 1992-2007 Pearson Education, Inc. All rights reserved. 1 25 Accessing Databases with JDBC.

 1992-2007 Pearson Education, Inc. All rights reserved. 2 OBJECTIVES In this chapter you will learn:  Relational database concepts.  To use Structured Query Language (SQL) to retrieve data from and manipulate data in a database.  To use the JDBC™ API of package java.sql to access databases.  To use the RowSet interface from package javax.sql to manipulate databases.  To use JDBC 4.0’s automatic JDBC driver discovery.  To use PreparedStatement s to create precompiled SQL statements with parameters.  How transaction processing makes database applications more robust.

 1992-2007 Pearson Education, Inc. All rights reserved. 3 25.1Introduction 25.2Relational Databases 25.3Relational Database Overview: The books Database 25.4SQL 25.4.1 Basic SELECT Query 25.4.2 WHERE Claus 25.4.3 ORDER BY Claus 25.4.4Merging Data from Multiple Tables: INNER JOIN 25.4.5 INSERT Statement 25.4.6 UPDATE Statement 25.4.7 DELETE Statement 25.5Instructions for installing MySQL and MySQL Connector/J

 1992-2007 Pearson Education, Inc. All rights reserved. 4 25.6Instructions for Setting Up a MySQL User Account 25.7 Creating Database book in MySQL 25.8 Manipulating Databases with JDBC 25.8.1 Connecting to and Querying a Database 25.8.2 Querying the books Database 25.9 RowSet Interface 25.10 Java DB/Apache Derby 25.11 PreparedStatement s 25.12 Stored Procedures 25.13 Transaction Processing 25.14 Wrap-Up 25.15 Web Resources and Recommended Readings

 1992-2007 Pearson Education, Inc. All rights reserved. 5 25.1 Introduction  Database – Collection of data  DBMS – Database management system – Storing and organizing data  SQL – Relational database – Structured Query Language

 1992-2007 Pearson Education, Inc. All rights reserved. 6 25.1 Introduction (Cont.)  RDBMS – Relational database management system – MySQL - Open source - Available for both Windows and Linux - dev.mysql.com/downloads/mysql/4.0.hml  JDBC – Java Database Connectivity – JDBC driver - Enable Java applications to connect to database - Enable programmers to manipulate databases using JDBC

 1992-2007 Pearson Education, Inc. All rights reserved. 7 Software Engineering Observation 25.1 Using the JDBC API enables developers to change the underlying DBMS without modifying the Java code that accesses the database.

 2005 Pearson Education, Inc. All rights reserved. 8 25.2 Relational Databases Relational database – Table Rows, columns – Primary key Unique data SQL queries – Specify which data to select from a table

 2005 Pearson Education, Inc. All rights reserved. 11 25.3 Relational Database Overview: The books Database Sample books database – Four tables authors – authorID, firstName, lastName titles – isbn, title, editionNumber, copyright, publisherID, imageFile, price authorISBN – authorID, isbn

 2005 Pearson Education, Inc. All rights reserved. 14 25.3 Relational Database Overview: The books Database (Cont.) Foreign key – A column matches the primary key column in another table – Helps maintain the Rule of Referential Integrity Every foreign key value must appear as another table’s primary key value

 2005 Pearson Education, Inc. All rights reserved. 19 25.3 Relational Database Overview: The books Database (Cont.) Entity-relationship (ER) diagram – Tables in the database – Relationships among tables Rule of Entity Integrity – Primary key uniquely identifies each row – Every row must have a value for every column of the primary key – Value of the primary key must be unique in the table

 1992-2007 Pearson Education, Inc. All rights reserved. 21 Common Programming Error 25.1 Not providing a value for every column in a primary key breaks the Rule of Entity Integrity and causes the DBMS to report an error.

 1992-2007 Pearson Education, Inc. All rights reserved. 23 Common Programming Error 25.3 Providing a foreign-key value that does not appear as a primary-key value in another table breaks the Rule of Referential Integrity and causes the DBMS to report an error.

 2005 Pearson Education, Inc. All rights reserved. 26 25.4.1 Basic SELECT Query Simplest format of a SELECT query – SELECT * FROM tableName SELECT * FROM authors Select specific fields from a table – SELECT authorID, lastName FROM authors

 1992-2007 Pearson Education, Inc. All rights reserved. 28 Software Engineering Observation 25.2 For most queries, the asterisk ( * ) should not be used to specify column names. In general, you process results by knowing in advance the order of the columns in the result—for example, selecting authorID and lastName from table authors ensures that the columns will appear in the result with authorID as the first column and lastName as the second column. Programs typically process result columns by specifying the column number in the result (starting from number 1 for the first column). Selecting columns by name also avoids returning unneeded columns and protects against changes in the actual order of the columns in the table(s).

 1992-2007 Pearson Education, Inc. All rights reserved. 29 Common Programming Error 25.4 If you assume that the columns are always returned in the same order from a query that uses the asterisk ( * ), the program may process the results incorrectly. If the column order in the table(s) changes or if additional columns are added at a later time, the order of the columns in the result would change accordingly.

