ReflectionHelper.java

/*
 * Copyright 2016 Hortonworks.
 *
 * 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 com.hortonworks.registries.common.util;

import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
import org.springframework.core.type.filter.AnnotationTypeFilter;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

public class ReflectionHelper {
    private static final Logger LOG = LoggerFactory.getLogger(ReflectionHelper.class);

    public static <T> T newInstance(String className) throws ClassNotFoundException, IllegalAccessException, InstantiationException {
        return (T) Class.forName(className).newInstance();
    }

    public static <T> T invokeGetter(String propertyName, Object object) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        String methodName = "get" + StringUtils.capitalize(propertyName);
        Method method = object.getClass().getMethod(methodName);
        return (T) method.invoke(object);
    }

    public static <T> T invokeSetter(String propertyName, Object object, Object valueToSet) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        String methodName = "set" + StringUtils.capitalize(propertyName);
        Method method = object.getClass().getMethod(methodName, valueToSet.getClass());
        return (T) method.invoke(object, valueToSet);
    }

    /**
     * Given a class, this method returns a map of names of all the instance (non static) fields -> type.
     * if the class has any super class it also includes those fields.
     *
     * @param clazz , not null
     * @return
     */
    public static Map<String, Class> getFieldNamesToTypes(Class clazz) {
        Field[] declaredFields = clazz.getDeclaredFields();
        Map<String, Class> instanceVariableNamesToTypes = new HashMap<>();
        for (Field field : declaredFields) {
            if (!Modifier.isStatic(field.getModifiers())) {
                LOG.trace("clazz {} has field {} with type {}", clazz.getName(), field.getName(), field.getType().getName());
                instanceVariableNamesToTypes.put(field.getName(), field.getType());
            } else {
                LOG.trace("clazz {} has field {} with type {}, which is static so ignoring", clazz.getName(), field.getName(), field.getType().getName());
            }
        }

        if (!clazz.getSuperclass().equals(Object.class)) {
            instanceVariableNamesToTypes.putAll(getFieldNamesToTypes(clazz.getSuperclass()));
        }
        return instanceVariableNamesToTypes;
    }

    public static Collection<Class<?>> getAnnotatedClasses(String basePackage, Class<? extends Annotation> annotation) {
        Collection<Class<?>> classes = new ArrayList<>();
        ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(false);
        provider.addIncludeFilter(new AnnotationTypeFilter(annotation));
        for (BeanDefinition beanDef : provider.findCandidateComponents(basePackage)) {
            try {
                classes.add(Class.forName(beanDef.getBeanClassName()));
            } catch (ClassNotFoundException e) {
                throw new RuntimeException(e);
            }
        }
        return classes;
    }

}