Java Database Connectivity

JDBC
JDBC
Developer(s)	Oracle Corporation
Stable release	JDBC 4.3 / September 21, 2017
Operating system	Cross-platform
Type	Data access API
Website	JDBC API Guide

Java Database Connectivity (JDBC) is an application programming interface (API) for the programming language Java, which defines how a client may access a database. It is a Java-based data access technology used for Java database connectivity. It is part of the Java Standard Edition platform, from Oracle Corporation. It provides methods to query and update data in a database, and is oriented towards relational databases. A JDBC-to-ODBC bridge enables connections to any ODBC-accessible data source in the Java virtual machine (JVM) host environment.

History and implementation

Sun Microsystems released JDBC as part of Java Development Kit (JDK) 1.1 on February 19, 1997.^[1] Since then it has been part of the Java Platform, Standard Edition (Java SE).

The JDBC classes are contained in the Java package java.sql and javax.sql.

Starting with version 3.1, JDBC has been developed under the Java Community Process. JSR 54 specifies JDBC 3.0 (included in J2SE 1.4), JSR 114 specifies the JDBC Rowset additions, and JSR 221 is the specification of JDBC 4.0 (included in Java SE 6).^[2]

JDBC 4.1, is specified by a maintenance release 1 of JSR 221^[3] and is included in Java SE 7.^[4]

JDBC 4.2, is specified by a maintenance release 2 of JSR 221^[5] and is included in Java SE 8.^[6]

The latest version, JDBC 4.3, is specified by a maintenance release 3 of JSR 221^[7] and is included in Java SE 9.^[8]

Functionality

JDBC ('Java Database Connectivity') 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:

Statement – the statement is sent to the database server each and every time.
PreparedStatement – 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.
CallableStatement – 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 javax.sql.

JDBC connections are often managed via a connection pool rather than obtained directly from the driver.

Host database types which Java can convert to with a function
Oracle Datatype	`setXXX()` Methods
CHAR	`setString()`
VARCHAR2	`setString()`
NUMBER	`setBigDecimal()`
	`setBoolean()`
	`setByte()`
	`setShort()`
	`setInt()`
	`setLong()`
	`setFloat()`
	`setDouble()`
INTEGER	`setInt()`
FLOAT	`setDouble()`
CLOB	`setClob()`
BLOB	`setBlob()`
RAW	`setBytes()`
LONGRAW	`setBytes()`
DATE	`setDate()`
	`setTime()`
	`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(
     "jdbc:somejdbcvendor:other data needed by some jdbc vendor",
     "myLogin",
     "myPassword");
try {
     /* you use the connection here */
} finally {
    //It's important to close the connection when you are done with it
    try { 
        conn.close();
    } catch (Throwable e) { /* Propagate the original exception
                                instead of this one that you want just logged */ 
        logger.warn("Could not close JDBC Connection",e);
    }
}

Starting from Java SE 7 you can use Java's try-with-resources statement to make the above code simpler:

try (Connection conn = DriverManager.getConnection(
     "jdbc:somejdbcvendor:other data needed by some jdbc vendor",
     "myLogin",
     "myPassword")) {
     /* you use the connection here */
}  // the VM will take care of closing the connection

Once a connection is established, a statement can be created.

try (Statement stmt = conn.createStatement()) {
    stmt.executeUpdate("INSERT INTO MyTable(name) VALUES ('my name')");
}

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 (Statement stmt = conn.createStatement();
    ResultSet rs = stmt.executeQuery("SELECT * FROM MyTable")
) {
    while (rs.next()) {
        int numColumns = rs.getMetaData().getColumnCount();
        for (int i = 1; i <= numColumns; i++) {
           // Column numbers start at 1.
           // Also there are many methods on the result set to return
           //  the column as a particular type. Refer to the Sun documentation
           //  for the list of valid conversions.
           System.out.println( "COLUMN " + i + " = " + rs.getObject(i));
        }
    }
}

An example of a PreparedStatement query, using conn and class from first example.

