出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/09/12 01:29:24」(JST)
| 開発元 | レッドハット |
|---|---|
| 最新版 | 5.1.2[1] / 2016年9月19日（11か月前） （2016-09-19） |
| リポジトリ | github |
| 対応OS | クロスプラットフォーム |
| プラットフォーム | Javaプラットフォーム |
| 種別 | ORM |
| ライセンス | LGPL |
| 公式サイト | www.hibernate.org |
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Hibernate は、Java のためのオブジェクト関係マッピング (ORM) ライブラリであり、オブジェクト指向のドメインモデルを関係データベースにマッピングするためのフレームワークを提供する。Hibernate は、永続性に関わるデータベースアクセスを直接高レベルなオブジェクト操作機能に置換することでオブジェクト指向と関係モデルの不整合を解決する。
Hibernate はオープンソースのフリーソフトウェアであり、GNU Lesser General Public License で提供されている。
第一の機能は、Javaクラスからデータベースの表（およびJavaデータ型からSQLデータ型）へのマッピングである。また、データのクエリと検索機能も提供する。SQL呼び出しを自動生成することで、開発者がSQL呼び出しの結果をいちいちオブジェクトに変換する手間から解放し、性能への影響を最小にしつつ、あらゆるSQLデータベースへの移植性を達成している。
Hibernate は Plain Old Java Object (POJO) のための透過的永続性を提供する。永続性クラスに要求されることは、引数のない コンストラクタ が存在することであり、コンストラクタの可視性が public でなくともよい（一部アプリケーションでは、equals() と hashCode() メソッドにも注意が必要[1]）。
Hibernate には「ダーティチェッキング」機能がある。この機能は、永続的オブジェクトの変更されたフィールドについてのみ SQL による更新を行うもので、不必要なデータベース更新を削減する。
Hibernate は「HQL」というSQLライクなクエリ言語を提供している。オブジェクト指向的な代替手段としてクライテリアクエリも提供されている。
Hibernate はスタンドアローンのJavaアプリケーションにも使えるし、Java Servlet や EJBセッションビーンを使った Java EE アプリケーションにも使える。
Hibernate は Gavin King をリーダーとして世界中の Java ソフトウェア開発者がチームを結成して開発した。その後、JBoss社（現在はレッドハットの一部）が Hibernate の主要開発者を雇い入れ、サポートを行うようになった。
バージョン3.xでは、Interceptor/Callback アーキテクチャ、ユーザ定義フィルタ、JDK 5.0 アノテーション（Javaのメタデータ機能）などの新機能が新たに追加された。このバージョンはEJB 3.0仕様とも非常に近く（ただし、EJB 3.0仕様が完成しJava Community Processによってリリースされる前にリリースされた）、JBossのEJB 3.0実装の基盤となった。
Hibernate はモジュール化され、それぞれ独立したチームが開発している。
Session サポート、トランザクション管理、オブジェクト・キャッシング、HQL）。JavaオブジェクトとSQLの変換をするには、JavaクラスとSQLテーブルの間の「マッピングデータ」がなければならない。Hibernate はこのためのいくつかの手段を提供する。
Configuration インスタンスに追加する）。アノテーション機能は別モジュール化されている。SessionFactory のインスタンスを生成する前に、マッピングの詳細を操作するAPI（Configuration インスタンスを使用）も提供している。不要なSQLによる更新を防ぐため、Hibernate はダーティチェッキングという機能を提供している。この機能は、永続的オブジェクトの変更されたフィールドやコレクションのみを更新できるようにするものである。コレクションに含まれない部分の更新が必要かどうかを確認するため、Hibernate はそれらのフィールドを Object.equals() メソッドで比較する。一方、コレクションフィールド（java.util.List や java.util.Set など）は同一性（参照）比較を行う。
Hibernate API は、パッケージ org.hibernate で提供されている。
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Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy that is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate. Although traditionally reserved for "deep" hibernators such as rodents, the term has been redefined to include animals such as bears and is now applied based on active metabolic suppression rather than based on absolute body temperature decline. Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms.[1][2] The equivalent during the summer months is known as aestivation. Some reptile species (ectotherms) are said to brumate, or undergo brumation, but any possible similarities between brumation and hibernation are not firmly established. Some insects, such as the wasp Polistes exclamans, hibernate by aggregating together in groups in protected places called hibernacula.[3]
Often associated with low temperatures, the function of hibernation is to conserve energy during a period when sufficient food is unavailable. To achieve this energy saving, an endotherm will first decrease its metabolic rate, which then decreases body temperature.[2] Hibernation may last several days, weeks, or months depending on the species, ambient temperature, time of year, and individual's body condition.
