dolejsky.com » spring http://www.dolejsky.com Things good to know... Wed, 16 Jun 2010 08:59:45 +0000 http://wordpress.org/?v=2.8.5 en hourly 1 Oracle CLOB / BLOB & Spring http://www.dolejsky.com/2008/02/24/oracle-clob-blob-spring/ http://www.dolejsky.com/2008/02/24/oracle-clob-blob-spring/#comments Sun, 24 Feb 2008 11:02:29 +0000 ludek http://www.dolejsky.com/2008/02/24/oracle-clob-blob-spring/ Reading and writing CLOBs and BLOBs from/to Oracle database via Spring's JdbcTemplate might be a little bit confusing as it significantly differs from dealing with other types. Interested? Read on... :-)

Reading BLOB from database

This is relatively simple. Just use ResultSet.getBlob() or ResultSet.getClob() method (usually in our custom Spring's RowMapper implementation) and read data using getBinaryStream() (for BLOBs) or getCharacterStream() (for CLOBs).

Inserting BLOB (CLOB) to database

Inserting must be done in two steps. First, we insert an empty BLOB (CLOB) into table row (along with other columns). Second, we lock & select currently inserted row from the table, open the stream and write data.

It is good to do both steps in one transaction (e.g. to prevent somebody from seeing empty BLOB in the meantime - but be sure to take transaction isolation level into account - READ COMMITTED or higher level is needed).

Let's say we declare jdbcTemplate bean in our spring.xml:

PLAIN TEXT
XML:
  1. <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
  2.     <constructor-arg>
  3.         <ref bean="dataSource" />
  4.     </constructor-arg>
  5. </bean>

where dataSource is (got from JNDI):

PLAIN TEXT
XML:
  1. <bean id="dataSource"
  2.     class="org.springframework.jndi.JndiObjectFactoryBean">
  3.     <property name="jndiName">
  4.         <value>some/jndi/name</value>
  5.     </property>
  6. </bean>

Running both steps of BLOB (CLOB) insertion code in transaction can be done like this:

PLAIN TEXT
JAVA:
  1. byte[] data = new byte[] { ... };
  2. TransactionTemplate txTemplate = new TransactionTemplate(transactionManager);
  3. MyTransaction transaction = new MyTransaction(data);
  4. try {
  5.     txTemplate.execute(transaction);
  6.     //there might be something like: return transaction.getResult();
  7. } catch (Exception e) {
  8.     //error... handle with care ;-)
  9. }

Where MyTransaction for inserting BLOB could be (Java 1.4 this time):

PLAIN TEXT
JAVA:
  1. private class MyTransaction extends TransactionCallbackWithoutResult {
  2.     private byte[] blobData;
  3.        
  4.     public InsertPacketTransaction(byte[] blobData) {
  5.         this.blobData = blobData;
  6.     }
  7.  
  8.     public void doInTransactionWithoutResult(TransactionStatus status) {
  9.         String sql = "insert into MYTABLE (MYID, ..., MYBLOB) values (?, ..., ?)";
  10.  
  11.         Integer myId = 0; //obtain ID for new record
  12.         BLOB blob = null;
  13.            
  14.         try {
  15.             blob = BLOB.empty_lob();
  16.         } catch (SQLException e) {
  17.             //probably shouldn't happen
  18.         }
  19.            
  20.         int types[] = new int[] { Types.INTEGER, ..., Types.BLOB };
  21.         Object args []= new Object[] { myId , ..., blob };
  22.            
  23.         jdbcTemplate.update(sql, args, types);
  24.  
  25.         List packetList = jdbcTemplate.query(
  26.             "select MYBLOB from MYTABLE where MYID = ? FOR UPDATE",
  27.             new Object[]{ myId },
  28.             new int[] { Types.INTEGER },
  29.             new RowMapper() {
  30.                 public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
  31.                     return rs.getBlob("MYBLOB");
  32.                 }
  33.             }
  34.         );
  35.  
  36.         if (packetList.size() == 1) {
  37.             OutputStream os;
  38.             try {
  39.                 os = ((BLOB)packetList.get(0)).getBinaryOutputStream();
  40.                 os.write(blobData);
  41.                 os.flush();
  42.                 os.close();
  43.             } catch (SQLException e) {
  44.                 //handle
  45.             } catch (IOException e) {
  46.                 //handle
  47.             }
  48.         } else {
  49.             //handle - this shouldn't happen
  50.         }
  51.     }
  52. }

Writing CLOB is very similar - just use oracle.sql.CLOB instead of oracle.sql.BLOB everywhere and write data to CLOB using getCharacterOutputStream() method.

]]> http://www.dolejsky.com/2008/02/24/oracle-clob-blob-spring/feed/ 3 OC4J, Spring and messaging http://www.dolejsky.com/2008/02/06/oc4j-spring-and-messaging/ http://www.dolejsky.com/2008/02/06/oc4j-spring-and-messaging/#comments Wed, 06 Feb 2008 20:43:19 +0000 ludek http://www.dolejsky.com/2008/02/06/oc4j-spring-and-messaging/ I ran into several issues during the development of an application which is to be run in OC4J 10.1.3.1 and needs to use SOAP web services and Oracle AQ (Advanced Queueing) messaging:

  • Classpath hell debugging
  • Oracle XML parser crashes on SOAP response
  • Using custom AQ message payload (Oracle ADT message)

If anyone encountered such problems, read the rest of the article for tips and solutions.

