batch.pot

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

#, no-c-format
msgid "Note that in this code example, the <literal>Customer</literal> instances returned by the query are immediately detached. They are never associated with any persistence context."
msgstr ""

#. Tag: para
#: batch.xml:121
#, no-c-format
msgid "The <literal>insert(), update()</literal> and <literal>delete()</literal> operations defined by the <literal>StatelessSession</literal> interface are considered to be direct database row-level operations, which result in immediate execution of a SQL <literal>INSERT, UPDATE</literal> or <literal>DELETE</literal> respectively. Thus, they have very different semantics to the <literal>save(), saveOrUpdate()</literal> and <literal>delete()</literal> operations defined by the <literal>Session</literal> interface."
msgstr ""

#. Tag: title
#: batch.xml:134
#, no-c-format
msgid "DML-style operations"
msgstr ""

#. Tag: para
#: batch.xml:136
#, no-c-format
msgid "As already discussed, automatic and transparent object/relational mapping is concerned with the management of object state. This implies that the object state is available in memory, hence manipulating (using the SQL <literal>Data Manipulation Language</literal> (DML) statements: <literal>INSERT</literal>, <literal>UPDATE</literal>, <literal>DELETE</literal>) data directly in the database will not affect in-memory state. However, Hibernate provides methods for bulk SQL-style DML statement execution which are performed through the Hibernate Query Language (<link linkend=\"queryhql\">HQL</link>)."
msgstr ""

#. Tag: para
#: batch.xml:146
#, no-c-format
msgid "The pseudo-syntax for <literal>UPDATE</literal> and <literal>DELETE</literal> statements is: <literal>( UPDATE | DELETE ) FROM? EntityName (WHERE where_conditions)?</literal>. Some points to note:"
msgstr ""

#. Tag: para
#: batch.xml:154
#, no-c-format
msgid "In the from-clause, the FROM keyword is optional"
msgstr ""

#. Tag: para
#: batch.xml:159
#, no-c-format
msgid "There can only be a single entity named in the from-clause; it can optionally be aliased. If the entity name is aliased, then any property references must be qualified using that alias; if the entity name is not aliased, then it is illegal for any property references to be qualified."
msgstr ""

#. Tag: para
#: batch.xml:167
#, no-c-format
msgid "No <link linkend=\"queryhql-joins-forms\">joins</link> (either implicit or explicit) can be specified in a bulk HQL query. Sub-queries may be used in the where-clause; the subqueries, themselves, may contain joins."
msgstr ""

#. Tag: para
#: batch.xml:174
#, no-c-format
msgid "The where-clause is also optional."
msgstr ""

#. Tag: para
#: batch.xml:180
#, no-c-format
msgid "As an example, to execute an HQL <literal>UPDATE</literal>, use the <literal>Query.executeUpdate()</literal> method (the method is named for those familiar with JDBC's <literal>PreparedStatement.executeUpdate()</literal>):"
msgstr ""

#. Tag: programlisting
#: batch.xml:186
#, no-c-format
msgid ""
      "<![CDATA[Session session = sessionFactory.openSession();\n"
      "Transaction tx = session.beginTransaction();\n"
      "\n"
      "String hqlUpdate = \"update Customer c set c.name = :newName where c.name = :oldName\";\n"
      "// or String hqlUpdate = \"update Customer set name = :newName where name = :oldName\";\n"
      "int updatedEntities = s.createQuery( hqlUpdate )\n"
      "        .setString( \"newName\", newName )\n"
      "        .setString( \"oldName\", oldName )\n"
      "        .executeUpdate();\n"
      "tx.commit();\n"
      "session.close();]]>"
msgstr ""

#. Tag: para
#: batch.xml:188
#, no-c-format
msgid "HQL <literal>UPDATE</literal> statements, by default do not effect the <link linkend=\"mapping-declaration-version\">version</link> or the <link linkend=\"mapping-declaration-timestamp\">timestamp</link> property values for the affected entities; this is in keeping with the EJB3 specification. However, you can force Hibernate to properly reset the <literal>version</literal> or <literal>timestamp</literal> property values through the use of a <literal>versioned update</literal>. This is achieved by adding the <literal>VERSIONED</literal> keyword after the <literal>UPDATE</literal> keyword."
msgstr ""

#. Tag: programlisting
#: batch.xml:198
#, no-c-format
msgid ""
      "<![CDATA[Session session = sessionFactory.openSession();\n"
      "Transaction tx = session.beginTransaction();\n"
      "String hqlVersionedUpdate = \"update versioned Customer set name = :newName where name = :oldName\";\n"
      "int updatedEntities = s.createQuery( hqlUpdate )\n"
      "        .setString( \"newName\", newName )\n"
      "        .setString( \"oldName\", oldName )\n"
      "        .executeUpdate();\n"
      "tx.commit();\n"
      "session.close();]]>"
msgstr ""

#. Tag: para
#: batch.xml:200
#, no-c-format
msgid "Note that custom version types (<literal>org.hibernate.usertype.UserVersionType</literal>) are not allowed in conjunction with a <literal>update versioned</literal> statement."
msgstr ""

