Java Database Connectivity (JDBC) is anapplication programming interface (API) for theJava programming language which defines how a client may access adatabase. It is a Java-based data access technology used for Java database connectivity. It is part of theJava Standard Edition platform, fromOracle Corporation. It provides methods to query and update data in a database, and is oriented towardrelational databases. A JDBC-to-ODBC bridge enables connections to any ODBC-accessible data source in theJava virtual machine (JVM) host environment.
| Developer(s) | Oracle Corporation |
|---|---|
| Stable release | JDBC 4.3 / September 21, 2017 (2017-09-21) |
| Operating system | Cross-platform |
| Type | Data access API |
| Website | JDBC API Guide |
Sun Microsystems released JDBC as part ofJava Development Kit (JDK) 1.1 on February 19, 1997.[1]Since then it has been part of theJava Platform, Standard Edition (Java SE).
The JDBC classes are contained in theJava packagejava.sql andjavax.sql.
Starting with version 3.1, JDBC has been developed under theJava 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]
| JDBC version | Java version | Release Type | Release date |
|---|---|---|---|
| 1.1 | JDK 1.1 | Main | 1997-02-19.[1] |
| 3.0 | J2SE 1.4 | Main | 2002-05-09 |
| 4.0 | Java SE 6 | Main | 2006-12-11 |
| 4.1 | Java SE 7 | Maintenance | 2011-10-13 |
| 4.2 | Java SE 8 | Maintenance | 2014-03-04 |
| 4.3 | Java SE 9 | Maintenance | 2017-09-21 |
| 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() |
Since JDBC 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 (DriverManager).DriverManager is used as aConnectionfactory for creating JDBC connections.
JDBC connections support creating and executing statements. JDBC connections support update statements such as SQL'sCREATE,INSERT,UPDATE andDELETE, or query statements such asSELECT. Additionally, stored procedures may be invoked through a JDBC connection. JDBC represents statements using one of the following classes:
Statement – theStatement is sent to the database server each and every time. In other words, theStatement methods are executed using SQL statements to obtain aResultSet object containing the data.[9]PreparedStatement –PreparedStatement is a subinterface of theStatement interface.[9] The statement is cached and then theexecution path is pre-determined on the database server, allowing it to be executed multiple times in an efficient manner.[9]PreparedStatement is used to execute pre-compiled SQL statements.[9] Running pre-compiled statements increases statement execution efficiency and performance. ThePreparedStatement is often used for dynamic statement where some input parameters must be passed into the target database.[10] ThePreparedStatement allows the dynamic query to vary depending on the query parameter.[11]
CallableStatement –CallableStatement is a subinterface of theStatement interface.[11] It is used for executingstored procedures on the database.[11][12] Both input and output parameters must be passed into the database for stored procedures.[13]Update statements such as INSERT, UPDATE and DELETE return an update count indicating the number ofrows affected in the database as an integer.[13] 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 theresult set. Individualcolumns 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 thejavax.sql.
JDBC connections are often managed via aconnection pool rather than obtained directly from the driver.[14]
When a Java application needs a database connection, one of theDriverManager.getConnection() methods is used to create a JDBCConnection. 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.
Connectionconn=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 ittry{conn.close();}catch(Throwablee){/* 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'stry-with-resources statement to simplify the above code:
try(Connectionconn=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, aStatement can be created.
try(Statementstmt=conn.createStatement()){stmt.executeUpdate("INSERT INTO MyTable(name) VALUES ('my name')");}
Note thatConnections,Statements, andResultSets often tie upoperating system resources such as sockets orfile descriptors. In the case ofConnections to remote database servers, further resources are tied up on the server, e.g.cursors for currently openResultSets.It is vital toclose() 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(Statementstmt=conn.createStatement();ResultSetrs=stmt.executeQuery("SELECT * FROM MyTable")){while(rs.next()){intnumColumns=rs.getMetaData().getColumnCount();for(inti=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));}}}
The following code is an example of aPreparedStatement query which usesconn and class from the first example:
try(PreparedStatementps=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(ResultSetrs=ps.executeQuery()){while(rs.next()){intnumColumns=rs.getMetaData().getColumnCount();for(inti=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 anSQLException. 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 theSQLException 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 adatabase transaction:
booleanautoCommitDefault=conn.getAutoCommit();try{conn.setAutoCommit(false);/* You execute statements against conn here transactionally */conn.commit();}catch(Throwablee){try{conn.rollback();}catch(Throwablee){logger.warn("Could not rollback transaction",e);}throwe;}finally{try{conn.setAutoCommit(autoCommitDefault);}catch(Throwablee){logger.warn("Could not restore AutoCommit setting",e);}}
For an example of aCallableStatement (to call stored procedures in the database), see theJDBC API Guide documentation.
importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.Statement;publicclassMydb1{staticStringURL="jdbc:mysql://localhost/mydb";publicstaticvoidmain(String[]args){try{Class.forName("com.mysql.jdbc.Driver");Connectionconn=DriverManager.getConnection(URL,"root","root");Statementstmt=conn.createStatement();Stringsql="INSERT INTO emp1 VALUES ('pctb5361', 'kiril', 'john', 968666668)";stmt.executeUpdate(sql);System.out.println("Inserted records into the table...");}catch(Exceptione){e.printStackTrace();}}}
JDBC drivers are client-sideadapters (installed on the client machine, not on the server) that convert requests from Java programs to a protocol that the DBMS can understand.
Commercial and free drivers provide connectivity to most relational-database servers. These drivers fall into one of the following types:
Note also a type called aninternal JDBC driver - a driver embedded withJRE in Java-enabled SQL databases. It is used forJava 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[16]supplied withOracle RDBMS. "jdbc:default:connection" offers a relatively standard way of making such a connection (at least the Oracle database andApache 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.
February 19, 1997 - The JDK 1.1 [...] is now available [...]. This release of the JDK includes: [...] Robust new features including JDBC for database connectivity
The in-database JDBC driver (JDBC KPRB)[:] Java code uses the JDBC KPRB (Kernel Program Bundled) version to access SQL on the same server.
java.sql APIJavadoc documentationjavax.sql API Javadoc documentation