try (PreparedStatement ps =
    conn.prepareStatement("SELECT i.*, j.* FROM Omega i, Zappa j WHERE i.name = ? AND j.num = ?")
) {
    // In the SQL statement being prepared, each question mark is a placeholder
    // that must be replaced with a value you provide through a "set" method invocation.
    // The following two method calls replace the two placeholders; the first is
    // replaced by a string value, and the second by an integer value.
    ps.setString(1, "Poor Yorick");
    ps.setInt(2, 8008);

    // The ResultSet, rs, conveys the result of executing the SQL statement.
    // Each time you call rs.next(), an internal row pointer, or cursor,
    // is advanced to the next row of the result.  The cursor initially is
    // positioned before the first row.
    try (ResultSet rs = ps.executeQuery()) {
        while (rs.next()) {
            int numColumns = rs.getMetaData().getColumnCount();
            for (int i = 1; i <= numColumns; i++) {
                // Column numbers start at 1.
                // Also there are many methods on the result set to return
                // the column as a particular type. Refer to the Sun documentation
                // for the list of valid conversions.
                System.out.println("COLUMN " + i + " = " + rs.getObject(i));
            } // for
        } // while
    } // try
} // try

If a database operation fails, JDBC raises an SQLException. 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 (an unchecked one) that eventually results in a transaction rollback and a notification to the user.

An example of a database transaction:

boolean autoCommitDefault = conn.getAutoCommit();
try {
    conn.setAutoCommit(false);

    /* You execute statements against conn here transactionally */

    conn.commit();
} catch (Throwable e) {
    try { conn.rollback(); } catch (Throwable e) { logger.warn("Could not rollback transaction", e); }
    throw e;
} finally {
    try { conn.setAutoCommit(autoCommitDefault); } catch (Throwable e) { logger.warn("Could not restore AutoCommit setting",e); }
}

For an example of a CallableStatement (to call stored procedures in the database), see the JDBC API Guide documentation.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class Mydb1 {
   static String URL = "jdbc:mysql://localhost/mydb";

   public static void main(String[] args) {
      try {
        Class.forName("com.mysql.jdbc.Driver");

        Connection conn = DriverManager.getConnection(URL, "root", "root");
        Statement stmt = conn.createStatement();
      
        String sql = "INSERT INTO emp1 VALUES ('pctb5361', ‘gajanan', 'krpuram', 968666668)";
        stmt.executeUpdate(sql);
           
        System.out.println("Inserted records into the table...");
      } catch (Exception e) {
        e.printStackTrace();
      }
   }
}

JDBC drivers

JDBC drivers are client-side adapters (installed on the client machine, not on the server) 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. (Note: In JDBC 4.2, JDBC-ODBC bridge has been removed^[9])
Type 2 that calls database vendor native library on a client side. This code then talks to database over the network.
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 (depending on whether the database itself is implemented in Java or not). An example of this is the KPRB (Kernel Program Bundled) driver^[10] supplied with Oracle RDBMS. "jdbc:default:connection" offers a relatively standard way of making such a connection (at least the Oracle database and Apache Derby support it). 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.Incident Identifier: 380215E6-2CC0-4F22-BA33-ADEC63899CD6 CrashReporter Key: a9c97b0521d9f92b07d8452e4e9e57d8a8b830d2 Hardware Model: iPhone4,1 Date/Time: 2019-10-29 16:44:59.493 -0500 OS Version: iOS 6.1.3 (10B329)

panic(cpu 0 caller 0x8d32f683): "AppleUSBEHCI[0x8f666800]::WaitForAsyncSchedule: USBCMD (0x00010351) and USBSTS (0x0000e000) did not synchronize" Debugger message: panic OS version: 10B329 Kernel version: Darwin Kernel Version 13.0.0: Wed Feb 13 21:37:19 PST 2013; root:xnu-2107.7.55.2.2~1/RELEASE_ARM_S5L8940X iBoot version: iBoot-1537.9.55 secure boot?: YES Paniclog version: 1 Kernel slide: 0x000000000ce00000 Kernel text base: 0x8ce01000 Epoch Time: sec usec

