inheritance_mapping.po

hibernate-distribution-3.3.1.GA-dist.zip源码

msgid ""
msgstr ""
"Project-Id-Version: PACKAGE VERSION\n"
"Report-Msgid-Bugs-To: http://bugs.kde.org\n"
"POT-Creation-Date: 2008-08-14 15:28+0000\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <[e-mail]>\n"
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"Content-Transfer-Encoding: 8bit\n"

#. Tag: title
#: inheritance_mapping.xml:29
#, no-c-format
msgid "Inheritance Mapping"
msgstr "继承映射(Inheritance Mappings)"

#. Tag: title
#: inheritance_mapping.xml:32
#, no-c-format
msgid "The Three Strategies"
msgstr "三种策略"

#. Tag: para
#: inheritance_mapping.xml:34
#, no-c-format
msgid "Hibernate supports the three basic inheritance mapping strategies:"
msgstr "Hibernate支持三种基本的继承映射策略："

#. Tag: para
#: inheritance_mapping.xml:40
#, no-c-format
msgid "table per class hierarchy"
msgstr "每个类分层结构一张表(table per class hierarchy)"

#. Tag: para
#: inheritance_mapping.xml:45
#, fuzzy, no-c-format
msgid "<para>table per subclass</para>"
msgstr ""
"#-#-#-#-#  - (PACKAGE VERSION)  #-#-#-#-#\n"
"每个子类一张表(table per subclass)\n"
"#-#-#-#-#  - (PACKAGE VERSION)  #-#-#-#-#\n"
"每个子类一张表"

#. Tag: para
#: inheritance_mapping.xml:50
#, no-c-format
msgid "table per concrete class"
msgstr "每个具体类一张表(table per concrete class)"

#. Tag: para
#: inheritance_mapping.xml:56
#, no-c-format
msgid ""
"In addition, Hibernate supports a fourth, slightly different kind of "
"polymorphism:"
msgstr "此外，Hibernate还支持第四种稍有不同的多态映射策略："

#. Tag: para
#: inheritance_mapping.xml:63
#, no-c-format
msgid "implicit polymorphism"
msgstr "隐式多态(implicit polymorphism)"

#. Tag: para
#: inheritance_mapping.xml:69
#, no-c-format
msgid ""
"It is possible to use different mapping strategies for different branches of "
"the same inheritance hierarchy, and then make use of implicit polymorphism "
"to achieve polymorphism across the whole hierarchy. However, Hibernate does "
"not support mixing <literal>&lt;subclass&gt;</literal>, and <literal>&lt;"
"joined-subclass&gt;</literal> and <literal>&lt;union-subclass&gt;</literal> "
"mappings under the same root <literal>&lt;class&gt;</literal> element. It is "
"possible to mix together the table per hierarchy and table per subclass "
"strategies, under the the same <literal>&lt;class&gt;</literal> element, by "
"combining the <literal>&lt;subclass&gt;</literal> and <literal>&lt;join&gt;</"
"literal> elements (see below)."
msgstr ""
"对于同一个继承层次内的不同分支，可以采用不同的映射策略，然后用隐式多 态来完成"
"跨越整个层次的多态。但是在同一个<literal>&lt;class&gt;</literal>根元素 下，"
"Hibernate不支持混合了元素<literal>&lt;subclass&gt;</literal>、 <literal>&lt;"
"joined-subclass&gt;</literal>和<literal>&lt;union-subclass&gt;</literal> 的映"
"射。在同一个<literal>&lt;class&gt;</literal>元素下，可以混合使用 “每个类分层"
"结构一张表”（table per hierarchy） 和“每个子类一张表”（table per subclass） "
"这两种映射策略，这是通过结合元素<literal>&lt;subclass&gt;</literal>和 "
"<literal>&lt;join&gt;</literal>来实现的（见后）。"

