it.f2informatica.pagination.utils.SafeGetterMethodExecutor.java Source code

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Here is the source code for it.f2informatica.pagination.utils.SafeGetterMethodExecutor.java

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/*
 * =============================================================================
 *
 *   Copyright (c) 2014, Fernando Aspiazu
 *
 *   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 it.f2informatica.pagination.utils;

import com.google.common.base.Optional;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

@Component
public class SafeGetterMethodExecutor {

    public <T> Object invokeGetterOnField(String fieldName, T entity) {
        try {
            // -------------------------------------
            return _invokeGetter(fieldName, entity);
            // -------------------------------------
        } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException
                | NoSuchMethodException | SecurityException e) {
            e.printStackTrace();
        }
        return null;
    }

    private <T> Object _invokeGetter(String fieldName, T entity)
            throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        Optional<Object> result = Optional.absent();
        for (String field : fieldName.split("_")) {
            if (fieldName.endsWith(".") || 0 == field.length()) {
                throw new IllegalArgumentException("Invalid property name '" + fieldName + "'");
            }

            Method getter = entity.getClass().getMethod("get" + StringUtils.capitalize(field));
            result = Optional.fromNullable(getter.invoke(entity));

            if (!result.isPresent()) {
                break;
            } else if (!field.equals(fieldName)) {
                // If the current field is not equals to the nested
                // field properties, then it will call itself until
                // reach the last property (via Recursive Call).
                // On the other hand, fieldName.substring(field.length() + 1)
                // means that I'm passing the entire nested field path
                // to the next recursive call, except the current property
                // evaluated considering also the 'dot'.
                // For example, if we have "someProperty." (will be excluded)
                return _invokeGetter(fieldName.substring(field.length() + 1), result.get());
            }
        }
        return result.orNull(); // Holds the final result from the last getter method
    }

}