org.springframework.beans.factory.config.YamlMapFactoryBean Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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
*
* 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.springframework.beans.factory.config;
import java.util.LinkedHashMap;
import java.util.Map;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.lang.Nullable;
/**
* Factory for a {@code Map} that reads from a YAML source, preserving the
* YAML-declared value types and their structure.
*
* YAML is a nice human-readable format for configuration, and it has some
* useful hierarchical properties. It's more or less a superset of JSON, so it
* has a lot of similar features.
*
*
If multiple resources are provided the later ones will override entries in
* the earlier ones hierarchically; that is, all entries with the same nested key
* of type {@code Map} at any depth are merged. For example:
*
*
* foo:
* bar:
* one: two
* three: four
*
*
* plus (later in the list)
*
*
* foo:
* bar:
* one: 2
* five: six
*
*
* results in an effective input of
*
*
* foo:
* bar:
* one: 2
* three: four
* five: six
*
*
* Note that the value of "foo" in the first document is not simply replaced
* with the value in the second, but its nested values are merged.
*
* Requires SnakeYAML 1.18 or higher, as of Spring Framework 5.0.6.
*
* @author Dave Syer
* @author Juergen Hoeller
* @since 4.1
*/
public class YamlMapFactoryBean extends YamlProcessor implements FactoryBean>, InitializingBean {
private boolean singleton = true;
@Nullable
private Map map;
/**
* Set if a singleton should be created, or a new object on each request
* otherwise. Default is {@code true} (a singleton).
*/
public void setSingleton(boolean singleton) {
this.singleton = singleton;
}
@Override
public boolean isSingleton() {
return this.singleton;
}
@Override
public void afterPropertiesSet() {
if (isSingleton()) {
this.map = createMap();
}
}
@Override
@Nullable
public Map getObject() {
return (this.map != null ? this.map : createMap());
}
@Override
public Class getObjectType() {
return Map.class;
}
/**
* Template method that subclasses may override to construct the object
* returned by this factory.
* Invoked lazily the first time {@link #getObject()} is invoked in
* case of a shared singleton; else, on each {@link #getObject()} call.
*
The default implementation returns the merged {@code Map} instance.
* @return the object returned by this factory
* @see #process(java.util.Map, MatchCallback)
*/
protected Map createMap() {
Map result = new LinkedHashMap<>();
process((properties, map) -> merge(result, map));
return result;
}
@SuppressWarnings({"unchecked", "rawtypes"})
private void merge(Map output, Map map) {
map.forEach((key, value) -> {
Object existing = output.get(key);
if (value instanceof Map && existing instanceof Map) {
// Inner cast required by Eclipse IDE.
Map result = new LinkedHashMap<>((Map) existing);
merge(result, (Map) value);
output.put(key, result);
}
else {
output.put(key, value);
}
});
}
}