spring-framework/spring-framework-reference/src/classic-spring.xml

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<!DOCTYPE appendix PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<appendix id="classic-spring">
  <title>Classic Spring Usage</title>

  <para>This appendix discusses some classic Spring usage patterns as a
  reference for developers maintaining legacy Spring applications. These usage
  patterns no longer reflect the recommended way of using these features and
  the current recommended usage is covered in the respective sections of the
  reference manual.</para>

  <section id="classic-spring-orm">
    <title>Classic ORM usage</title>

    <para>This section documents the classic usage patterns that you might
    encounter in a legacy Spring application. For the currently recommended
    usage patterns, please refer to the <xref linkend="orm" /> chapter.</para>

    <section id="classic-spring-hibernate">
      <title>Hibernate</title>

      <para>For the currently recommended usage patterns for Hibernate see
      <xref linkend="orm-hibernate" /></para>

      <section id="orm-hibernate-template">
        <title>The <classname>HibernateTemplate</classname></title>

        <para>The basic programming model for templating looks as follows, for
        methods that can be part of any custom data access object or business
        service. There are no restrictions on the implementation of the
        surrounding object at all, it just needs to provide a Hibernate
        <interfacename>SessionFactory</interfacename>. It can get the latter
        from anywhere, but preferably as bean reference from a Spring IoC
        container - via a simple
        <methodname>setSessionFactory(..)</methodname> bean property setter.
        The following snippets show a DAO definition in a Spring container,
        referencing the above defined
        <interfacename>SessionFactory</interfacename>, and an example for a
        DAO method implementation.</para>

        <programlisting language="xml">&lt;beans&gt;

  &lt;bean id="myProductDao" class="product.ProductDaoImpl"&gt;
    &lt;property name="sessionFactory" ref="mySessionFactory"/&gt;
  &lt;/bean&gt;

&lt;/beans&gt;</programlisting>

        <programlisting language="java">public class ProductDaoImpl implements ProductDao {

    private HibernateTemplate hibernateTemplate;

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.hibernateTemplate = new HibernateTemplate(sessionFactory);
    }

    public Collection loadProductsByCategory(String category) throws DataAccessException {
    	return this.hibernateTemplate.find("from test.Product product where product.category=?", category);
    }
}</programlisting>

        <para>The <classname>HibernateTemplate</classname> class provides many
        methods that mirror the methods exposed on the Hibernate
        <interfacename>Session</interfacename> interface, in addition to a
        number of convenience methods such as the one shown above. If you need
        access to the <interfacename>Session</interfacename> to invoke methods
        that are not exposed on the <classname>HibernateTemplate</classname>,
        you can always drop down to a callback-based approach like so.</para>

        <programlisting language="java">public class ProductDaoImpl implements ProductDao {

    private HibernateTemplate hibernateTemplate;

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.hibernateTemplate = new HibernateTemplate(sessionFactory);
    }

    public Collection loadProductsByCategory(final String category) throws DataAccessException {
        return this.hibernateTemplate.execute(new HibernateCallback() {

            public Object doInHibernate(Session session) {
                Criteria criteria = session.createCriteria(Product.class);
                criteria.add(Expression.eq("category", category));
                criteria.setMaxResults(6);
                return criteria.list();
            }
        };
    }
}</programlisting>

        <para>A callback implementation effectively can be used for any
        Hibernate data access. <classname>HibernateTemplate</classname> will
        ensure that <interfacename>Session</interfacename> instances are
        properly opened and closed, and automatically participate in
        transactions. The template instances are thread-safe and reusable,
        they can thus be kept as instance variables of the surrounding class.
        For simple single step actions like a single find, load, saveOrUpdate,
        or delete call, <classname>HibernateTemplate</classname> offers
        alternative convenience methods that can replace such one line
        callback implementations. Furthermore, Spring provides a convenient
        <classname>HibernateDaoSupport</classname> base class that provides a
        <methodname>setSessionFactory(..)</methodname> method for receiving a
        <interfacename>SessionFactory</interfacename>, and
        <methodname>getSessionFactory()</methodname> and
        <methodname>getHibernateTemplate()</methodname>for use by subclasses.
        In combination, this allows for very simple DAO implementations for
        typical requirements:</para>

        <programlisting language="java">public class ProductDaoImpl extends HibernateDaoSupport implements ProductDao {

    public Collection loadProductsByCategory(String category) throws DataAccessException {
        return this.getHibernateTemplate().find(
            "from test.Product product where product.category=?", category);
    }
}</programlisting>
      </section>

      <section id="orm-hibernate-daos">
        <title>Implementing Spring-based DAOs without callbacks</title>