#. Tag: para
#: inheritance_mapping.xml:83
#, no-c-format
msgid ""
"It is possible to define <literal>subclass</literal>, <literal>union-"
"subclass</literal>, and <literal>joined-subclass</literal> mappings in "
"separate mapping documents, directly beneath <literal>hibernate-mapping</"
"literal>. This allows you to extend a class hierachy just by adding a new "
"mapping file. You must specify an <literal>extends</literal> attribute in "
"the subclass mapping, naming a previously mapped superclass. Note: "
"Previously this feature made the ordering of the mapping documents "
"important. Since Hibernate3, the ordering of mapping files does not matter "
"when using the extends keyword. The ordering inside a single mapping file "
"still needs to be defined as superclasses before subclasses."
msgstr ""
"在多个映射文件中，可以直接在<literal>hibernate-mapping</literal>根下定义"
"<literal>subclass</literal>，<literal>union-subclass</literal>和"
"<literal>joined-subclass</literal>。也就是说，你可以仅加入一个新的映射文件来"
"扩展类层次。你必须在subclass的映射中指明<literal>extends</literal>属性，给出"
"一个之前定义的超类的名字。注意，在以前，这一功能对映射文件的顺序有严格的要"
"求，从Hibernate 3开始，使用extends关键字的时侯，对映射文件的顺序不再有要求；"
"但在每个映射文件里，超类必须在子类之前定义。"

#. Tag: programlisting
#: inheritance_mapping.xml:94
#, no-c-format
msgid ""
"<![CDATA[\n"
" <hibernate-mapping>\n"
"     <subclass name=\"DomesticCat\" extends=\"Cat\" discriminator-value=\"D"
"\">\n"
"          <property name=\"name\" type=\"string\"/>\n"
"     </subclass>\n"
" </hibernate-mapping>]]>"
msgstr ""

#. Tag: title
#: inheritance_mapping.xml:98
#, no-c-format
msgid "Table per class hierarchy"
msgstr "每个类分层结构一张表(Table per class hierarchy)"

#. Tag: para
#: inheritance_mapping.xml:100
#, no-c-format
msgid ""
"Suppose we have an interface <literal>Payment</literal>, with implementors "
"<literal>CreditCardPayment</literal>, <literal>CashPayment</literal>, "
"<literal>ChequePayment</literal>. The table per hierarchy mapping would look "
"like:"
msgstr ""
"假设我们有接口<literal>Payment</literal>和它的几个实现类： "
"<literal>CreditCardPayment</literal>, <literal>CashPayment</literal>, 和"
"<literal>ChequePayment</literal>。则“每个类分层结构一张表”(Table per class "
"hierarchy)的映射代码如下所示："

#. Tag: programlisting
#: inheritance_mapping.xml:107
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Payment\" table=\"PAYMENT\">\n"
"    <id name=\"id\" type=\"long\" column=\"PAYMENT_ID\">\n"
"        <generator class=\"native\"/>\n"
"    </id>\n"
"    <discriminator column=\"PAYMENT_TYPE\" type=\"string\"/>\n"
"    <property name=\"amount\" column=\"AMOUNT\"/>\n"
"    ...\n"
"    <subclass name=\"CreditCardPayment\" discriminator-value=\"CREDIT\">\n"
"        <property name=\"creditCardType\" column=\"CCTYPE\"/>\n"
"        ...\n"
"    </subclass>\n"
"    <subclass name=\"CashPayment\" discriminator-value=\"CASH\">\n"
"        ...\n"
"    </subclass>\n"
"    <subclass name=\"ChequePayment\" discriminator-value=\"CHEQUE\">\n"
"        ...\n"
"    </subclass>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: inheritance_mapping.xml:109
#, no-c-format
msgid ""
"Exactly one table is required. There is one big limitation of this mapping "
"strategy: columns declared by the subclasses, such as <literal>CCTYPE</"
"literal>, may not have <literal>NOT NULL</literal> constraints."
msgstr ""
"采用这种策略只需要一张表即可。它有一个很大的限制：要求那些由子类定义的字段， "
"如<literal>CCTYPE</literal>，不能有<literal>非空(NOT NULL)</literal>约束。"

#. Tag: title
#: inheritance_mapping.xml:118
#, no-c-format
msgid "Table per subclass"
msgstr "每个子类一张表(Table per subclass)"

#. Tag: para
#: inheritance_mapping.xml:120
#, no-c-format
msgid "A table per subclass mapping would look like:"
msgstr "对于上例中的几个类而言，采用“每个子类一张表”的映射策略，代码如下所示："

