io.wcm.config.spi.helpers.AbstractParameterProvider.java Source code

Introduction

Here is the source code for io.wcm.config.spi.helpers.AbstractParameterProvider.java

Source

/*
 * #%L
 * wcm.io
 * %%
 * Copyright (C) 2014 wcm.io
 * %%
 * 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.
 * #L%
 */
package io.wcm.config.spi.helpers;

import io.wcm.config.api.Parameter;
import io.wcm.config.spi.ParameterProvider;

import java.lang.reflect.Field;
import java.util.HashSet;
import java.util.Set;

import org.osgi.annotation.versioning.ConsumerType;

import com.google.common.collect.ImmutableSet;

/**
 * Abstract implementation of {@link ParameterProvider} providing list of parameters either from given
 * parameter set, or from reading all public static fields from a given class definition.
 */
@ConsumerType
public abstract class AbstractParameterProvider implements ParameterProvider {

    private final Set<Parameter<?>> parameters;

    /**
     * @param parameters Set of parameters for parameter provider
     */
    protected AbstractParameterProvider(Set<Parameter<?>> parameters) {
        this.parameters = parameters;
    }

    /**
     * @param type Type containing parameter definitions as public static fields.
     */
    protected AbstractParameterProvider(Class<?> type) {
        this(getParametersFromPublicFields(type));
    }

    @Override
    public final Set<Parameter<?>> getParameters() {
        return parameters;
    }

    /**
     * Get all parameters defined as public static fields in the given type.
     * @param type Type
     * @return Set of parameters
     */
    private static Set<Parameter<?>> getParametersFromPublicFields(Class<?> type) {
        Set<Parameter<?>> params = new HashSet<>();
        try {
            Field[] fields = type.getFields();
            for (Field field : fields) {
                if (field.getType().isAssignableFrom(Parameter.class)) {
                    params.add((Parameter<?>) field.get(null));
                }
            }
        } catch (IllegalArgumentException | IllegalAccessException ex) {
            throw new RuntimeException("Unable to access fields of " + type.getName(), ex);
        }
        return ImmutableSet.copyOf(params);
    }

}