#. Tag: para
#: batch.xml:205
#, no-c-format
msgid "To execute an HQL <literal>DELETE</literal>, use the same <literal>Query.executeUpdate()</literal> method:"
msgstr ""

#. Tag: programlisting
#: batch.xml:210
#, no-c-format
msgid ""
      "<![CDATA[Session session = sessionFactory.openSession();\n"
      "Transaction tx = session.beginTransaction();\n"
      "\n"
      "String hqlDelete = \"delete Customer c where c.name = :oldName\";\n"
      "// or String hqlDelete = \"delete Customer where name = :oldName\";\n"
      "int deletedEntities = s.createQuery( hqlDelete )\n"
      "        .setString( \"oldName\", oldName )\n"
      "        .executeUpdate();\n"
      "tx.commit();\n"
      "session.close();]]>"
msgstr ""

#. Tag: para
#: batch.xml:212
#, no-c-format
msgid "The <literal>int</literal> value returned by the <literal>Query.executeUpdate()</literal> method indicate the number of entities effected by the operation. Consider this may or may not correlate to the number of rows effected in the database. An HQL bulk operation might result in multiple actual SQL statements being executed, for joined-subclass, for example. The returned number indicates the number of actual entities affected by the statement. Going back to the example of joined-subclass, a delete against one of the subclasses may actually result in deletes against not just the table to which that subclass is mapped, but also the \"root\" table and potentially joined-subclass tables further down the inheritence hierarchy."
msgstr ""

#. Tag: para
#: batch.xml:223
#, no-c-format
msgid "The pseudo-syntax for <literal>INSERT</literal> statements is: <literal>INSERT INTO EntityName properties_list select_statement</literal>. Some points to note:"
msgstr ""

#. Tag: para
#: batch.xml:231
#, no-c-format
msgid "Only the INSERT INTO ... SELECT ... form is supported; not the INSERT INTO ... VALUES ... form."
msgstr ""

#. Tag: para
#: batch.xml:234
#, no-c-format
msgid "The properties_list is analogous to the <literal>column speficiation</literal> in the SQL <literal>INSERT</literal> statement. For entities involved in mapped inheritence, only properties directly defined on that given class-level can be used in the properties_list. Superclass properties are not allowed; and subclass properties do not make sense. In other words, <literal>INSERT</literal> statements are inherently non-polymorphic."
msgstr ""

#. Tag: para
#: batch.xml:244
#, no-c-format
msgid "select_statement can be any valid HQL select query, with the caveat that the return types must match the types expected by the insert. Currently, this is checked during query compilation rather than allowing the check to relegate to the database. Note however that this might cause problems between Hibernate <literal>Type</literal>s which are <emphasis>equivalent</emphasis> as opposed to <emphasis>equal</emphasis>. This might cause issues with mismatches between a property defined as a <literal>org.hibernate.type.DateType</literal> and a property defined as a <literal>org.hibernate.type.TimestampType</literal>, even though the database might not make a distinction or might be able to handle the conversion."
msgstr ""

#. Tag: para
#: batch.xml:256
#, no-c-format
msgid "For the id property, the insert statement gives you two options. You can either explicitly specify the id property in the properties_list (in which case its value is taken from the corresponding select expression) or omit it from the properties_list (in which case a generated value is used). This later option is only available when using id generators that operate in the database; attempting to use this option with any \"in memory\" type generators will cause an exception during parsing. Note that for the purposes of this discussion, in-database generators are considered to be <literal>org.hibernate.id.SequenceGenerator</literal> (and its subclasses) and any implementors of <literal>org.hibernate.id.PostInsertIdentifierGenerator</literal>. The most notable exception here is <literal>org.hibernate.id.TableHiLoGenerator</literal>, which cannot be used because it does not expose a selectable way to get its values."
msgstr ""

#. Tag: para
#: batch.xml:271
#, no-c-format
msgid "For properties mapped as either <literal>version</literal> or <literal>timestamp</literal>, the insert statement gives you two options. You can either specify the property in the properties_list (in which case its value is taken from the corresponding select expressions) or omit it from the properties_list (in which case the <literal>seed value</literal> defined by the <literal>org.hibernate.type.VersionType</literal> is used)."
msgstr ""

#. Tag: para
#: batch.xml:281
#, no-c-format
msgid "An example HQL <literal>INSERT</literal> statement execution:"
msgstr ""

#. Tag: programlisting
#: batch.xml:285
#, no-c-format
msgid ""
      "<![CDATA[Session session = sessionFactory.openSession();\n"
      "Transaction tx = session.beginTransaction();\n"
      "\n"
      "String hqlInsert = \"insert into DelinquentAccount (id, name) select c.id, c.name from Customer c where ...\";\n"
      "int createdEntities = s.createQuery( hqlInsert )\n"
      "        .executeUpdate();\n"
      "tx.commit();\n"
      "session.close();]]>"
msgstr ""