Castor JDO - Configuration The Castor configuration file Transaction demarcation Local Mode Global Mode Sample Configuration File Configuration For Various Databases The JDO Configuration DTD JDOConfFactory
The Castor configuration file The default way to configure how Castor interacts with a specific database system is by using a configuration file. It specifies the means to obtain a connection to the database server, the mapping between Java classes and tables in that database server, and the service provider to use for talking to that server (For a more flexible, programmatic way without configuration files see section JDOConfFactory). The application will access the database(s) by its given name (database/name) and will be able to persist all objects specified in the included mapping file(s). The engine attribute specifies the persistence engine for this database server. Different database servers vary in the SQL syntax and capabilites they support, and this attribute names the service provider to use. The following names are supported in Castor: engine name | RDBMS | db2 | DB/2 | derby | Derby | generic | Generic JDBC support | hsql | Hypersonic SQL | informix | Informix | instantdb | InstantDB | interbase | Interbase | mysql | MySQL | oracle | Oracle 7 - Oracle 9i | postgresql | PostgreSQL 7.1 | sapdb | SAP DB / MaxDB | sql-server | Microsoft SQL Server | sybase | Sybase 11 | | Note: Castor doesn't work with JDBC-ODBC bridge from Sun. In particular, MS Access is not supported. The means to acquire a database connection is specified in one of three ways: as a JDBC driver URL, as a JDBC DataSource, or as a DataSource to lookup through JNDI. When Castor is used inside a J2EE application server it is recommended to use JNDI lookup (see the jndi element), allowing the application server to manage connection pooling and distributed transactions. The class mapping is included from an external mapping file, allowing multiple mappings to be included in the same database configuration, or two databases to share the same mappings. For concurrency and integrity reasons, two database configurations should never attempt to use overlapping mappings. It is recommended to use one database configuration per database server. The mapping file is specified using a URL, typically a file: URL. If the database configuration file and mapping file reside in the same directory, use a relative URL. Relative URLs also work if the database configuration and mapping files are obtained from the application JAR and reside in the same classpath. The driver element specifies the JDBC driver for obtaining new connections to the database server. The driver is obtained from the JDBC DriverManager and must be located in the class path. The JDBC URL locates the driver and provides the access properties. Additional properties may be specified using param elements (e.g. buffer size, network protocol, etc). Use the class-name attribute to specify the driver class for automatic registration with the JDBC DriverManager. If missing, the driver must be registered in any other means, including properties file, Class.forName(), etc. For example, to configure an Oracle 8 thin driver, use:
<jdo-conf>
<database name="ebiz" engine="oracle">
<driver class-name="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@host:port:SID">
<param name="user" value="scott" />
<param name="password" value="tiger" />
</driver>
...
</database>
...
</jdo-conf> |
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The data-source element specifies the JDBC DataSource for obtaining new connections to the database server. DataSources are defined in the JDBC 2.0 standard extension API which is included with Castor, and implement the interface javax.sql.DataSource. The DataSource implementation class name is specified by the class-name attribute and configured through Bean-like accessor methods specified for the param element. The DTD for the param element is undefined and depends on the DataSource being used. For example, to configure a PostgreSQL 7.1 DataSource, use:
<jdo-conf>
<database name="ebiz" engine="oracle">
<data-source class-name="org.postgresql.PostgresqlDataSource">
<param name="serverName" value="host" />
<param name="portNumber" value="5432" />
<param name="databaseName" value="db" />
<param name="user" value="user" />
<param name="password=" value="secret" />
</data-source>
...
</database>
...
</jdo-conf> |
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The jndi element specifies the JDBC DataSource for obtaining new connections to the database server through a JNDI lookup. The JNDI environment naming context (ENC) is used to obtain a suitable DataSource.. When running inside a J2EE application server, this is the preferred method for obtaining database connections. It enables the J2EE application server to configure the connection, maintain a connection pool, and manage distributed transactions. For example, to specify a J2EE DataSource, use:
<jdo-conf>
<database name="ebiz" engine="oracle">
<jndi name="java:comp/env/jdbc/mydb" />
</database>
...
