Sun Java System Application Server Platform Edition 8.1 2005Q1 Developer's Guide |
Chapter 11
Using the JDBC API for Database AccessThis chapter describes how to use the Java Database Connectivity (JDBC) API for database access with the Sun Java System Application Server. This chapter also provides high level JDBC implementation instructions for servlets and EJB components using the Sun Java System Application Server. The Sun Java System Application Server supports the JDBC 3.0 API, which encompasses the JDBC 2.0 Optional Package API.
The JDBC specifications are available here:
http://java.sun.com/products/jdbc/download.html
A useful JDBC tutorial is located here:
http://java.sun.com/docs/books/tutorial/jdbc/index.html
For explanations of two-tier and three-tier database access models, see the Sun Java System Application Server Administration Guide.
Note
Sun Java System Application Server does not support connection pooling or transactions for an application’s database access if it does not use standard J2EE DataSource objects.
This chapter discusses the following topics:
General Steps for Creating a JDBC ResourceTo prepare a JDBC resource for use in J2EE applications deployed to the Sun Java System Application Server, perform the following tasks:
For information about how to configure some specific JDBC drivers, see the Sun Java System Application Server Administration Guide.
Integrating the JDBC Driver
To use JDBC features, you must choose a JDBC driver to work with the Sun Java System Application Server, then you must set up the driver. This section covers these topics:
Supported Database Drivers
Supported JDBC drivers are those that have been fully tested by Sun. For a list of the JDBC drivers currently supported by the Sun Java System Application Server, see the Sun Java System Application Server 8.1 Release Notes. For configurations of supported and other drivers, see the Sun Java System Application Server Administration Guide.
Making the JDBC Driver JAR Files Accessible
To integrate the JDBC driver into a Sun Java System Application Server domain, copy the JAR files into the domain_dir/lib/ext directory, then restart the server. This makes classes accessible to any application or module across the domain. For more information about Sun Java System Application Server classloaders, see “Classloaders” on page 73.
Creating a Connection Pool
When you create a connection pool that uses JDBC technology (“JDBC connection pool”) in the Sun Java System Application Server, you can define many of the characteristics of your database connections.
You can create a JDBC connection pool in one of these ways:
- In the Administration Console, open the Resources component, open the JDBC component, and select Connection Pools. For details, see the Sun Java System Application Server Administration Guide.
- Use the asadmin create-jdbc-connection-pool command. For details, see the Sun Java System Application Server Reference Manual.
Testing a Connection Pool
You can test a JDBC connection pool for usability in one of these ways:
- In the Administration Console, open the Resources component, open the JDBC component, select Connection Pools, and select the connection pool you want to test. Then select the Ping button in the top right corner of the page. For details, see the Sun Java System Application Server Administration Guide.
- Use the asadmin ping-connection-pool command. For details, see the Sun Java System Application Server Reference Manual
Both these commands fail and display an error message unless they successfully connect to the connection pool.
For information about how to tune a connection pool, see the Sun Java System Application Server Performance Tuning Guide.
Creating a JDBC Resource
A JDBC resource, also called a data source, lets you make connections to a database using getConnection(). Create a JDBC resource in one of these ways:
- In the Administration Console, open the Resources component, open the JDBC component, and select JDBC Resources. For details, see the Sun Java System Application Server Administration Guide.
- Use the asadmin create-jdbc-resource command. For details, see the Sun Java System Application Server Reference Manual.
Creating Applications That Use the JDBC APIAn application that uses the JDBC API is an application that looks up and connects to one or more databases. This section covers these topics:
Sharing Connections
When multiple connections acquired by an application use the same JDBC resource, the connection pool provides connection sharing within the same transaction scope. For example, suppose Bean_A starts a transaction and obtains a connection, then calls a method in Bean_B. If Bean_B acquires a connection to the same JDBC resource with the same sign-on information, and if Bean_A completes the transaction, the connection can be shared.
Connections obtained through a resource are shared only if the resource reference declared by the J2EE component allows it to be shareable. This is specified in a component’s deployment descriptor by setting the res-sharing-scope element to Shareable for the particular resource reference. To turn off connection sharing, set res-sharing-scope to Unshareable.
For general information about connections and JDBC URLs, see the Sun Java System Application Server Administration Guide.
Obtaining a Physical Connection from a Wrapped Connection
The DataSource implementation in the Sun Java System Application Server provides a getConnection method that retrieves the JDBC driver’s SQLConnection from the Application Server’s Connection wrapper. The method signature is as follows:
public java.sql.Connection getConnection(java.sql.Connection con) throws java.sql.SQLException
For example:
InitialContext ctx = new InitialContext();
com.sun.appserv.DataSource ds = (com.sun.appserv.DataSource) ctx.lookup("jdbc/MyBase");
Connection con = ds.getConnection();
Connection drivercon = ds.getConnection(con);
// Do db operations.
con.close();
Using Non-Transactional Connections
The DataSource implementation in the Sun Java System Application Server provides a getNonTxConnection method, which retrieves a JDBC connection that is not in the scope of any transaction. There are two variants, as follows:
public java.sql.Connection getNonTxConnection() throws java.sql.SQLException
public java.sql.Connection getNonTxConnection(String user, String password) throws java.sql.SQLException
Another way to get a non-transactional connection is to create a resource with the JNDI name ending in __nontx. This forces all connections looked up using this resource to be non transactional.
