View source for Software:Java Database Connectivity

{{Short description|API for Java}}
{{Infobox software
|name = JDBC
|logo =
|caption =
|developer = Oracle Corporation
|latest release version = JDBC 4.3
|latest release date = {{Start date|2017|09|21}}
|latest preview version =
|latest preview date =
|operating system = Cross-platform
|genre = Data access API
|license =
|website = {{Javadoc:SE-guide|jdbc|JDBC API Guide}}
}}

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

==History and implementation==
[[Company:Sun Microsystems|Sun Microsystems]] released JDBC as part of [[Software:Java Development Kit|Java Development Kit]] (JDK) 1.1 on February 19, 1997.<ref>
{{cite web
| title       = Sun Ships JDK 1.1 -- Javabeans Included
| date        = 1997-02-19
| work        = www.sun.com
| publisher   = [[Company:Sun Microsystems|Sun Microsystems]]
| url       = http://www.sun.com/smi/Press/sunflash/1997-02/sunflash.970219.0001.xml
| archive-url = https://web.archive.org/web/20080210044125/http://www.sun.com/smi/Press/sunflash/1997-02/sunflash.970219.0001.xml
| url-status  = dead
| archive-date =2008-02-10
| access-date  = 2010-02-15
| quote       = February 19, 1997 - The JDK 1.1 [...] is now available [...]. This release of the JDK includes: [...] Robust new features including JDBC for database connectivity
}}
</ref>
Since then it has been part of the [[Java Platform, Standard Edition]] (Java SE).

The JDBC classes are contained in the [[Java package]] {{Javadoc:SE|package=java.sql|java/sql|module=java.sql}} and {{Javadoc:SE|package=javax.sql|javax/sql|module=java.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).<ref>[http://java.sun.com/products/jdbc/download.html#corespec40 JDBC API Specification Version: 4.0].</ref>

JDBC 4.1, is specified by a maintenance release 1 of JSR 221<ref>{{cite web|url=http://jcp.org/aboutJava/communityprocess/mrel/jsr221/index.html|title=The Java Community Process(SM) Program - communityprocess - mrel|website=jcp.org|access-date=22 March 2018}}</ref> and is included in Java SE 7.<ref>{{cite web|url=http://docs.oracle.com/javase/7/docs/technotes/guides/jdbc/jdbc_41.html|title=JDBC 4.1|website=docs.oracle.com|access-date=22 March 2018}}</ref>

JDBC 4.2, is specified by a maintenance release 2 of JSR 221<ref>{{cite web|url=https://jcp.org/aboutJava/communityprocess/mrel/jsr221/index2.html|title=The Java Community Process(SM) Program - communityprocess - mrel|website=jcp.org|access-date=22 March 2018}}</ref> and is included in Java SE 8.<ref>{{cite web|url=http://docs.oracle.com/javase/8/docs/technotes/guides/jdbc/jdbc_42.html|title=JDBC 4.2|website=docs.oracle.com|access-date=22 March 2018}}</ref>

The latest version, JDBC 4.3, is specified by a maintenance release 3 of JSR 221<ref>{{cite web|url=https://jcp.org/aboutJava/communityprocess/mrel/jsr221/index3.html|title=The Java Community Process(SM) Program - communityprocess - mrel|website=jcp.org|access-date=22 March 2018}}</ref> and is included in Java SE 9.<ref>{{cite web|url=http://docs.oracle.com/javase/9/docs/api/java/sql/package-summary.html|title=java.sql (Java SE 9 & JDK 9)|website=docs.oracle.com|access-date=22 March 2018}}</ref>