#. Tag: programlisting
#: inheritance_mapping.xml:124
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Payment\" table=\"PAYMENT\">\n"
"    <id name=\"id\" type=\"long\" column=\"PAYMENT_ID\">\n"
"        <generator class=\"native\"/>\n"
"    </id>\n"
"    <property name=\"amount\" column=\"AMOUNT\"/>\n"
"    ...\n"
"    <joined-subclass name=\"CreditCardPayment\" table=\"CREDIT_PAYMENT\">\n"
"        <key column=\"PAYMENT_ID\"/>\n"
"        <property name=\"creditCardType\" column=\"CCTYPE\"/>\n"
"        ...\n"
"    </joined-subclass>\n"
"    <joined-subclass name=\"CashPayment\" table=\"CASH_PAYMENT\">\n"
"        <key column=\"PAYMENT_ID\"/>\n"
"        ...\n"
"    </joined-subclass>\n"
"    <joined-subclass name=\"ChequePayment\" table=\"CHEQUE_PAYMENT\">\n"
"        <key column=\"PAYMENT_ID\"/>\n"
"        ...\n"
"    </joined-subclass>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: inheritance_mapping.xml:126
#, no-c-format
msgid ""
"Four tables are required. The three subclass tables have primary key "
"associations to the superclass table (so the relational model is actually a "
"one-to-one association)."
msgstr ""
"需要四张表。三个子类表通过主键关联到超类表(因而关系模型实际上是一对一关联)。"

#. Tag: title
#: inheritance_mapping.xml:135
#, no-c-format
msgid "Table per subclass, using a discriminator"
msgstr "每个子类一张表(Table per subclass)，使用辨别标志(Discriminator)"

#. Tag: para
#: inheritance_mapping.xml:137
#, no-c-format
msgid ""
"Note that Hibernate's implementation of table per subclass requires no "
"discriminator column. Other object/relational mappers use a different "
"implementation of table per subclass which requires a type discriminator "
"column in the superclass table. The approach taken by Hibernate is much more "
"difficult to implement but arguably more correct from a relational point of "
"view. If you would like to use a discriminator column with the table per "
"subclass strategy, you may combine the use of <literal>&lt;subclass&gt;</"
"literal> and <literal>&lt;join&gt;</literal>, as follow:"
msgstr ""
"注意，对“每个子类一张表”的映射策略，Hibernate的实现不需要辨别字段，而其他 的"
"对象/关系映射工具使用了一种不同于Hibernate的实现方法，该方法要求在超类 表中有"
"一个类型辨别字段(type discriminator column)。Hibernate采用的方法更 难实现，但"
"从关系（数据库）的角度来看，按理说它更正确。若你愿意使用带有辨别字 段的“每个"
"子类一张表”的策略，你可以结合使用<literal>&lt;subclass&gt;</literal> 与"
"<literal>&lt;join&gt;</literal>，如下所示："

#. Tag: programlisting
#: inheritance_mapping.xml:149
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Payment\" table=\"PAYMENT\">\n"
"    <id name=\"id\" type=\"long\" column=\"PAYMENT_ID\">\n"
"        <generator class=\"native\"/>\n"
"    </id>\n"
"    <discriminator column=\"PAYMENT_TYPE\" type=\"string\"/>\n"
"    <property name=\"amount\" column=\"AMOUNT\"/>\n"
"    ...\n"
"    <subclass name=\"CreditCardPayment\" discriminator-value=\"CREDIT\">\n"
"        <join table=\"CREDIT_PAYMENT\">\n"
"            <key column=\"PAYMENT_ID\"/>\n"
"            <property name=\"creditCardType\" column=\"CCTYPE\"/>\n"
"            ...\n"
"        </join>\n"
"    </subclass>\n"
"    <subclass name=\"CashPayment\" discriminator-value=\"CASH\">\n"
"        <join table=\"CASH_PAYMENT\">\n"
"            <key column=\"PAYMENT_ID\"/>\n"
"            ...\n"
"        </join>\n"
"    </subclass>\n"
"    <subclass name=\"ChequePayment\" discriminator-value=\"CHEQUE\">\n"
"        <join table=\"CHEQUE_PAYMENT\" fetch=\"select\">\n"
"            <key column=\"PAYMENT_ID\"/>\n"
"            ...\n"
"        </join>\n"
"    </subclass>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: inheritance_mapping.xml:151
#, no-c-format
msgid ""
"The optional <literal>fetch=\"select\"</literal> declaration tells Hibernate "
"not to fetch the <literal>ChequePayment</literal> subclass data using an "
"outer join when querying the superclass."
msgstr ""
"可选的声明<literal>fetch=\"select\"</literal>，是用来告诉Hibernate，在查询超"
"类时， 不要使用外部连接(outer join)来抓取子类<literal>ChequePayment</literal>"
"的数据。"

