Java Database Connectivity

Transcription

1 Java Database Connectivity PROGRAMMING Dr. Syed Imtiyaz Hassan Assistant Professor, Deptt. of CSE, Jamia Hamdard (Deemed to be University), New Delhi, India.

2 Agenda PreparedStatement Batch Updates Transactions DatabaseMetaData ResultSetMetaData Summary References

3 PreparedStatement Holds precompiled SQL statements. Use when you want to execute more than once. Can contain variables that you supply each time you execute the statement.

4 PreparedStatement (cont.)

5 PreparedStatement (cont.) Create PreparedStatement pstmt = con.preparestatement("update STUDENTS set stdname =? where ID =?"); PreparedStatement pstmt = con.preparestatement("select * from STUDENTS where ID =?");

6 PreparedStatement (cont.) 1. Bind the variables. pstmt.setxxx(index, value); 2. Execute the statement. pstmt.executequery(); pstmt.executeupdate(); PreparedStatement pstmt = con.preparestatement("update STUDENTS set stdname =? where ID =?"); pstmt.setstring(1, AAA"); pstmt.setint(2, 15); pstmt.executeupdate();

7 PreparedStatement Program package advancedjava.jdbc; import java.sql.*; public class PreparedStatementClass { public static void main(string[] args) { try { Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/students"; Connection con = DriverManager.getConnection(url, "root", "password"); PreparedStatement pstmt = con.preparestatement ("select * from btcse WHERE enrollment_number =?"); Scanner sc = new Scanner(System.in); System.out.print("Enter Your Enrollment Number"); String enroll = sc.next(); pstmt.setstring(1, enroll); ResultSet rs = pstmt.executequery(); while (rs.next()) System.out.println(rs.getString(1) + "," + rs.getstring(2)); pstmt.close(); con.close(); catch (Exception e) { e.printstacktrace();

8 Batch Updates Grouping multiple UPDATE, DELETE, or INSERT statements into a single "batch. Performance improvement because of reducing round trip. Execute batch updates Using a Statement Using a PreparedStatement

9 Batch Updates (cont.) Add statement to the batch using addbatch() method stmt.addbatch("insert INTO btcse VALUES('33','cc', 'B')"); stmt.addbatch("insert INTO btcse VALUES('44','dd', 'C')"); Execute the batch using an executebatch() method int[] counts = stmt.executebatch();

10 Batch Updates Program package advancedjava.jdbc; import java.sql.*; public class BatchUpdateClass { public static void main(string argv[]) { try { Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/students"; Connection con = DriverManager.getConnection(url,"root", "password"); Statement stmt = con.createstatement(); stmt.addbatch("insert INTO btcse VALUES('33','cc', 'A')"); stmt.addbatch("insert INTO btcse VALUES('44','dd', 'B')"); int[] counts = stmt.executebatch(); System.out.println("Record Inserted"); con.close(); catch (Exception e) { System.out.println("** Error on data select. ** " + e); Program BatchUpdateWithPr eparedclass.java

11 Transaction A transaction is a set of one or more statements that is executed as a unit either all of the statements are executed, or none of the statements is executed When a connection is created, it is in auto-commit mode. Disabling Auto-Commit Mode con.setautocommit(false); Commit/Rollback Explicitly con.commit(); con.rollback();

12 Transaction Program package advancedjava.jdbc; import java.sql.*; public class TransactionClass { public static void main(string argv[]) { try { Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/students"; Connection con = DriverManager.getConnection(url, "root", "password"); Statement stmt = con.createstatement(); con.setautocommit(false); String sql; try { sql = "update btcse set student_name='abc' where enrollment_number='33'"; int r = stmt.executeupdate(sql); sql = "update btcse set student_name='xyz' where enrollment_number='44'"; r = stmt.executeupdate(sql); con.commit(); System.out.println("Record Updated"); catch (SQLException se) { con.rollback(); System.out.println("Record Not Inserted"); con.setautocommit(true); con.close(); catch (Exception e) { System.out.println("** Error on data select. ** " + e);

13 DatabaseMetaData Comprehensive information about the database as a whole. Database Product Name and Version Database Driver Version Listing Tables Listing Columns in a Table Primary Key for Table etc

14 DatabaseMetaData (cont.) 1. Get the DatabaseMetaData object. DatabaseMetaData dbmd = con.getmetadata(); 2. Use the object s methods to get the metadata. dbmd.getdrivername(); dbmd.getdriverversion(); dbmd.getusername(); dbmd.getdatabaseproductname(); dbmd.getdatabaseproductversion(); dbmd.geturl();

15 package advancedjava.jdbc; import java.sql.*; DatabaseMetaData Program public class DatabaseMetaDataClass { public static void main(string argv[]) { try { Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/students"; Connection con = DriverManager.getConnection(url, "root", "password"); DatabaseMetaData dbmd = con.getmetadata(); System.out.println("Driver Name: " + dbmd.getdrivername()); System.out.println("Driver Version: " + dbmd.getdriverversion()); System.out.println("UserName: " + dbmd.getusername()); System.out.println("Database Product Name: " + dbmd.getdatabaseproductname()); System.out.println("Database Product Version: " + dbmd.getdatabaseproductversion()); System.out.println("Database: " + dbmd.geturl()); con.close(); catch (Exception e) { e.printstacktrace(); Program DatabaseMeta DataTableClass

16 ResultSetMetaData used to get information about the types and properties of the columns in a ResultSet object Information ResultSetMetaData rsmd = rs.getmetadata(); Number of columns Column type Column name int ncols=rsmd.getcolumncount(); String colname = rsmd.getcolumnname(int column); int coltype = rsmd.getcolumntype(int column);

17 ResultSetMetaData Program package advancedjava.jdbc; import java.sql.*; public class ResultsetMetaDataClass { public static void main(string argv[]) { try { Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/students"; Connection con = DriverManager.getConnection(url, "root", "password"); String sql = "select * from BTCSE"; Statement stmt = con.createstatement(); ResultSet rs = stmt.executequery(sql); ResultSetMetaData rsmd = rs.getmetadata(); int col = rsmd.getcolumncount(); for (int n = 1; n <= col; n++) System.out.print(rsmd.getColumnName(n) + "\t"); System.out.println(""); while (rs.next()) { System.out.println(rs.getString(1) + "\t" + rs.getstring(2) + "\t" + rs.getstring(3)); catch (Exception e) { System.out.println("** Error on data select. ** " + e);

18 Summary PreparedStatement Performace Enhancement Batch Updates Grouping multiple transactions Transactions Atomicity of ACID DatabaseMetaData Getting comprehensive information of Database ResultSetMetaData Getting types and properties of the columns in a ResultSet

19 References JDBC Basics