 Boot    : 0x5db8b21e 0x00000000
 Sleep   : 0x00000000 0x00000000
 Wake    : 0x00000000 0x00000000
 Calendar: 0x5db8b233 0x00072300

Task 0x80036c20: 14320 pages, 118 threads: pid 0: kernel_task thread 0x80ac70a0 kernel backtrace: 8bdb3b40 lr: 0x8ce884d1 fp: 0x8bdb3b70 lr: 0x8ce88d6d fp: 0x8bdb3b9c lr: 0x8ce17ca7 fp: 0x8bdb3bb4 lr: 0x8d32f683 fp: 0x8bdb3d0c lr: 0x8d35da11 fp: 0x8bdb3d28 lr: 0x8d3572ef fp: 0x8bdb3d50 lr: 0x8d358eb5 fp: 0x8bdb3d64 lr: 0x8d356ccd fp: 0x8bdb3d90 lr: 0x8d356c53 fp: 0x8bdb3d9c lr: 0x8d05792f fp: 0x8bdb3dc4 lr: 0x8d32405d fp: 0x8bdb3dd8 lr: 0x8db1ec61 fp: 0x8bdb3dec lr: 0x8d32812d fp: 0x8bdb3e04 lr: 0x8d325b49 fp: 0x8bdb3e1c lr: 0x8d045ec1 fp: 0x8bdb3e54 lr: 0x8d046105 fp: 0x8bdb3e64 lr: 0x8d042f27 fp: 0x8bdb3e80 lr: 0x8d045fdd fp: 0x8bdb3e98 lr: 0x8d0460db fp: 0x8bdb3eb4 lr: 0x8d32ea89 fp: 0x8bdb3ed0 lr: 0x8d04fa75 fp: 0x8bdb3f50 lr: 0x8d04c09f fp: 0x8bdb3f68 lr: 0x8ce2fefd fp: 0x8bdb3fa8 lr: 0x8ce8655c fp: 0x00000000

Task 0x80036968: 266 pages, 3 threads: pid 1: launchd Task 0x800366b0: 310 pages, 1 threads: pid 2: launchctl Task 0x80035e88: 954 pages, 26 threads: pid 13: UserEventAgent Task 0x800363f8: 622 pages, 7 threads: pid 14: wifid Task 0x80036140: 583 pages, 6 threads: pid 15: awdd Task 0x80035bd0: 377 pages, 5 threads: pid 16: timed Task 0x80035660: 304 pages, 9 threads: pid 18: misd Task 0x800353a8: 404 pages, 3 threads: pid 19: mediaremoted Task 0x800350f0: 707 pages, 6 threads: pid 20: backupd Task 0x80034b80: 438 pages, 4 threads: pid 22: iaptransportd Task 0x800348c8: 697 pages, 5 threads: pid 23: ptpd Task 0x80034358: 236 pages, 4 threads: pid 25: softwareupdated Task 0x800340a0: 987 pages, 15 threads: pid 26: backboardd Task 0x80033b30: 207 pages, 4 threa

Sources

Oracle provides a list of some JDBC drivers and vendors
Simba Technologies ships an SDK for building custom JDBC Drivers for any custom/proprietary relational data source
CData Software ships type 4 JDBC Drivers for various applications, databases, and Web APIs.^[11]
RSSBus Type 4 JDBC Drivers for applications, databases, and web services^[12]
DataDirect Technologies provides a comprehensive suite of fast Type 4 JDBC drivers for all major database they advertise as Type 5^[13]
IDS Software provides a Type 3 JDBC driver for concurrent access to all major databases. Supported features include resultset caching, SSL encryption, custom data source, dbShield
JDBaccess is a Java persistence library for MySQL and Oracle which defines major database access operations in an easy usable API above JDBC
JNetDirect provides a suite of fully Sun J2EE certified high-performance JDBC drivers.
JDBCR4 is a service program written by Scott Klement to allow access to JDBC from RPG on the IBM i.^[14]
HSQLDB is a RDBMS with a JDBC driver and is available under a BSD license.
SchemaCrawler^[15] is an open source API that leverages JDBC, and makes database metadata available as plain old Java objects (POJOs)