Typically, a connection is enlisted in the context of the transaction in which a getConnection call is invoked. However, a non-transactional connection is not enlisted in a transaction context even if a transaction is in progress.
The main advantage of using non-transactional connections is that the overhead incurred in enlisting and delisting connections in transaction contexts is avoided. However, use such connections carefully. For example, if a non-transactional connection is used to query the database while a transaction is in progress that modifies the database, the query retrieves the unmodified data in the database. This is because the in-progress transaction hasn’t committed. For another example, if a non-transactional connection modifies the database and a transaction that is running simultaneously rolls back, the changes made by the non-transactional connection are not rolled back.
Here is a typical use case for a non-transactional connection: a component that is updating a database in a transaction context spanning over several iterations of a loop can refresh cached data by using a non-transactional connection to read data before the transaction commits.
Using JDBC Transaction Isolation Levels
For general information about transactions, see Chapter 12, "Using the Transaction Service," and the Sun Java System Application Server Administration Guide. For information about last agent optimization, which can improve performance, see Transaction Scope.
Not all database vendors support all transaction isolation levels available in the JDBC API. The Sun Java System Application Server permits specifying any isolation level your database supports. The following table defines transaction isolation levels.
Note that you cannot call setTransactionIsolation() during a transaction.
You can set the default transaction isolation level for a JDBC connection pool. For details, see Creating a Connection Pool.
To verify that a level is supported by your database management system, test your database programmatically using the supportsTransactionIsolationLevel() method in java.sql.DatabaseMetaData, as shown in the following example:
java.sql.DatabaseMetaData db;
if (db.supportsTransactionIsolationLevel(TRANSACTION_SERIALIZABLE)
{ Connection.setTransactionIsolation(TRANSACTION_SERIALIZABLE); }For more information about these isolation levels and what they mean, see the JDBC 3.0 API specification.
Note
Applications that change the isolation level on a pooled connection programmatically risk polluting the pool, which can lead to errors.
Configurations for Specific JDBC DriversSun Java System Application Server 8.1 is designed to support connectivity to any database management system with a corresponding JDBC driver. The following JDBC driver and database combinations are supported. These combinations have been tested with Sun Java System Application Server 8.1 and are found to be J2EE compatible. They are also supported for CMP.
For an up to date list of currently supported JDBC drivers, see the Sun Java System Application Server 8.1 Release Notes.
Other JDBC drivers can be used with Sun Java System Application Server Platform Edition 8.1, but J2EE compliance tests have not been completed with these drivers. Although Sun offers no product support for these drivers, Sun offers limited support of the use of these drivers with the Sun Java System Application Server.
For details about how to integrate a JDBC driver and how to use the Administration Console or the command line interface to implement the configuration, see the Sun Java System Application Server Administration Guide.
Note
An Oracle database user running the capture-schema command needs ANALYZE ANY TABLE privileges if that user does not own the schema. These privileges are granted to the user by the database administrator. For information about capture-schema, see Using the capture-schema Utility.
PointBase Type4 Driver
The PointBase JDBC driver is included with the Sun Java System Application Server by default, except for the Solaris bundled installation, which does not include PointBase. Therefore, unless you have the Solaris bundled installation, you do not need to integrate this JDBC driver with the Sun Java System Application Server.
PointBase is intended for evaluation use only, not for production or deployment use.
The JAR file for the PointBase driver is pbclient.jar.
Configure the connection pool using the following settings:
Sun Java System JDBC Driver for DB2 Databases
The JAR files for this driver are smbase.jar, smdb2.jar, and smutil.jar. Configure the connection pool using the following settings:
Sun Java System JDBC Driver for Oracle 8.1.7 and 9.x Databases
The JAR files for this driver are smbase.jar, smoracle.jar, and smutil.jar. Configure the connection pool using the following settings:
Sun Java System JDBC Driver for Microsoft SQL Server Databases
The JAR files for this driver are smbase.jar, smsqlserver.jar, and smutil.jar. Configure the connection pool using the following settings:
Sun Java System JDBC Driver for Sybase Databases
The JAR files for this driver are smbase.jar, smsybase.jar, and smutil.jar. Configure the connection pool using the following settings:
IBM DB2 8.1 Type2 Driver
The JAR files for the DB2 driver are db2jcc.jar, db2jcc_license_cu.jar, and db2java.zip. Set environment variables as follows:
LD_LIBRARY_PATH=/usr/db2user/sqllib/lib:${j2ee.home}/lib
DB2DIR=/opt/IBM/db2/V8.1
DB2INSTANCE=db2user
INSTHOME=/usr/db2user
VWSPATH=/usr/db2user/sqllib
THREADS_FLAG=native
Configure the connection pool using the following settings:
JConnect/Type4 Driver for Sybase ASE 12.5 Databases
The JAR file for the Sybase driver is jconn2.jar. Configure the connection pool using the following settings:
- Name: Use this name when you configure the JDBC resource later.