Classpath hell

Really useful technique for solving classpath issues is to turn on OC4J class load tracing. It can be done by passing special arguments to VM.

If starting OC4J manually via oc4j/bin/oc4j.cmd you can run the following one-line command before:

SET OC4J_JVM_ARGS=-Dclass.load.trace=class+loader
-Dclass.load.log.file=c:/classloadlog.txt
-Dclass.load.log.level=all

If you're running OC4J server directly from Eclipse's Server view, put these arguments into VM arguments section of Run dialog.

Oracle XML parser crashes on SOAP response

Oracle XML parser is somewhat buggy and crashes on manually created SOAP response if the message body isn't surrounded with <Envelope> element (the same one which surrounds the whole SOAP message).

One way of getting rid of this is to completely replace Oracle XML parser with e.g. Apache Xerces parser. If you have full access to application server you can try adding Xerces as OC4J's shared library. As this wasn't our case (we weren't allowed to change the configuration of production server) we needed to find another way.

The first step was to add Xerces jars to our application.

If you only deploy manually via server's web interface, second step is quite easy as it is sufficient to remove oracle.xml shared library at the very last step of the deployment process.

If you use Eclipse's automatic publishing (which you probably are because nobody wants to manually deploy the application after every modification when developing) things get more complicated.

Upon every publishing, new orion-application.xml file for our application is created. We need it to keep containing the following snippet:

PLAIN TEXT
XML:
  1. <imported-shared-libraries>
  2.     <remove-inherited name="oracle.xml"/>
  3. </imported-shared-libraries>

This can be achieved by:

  1. creating deployment plan with removed reference to oracle.xml shared library (via manual web deployment)
  2. saving the plan to some place on disk
  3. modifying oracle.10.1.3.xml file in [eclipse_dir]/plugins/org.eclipse.jst.server.generic.oc4j/buildfiles:
    PLAIN TEXT
    XML:
    1. ...
    2. <target name="deploy.j2ee.ear"
    3. depends="check.skip.ear.deploy"
    4. unless="skip.deploy">
    5. ...
    6. <oracle:deploy ... deploymentPlan="path_to_deployment_plan" ...
    7. ...

Using custom AQ message payload (Oracle ADT message)

Using standard JMS message types for AQ works just fine (see this great techblog's article for description). To turn on JTA transactions, add the following to your Spring configuration file:

PLAIN TEXT
XML:
  1. <bean id="jmsTransactionManager"
  2.     class="org.springframework.transaction.jta.JtaTransactionManager" />
  3.  
  4. <bean id="jmsContainer"
  5.     class="org.springframework.jms.listener.DefaultMessageListenerContainer">
  6. ...
  7.     <property name="transactionManager" ref="jmsTransactionManager" />
  8. ...
  9. </bean>

A little more advanced is to use custom objects as message payload. Follow these steps:

  1. Create custom type & queue in your Oracle database
  2. Use jpub to generate Java class for the type
  3. Sending message is pretty straightforward
  4. For receiving message, an extension of Spring's DefaultMessageListenerContainer is needed

Ad 1)

For type:
CREATE OR REPLACE TYPE MyCustomType...

For queue table:
execute dbms_aqadm.create_queue_table(
queue_table => 'MyQueueTable',
queue_payload_type => 'MyCustomType'
...

Ad 2)

Download JPublisher, unpack it to e.g. c:\oracle\sqlj and run it:

SET CLASSPATH = <path_to_driver>\ojdbc14.jar; c:\oracle\sqlj\lib\translator.jar; c:\oracle\sqlj\lib\runtime12.jar;

SET PATH = c:\Program Files\Java\j2sdk1.4.2_16\bin

java -cp %CLASSPATH% oracle.jpub.Doit -user=autopub/autopub -url=<url to your db> -sql=<name of type> -case=mixed -compatible=CustomDatum -usertypes=oracle

Ad 3)

PLAIN TEXT
JAVA:
  1. jmsTemplate.send(new MessageCreator() {
  2.     public Message createMessage(Session session) throws JMSException {
  3.         Message msg = null;
  4.         if (session instanceof AQjmsSession) {
  5.             MyCustomType type = new MyCustomType();
  6.             msg = ((AQjmsSession)session).createAdtMessage(vzp);
  7.             return msg;
  8.         } else {
  9.             //this is bad... deal with it
  10.         }
  11.     }
  12. }

Ad 4)

We need to extend DefaultMessageListenerContainer's createConsumer method to slip payload factory which can handle our new custom object type:

PLAIN TEXT
JAVA:
  1. public class MyCustomTypeMessageListenerContainer
  2.     extends DefaultMessageListenerContainer {
  3.     protected MessageConsumer createConsumer(Session session, Destination destination)
  4.         throws JMSException {
  5.         if (session instanceof AQjmsSession) {
  6.             return ((AQjmsSession)session).createConsumer(
  7.                 destination,
  8.                 getMessageSelector(),
  9.                 new MyCustomType(),
  10.                 null,
  11.                 false
  12.             );
  13.         } else {
  14.             //...strange...we can always failback to super.createConsumer()
  15.         }
  16.     }
  17. }

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