==Functionality==
{| class="wikitable floatright"
|+  Host database types which Java can convert to with a function
|-
! Oracle Datatype
! <code>setXXX()</code> Methods
|-
| CHAR
| <code>setString()</code>
|-
| VARCHAR2
| <code>setString()</code>
|-
|rowspan="8"| NUMBER
| <code>setBigDecimal()</code>
|-
| <code>setBoolean()</code>
|-
| <code>setByte()</code>
|-
| <code>setShort()</code>
|-
| <code>setInt()</code>
|-
| <code>setLong()</code>
|-
| <code>setFloat()</code>
|-
| <code>setDouble()</code>
|-
| INTEGER
| <code>setInt()</code>
|-
| FLOAT
| <code>setDouble()</code>
|-
| CLOB
| <code>setClob()</code>
|-
| BLOB
| <code>setBlob()</code>
|-
| RAW
| <code>setBytes()</code>
|-
| LONGRAW
| <code>setBytes()</code>
|-
|rowspan="3"| DATE
| <code>setDate()</code>
|-
| <code>setTime()</code>
|-
| <code>setTimestamp()</code>
|}

Since JDBC ('Java Database Connectivity') is mostly a collection of interface definitions and specifications, it allows multiple implementations of these interfaces to exist and be used by the same application at runtime. The API provides a mechanism for dynamically loading the correct Java packages and registering them with the JDBC Driver Manager ({{code|DriverManager}}). {{code|DriverManager}} is used as a {{java|Connection}} [[Factory (object-oriented programming)|factory]] for creating JDBC connections.

JDBC connections support creating and executing statements. JDBC connections support update statements such as SQL's CREATE, INSERT, UPDATE and DELETE, or query statements such as SELECT. Additionally, stored procedures may be invoked through a JDBC connection. JDBC represents statements using one of the following classes:
* {{Javadoc:SE|java/sql|Statement|module=java.sql}} &ndash; the {{java|Statement}} is sent to the database server each and every time. In other words, the {{java|Statement}} methods are executed using SQL statements to obtain a {{code|ResultSet}} object containing the data.{{sfn | Bai | 2022 | p=74}}
* {{Javadoc:SE|java/sql|PreparedStatement|module=java.sql}} &ndash; {{code|PreparedStatement}} is a subinterface of the {{code|Statement}} interface.{{sfn | Bai | 2022 | p=74}} The statement is cached and then the [[Query plan|execution path]] is pre-determined on the database server, allowing it to be executed multiple times in an efficient manner.{{sfn | Bai | 2022 | p=74}} {{code|PreparedStatement}} is used to execute pre-compiled SQL statements.{{sfn | Bai | 2022 | p=74}} Running pre-compiled statements increases statement execution efficiency and performance. The {{code|PreparedStatement}} is often used for dynamic statement where some input parameters must be passed into the target database.{{sfn | Bai | 2022 | loc=§4.2.3.5 More About the Execution Methods | pp=122-124}} The 
{{code|PreparedStatement}} allows the dynamic query to vary depending on the query parameter.{{sfn | Bai | 2022 | loc= §3.2 JDBC Components and Architecture | pp=72-74}} 
* {{Javadoc:SE|java/sql|CallableStatement|module=java.sql}} &ndash; {{code|CallableStatement}} is a subinterface of the {{code|Statement}} interface.{{sfn | Bai | 2022 | loc= §3.2 JDBC Components and Architecture | pp=72-74}} It is used for executing stored procedures on the database.{{sfn | Bai | 2022 | loc= §3.2 JDBC Components and Architecture | pp=72-74}}{{sfn | Horstmann | 2022 | loc=§5.5.3 SQL Escapes}} Both input and output parameters must be passed into the database for stored procedures.{{sfn | Bai | 2022 | loc= §4.2.3.5 JDBC Components and Architecture | pp=122-124}}

Update statements such as INSERT, UPDATE and DELETE return an update count indicating the number of [[Software:Row (database)|rows]] affected in the database as an integer.{{sfn | Bai | 2022 | loc= §4.2.3.5 JDBC Components and Architecture | pp=122-124}} 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|result set]]. Individual [[Software:Column (database)|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 {{Javadoc|module=java.sql|package=javax.sql|monotype=y}}.