</jdo-conf> |
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Transaction demarcation As opposed to release pre 0.9.6, transaction demarcation is now configured in the JDO configuration file. As such, the user has to specify which transaction demarcation to use. Transactions when used with Castor JDO can either be local or global, and you instruct Castor to use a specific mode by supplying a <transaction-demarcation> element. Local Mode When using Castor JDO stand-alone and you want Castor to control transaction demarcation, please use the <transaction-demarcation> element as follows:
<transaction-demarcation mode="local" /> |
| Global Mode When running inside a J2EE application server, and you want to use global (XA) transactions, please make use the <transaction-demarcation> element as follows:
<transaction-demarcation mode="global">
<transaction-manager name="jndi" />
</transaction-demarcation> |
| In this mode, the <transaction-manager> element specifies the transaction manager that is used by your J2EE container to control these transactions. The following transaction managers are supported in Castor: Name | Description | jndi | TM looked up in the JNDI ENC | websphere | IBM WebSphere 4 and previous releases | websphere5 | IBM WebSphere 5 | websphere51 | IBM WebSphere 5.1 | jotm | JOTM | | In addition to specifying the transaction manager name, it is possible to pass arbitrary name/value pairs to the transaction manager instance. Note: At the moment, only the JNDI transaction manager factory supports such an attribute. In this context, the jndiEnc attribute can be used to specify what JNDI ENC to use to lookup the transaction manager as shown below:
<transaction-demarcation mode="global">
<transaction-manager name="jndi">
<param name="jndiEnc" value="java:comp/env/TransactionManager"/>
</transaction-manager>
</transaction-demarcation> |
| Sample Configuration File The following configuration file uses an Oracle 8 thin JDBC driver and three mapping files:
<jdo-conf>
<database name="ebiz" engine="oracle">
<driver class-name="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@machine:post:SID">
<param name="user" value="scott"/>
<param name="password" value="tiger"/>
</driver>
<mapping href="products.xml"/>
<mapping href="orders.xml"/>
<mapping href="customers.xml"/>
</database>
<transaction-demarcation mode="local"/>
</jdo-conf> |
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The following configuration file uses a connection obtained from the J2EE application server and a single mapping file:
<jdo-conf>
<database name="ebiz" engine="oracle">
<jndi name="java:comp/env/jdbc/mydb"/>
<mapping href="ebiz.xml"/>
</database>
<transaction-demarcation mode="global">
<transaction-manager name="jndi">
<param name="jndiEnc" value="java:comp/env/TransactionManager"/>
</transaction-manager>
</transaction-demarcation>
</jdo-conf> |
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Configuration For Various Databases Driver | Configuration | Sybase jConnect |
<data-source class-name="com.sybase.jdbc2.jdbc.SybDataSource">
<param name="user" value="user" />
<param name="password value="secret" />
<param name="portNumber" value="4100" />
<param name="serverName" value="host" />
</data-source> | Oracle Thin Driver |
<driver class-name="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@host:post:SID">
<param name="user" value="scott" />
<param name="password" value="tiger" />
</driver> | mySQL JDBC Driver |
<driver class-name="com.mysql.jdbc.Driver"
url="jdbc:mysql:/localhost:2206/test">
<param name="user" value="scott" />
<param name="password" value="tiger" />
</driver> | PostgreSQL |
<data-source class-name="org.postgresql.PostgresqlDataSource">
<param name="serverName" value="host" />
<param name="portNumber" value="5432" />
<param name="databaseName" value="db" />
<param name="user" value="user" />
<param name="password" value="secret" />
</data-source> | InstantDB |
<driver class-name="org.enhydra.instantdb.jdbc.idbDriver"
url="jdbc:idb:C:\\castor-0.8.8\\db\\test\\test.prp">
<param name="user" value="" />
<param name="password" value="" />
</driver> | NOTE: Besides the examples listed above, a good source of configuraton examples are the JDO tests (src/tests/jdo). See the XML decriptor for each database type. The JDO Configuration DTD For validation, the configuration file should include the following document type definition. For DTD validation use:
