released JDBC as part of Java Development Kit 1.1 on February 19, 1997. Since then it has been part of the Java Platform, Standard Edition. The JDBC classes are contained in the Java package and. Starting with version 3.1, JDBC has been developed under the Java Community Process. JSR 54 specifies JDBC 3.0, JSR 114 specifies the JDBC Rowset additions, and JSR 221 is the specification of JDBC 4.0. JDBC 4.1, is specified by a maintenance release 1 of JSR 221 and is included in Java SE 7. JDBC 4.2, is specified by a maintenance release 2 of JSR 221 and is included in Java SE 8. The latest version, JDBC 4.3, is specified by a maintenance release 3 of JSR 221 and is included in Java SE 9.
Functionality
JDBC allows multiple implementations to exist and be used by the same application. The API provides a mechanism for dynamically loading the correct Java packages and registering them with the JDBC Driver Manager. The Driver Manager is used as a connection factory for creating JDBC connections. JDBC connections support creating and executing statements. These may be update statements such as SQL's CREATE, INSERT, UPDATE and DELETE, or they may be query statements such as SELECT. Additionally, stored procedures may be invoked through a JDBC connection. JDBC represents statements using one of the following classes:
- the statement is sent to the database server each and every time.
- the statement is cached and then the execution path is pre-determined on the database server allowing it to be executed multiple times in an efficient manner.
- used for executing stored procedures on the database.
Update statements such as INSERT, UPDATE and DELETE return an update count that indicates how many rows were affected in the database. These statements do not return any other information. Query statements return a JDBC row result set. The row result set is used to walk over the result set. Individual columns in a row are retrieved either by name or by column number. There may be any number of rows in the result set. The row result set has metadata that describes the names of the columns and their types. There is an extension to the basic JDBC API in the. JDBC connections are often managed via a connection pool rather than obtained directly from the driver.
Oracle Datatype
setXXX Methods
CHAR
setString
VARCHAR2
setString
NUMBER
setBigDecimal
NUMBER
setBoolean
NUMBER
setByte
NUMBER
setShort
NUMBER
setInt
NUMBER
setLong
NUMBER
setFloat
NUMBER
setDouble
INTEGER
setInt
FLOAT
setDouble
CLOB
setClob
BLOB
setBlob
RAW
setBytes
LONGRAW
setBytes
DATE
setDate
DATE
setTime
DATE
setTimestamp
Examples
When a Java application needs a database connection, one of the DriverManager.getConnection methods is used to create a JDBC connection. The URL used is dependent upon the particular database and JDBC driver. It will always begin with the "jdbc:" protocol, but the rest is up to the particular vendor. Connection conn = DriverManager.getConnection; try finally
Starting from Java SE 7 you can use Java's statement to make the above code simpler: try // the VM will take care of closing the connection
Once a connection is established, a statement can be created. try )
Note that Connections, Statements, and ResultSets often tie up operating system resources such as sockets or file descriptors. In the case of Connections to remote database servers, further resources are tied up on the server, e.g., cursors for currently open ResultSets. It is vital to close any JDBC object as soon as it has played its part; garbage collection should not be relied upon. The above try-with-resources construct is a code pattern that obviates this. Data is retrieved from the database using a database query mechanism. The example below shows creating a statement and executing a query. try ; ResultSet rs = stmt.executeQuery )
An example of a PreparedStatement query, using conn and class from first example. try // try
If a database operation fails, JDBC raises an. There is typically very little one can do to recover from such an error, apart from logging it with as much detail as possible. It is recommended that the SQLException be translated into an application domain exception that eventually results in a transaction rollback and a notification to the user. An example of a database transaction: boolean autoCommitDefault = conn.getAutoCommit; try catch finally
For an example of a CallableStatement, see the documentation. import java.sql.Connection; import java.sql.DriverManager; import java.sql.Statement; public class Mydb1
JDBC drivers
JDBC drivers are client-side adapters that convert requests from Java programs to a protocol that the DBMS can understand.
Types
Commercial and free drivers provide connectivity to most relational-database servers. These drivers fall into one of the following types:
Type 1 that calls native code of the locally available ODBC driver.
Type 3, the pure-java driver that talks with the server-side middleware that then talks to the database.
Type 4, the pure-java driver that uses database native protocol.
Note also a type called an internal JDBC driver - a driver embedded with JRE in Java-enabled SQL databases. It is used for Java stored procedures. This does not fit into the classification scheme above, although it would likely resemble either a type 2 or type 4 driver. An example of this is the KPRB driver supplied with Oracle RDBMS. "jdbc:default:connection" offers a relatively standard way of making such a connection. However, in the case of an internal JDBC driver, the JDBC client actually runs as part of the database being accessed, and so can access data directly rather than through network protocols.