        <para>As alternative to using Spring's
        <classname>HibernateTemplate</classname> to implement DAOs, data
        access code can also be written in a more traditional fashion, without
        wrapping the Hibernate access code in a callback, while still
        respecting and participating in Spring's generic
        <classname>DataAccessException</classname> hierarchy. The
        <classname>HibernateDaoSupport</classname> base class offers methods
        to access the current transactional
        <interfacename>Session</interfacename> and to convert exceptions in
        such a scenario; similar methods are also available as static helpers
        on the <classname>SessionFactoryUtils</classname> class. Note that
        such code will usually pass '<literal>false</literal>' as the value of
        the <methodname>getSession(..)</methodname> methods
        '<literal>allowCreate</literal>' argument, to enforce running within a
        transaction (which avoids the need to close the returned
        <interfacename>Session</interfacename>, as its lifecycle is managed by
        the transaction).</para>

        <programlisting language="java">public class HibernateProductDao extends HibernateDaoSupport implements ProductDao {

    public Collection loadProductsByCategory(String category) throws DataAccessException, MyException {
        Session session = getSession(false);
        try {
            Query query = session.createQuery("from test.Product product where product.category=?");
            query.setString(0, category);
            List result = query.list();
            if (result == null) {
                throw new MyException("No search results.");
            }
            return result;
        }
        catch (HibernateException ex) {
            throw convertHibernateAccessException(ex);
        }
    }
}</programlisting>

        <para>The advantage of such direct Hibernate access code is that it
        allows <emphasis>any</emphasis> checked application exception to be
        thrown within the data access code; contrast this to the
        <classname>HibernateTemplate</classname> class which is restricted to
        throwing only unchecked exceptions within the callback. Note that you
        can often defer the corresponding checks and the throwing of
        application exceptions to after the callback, which still allows
        working with <classname>HibernateTemplate</classname>. In general, the
        <classname>HibernateTemplate</classname> class' convenience methods
        are simpler and more convenient for many scenarios.</para>
      </section>
    </section>

    <section id="classic-spring-jdo">
      <title>JDO</title>

      <para>For the currently recommended usage patterns for JDO see <xref
      linkend="orm-jdo" /></para>

      <section id="orm-jdo-template">
        <title><classname>JdoTemplate</classname> and
        <classname>JdoDaoSupport</classname></title>

        <para>Each JDO-based DAO will then receive the
        <interfacename>PersistenceManagerFactory</interfacename> through
        dependency injection. Such a DAO could be coded against plain JDO API,
        working with the given
        <interfacename>PersistenceManagerFactory</interfacename>, but will
        usually rather be used with the Spring Framework's
        <classname>JdoTemplate</classname>:</para>

        <programlisting language="xml">&lt;beans&gt;
  
  &lt;bean id="myProductDao" class="product.ProductDaoImpl"&gt;
    &lt;property name="persistenceManagerFactory" ref="myPmf"/&gt;
  &lt;/bean&gt;
  
&lt;/beans&gt;</programlisting>

        <programlisting language="java">public class ProductDaoImpl implements ProductDao {
  
    private JdoTemplate jdoTemplate;

    public void setPersistenceManagerFactory(PersistenceManagerFactory pmf) {
        this.jdoTemplate = new JdoTemplate(pmf);
    }

    public Collection loadProductsByCategory(final String category) throws DataAccessException {
        return (Collection) this.jdoTemplate.execute(new JdoCallback() {
            public Object doInJdo(PersistenceManager pm) throws JDOException {
                Query query = pm.newQuery(Product.class, "category = pCategory");
                query.declareParameters("String pCategory"); 
                List result = query.execute(category);
                <lineannotation>// do some further stuff with the result list</lineannotation>
                return result;
            }
        });
    }
}</programlisting>

        <para>A callback implementation can effectively be used for any JDO
        data access. <classname>JdoTemplate</classname> will ensure that
        <classname>PersistenceManager</classname>s are properly opened and
        closed, and automatically participate in transactions. The template
        instances are thread-safe and reusable, they can thus be kept as
        instance variables of the surrounding class. For simple single-step
        actions such as a single <literal>find</literal>,
        <literal>load</literal>, <literal>makePersistent</literal>, or
        <literal>delete</literal> call, <classname>JdoTemplate</classname>
        offers alternative convenience methods that can replace such one line
        callback implementations. Furthermore, Spring provides a convenient
        <classname>JdoDaoSupport</classname> base class that provides a
        <literal>setPersistenceManagerFactory(..)</literal> method for
        receiving a <classname>PersistenceManagerFactory</classname>, and
        <methodname>getPersistenceManagerFactory()</methodname> and
        <methodname>getJdoTemplate()</methodname> for use by subclasses. In
        combination, this allows for very simple DAO implementations for
        typical requirements:</para>

