Retrieve a Long bean property value. - Java Reflection

Java examples for Reflection:Java Bean

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Description

Retrieve a Long bean property value.

Demo Code

/*//  ww  w. j  a  v a  2 s .com
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
//package com.java2s;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class Main {


    /**
     * Retrieve a Long bean property value.
     *
     * @param bean The bean instance
     * @param propertyName The name of the property whose value to extract
     *
     * @return long value
     *
     * @throws NoSuchFieldException If the value is null (wow)
     */
    public static long getLongBeanProperty(final Object bean,
            final String propertyName) throws NoSuchFieldException {
        validateArgs(bean, propertyName);
        final Object o = getBeanProperty(bean, propertyName);
        if (o == null) {
            throw new NoSuchFieldException(propertyName);
        } else if (!(o instanceof Number)) {
            throw new IllegalArgumentException(propertyName
                    + " not an Number");
        }
        return ((Number) o).longValue();
    }

    private static void validateArgs(Object bean, String propertyName) {
        if (bean == null) {
            throw new IllegalArgumentException("bean is null");
        }
        if (propertyName == null) {
            throw new IllegalArgumentException("propertyName is null");
        }
        if (propertyName.trim().length() == 0) {
            throw new IllegalArgumentException("propertyName is empty");
        }
    }

    /**
     * Retrieve a named bean property value.
     *
     * @param bean The bean instance
     * @param propertyName The name of the property whose value to extract
     *
     * @return the property value
     */
    public static Object getBeanProperty(Object bean, String propertyName) {
        validateArgs(bean, propertyName);

        // try getters first
        final Method getter = getMethod(bean, propertyName);
        if (getter != null) {
            try {
                return getter.invoke(bean);
            } catch (Exception e) {
                /**/
            }
        }

        // then try fields
        final Field field = getField(bean, propertyName);
        if (field != null) {
            try {
                field.setAccessible(true);
                return field.get(bean);
            } catch (Exception e) {
                /**/
            }
        }

        return null;
    }

    /**
     * Return the named getter method on the bean or null if not found.
     *
     * @param bean The bean
     * @param propertyName The property to get the getter for
     *
     * @return the named getter method
     */
    private static Method getMethod(Object bean, String propertyName) {
        final StringBuilder sb = new StringBuilder("get").append(Character
                .toUpperCase(propertyName.charAt(0)));
        if (propertyName.length() > 1) {
            sb.append(propertyName.substring(1));
        }
        final String getterName = sb.toString();
        for (Method m : bean.getClass().getMethods()) {
            if (getterName.equals(m.getName())
                    && m.getParameterTypes().length == 0) {
                return m;
            }
        }
        return null;
    }

    private static Field getField(Object bean, String propertyName) {
        for (Field f : bean.getClass().getDeclaredFields()) {
            if (propertyName.equals(f.getName())) {
                return f;
            }
        }
        return null;
    }
}

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