JDBC connections are often managed via a [[Software:Connection pool|connection pool]] rather than obtained directly from the driver.{{sfn | Bai | 2022 | loc=§3.5.1 JDBC DataSource | p=83}}

==Examples==

When a Java application needs a database connection, one of the <code>DriverManager.getConnection()</code> methods is used to create a JDBC {{java|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.

<source lang="java">
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);
    }
}
</source>

Starting from Java SE 7 you can use Java's [http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html try-with-resources] statement to simplify the above code:
<source lang="java">
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
</source>

Once a connection is established, a {{java|Statement}} can be created.

<source lang="java">
try (Statement stmt = conn.createStatement()) {
    stmt.executeUpdate("INSERT INTO MyTable(name) VALUES ('my name')");
}
</source>

Note that {{java|Connection}}s, {{java|Statement}}s, and {{java|ResultSet}}s often tie up [[Operating system|operating system]] resources such as sockets or [[File descriptor|file descriptor]]s. In the case of {{java|Connection}}s to remote database servers, further resources are tied up on the server, e.g. [[Cursor (databases)|cursors]] for currently open {{java|ResultSet}}s.
It is vital to <code>close()</code> any JDBC object as soon as it has played its part;
[[Garbage collection (computer science)|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.

<source lang="java">
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));
        }
    }
}
</source>

The following code is an example of a <code>PreparedStatement</code> query which uses <code>conn</code> and class from the first example:

<source lang="java">
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
</source>

If a database operation fails, JDBC raises an {{Javadoc:SE|java/sql|SQLException|module=java.sql}}. 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 {{code|SQLException}} be translated into an application domain exception (an unchecked one) that eventually results in a transaction rollback and a notification to the user.

The following code is an example of a [[Database transaction|database transaction]]:
<source lang="java">
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); }
}
</source>

For an example of a <code>CallableStatement</code> (to call stored procedures in the database), see the {{Javadoc:SE-guide|jdbc/getstart/callablestatement.html|JDBC API Guide}} documentation.

<source lang="java">
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', 'kiril', 'john', 968666668)";
        stmt.executeUpdate(sql);
           
        System.out.println("Inserted records into the table...");
      } catch (Exception e) {
        e.printStackTrace();
      }
   }
}
</source>

==JDBC drivers==
{{Main | JDBC driver}}

JDBC drivers are client-side [[Adapter pattern|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:

* [[JDBC driver#Type 1 Driver - JDBC-ODBC bridge|Type 1]] that calls native code of the locally available ODBC driver. (Note: In JDBC 4.2, JDBC-ODBC bridge has been removed<ref>{{cite web|url=https://docs.oracle.com/javase/8/docs/technotes/guides/jdbc/|title=Java JDBC API|website=docs.oracle.com|access-date=22 March 2018}}</ref>)
* [[JDBC driver#Type 2 Driver - Native-API Driver|Type 2]] that calls database vendor native library on a client side. This code then talks to database over the network.
* [[JDBC driver#Type 3 Driver - Network-Protocol Driver(MiddleWare Driver)|Type 3]], the pure-java driver that talks with the server-side middleware that then talks to the database.
* [[JDBC driver#Type 4 Driver - Database-Protocol Driver(Pure Java Driver)|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<ref>
{{cite book
| last1 = Greenwald
| first1 = Rick
| last2 = Stackowiak
| first2 = Robert
| last3 = Stern
| first3 = Jonathan
| year = 1999
| title = Oracle Essentials: Oracle Database 10g
| url = https://books.google.com/books?id=CTebAgAAQBAJ
| series = Essentials Series
| edition = 3
| location = Sebastopol, California
| publisher = O'Reilly Media, Inc.
| publication-date = 2004
| page = 318
| isbn = 9780596005856
| access-date = 2016-11-03
| quote = ''The in-database JDBC driver (JDBC KPRB)''[:] Java code uses the JDBC KPRB (Kernel Program Bundled) version to access SQL on the same server.
}}
</ref>
supplied with [[Software:Oracle Database|Oracle RDBMS]]. "jdbc:default:connection" offers a relatively standard way of making such a connection (at least the Oracle database and [[Software:Apache Derby|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.

