass != null && currentClass != Object.class) {
if (currentClass.isAnnotationPresent(JsonApiResource.class)) {
return currentClass;
}
currentClass = currentClass.getSuperclass();
}
return null;
}
/**
* Create a new instance of a resource using a default constructor
*
* @param clazz new instance class
* @param new instance class
* @return new instance
*/
public static T newInstance(Class clazz) {
try {
return clazz.newInstance();
} catch (InstantiationException | IllegalAccessException e) {
throw new ResourceException(String.format("couldn't create a new instance of %s", clazz));
}
}
private boolean isGetter(Method method) {
return isBooleanGetter(method) || isNonBooleanGetter(method);
}
public static boolean isBooleanGetter(Method method) {
if (!method.getName().startsWith("is"))
return false;
if (method.getName().length() < 3)
return false;
if (method.getParameterTypes().length != 0) {
return false;
}
return boolean.class.equals(method.getReturnType()) || Boolean.class.equals(method.getReturnType());
}
private boolean isNonBooleanGetter(Method method) {
if (!method.getName().startsWith("get"))
return false;
if (method.getName().length() < 4)
return false;
if (method.getParameterTypes().length != 0)
return false;
return !void.class.equals(method.getReturnType());
}
private static boolean isSetter(Method method) {
if (!method.getName().startsWith("set"))
return false;
if (method.getName().length() < 4)
return false;
return method.getParameterTypes().length == 1;
}
}
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