#. Tag: title
#: inheritance_mapping.xml:160
#, no-c-format
msgid "Mixing table per class hierarchy with table per subclass"
msgstr "混合使用“每个类分层结构一张表”和“每个子类一张表”"

#. Tag: para
#: inheritance_mapping.xml:162
#, no-c-format
msgid ""
"You may even mix the table per hierarchy and table per subclass strategies "
"using this approach:"
msgstr ""
"你甚至可以采取如下方法混和使用“每个类分层结构一张表”和“每个子类一张表”这两种"
"策略："

#. Tag: programlisting
#: inheritance_mapping.xml:167
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Payment\" table=\"PAYMENT\">\n"
"    <id name=\"id\" type=\"long\" column=\"PAYMENT_ID\">\n"
"        <generator class=\"native\"/>\n"
"    </id>\n"
"    <discriminator column=\"PAYMENT_TYPE\" type=\"string\"/>\n"
"    <property name=\"amount\" column=\"AMOUNT\"/>\n"
"    ...\n"
"    <subclass name=\"CreditCardPayment\" discriminator-value=\"CREDIT\">\n"
"        <join table=\"CREDIT_PAYMENT\">\n"
"            <property name=\"creditCardType\" column=\"CCTYPE\"/>\n"
"            ...\n"
"        </join>\n"
"    </subclass>\n"
"    <subclass name=\"CashPayment\" discriminator-value=\"CASH\">\n"
"        ...\n"
"    </subclass>\n"
"    <subclass name=\"ChequePayment\" discriminator-value=\"CHEQUE\">\n"
"        ...\n"
"    </subclass>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: inheritance_mapping.xml:169
#, no-c-format
msgid ""
"For any of these mapping strategies, a polymorphic association to the root "
"<literal>Payment</literal> class is mapped using <literal>&lt;many-to-one&gt;"
"</literal>."
msgstr ""
"对上述任何一种映射策略而言，指向根类<literal>Payment</literal>的 关联是使用"
"<literal>&lt;many-to-one&gt;</literal>进行映射的。"

#. Tag: programlisting
#: inheritance_mapping.xml:175
#, no-c-format
msgid ""
"<![CDATA[<many-to-one name=\"payment\" column=\"PAYMENT_ID\" class=\"Payment"
"\"/>]]>"
msgstr ""

#. Tag: title
#: inheritance_mapping.xml:180
#, no-c-format
msgid "Table per concrete class"
msgstr "每个具体类一张表(Table per concrete class)"

#. Tag: para
#: inheritance_mapping.xml:182
#, no-c-format
msgid ""
"There are two ways we could go about mapping the table per concrete class "
"strategy. The first is to use <literal>&lt;union-subclass&gt;</literal>."
msgstr ""
"对于“每个具体类一张表”的映射策略，可以采用两种方法。第一种方法是使用 "
"<literal>&lt;union-subclass&gt;</literal>。"

#. Tag: programlisting
#: inheritance_mapping.xml:187
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Payment\">\n"
"    <id name=\"id\" type=\"long\" column=\"PAYMENT_ID\">\n"
"        <generator class=\"sequence\"/>\n"
"    </id>\n"
"    <property name=\"amount\" column=\"AMOUNT\"/>\n"
"    ...\n"
"    <union-subclass name=\"CreditCardPayment\" table=\"CREDIT_PAYMENT\">\n"
"        <property name=\"creditCardType\" column=\"CCTYPE\"/>\n"
"        ...\n"
"    </union-subclass>\n"
"    <union-subclass name=\"CashPayment\" table=\"CASH_PAYMENT\">\n"
"        ...\n"
"    </union-subclass>\n"
"    <union-subclass name=\"ChequePayment\" table=\"CHEQUE_PAYMENT\">\n"
"        ...\n"
"    </union-subclass>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: inheritance_mapping.xml:189
#, no-c-format
msgid ""
"Three tables are involved for the subclasses. Each table defines columns for "
"all properties of the class, including inherited properties."
msgstr ""
"这里涉及三张与子类相关的表。每张表为对应类的所有属性（包括从超类继承的属性）"
"定义相应字段。"

#. Tag: para