===Sources===
* [[Company:Oracle Corporation|Oracle]] provides a [http://www.oracle.com/technetwork/java/index-136695.html 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.<ref>{{cite web|url=http://www.cdata.com/jdbc/|title=JDBC Drivers - CData Software|website=CData Software|access-date=22 March 2018}}</ref>
* RSSBus Type 4 JDBC Drivers for applications, databases, and web services<ref>{{cite web|url=http://www.rssbus.com/jdbc/|title=JDBC Drivers - CData Software|website=CData Software|access-date=22 March 2018}}</ref>
* DataDirect Technologies provides a comprehensive suite of fast Type 4 JDBC drivers for all major database they advertise as Type 5<ref name=datadirect>{{cite web
| url=http://www.datadirect.com/products/features/data-connectivity/type-5-jdbc/index.html
| title=New Type 5 JDBC Driver&nbsp;— DataDirect Connect
}}</ref>
* 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 [[Software:MySQL|MySQL]] and [[Software:Oracle database|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 [[Biography:Scott Klement|Scott Klement]] to allow access to JDBC from [[IBM RPG|RPG]] on the [[Software:IBM i|IBM i]].<ref>{{cite web|title=Access External Databases from RPG with JDBCR4 Meat of the Matter|url=http://iprodeveloper.com/rpg-programming/access-external-databases-rpg-jdbcr4|access-date=12 April 2016|date=28 June 2012}}</ref>
* [[Software:HSQLDB|HSQLDB]] is a [[Software:Relational database management system|RDBMS]] with a JDBC driver and is available under a BSD license.
* SchemaCrawler<ref name=schemacrawler>{{cite web
| author=Sualeh Fatehi
| url=https://github.com/schemacrawler/SchemaCrawler
| title=SchemaCrawler
| work=GitHub
}}</ref> is an open source API that leverages JDBC, and makes database metadata available as plain old Java objects (POJOs)

==See also==
* GNU Data Access (GDA)
* [[Software:JDBCFacade|JDBCFacade]]
* [[Open Database Connectivity]] (ODBC)
* [[Object–relational mapping]] (ORM)

== Citations ==
{{reflist}}

== References ==
* {{cite book | last=Bai | first=Ying | title=SQL Server Database Programming with Java | publisher=Springer International Publishing | publication-place=Cham | year=2022 | isbn=978-3-030-92686-1 | doi=10.1007/978-3-031-06553-8}}
* {{cite book | last=Horstmann | first=Cay | title=Core Java | publisher=Oracle Press Java | date=April 15, 2022 | isbn=0-13-787107-4}}

==External links==
* {{Javadoc:SE-guide|jdbc|JDBC API Guide}}
* {{Javadoc:SE|package=java.sql|java/sql|module=java.sql}} API [[Software:Javadoc|Javadoc]] documentation
* {{Javadoc:SE|package=javax.sql|javax/sql|module=java.sql}} API Javadoc documentation
* [https://web.archive.org/web/20160111210342/http://orbroker.org/ O/R Broker] Scala JDBC framework
* [http://www.hsqldb.org/doc/2.0/util-guide/sqltool-chapt.html SqlTool] Open source, command-line, generic JDBC client utility. Works with any JDBC-supporting database.
* [http://codeoftheday.blogspot.com/2012/12/java-database-connectivity-jdbc-url.html JDBC URL Strings and related information of All Databases.]

{{DEFAULTSORT:Database Connectivity}}
[[Category:Java specification requests]]
[[Category:SQL data access]]

{{Sourceattribution|Java Database Connectivity}}