References

^ Template:Cite web wrong
^ JDBC API Specification Version: 4.0.
^ "The Java Community Process(SM) Program - communityprocess - mrel". jcp.org. Retrieved 22 March 2018.
^ "JDBC 4.1". docs.oracle.com. Retrieved 22 March 2018.
^ "The Java Community Process(SM) Program - communityprocess - mrel". jcp.org. Retrieved 22 March 2018.
^ "JDBC 4.2". docs.oracle.com. Retrieved 22 March 2018.
^ "The Java Community Process(SM) Program - communityprocess - mrel". jcp.org. Retrieved 22 March 2018.
^ "java.sql (Java SE 9 & JDK 9)". docs.oracle.com. Retrieved 22 March 2018.
^ "Java JDBC API". docs.oracle.com. Retrieved 22 March 2018.
^ Greenwald, Rick; Stackowiak, Robert; Stern, Jonathan (1999). Oracle Essentials: Oracle Database 10g. Essentials Series (3 ed.). Sebastopol, California: O'Reilly Media, Inc. (published 2004). p. 318. ISBN 9780596005856. Retrieved 2016-11-03. The in-database JDBC driver (JDBC KPRB)[:] Java code uses the JDBC KPRB (Kernel Program Bundled) version to access SQL on the same server.
^ "JDBC Drivers - CData Software". CData Software. Retrieved 22 March 2018.
^ "JDBC Drivers - CData Software". CData Software. Retrieved 22 March 2018.
^ "New Type 5 JDBC Driver — DataDirect Connect".
^ "Access External Databases from RPG with JDBCR4 Meat of the Matter". 28 June 2012. Retrieved 12 April 2016.
^ Sualeh Fatehi. "SchemaCrawler". SourceForge.

External links

JDBC API Guide This documentation has examples where the JDBC resources are not closed appropriately (swallowing primary exceptions and being able to cause NullPointerExceptions) and has code prone to SQL injection^{[citation needed]}
java.sql API Javadoc documentation
javax.sql API Javadoc documentation
O/R Broker Scala JDBC framework
SqlTool Open source, command-line, generic JDBC client utility. Works with any JDBC-supporting database.
JDBC URL Strings and related information of All Databases.

[1] Template:Cite web wrong

[2] JDBC API Specification Version: 4.0.

[3] "The Java Community Process(SM) Program - communityprocess - mrel". jcp.org. Retrieved 22 March 2018.

[4] "JDBC 4.1". docs.oracle.com. Retrieved 22 March 2018.

[5] "The Java Community Process(SM) Program - communityprocess - mrel". jcp.org. Retrieved 22 March 2018.

[6] "JDBC 4.2". docs.oracle.com. Retrieved 22 March 2018.

[7] "The Java Community Process(SM) Program - communityprocess - mrel". jcp.org. Retrieved 22 March 2018.

[8] "java.sql (Java SE 9 & JDK 9)". docs.oracle.com. Retrieved 22 March 2018.

[9] "Java JDBC API". docs.oracle.com. Retrieved 22 March 2018.

[10] Greenwald, Rick; Stackowiak, Robert; Stern, Jonathan (1999). Oracle Essentials: Oracle Database 10g. Essentials Series (3 ed.). Sebastopol, California: O'Reilly Media, Inc. (published 2004). p. 318. ISBN 9780596005856. Retrieved 2016-11-03. The in-database JDBC driver (JDBC KPRB)[:] Java code uses the JDBC KPRB (Kernel Program Bundled) version to access SQL on the same server.

[11] "JDBC Drivers - CData Software". CData Software. Retrieved 22 March 2018.

[12] "JDBC Drivers - CData Software". CData Software. Retrieved 22 March 2018.

[datadirect-13] "New Type 5 JDBC Driver — DataDirect Connect".

[14] "Access External Databases from RPG with JDBCR4 Meat of the Matter". 28 June 2012. Retrieved 12 April 2016.

[schemacrawler-15] Sualeh Fatehi. "SchemaCrawler". SourceForge.

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