<!DOCTYPE jdo-conf PUBLIC "-//EXOLAB/Castor JDO Configuration DTD Version 1.0//EN"
"http://castor.org/jdo-conf.dtd">
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| For XML Schema validation use:
<!DOCTYPE jdo-conf PUBLIC "-//EXOLAB/Castor JDO Configuration Schema Version 1.0//EN"
"http://castor.org/jdo-conf.xsd">
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| The Castor namespace URI is http://castor.org/. The Castor JDO database configuration DTD is:
<!ELEMENT jdo-conf ( database+, transaction-demarcation )>
<!ELEMENT database ( ( driver | data-source | jndi )?,
mapping+ )>
<!ATTLIST database
name ID #REQUIRED
engine CDATA "generic">
<!ELEMENT mapping EMPTY>
<!ATTLIST mapping
href CDATA #REQUIRED>
<!ELEMENT driver ( param* )>
<!ATTLIST driver
url CDATA #REQUIRED
class-name CDATA #IMPLIED>
<!ELEMENT data-source ( param* )>
<!ATTLIST data-source
class-name CDATA #REQUIRED>
<!ELEMENT jndi ANY>
<!ATTLIST jndi
name CDATA #REQUIRED>
<!ELEMENT transaction-demarcation ( transaction-manager? )>
<!ATTLIST transaction-demarcation
mode CDATA #REQUIRED>
<!ELEMENT transaction-manager ( param* )>
<!ATTLIST transaction-manager
name CDATA #REQUIRED>
<!ELEMENT param EMPTY>
<!ATTLIST param
name CDATA #REQUIRED
value CDATA #REQUIRED>
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JDOConfFactory Many applications need to connect to a database using varying user accounts or database instances. To accomplish this, the utility class JDOConfFactory and a JDOManager.loadConfiguration(org.exolab.castor.jdo.conf.JdoConf) method has been added to Castor. The following code snippet shows an example how to create a JDO configuration without the use of a default XML-based database configuration file:
private static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
private static final String CONNECT = "jdbc:oracle:thin:localhost:1521:SID";
private static final String USERNAME = "scott";
private static final String PASSWORD = "tiger";
private static final String MAPPING = "mapping.xml";
private static final String DATABASE = "mydb";
private static final String ENGINE = "oracle";
// create driver configuration
org.exolab.castor.jdo.conf.Driver driverConf =
JDOConfFactory.createDriver(DRIVER, CONNECT, USERNAME, PASSWORD);
// create mapping configuration
org.exolab.castor.jdo.conf.Mapping mappingConf =
JDOConfFactory.createMapping(getClass().getResource(MAPPING).toString());
// create database configuration
org.exolab.castor.jdo.conf.Database dbConf =
JDOConfFactory.createDatabase(DATABASE, ENGINE, driverConf, mappingConf);
// create and load jdo configuration
JDOManager.loadConfiguration(JDOConfFactory.createJdoConf(dbConf));
// Construct a new JDOManager for the database
jdoManager = JDOManager.createInstance(DATABASE);
// Obtain a new database
Database db = jdoManager.getDatabase();
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| As an alternative to using a org.exolab.castor.jdo.conf.Driver, you can also configure Castor to use a JDBC 2.0 DataSource:
private static final String DS = "oracle.jdbc.pool.OracleConnectionCacheImpl";
private static final String CONNECT = "jdbc:oracle:thin:localhost:1521:SID";
private static final String USERNAME = "scott";
private static final String PASSWORD = "tiger";
private static final String MAPPING = "mapping.xml";
private static final String DATABASE = "mydb";
private static final String ENGINE = "oracle";
// setup properties for datasource configuration
Properties props = new Properties();
props.put("URL", CONNECT);
props.put("user", USERNAME);
props.put("password", PASSWORD);
// create datasource configuration
org.exolab.castor.jdo.conf.DataSource dsConf =
JDOConfFactory.createDataSource(DS, props);
// create mapping configuration
org.exolab.castor.jdo.conf.Mapping mappingConf =
JDOConfFactory.createMapping(getClass().getResource(MAPPING).toString());
// create database configuration
org.exolab.castor.jdo.conf.Database dbConf =
JDOConfFactory.createDatabase(DATABASE, ENGINE, dsConf, mappingConf);
// create and load jdo configuration
JDOManager.loadConfiguration(JDOConfFactory.createJdoConf(dbConf));
// Construct a new JDOManager for the database
jdoManager = JDOManager.createInstance(DATABASE);
// Obtain a new database
Database db = jdoManager.getDatabase();
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