com.google.gerrit.metrics.Field.java Source code

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Here is the source code for com.google.gerrit.metrics.Field.java

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// Copyright (C) 2015 The Android Open Source Project
//
// 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 com.google.gerrit.metrics;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.base.Function;
import com.google.common.base.Functions;

/**
 * Describes a bucketing field used by a metric.
 *
 * @param <T> type of field
 */
public class Field<T> {
    /**
     * Break down metrics by boolean true/false.
     *
     * @param name field name
     * @return boolean field
     */
    public static Field<Boolean> ofBoolean(String name) {
        return ofBoolean(name, null);
    }

    /**
     * Break down metrics by boolean true/false.
     *
     * @param name field name
     * @param description field description
     * @return boolean field
     */
    public static Field<Boolean> ofBoolean(String name, String description) {
        return new Field<>(name, Boolean.class, description);
    }

    /**
     * Break down metrics by cases of an enum.
     *
     * @param enumType type of enum
     * @param name field name
     * @return enum field
     */
    public static <E extends Enum<E>> Field<E> ofEnum(Class<E> enumType, String name) {
        return ofEnum(enumType, name, null);
    }

    /**
     * Break down metrics by cases of an enum.
     *
     * @param enumType type of enum
     * @param name field name
     * @param description field description
     * @return enum field
     */
    public static <E extends Enum<E>> Field<E> ofEnum(Class<E> enumType, String name, String description) {
        return new Field<>(name, enumType, description);
    }

    /**
     * Break down metrics by string.
     *
     * <p>Each unique string will allocate a new submetric. <b>Do not use user content as a field
     * value</b> as field values are never reclaimed.
     *
     * @param name field name
     * @return string field
     */
    public static Field<String> ofString(String name) {
        return ofString(name, null);
    }

    /**
     * Break down metrics by string.
     *
     * <p>Each unique string will allocate a new submetric. <b>Do not use user content as a field
     * value</b> as field values are never reclaimed.
     *
     * @param name field name
     * @param description field description
     * @return string field
     */
    public static Field<String> ofString(String name, String description) {
        return new Field<>(name, String.class, description);
    }

    /**
     * Break down metrics by integer.
     *
     * <p>Each unique integer will allocate a new submetric. <b>Do not use user content as a field
     * value</b> as field values are never reclaimed.
     *
     * @param name field name
     * @return integer field
     */
    public static Field<Integer> ofInteger(String name) {
        return ofInteger(name, null);
    }

    /**
     * Break down metrics by integer.
     *
     * <p>Each unique integer will allocate a new submetric. <b>Do not use user content as a field
     * value</b> as field values are never reclaimed.
     *
     * @param name field name
     * @param description field description
     * @return integer field
     */
    public static Field<Integer> ofInteger(String name, String description) {
        return new Field<>(name, Integer.class, description);
    }

    private final String name;
    private final Class<T> keyType;
    private final Function<T, String> formatter;
    private final String description;

    private Field(String name, Class<T> keyType, String description) {
        checkArgument(name.matches("^[a-z_]+$"), "name must match [a-z_]");
        this.name = name;
        this.keyType = keyType;
        this.formatter = initFormatter(keyType);
        this.description = description;
    }

    /** @return name of this field within the metric. */
    public String getName() {
        return name;
    }

    /** @return type of value used within the field. */
    public Class<T> getType() {
        return keyType;
    }

    /** @return description text for the field explaining its range of values. */
    public String getDescription() {
        return description;
    }

    public Function<T, String> formatter() {
        return formatter;
    }

    @SuppressWarnings("unchecked")
    private static <T> Function<T, String> initFormatter(Class<T> keyType) {
        if (keyType == String.class) {
            return (Function<T, String>) Functions.<String>identity();
        } else if (keyType == Integer.class || keyType == Boolean.class) {
            return (Function<T, String>) Functions.toStringFunction();
        } else if (Enum.class.isAssignableFrom(keyType)) {
            return in -> ((Enum<?>) in).name();
        }
        throw new IllegalStateException("unsupported type " + keyType.getName());
    }
}