collection_mapping.po

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#. Tag: para
#: collection_mapping.xml:639
#, no-c-format
msgid ""
"Associations may even be sorted by some arbitrary criteria at runtime using "
"a collection <literal>filter()</literal>."
msgstr ""
"关联还可以在运行时使用集合<literal>filter()</literal>根据任意的条件来排序。"

#. Tag: programlisting
#: collection_mapping.xml:644
#, no-c-format
msgid ""
"<![CDATA[sortedUsers = s.createFilter( group.getUsers(), \"order by this.name"
"\" ).list();]]>"
msgstr ""

#. Tag: title
#: collection_mapping.xml:649
#, no-c-format
msgid "Bidirectional associations"
msgstr "双向关联（Bidirectional associations）"

#. Tag: para
#: collection_mapping.xml:651
#, fuzzy, no-c-format
msgid ""
"A <emphasis>bidirectional association</emphasis> allows navigation from both "
"\"ends\" of the association. Two kinds of bidirectional association are "
"supported:"
msgstr ""
"<emphasis>双向关联</emphasis>允许通过关联的任一端访问另外一端。在Hibernate"
"中, 支持两种类型的双向关联: <placeholder-1/>"

#. Tag: term
#: collection_mapping.xml:658
#, no-c-format
msgid "one-to-many"
msgstr "一对多（one-to-many）"

#. Tag: para
#: collection_mapping.xml:660
#, no-c-format
msgid "set or bag valued at one end, single-valued at the other"
msgstr "Set或者bag值在一端, 单独值(非集合)在另外一端"

#. Tag: term
#: collection_mapping.xml:666
#, no-c-format
msgid "many-to-many"
msgstr "多对多（many-to-many）"

#. Tag: para
#: collection_mapping.xml:668
#, no-c-format
msgid "set or bag valued at both ends"
msgstr "两端都是set或bag值"

#. Tag: para
#: collection_mapping.xml:677
#, no-c-format
msgid ""
"You may specify a bidirectional many-to-many association simply by mapping "
"two many-to-many associations to the same database table and declaring one "
"end as <emphasis>inverse</emphasis> (which one is your choice, but it can "
"not be an indexed collection)."
msgstr ""
"要建立一个双向的多对多关联，只需要映射两个many-to-many关联到同一个数据库表"
"中，并再定义其中的一端为<emphasis>inverse</emphasis>(使用哪一端要根据你的选"
"择，但它不能是一个索引集合)。"

#. Tag: para
#: collection_mapping.xml:684
#, no-c-format
msgid ""
"Here's an example of a bidirectional many-to-many association; each category "
"can have many items and each item can be in many categories:"
msgstr ""
"这里有一个many-to-many的双向关联的例子;每一个category都可以有很多items,每一个"
"items可以属于很多categories："

#. Tag: programlisting
#: collection_mapping.xml:689
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Category\">\n"
"    <id name=\"id\" column=\"CATEGORY_ID\"/>\n"
"    ...\n"
"    <bag name=\"items\" table=\"CATEGORY_ITEM\">\n"
"        <key column=\"CATEGORY_ID\"/>\n"
"        <many-to-many class=\"Item\" column=\"ITEM_ID\"/>\n"
"    </bag>\n"
"</class>\n"
"\n"
"<class name=\"Item\">\n"
"    <id name=\"id\" column=\"ITEM_ID\"/>\n"
"    ...\n"
"\n"
"    <!-- inverse end -->\n"
"    <bag name=\"categories\" table=\"CATEGORY_ITEM\" inverse=\"true\">\n"
"        <key column=\"ITEM_ID\"/>\n"
"        <many-to-many class=\"Category\" column=\"CATEGORY_ID\"/>\n"
"    </bag>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: collection_mapping.xml:691
#, no-c-format
msgid ""
"Changes made only to the inverse end of the association are <emphasis>not</"
"emphasis> persisted. This means that Hibernate has two representations in "
"memory for every bidirectional association, one link from A to B and another "
"link from B to A. This is easier to understand if you think about the Java "
"object model and how we create a many-to-many relationship in Java:"
msgstr ""
"如果只对关联的反向端进行了改变，这个改变<emphasis>不会</emphasis>被持久化。 "
"这表示Hibernate为每个双向关联在内存中存在两次表现,一个从A连接到B,另一个从B连"
"接到A。如果你回想一下Java对象模型，我们是如何在Java中创建多对多关系的，这可以"
"让你更容易理解："