- Resource Type: Specify the appropriate value.
- Database Vendor: Sybase
- Datasource Classname: one of the following:
com.sybase.jdbc2.jdbc.SybDataSource
com.sybase.jdbc2.jdbc.SybXADataSource
- Properties:
- serverName - Specify the host name or IP address of the database server.
- portNumber - Specify the port number of the database server.
- user - Set as appropriate.
- password - Set as appropriate.
- databaseName - Set as appropriate. Do not specify the complete URL, only the database name.
- BE_AS_JDBC_COMPLIANT_AS_POSSIBLE - Set to true.
- FAKE_METADATA - Set to true.
Inet Oraxo JDBC Driver for Oracle 8.1.7 and 9.x Databases
The JAR file for the Inet Oracle driver is Oranxo.jar. Configure the connection pool using the following settings:
- Name: Use this name when you configure the JDBC resource later.
- Resource Type: Specify the appropriate value.
- Database Vendor: Oracle
- Datasource Classname: com.inet.ora.OraDataSource
- Properties:
For example:
jdbc:inetora:localhost:1521:payrolldb
In this example,localhost is the host name of the machine running the Oracle server, 1521 is the Oracle server’s port number, and payrolldb is the SID of the database. For more information about the syntax of the database URL, see the Oracle documentation.
- serverName - Specify the host name or IP address of the database server.
- port - Specify the port number of the database server.
- streamstolob - If the size of BLOB or CLOB datatypes exceeds 4 KB and this driver is used for CMP, this property must be set to true.
- xa-driver-does-not-support-non-tx-operations - Set to the value true. Optional: only needed if both non-XA and XA connections are retrieved from the same connection pool. Might degrade performance.
Inet Merlia JDBC Driver for Microsoft SQL Server Databases
The JAR file for the Inet Microsoft SQL Server driver is Merlia.jar. Configure the connection pool using the following settings:
Inet Sybelux JDBC Driver for Sybase Databases
The JAR file for the Inet Sybase driver is Sybelux.jar. Configure the connection pool using the following settings:
Oracle Thin/Type4 Driver for Oracle 8.1.7 and 9.x Databases
The JAR file for the Oracle driver is ojdbc14.jar. Configure the connection pool using the following settings:
- Name: Use this name when you configure the JDBC resource later.
- Resource Type: Specify the appropriate value.
- Database Vendor: Oracle
- Datasource Classname: one of the following:
oracle.jdbc.pool.OracleDataSource
oracle.jdbc.xa.client.OracleXADataSource
- Properties:
As an alternative to setting this property, you can create two connection pools, one for non-XA connections and one for XA connections.
Note
You must set the oracle-xa-recovery-workaround property in the Transaction Service for recovery of global transactions to work correctly. For details, see Transaction Scope.
When using this driver, it is not possible to insert more than 2000 bytes of data into a column. To circumvent this problem, use the OCI driver (JDBC type 2).
OCI Oracle Type2 Driver for Oracle 8.1.7 and 9.x Databases
The JAR file for the OCI Oracle driver is ojdbc14.jar. Make sure that the shared library is available through LD_LIBRARY_PATH and that the ORACLE_HOME property is set. Configure the connection pool using the following settings:
IBM Informix Type4 Driver
Configure the connection pool using the following settings:
- Name: Use this name when you configure the JDBC resource later.
- Resource Type: Specify the appropriate value.
- Database Vendor: Informix
- Datasource Classname: one of the following:
com.informix.jdbcx.IfxDataSource
com.informix.jdbcx.IfxXADataSource
- Properties:
- serverName - Specify the Informix database server name.
- portNumber - Specify the port number of the database server.
- user - Set as appropriate.
- password - Set as appropriate.
- databaseName - Set as appropriate. This is optional.
- IfxIFXHost - Specify the host name or IP address of the database server.
MM MySQL Type4 Driver
Configure the connection pool using the following settings:
- Name: Use this name when you configure the JDBC resource later.
- Resource Type: Specify the appropriate value.
- Database Vendor: mysql
- Datasource Classname: one of the following:
com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource
com.mysql.jdbc.jdbc2.optional.MysqlXaConnectionPoolDataSource
- Properties:
- serverName - Specify the host name or IP address of the database server.
- port - Specify the port number of the database server.
- user - Set as appropriate.
- password - Set as appropriate.
- databaseName - Set as appropriate.
- URL - If you are using global transactions, you can set this property instead of serverName, port, and databaseName.
CloudScape 5.1 Type4 Driver
The JAR files for the CloudScape driver are db2j.jar, db2jtools.jar, db2jcview.jar, jh.jar, db2jcc.jar, and db2jnet.jar. Configure the connection pool using the following settings: