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Some stellar general purpose utils.
/*
* Copyright (C) Posten Norge AS
*
* 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 no.digipost.util;
import no.digipost.tuple.ViewableAsTuple;
import java.io.Serializable;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.Supplier;
import static java.util.Arrays.asList;
import static java.util.Collections.unmodifiableMap;
import static java.util.EnumSet.copyOf;
import static java.util.EnumSet.noneOf;
/**
* An immutable collection of {@link Attribute attributes}.
*/
public final class AttributesMap implements Serializable {
/**
* Switches to indicate behavior other than default.
*/
public enum Config implements Supplier {
/**
* If one needs to be able to retrieve {@code null} values from an {@code AttributeMap},
* this {@code Config} switch can be passed to the builder. By default, the {@link AttributesMap.Builder} will ignore any
* values which are {@code null}, and consequently the resulting {@link AttributesMap} will throw an exception if one tries
* to {@link AttributesMap#get(GetsNamedValue) get} a particular value which was null.
*/
ALLOW_NULL_VALUES;
@Override
public Builder get() {
return AttributesMap.buildNew(this);
}
}
/**
* An empty map with no attributes.
*/
public static final AttributesMap EMPTY = buildNew().build();
public static AttributesMap.Builder with(ViewableAsTuple, V> attributeWithValue, Config ... configSwitches) {
return buildNew(configSwitches).and(attributeWithValue);
}
public static AttributesMap.Builder with(SetsNamedValue attribute, V value, Config ... configSwitches) {
return buildNew(configSwitches).and(attribute, value);
}
public static AttributesMap.Builder buildNew(Config ... configSwitches) {
return new Builder(configSwitches);
}
private static final Serializable NON_EXISTING_VALUE = new Serializable() {
private Object readResolve() {
return NON_EXISTING_VALUE;
}
@Override
public String toString() {
return "[non-existing value]";
};
};
/**
* Builder to incrementally construct an immutable {@link AttributesMap}.
*/
public static class Builder {
private final ConcurrentMap incrementalMap = new ConcurrentHashMap<>();
private final Set configSwitches;
private Builder(Config ... configSwitches) {
this.configSwitches = configSwitches.length == 0 ? noneOf(Config.class) : copyOf(asList(configSwitches));
}
/**
* Add an attribute coupled with a value.
*
* @param attributeWithValue the attribute and the value.
* @return the builder
*/
public Builder and(ViewableAsTuple, V> attributeWithValue) {
return attributeWithValue.asTuple().to(this::and);
}
/**
* Add an attribute with a value.
*
* @param attribute the attribute
* @param value the value to bind to the attribute
* @return the builder
*/
public Builder and(SetsNamedValue attribute, V value) {
if (value != null || configSwitches.contains(Config.ALLOW_NULL_VALUES)) {
attribute.setOn((name, v) -> incrementalMap.put(name, v != null ? v : NON_EXISTING_VALUE), value);
}
return this;
}
/**
* Add all attributes from an existing {@link AttributesMap}.
*
* @param otherMap contains the other attributes to add.
* @return the builder
*/
public Builder and(AttributesMap otherMap) {
incrementalMap.putAll(otherMap.untypedMap);
return this;
}
/**
* Add all attributes from another {@link AttributesMap.Builder}
*
* @param otherBuilder contains the other attributes to add
* @return the builder
*/
public Builder and(AttributesMap.Builder otherBuilder) {
incrementalMap.putAll(otherBuilder.incrementalMap);
return this;
}
/**
* @return a new immutable {@link AttributesMap} containing the attributes and
* values added to the builder.
*/
public AttributesMap build() {
return new AttributesMap(incrementalMap);
}
}
private static final long serialVersionUID = 1L;
private final Map untypedMap;
private AttributesMap(Map untypedMap) {
this.untypedMap = unmodifiableMap(untypedMap);
}
/**
* Retrieve a required attribute value. This method throws an exception
* if the attribute value is not present.
*
* @param attribute the attribute to retrieve.
* @return the value
* @throws GetsNamedValue.NotFound if the attribute is not present.
*/
public V get(GetsNamedValue attribute) {
V value = attribute.requireFrom(untypedMap);
return value != NON_EXISTING_VALUE ? value : null;
}
/**
* @return the number of attributes contained in this map.
*/
public int size() {
return untypedMap.size();
}
/**
* @return {@code true} if this map contains no attributes, {@code false} otherwise.
*/
public boolean isEmpty() {
return untypedMap.isEmpty();
}
@Override
public String toString() {
return untypedMap.isEmpty() ? "no attributes" : "attributes: " + untypedMap.toString();
}
@Override
public boolean equals(Object obj) {
if (obj instanceof AttributesMap) {
AttributesMap that = (AttributesMap) obj;
return Objects.equals(this.untypedMap, that.untypedMap);
}
return false;
}
@Override
public int hashCode() {
return Objects.hash(untypedMap);
}
}