#. Tag: programlisting
#: collection_mapping.xml:699
#, no-c-format
msgid ""
"<![CDATA[\n"
"category.getItems().add(item);          // The category now \"knows\" about "
"the relationship\n"
"item.getCategories().add(category);     // The item now \"knows\" about the "
"relationship\n"
"\n"
"session.persist(item);                   // The relationship won't be "
"saved!\n"
"session.persist(category);               // The relationship will be saved]]>"
msgstr ""

#. Tag: para
#: collection_mapping.xml:701
#, no-c-format
msgid ""
"The non-inverse side is used to save the in-memory representation to the "
"database."
msgstr "非反向端用于把内存中的表示保存到数据库中。"

#. Tag: para
#: collection_mapping.xml:705
#, no-c-format
msgid ""
"You may define a bidirectional one-to-many association by mapping a one-to-"
"many association to the same table column(s) as a many-to-one association "
"and declaring the many-valued end <literal>inverse=\"true\"</literal>."
msgstr ""
"要建立一个一对多的双向关联，你可以通过把一个一对多关联，作为一个多对一关联映"
"射到到同一张表的字段上，并且在\"多\"的那一端定义<literal>inverse=\"true\"</"
"literal>。"

#. Tag: programlisting
#: collection_mapping.xml:711
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Parent\">\n"
"    <id name=\"id\" column=\"parent_id\"/>\n"
"    ....\n"
"    <set name=\"children\" inverse=\"true\">\n"
"        <key column=\"parent_id\"/>\n"
"        <one-to-many class=\"Child\"/>\n"
"    </set>\n"
"</class>\n"
"\n"
"<class name=\"Child\">\n"
"    <id name=\"id\" column=\"child_id\"/>\n"
"    ....\n"
"    <many-to-one name=\"parent\" \n"
"        class=\"Parent\" \n"
"        column=\"parent_id\"\n"
"        not-null=\"true\"/>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: collection_mapping.xml:713
#, no-c-format
msgid ""
"Mapping one end of an association with <literal>inverse=\"true\"</literal> "
"doesn't affect the operation of cascades, these are orthogonal concepts!"
msgstr ""
"在“一”这一端定义<literal>inverse=\"true\"</literal>不会影响级联操作，二者是正"
"交的概念！"

#. Tag: title
#: collection_mapping.xml:721
#, no-c-format
msgid "Bidirectional associations with indexed collections"
msgstr "双向关联，涉及有序集合类"

#. Tag: para
#: collection_mapping.xml:722
#, no-c-format
msgid ""
"A bidirectional association where one end is represented as a <literal>&lt;"
"list&gt;</literal> or <literal>&lt;map&gt;</literal> requires special "
"consideration. If there is a property of the child class which maps to the "
"index column, no problem, we can continue using <literal>inverse=\"true\"</"
"literal> on the collection mapping:"
msgstr ""
"对于有一端是<literal>&lt;list&gt;</literal>或者<literal>&lt;map&gt;</literal>"
"的双向关联，需要加以特别考虑。假若子类中的一个属性映射到索引字段，没问题，我"
"们仍然可以在集合类映射上使用<literal>inverse=\"true\"</literal>："

