org.apache.nifi.registry.VariableRegistry Maven / Gradle / Ivy
/*
* 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.nifi.registry;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
/**
* Provides a registry of variables available for use by various components and
* extension points. This enables components to reference variable names rather
* than explicit values which can make configurations of those components more
* portable.
*/
public interface VariableRegistry {
/**
* Returns an empty registry which can be used as a more intentional null
* value.
*/
public static final VariableRegistry EMPTY_REGISTRY = () -> Collections.emptyMap();
/**
* Provides a registry containing all environment variables and system
* properties. System properties receive precedence.
*/
public static final VariableRegistry ENVIRONMENT_SYSTEM_REGISTRY = new VariableRegistry() {
final Map map = new HashMap<>();
{
System.getenv().entrySet().stream().forEach((entry) -> {
final VariableDescriptor desc = new VariableDescriptor.Builder(entry.getKey())
.description("Env Var")
.sensitive(false)
.build();
map.put(desc, entry.getValue());
});
System.getProperties().entrySet().stream().forEach((entry) -> {
final VariableDescriptor desc = new VariableDescriptor.Builder(entry.getKey().toString())
.description("System Property")
.sensitive(false)
.build();
map.put(desc, entry.getValue().toString());
});
}
@Override
public Map getVariableMap() {
return Collections.unmodifiableMap(map);
}
};
/**
* Provides access to a map of variable key/value pairs. For variables
* considered to be sensitive care must be taken to ensure their values are
* protected whenever stored or exposed.
*
* @return An immutable map of all variables in the registry
*/
Map getVariableMap();
/**
* Returns the VariableDescriptor for the given key name if it exists.
*
* @param name the string name of the VariableDescriptor to lookup.
* @return the variable descriptor registered for this name if it exists;
* null otherwise
*/
default VariableDescriptor getVariableKey(final String name) {
if (name == null) {
return null;
}
final VariableDescriptor spec = new VariableDescriptor(name);
for (final Map.Entry entry : getVariableMap().entrySet()) {
if (entry.getKey().equals(spec)) {
return entry.getKey();
}
}
return null;
}
/**
* Gets the variable value
*
* @param name the string name of the VariableDescriptor that is the key of
* the value to lookup.
* @return the value associated with the given variable name if found; null
* otherwise
*/
default String getVariableValue(final String name) {
if (name == null) {
return null;
}
return getVariableMap().get(new VariableDescriptor(name));
}
/**
* Gets the variable value
*
* @param descriptor the descriptor for which to lookup the variable value.
* @return the variable value if the given descriptor is equivalent to one
* of the entries in the registry; null otherwise
*/
default String getVariableValue(final VariableDescriptor descriptor) {
if (descriptor == null) {
return null;
}
return getVariableMap().get(descriptor);
}
}