modules/cassandra/store/src/main/java/org/apache/ignite/cache/store/cassandra/persistence/PojoFieldAccessor.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.ignite.cache.store.cassandra.persistence;

import java.beans.PropertyDescriptor;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import org.apache.ignite.IgniteException;

/**
 * Property accessor provides read/write access to POJO object properties defined through:
 *  1) Getter/setter methods
 *  2) Raw class members
 */
public class PojoFieldAccessor {
    /** Java Bean property descriptor */
    private PropertyDescriptor desc;

    /** Object field associated with property descriptor. Used just to get annotations which
     * applied not to property descriptor, but directly to object field associated with the property. */
    private Field descField;

    /** Object field */
    private Field field;

    /**
     * Constructs object instance from Java Bean property descriptor, providing access to getter/setter.
     *
     * @param desc Java Bean property descriptor.
     * @param field object field associated with property descriptor.
     */
    public PojoFieldAccessor(PropertyDescriptor desc, Field field) {
        if (desc.getReadMethod() == null) {
            throw new IllegalArgumentException("Field '" + desc.getName() +
                    "' of the class instance '" + desc.getPropertyType().getName() +
                    "' doesn't provide getter method");
        }

        desc.getReadMethod().setAccessible(true);

        if (desc.getWriteMethod() != null)
            desc.getWriteMethod().setAccessible(true);

        this.desc = desc;
        this.descField = field;
    }

    /**
     * Constructs object instance from Field, providing direct access to class member.
     *
     * @param field Field descriptor.
     */
    public PojoFieldAccessor(Field field) {
        field.setAccessible(true);
        this.field = field;
    }

    /**
     * Returns POJO field name.
     *
     * @return field name.
     */
    public String getName() {
        return desc != null ? desc.getName() : field.getName();
    }

    /**
     * Indicates if it's read-only field.
     *
     * @return true if field read-only, false if not.
     */
    public boolean isReadOnly() {
        return desc != null && desc.getWriteMethod() == null;
    }

    /**
     * Returns POJO field annotation.
     *
     * @param clazz Class of the annotation to get.
     * @return annotation.
     */
    public Annotation getAnnotation(Class clazz) {
        if (field != null)
            return field.getAnnotation(clazz);

        Annotation ann = desc.getReadMethod().getAnnotation(clazz);

        if (ann != null)
            return ann;

        ann = desc.getWriteMethod() == null ? null : desc.getWriteMethod().getAnnotation(clazz);

        if (ann != null)
            return ann;

        return descField == null ? null : descField.getAnnotation(clazz);
    }

    /**
     * Returns field value for the object instance.
     *
     * @param obj object instance.
     * @return field value.
     */
    public Object getValue(Object obj) {
        try {
            return desc != null ? desc.getReadMethod().invoke(obj) : field.get(obj);
        }
        catch (Throwable e) {
            throw new IgniteException("Failed to get value of the field '" + getName() + "' from the instance " +
                    " of '" + obj.getClass().toString() + "' class", e);
        }
    }

    /**
     * Assigns value for the object field.
     *
     * @param obj object instance.
     * @param val value to assign.
     */
    public void setValue(Object obj, Object val) {
        if (isReadOnly())
            throw new IgniteException("Can't assign value to read-only field '" + getName() + "' of the instance " +
                    " of '" + obj.getClass().toString() + "' class");

        try {
            if (desc != null)
                desc.getWriteMethod().invoke(obj, val);
            else
                field.set(obj, val);
        }
        catch (Throwable e) {
            throw new IgniteException("Failed to set value of the field '" + getName() + "' of the instance " +
                    " of '" + obj.getClass().toString() + "' class", e);
        }
    }

    /**
     * Returns field type.
     *
     * @return field type.
     */
    public Class getFieldType() {
        return desc != null ? desc.getPropertyType() : field.getType();
    }
}