#. Tag: programlisting
#: collection_mapping.xml:729
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Parent\">\n"
"    <id name=\"id\" column=\"parent_id\"/>\n"
"    ....\n"
"    <map name=\"children\" inverse=\"true\">\n"
"        <key column=\"parent_id\"/>\n"
"        <map-key column=\"name\" \n"
"            type=\"string\"/>\n"
"        <one-to-many class=\"Child\"/>\n"
"    </map>\n"
"</class>\n"
"\n"
"<class name=\"Child\">\n"
"    <id name=\"id\" column=\"child_id\"/>\n"
"    ....\n"
"    <property name=\"name\" \n"
"        not-null=\"true\"/>\n"
"    <many-to-one name=\"parent\" \n"
"        class=\"Parent\" \n"
"        column=\"parent_id\"\n"
"        not-null=\"true\"/>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: collection_mapping.xml:731
#, no-c-format
msgid ""
"But, if there is no such property on the child class, we can't think of the "
"association as truly bidirectional (there is information available at one "
"end of the association that is not available at the other end). In this "
"case, we can't map the collection <literal>inverse=\"true\"</literal>. "
"Instead, we could use the following mapping:"
msgstr ""
"但是，假若子类中没有这样的属性存在，我们不能认为这个关联是真正的双向关联（信"
"息不对称，在关联的一端有一些另外一端没有的信息）。在这种情况下，我们不能使用"
"<literal>inverse=\"true\"</literal>。我们需要这样用："

#. Tag: programlisting
#: collection_mapping.xml:738
#, no-c-format
msgid ""
"<![CDATA[<class name=\"Parent\">\n"
"    <id name=\"id\" column=\"parent_id\"/>\n"
"    ....\n"
"    <map name=\"children\">\n"
"        <key column=\"parent_id\"\n"
"            not-null=\"true\"/>\n"
"        <map-key column=\"name\" \n"
"            type=\"string\"/>\n"
"        <one-to-many class=\"Child\"/>\n"
"    </map>\n"
"</class>\n"
"\n"
"<class name=\"Child\">\n"
"    <id name=\"id\" column=\"child_id\"/>\n"
"    ....\n"
"    <many-to-one name=\"parent\" \n"
"        class=\"Parent\" \n"
"        column=\"parent_id\"\n"
"        insert=\"false\"\n"
"        update=\"false\"\n"
"        not-null=\"true\"/>\n"
"</class>]]>"
msgstr ""

#. Tag: para
#: collection_mapping.xml:740
#, no-c-format
msgid ""
"Note that in this mapping, the collection-valued end of the association is "
"responsible for updates to the foreign key. TODO: Does this really result in "
"some unnecessary update statements?"
msgstr ""
"注意在这个映射中，关联中集合类\"值\"一端负责来更新外键.TODO: Does this "
"really result in some unnecessary update statements?"

#. Tag: title
#: collection_mapping.xml:748
#, no-c-format
msgid "Ternary associations"
msgstr "三重关联（Ternary associations）"

#. Tag: para
#: collection_mapping.xml:750
#, no-c-format
msgid ""
"There are three possible approaches to mapping a ternary association. One is "
"to use a <literal>Map</literal> with an association as its index:"
msgstr ""
"有三种可能的途径来映射一个三重关联。第一种是使用一个<literal>Map</literal>，"
"把一个关联作为其索引："

#. Tag: programlisting
#: collection_mapping.xml:755
#, no-c-format
msgid ""
"<![CDATA[<map name=\"contracts\">\n"
"    <key column=\"employer_id\" not-null=\"true\"/>\n"
"    <map-key-many-to-many column=\"employee_id\" class=\"Employee\"/>\n"
"    <one-to-many class=\"Contract\"/>\n"
"</map>]]>"
msgstr ""

#. Tag: programlisting
#: collection_mapping.xml:757
#, no-c-format
msgid ""
"<![CDATA[<map name=\"connections\">\n"
"    <key column=\"incoming_node_id\"/>\n"
"    <map-key-many-to-many column=\"outgoing_node_id\" class=\"Node\"/>\n"
"    <many-to-many column=\"connection_id\" class=\"Connection\"/>\n"
"</map>]]>"
msgstr ""

#. Tag: para
#: collection_mapping.xml:759
#, no-c-format
msgid ""
"A second approach is to simply remodel the association as an entity class. "
"This is the approach we use most commonly."
msgstr ""
"第二种方法是简单的把关联重新建模为一个实体类。这使我们最经常使用的方法。"

#. Tag: para
#: collection_mapping.xml:764
#, no-c-format
msgid ""
"A final alternative is to use composite elements, which we will discuss "
"later."
msgstr "最后一种选择是使用复合元素，我们会在后面讨论"