        <programlisting language="java">public class ProductDaoImpl extends JdoDaoSupport implements ProductDao {
  
    public Collection loadProductsByCategory(String category) throws DataAccessException {
        return getJdoTemplate().find(
            Product.class, "category = pCategory", "String category", new Object[] {category});
    }
}</programlisting>

        <para>As alternative to working with Spring's
        <classname>JdoTemplate</classname>, you can also code Spring-based
        DAOs at the JDO API level, explicitly opening and closing a
        <interfacename>PersistenceManager</interfacename>. As elaborated in
        the corresponding Hibernate section, the main advantage of this
        approach is that your data access code is able to throw checked
        exceptions. <classname>JdoDaoSupport</classname> offers a variety of
        support methods for this scenario, for fetching and releasing a
        transactional <interfacename>PersistenceManager</interfacename> as
        well as for converting exceptions.</para>
      </section>
    </section>

    <section id="classic-spring-jpa">
      <title>JPA</title>

      <para>For the currently recommended usage patterns for JPA see <xref
      linkend="orm-jpa" /></para>

      <section id="orm-jpa-template">
        <title><classname>JpaTemplate</classname> and
        <classname>JpaDaoSupport</classname></title>

        <para>Each JPA-based DAO will then receive a
        <interfacename>EntityManagerFactory</interfacename> via dependency
        injection. Such a DAO can be coded against plain JPA and work with the
        given <interfacename>EntityManagerFactory</interfacename> or through
        Spring's <classname>JpaTemplate</classname>:</para>

        <programlisting language="xml">&lt;beans&gt;

  &lt;bean id="myProductDao" class="product.ProductDaoImpl"&gt;
    &lt;property name="entityManagerFactory" ref="myEmf"/&gt;
  &lt;/bean&gt;

&lt;/beans&gt;</programlisting>

        <programlisting language="java">public class JpaProductDao implements ProductDao {
  
    private JpaTemplate jpaTemplate;

    public void setEntityManagerFactory(EntityManagerFactory emf) {
        this.jpaTemplate = new JpaTemplate(emf);
    }

    public Collection loadProductsByCategory(final String category) throws DataAccessException {
        return (Collection) this.jpaTemplate.execute(new JpaCallback() {
            public Object doInJpa(EntityManager em) throws PersistenceException {
                Query query = em.createQuery("from Product as p where p.category = :category");
                query.setParameter("category", category);
                List result = query.getResultList(); 
                <lineannotation>// do some further processing with the result list</lineannotation>
                return result;
            }
        });
    }
}</programlisting>

        <para>The <interfacename>JpaCallback</interfacename> implementation
        allows any type of JPA data access. The
        <classname>JpaTemplate</classname> will ensure that
        <interfacename>EntityManager</interfacename>s are properly opened and
        closed and automatically participate in transactions. Moreover, the
        <classname>JpaTemplate</classname> properly handles exceptions, making
        sure resources are cleaned up and the appropriate transactions rolled
        back. The template instances are thread-safe and reusable and they can
        be kept as instance variable of the enclosing class. Note that
        <classname>JpaTemplate</classname> offers single-step actions such as
        find, load, merge, etc along with alternative convenience methods that
        can replace one line callback implementations.</para>

        <para>Furthermore, Spring provides a convenient
        <classname>JpaDaoSupport</classname> base class that provides the
        <literal>get/setEntityManagerFactory</literal> and
        <methodname>getJpaTemplate()</methodname> to be used by
        subclasses:</para>

        <programlisting language="java">public class ProductDaoImpl extends JpaDaoSupport implements ProductDao {
  
    public Collection loadProductsByCategory(String category) throws DataAccessException {
        Map&lt;String, String&gt; params = new HashMap&lt;String, String&gt;();
        params.put("category", category);
        return getJpaTemplate().findByNamedParams("from Product as p where p.category = :category", params);
    }
}</programlisting>

        <para>Besides working with Spring's
        <classname>JpaTemplate</classname>, one can also code Spring-based
        DAOs against the JPA, doing one's own explicit
        <interfacename>EntityManager</interfacename> handling. As also
        elaborated in the corresponding Hibernate section, the main advantage
        of this approach is that your data access code is able to throw
        checked exceptions. <classname>JpaDaoSupport</classname> offers a
        variety of support methods for this scenario, for retrieving and
        releasing a transaction <interfacename>EntityManager</interfacename>,
        as well as for converting exceptions.</para>

