org.springframework.core.env.CompositePropertySource.java Source code

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Here is the source code for org.springframework.core.env.CompositePropertySource.java

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/*
 * Copyright 2002-2017 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.core.env;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;

/**
 * Composite {@link PropertySource} implementation that iterates over a set of
 * {@link PropertySource} instances. Necessary in cases where multiple property sources
 * share the same name, e.g. when multiple values are supplied to {@code @PropertySource}.
 *
 * <p>As of Spring 4.1.2, this class extends {@link EnumerablePropertySource} instead
 * of plain {@link PropertySource}, exposing {@link #getPropertyNames()} based on the
 * accumulated property names from all contained sources (as far as possible).
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @author Phillip Webb
 * @since 3.1.1
 */
public class CompositePropertySource extends EnumerablePropertySource<Object> {

    private final Set<PropertySource<?>> propertySources = new LinkedHashSet<>();

    /**
     * Create a new {@code CompositePropertySource}.
     * @param name the name of the property source
     */
    public CompositePropertySource(String name) {
        super(name);
    }

    @Override
    @Nullable
    public Object getProperty(String name) {
        for (PropertySource<?> propertySource : this.propertySources) {
            Object candidate = propertySource.getProperty(name);
            if (candidate != null) {
                return candidate;
            }
        }
        return null;
    }

    @Override
    public boolean containsProperty(String name) {
        for (PropertySource<?> propertySource : this.propertySources) {
            if (propertySource.containsProperty(name)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public String[] getPropertyNames() {
        Set<String> names = new LinkedHashSet<>();
        for (PropertySource<?> propertySource : this.propertySources) {
            if (!(propertySource instanceof EnumerablePropertySource)) {
                throw new IllegalStateException(
                        "Failed to enumerate property names due to non-enumerable property source: "
                                + propertySource);
            }
            names.addAll(Arrays.asList(((EnumerablePropertySource<?>) propertySource).getPropertyNames()));
        }
        return StringUtils.toStringArray(names);
    }

    /**
     * Add the given {@link PropertySource} to the end of the chain.
     * @param propertySource the PropertySource to add
     */
    public void addPropertySource(PropertySource<?> propertySource) {
        this.propertySources.add(propertySource);
    }

    /**
     * Add the given {@link PropertySource} to the start of the chain.
     * @param propertySource the PropertySource to add
     * @since 4.1
     */
    public void addFirstPropertySource(PropertySource<?> propertySource) {
        List<PropertySource<?>> existing = new ArrayList<>(this.propertySources);
        this.propertySources.clear();
        this.propertySources.add(propertySource);
        this.propertySources.addAll(existing);
    }

    /**
     * Return all property sources that this composite source holds.
     * @since 4.1.1
     */
    public Collection<PropertySource<?>> getPropertySources() {
        return this.propertySources;
    }

    @Override
    public String toString() {
        return getClass().getSimpleName() + " {name='" + this.name + "', propertySources=" + this.propertySources
                + "}";
    }

}