Before entering hibernation, animals need to store enough energy to last through the entire winter. Larger species become hyperphagic and eat a large amount of food and store the energy in fat deposits. In many small species, food caching replaces eating and becoming fat.[4] Some species of mammals hibernate while gestating young, which are either born while the mother hibernates or shortly afterwards.[5]
For example, the female polar bear goes into hibernation during the cold winter months to give birth to her offspring. She loses 15–27% of her pre-hibernation weight and uses stored fats for energy during times of food scarcity, or hibernation. It is evident that pregnant female polar bears significantly increase body mass prior to hibernation, and this increase is further reflected in the weight of their offspring. The fat accumulation prior to hibernation in female polar bears enables them to provide a sufficient and warm, nurturing environment for their newborns.[6]
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While hibernation has long been studied in rodents, namely ground squirrels, no primate or tropical mammal was known to hibernate prior to the discovery that the fat-tailed dwarf lemur of Madagascar hibernates in tree holes for seven months of the year.[7] Malagasy winter temperatures sometimes rise to over 30 °C (86 °F), so hibernation is not exclusively an adaptation to low ambient temperatures. The hibernation of this lemur is strongly dependent on the thermal behaviour of its tree hole: if the hole is poorly insulated, the lemur's body temperature fluctuates widely, passively following the ambient temperature; if well insulated, the body temperature stays fairly constant and the animal undergoes regular spells of arousal.[8] Dausmann found that hypometabolism in hibernating animals is not necessarily coupled to a low body temperature.[9]
Hibernating bears are able to recycle their proteins and urine, allowing them both to stop urinating for months and to avoid muscle atrophy.[10][11]
Obligate hibernators are animals that spontaneously, and annually, enter hibernation regardless of ambient temperature and access to food. Obligate hibernators include many species of ground squirrels, other rodents, mouse lemurs, the European hedgehog and other insectivores, monotremes, marsupials, and even butterflies such as the small tortoiseshell.[12] These undergo what has been traditionally called "hibernation": the physiological state where the body temperature drops to near ambient (environmental) temperature, and heart and respiration rates slow drastically. The typical winter season for these hibernators is characterized by periods of torpor interrupted by periodic, euthermic arousals, wherein body temperatures and heart rates are restored to euthermic (more typical) levels. The cause and purpose of these arousals is still not clear.
The question of why hibernators may experience the periodic arousals (returns to high body temperature) has plagued researchers for decades, and while there is still no clear-cut explanation, there are myriad hypotheses on the topic. One favored hypothesis is that hibernators build a 'sleep debt' during hibernation, and so must occasionally warm up in order to sleep. This has been supported by evidence in the Arctic ground squirrel.[13] Another theory states that the brief periods of high body temperature during hibernation are used by the animal to restore its available energy sources.[14] Yet another theory states that the frequent returns to high body temperature allow mammals to initiate an immune response.[15]
Hibernating Arctic ground squirrels may exhibit abdominal temperatures as low as −2.9 °C, maintaining sub-zero abdominal temperatures for more than three weeks at a time, although the temperatures at the head and neck remain at 0 ˚C or above.[16]
Historically there was a question of whether or not bears truly hibernate, since they experience only a modest decline in body temperature (3–5 K) compared with what other hibernators undergo (32 K or more). Many researchers thought that their deep sleep was not comparable with true, deep hibernation. This theory has been refuted by recent research in captive black bears.[17]
Unlike obligate hibernators, facultative hibernators only enter hibernation when either cold stressed or food deprived, or both. A good example of the differences between the two types of hibernation can be seen among the prairie dogs: the white-tailed prairie dog is an obligate hibernator and the closely related black-tailed prairie dog is a facultative hibernator.[18]
Historically, Pliny the Elder believed swallows hibernated, and ornithologist Gilbert White documented anecdotal evidence in his 1789 book The Natural History of Selborne that indicated the belief was still current in his time. Birds typically do not hibernate, instead utilizing torpor. One known exception is the common poorwill (Phalaenoptilus nuttallii), first documented by Edmund Jaeger.[19][20]
Fish are ectothermic, and so, by definition, cannot hibernate because they cannot actively down-regulate their body temperature or their metabolic rate. However, they can experience decreased metabolic rates associated with colder environments and/or low oxygen availability (hypoxia) and can experience dormancy. For a couple of generations[vague] during the 20th century it was thought that basking sharks settled to the floor of the North Sea and became dormant. Research by Dr David Sims in 2003 dispelled this hypothesis,[21] showing that the sharks actively traveled huge distances throughout the seasons, tracking the areas with the highest quantity of plankton. The epaulette sharks have been documented to be able to survive for long periods of time without oxygen, even being left high and dry, and at temperatures of up to 26 °C (79 °F).[22] Other animals able to survive long periods with no or very little oxygen include the goldfish, the red-eared slider turtle, the wood frog, and the bar-headed goose.[23] However, the ability to survive hypoxic or anoxic conditions is not the same, nor closely related, to endotherm hibernation.
Hibernation induction trigger (HIT) is somewhat of a misnomer. Although research in the 1990s hinted at the ability to induce torpor in animals by injection of blood taken from a hibernating animal, further research has been unable to reproduce this phenomenon. Despite the inability to induce torpor, there are substances in hibernator blood that can lend protection to organs for possible transplant. Researchers were able to prolong the life of an isolated pig's heart with a HIT.[24] This may have potentially important implications for organ transplant, as it could allow organs to survive for up to 18 or more hours, outside the human body. This would be a great improvement from the current 6 hours.
This supposed HIT is a mixture derived from serum, including at least one opioid-like substance. DADLE is an opioid that in some experiments has been shown to have similar functional properties.[25]
There are many research projects currently investigating how to achieve "induced hibernation" in humans.[26][27] The ability to hibernate would be useful for a number of reasons, such as saving the lives of seriously ill or injured people by temporarily putting them in a state of hibernation until treatment can be given.
Earlier I gave an account (Condor, 50, 1948:45) of the behavior of a Poor-will (Phalaenoptilus nuttallinii) which I found in a state of profound torpidity in the winter of 1946–47 in the Chuckawalla Mountains of the Colorado Desert, California
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| リンク元 | 「hibernation」「冬眠」「winter sleep」 |
| 関連記事 | 「hibernating」 |