        <para><emphasis>JpaTemplate mainly exists as a sibling of JdoTemplate
        and HibernateTemplate, offering the same style for people used to
        it.</emphasis></para>
      </section>
    </section>
  </section>

  <section id="clasic-spring-mvc">
    <title>Classic Spring MVC</title>

    <para>...</para>
  </section>

  <section id="classic-spring-jms">
    <title>JMS Usage</title>

    <para>One of the benefits of Spring's JMS support is to shield the user
    from differences between the JMS 1.0.2 and 1.1 APIs. (For a description of
    the differences between the two APIs see sidebar on Domain Unification).
    Since it is now common to encounter only the JMS 1.1 API the use of
    classes that are based on the JMS 1.0.2 API has been deprecated in Spring
    3.0. This section describes Spring JMS support for the JMS 1.0.2
    deprecated classes. </para>

    <sidebar>
      <title>Domain Unification</title>

      <para>There are two major releases of the JMS specification, 1.0.2 and
      1.1.</para>

      <para>JMS 1.0.2 defined two types of messaging domains, point-to-point
      (Queues) and publish/subscribe (Topics). The 1.0.2 API reflected these
      two messaging domains by providing a parallel class hierarchy for each
      domain. As a result, a client application became domain specific in its
      use of the JMS API. JMS 1.1 introduced the concept of domain unification
      that minimized both the functional differences and client API
      differences between the two domains. As an example of a functional
      difference that was removed, if you use a JMS 1.1 provider you can
      transactionally consume a message from one domain and produce a message
      on the other using the same
      <interfacename>Session</interfacename>.</para>

      <note>
        <para>The JMS 1.1 specification was released in April 2002 and
        incorporated as part of J2EE 1.4 in November 2003. As a result, common
        J2EE 1.3 application servers which are still in widespread use (such
        as BEA WebLogic 8.1 and IBM WebSphere 5.1) are based on JMS
        1.0.2.</para>
      </note>
    </sidebar>

    <section id="classic-spring-jms-template">
      <title>JmsTemplate</title>

      <para>Located in the package
      <literal>org.springframework.jms.core</literal> the class
      <classname>JmsTemplate102</classname> provides all of the features of
      the <classname>JmsTemplate</classname> described the JMS chapter, but is
      based on the JMS 1.0.2 API instead of the JMS 1.1 API. As a consequence,
      if you are using JmsTemplate102 you need to set the boolean property
      <property>pubSubDomain</property> to configure the
      <classname>JmsTemplate</classname> with knowledge of what JMS domain is
      being used. By default the value of this property is false, indicating
      that the point-to-point domain, Queues, will be used.</para>
    </section>

    <section id="classic-spring-aysnc-messages">
      <title>Asynchronous Message Reception </title>

      <para><link
      linkend="jms-receiving-async-message-listener-adapter">MessageListenerAdapter's</link>
      are used in conjunction with Spring's <link linkend="jms-mdp">message
      listener containers</link> to support asynchronous message reception by
      exposing almost any class as a Message-driven POJO. If you are using the
      JMS 1.0.2 API, you will want to use the 1.0.2 specific classes such as
      <classname>MessageListenerAdapter102</classname>,
      <classname>SimpleMessageListenerContainer102</classname>, and
      <classname>DefaultMessageListenerContainer102</classname>. These classes
      provide the same functionality as the JMS 1.1 based counterparts but
      rely only on the JMS 1.0.2 API. </para>
    </section>

    <section id="classic-spring-jms-connections">
      <title>Connections</title>

      <para>The <classname>ConnectionFactory</classname> interface is part of
      the JMS specification and serves as the entry point for working with
      JMS. Spring provides an implementation of the
      <classname>ConnectionFactory</classname> interface,
      <classname>SingleConnectionFactory102</classname>, based on the JMS
      1.0.2 API that will return the same <classname>Connection</classname> on
      all <methodname>createConnection()</methodname> calls and ignore calls to
      <methodname>close()</methodname>. You will need to set the boolean
      property <property>pubSubDomain</property> to indicate which messaging
      domain is used as <classname>SingleConnectionFactory102</classname> will
      always explicitly differentiate between a
      <classname>javax.jms.QueueConnection</classname> and a
      <classname>javax.jmsTopicConnection</classname>.</para>
    </section>

    <section id="classic-spring-jms-tx-management">
      <title>Transaction Management</title>

      <para>In a JMS 1.0.2 environment the class
      <classname>JmsTransactionManager102</classname> provides support for
      managing JMS transactions for a single Connection Factory. Please refer
      to the reference documentation on <link linkend="jms-tx">JMS Transaction
      Management</link> for more information on this functionality.</para>
    </section>
  </section>
</appendix>