 2005 Pearson Education, Inc. All rights reserved. 30 25.4.2 WHERE Clause specify the selection criteria – SELECT columnName1, columnName2, … FROM tableName WHERE criteria SELECT title, editionNumber, copyright FROM titles WHERE copyright > 2002

 1992-2007 Pearson Education, Inc. All rights reserved. 31 Portability Tip 25.1 See the documentation for your database system to determine whether SQL is case sensitive on your system and to determine the syntax for SQL keywords (i.e., should they be all uppercase letters, all lowercase letters or some combination of the two?).

 2005 Pearson Education, Inc. All rights reserved. 33 25.4.2 WHERE Clause (Cont.) WHERE clause condition operators –, =, =, <> – LIKE wildcard characters % and _ SELECT authorID, firstName, lastName FROM authors WHERE lastName LIKE ‘D%’

 1992-2007 Pearson Education, Inc. All rights reserved. 35 Portability Tip 25.2 Read your database system’s documentation carefully to determine whether your system supports the LIKE operator. The SQL we discuss is supported by most RDBMSs, but it is always a good idea to check the features of SQL that are supported by your RDBMS.

 2005 Pearson Education, Inc. All rights reserved. 38 25.4.3 ORDER BY Clause Optional ORDER BY clause – SELECT columnName1, columnName2, … FROM tableName ORDER BY column ASC SELECT authorID, firstName, lastName FROM authors ORDER BY lastName ASC – SELECT columnName1, columnName2, … FROM tableName ORDER BY column DESC SELECT authorID, firstName, lastName FROM authors ORDER BY lastName DESC

 2005 Pearson Education, Inc. All rights reserved. 41 25.4.3 ORDER BY Clause (Cont.) ORDER BY multiple fields – ORDER BY column1 sortingOrder, column2 sortingOrder, … SELECT authorID, firstName, lastName FROM authors ORDER BY lastName, firstName

 2005 Pearson Education, Inc. All rights reserved. 43 25.4.3 ORDER BY Clause (Cont.) Combine the WHERE and ORDER BY clauses SELECT isbn, title, editionNumber, copyright, price FROM titles WHERE title LIKE ‘%How to Program’ ORDER BY title ASC

 2005 Pearson Education, Inc. All rights reserved. 45 25.4.4 Merging Data from Multiple Tables: INNER JOIN Split related data into separate tables Join the tables – Merge data from multiple tables into a single view – INNER JOIN SELECT columnName1, columnName2, … FROM table1 INNER JOIN table2 ON table1.columnName = table2.column2Name SELECT firstName, lastName, isbn FROM authors, authorISBN INNER JOIN authorISBN ON authors.authorID = authorISBN.authorID ORDER BY lastName, firstName

 1992-2007 Pearson Education, Inc. All rights reserved. 47 Software Engineering Observation 25.3 If a SQL statement includes columns with the same name from multiple tables, the statement must precede those column names with their table names and a dot (e.g., authors.authorID ).

 2005 Pearson Education, Inc. All rights reserved. 49 25.4.5 INSERT Statement Insert a row into a table – INSERT INTO tableName ( columnName1, …, columnNameN ) VALUES ( value1, …, valueN ) INSERT INTO authors ( firstName, lastName ) VALUES ( ‘Sue’, ‘Smith’ )

 1992-2007 Pearson Education, Inc. All rights reserved. 52 Common Programming Error 25.7 SQL uses the single-quote ( ' ) character as a delimiter for strings. To specify a string containing a single quote (e.g., O’Malley) in a SQL statement, the string must have two single quotes in the position where the single-quote character appears in the string (e.g., 'O''Malley' ). The first of the two single-quote characters acts as an escape character for the second. Not escaping single-quote characters in a string that is part of a SQL statement is a SQL syntax error.

 2005 Pearson Education, Inc. All rights reserved. 53 25.4.6 UPDATE Statement Modify data in a table – UPDATE tableName SET columnName1 = value1, …, columnNameN = valueN WHERE criteria UPDATE authors SET lastName = ‘Jones’ WHERE lastName = ‘Smith’ AND firstName = ‘Sue’

 2005 Pearson Education, Inc. All rights reserved. 55 25.4.7 DELETE Statement Remove data from a table – DELETE FROM tableName WHERE criteria DELETE FROM authors WHERE lastName = ‘Jones’ AND firstName = ‘Sue’

 2005 Pearson Education, Inc. All rights reserved. 57 25.5 Instructions to Install MySQL and MySQL Connector/J Install MySQL – Platform-specific installation requirements: dev.mysql.com/doc/refman/5.0/en/general- installation-issues.html – Download your platform’s installer from: dev.mysql.com/downloads/mysql/5.0.html Need only the Windows Essentials package on Microsoft Windows – Follow installation instructions for your platform: dev.mysql.com/doc/refman/5.0/en/installing. html

 2005 Pearson Education, Inc. All rights reserved. 58 25.5 Instructions to Install MySQL and MySQL Connector/J MySQL Server Instance Configuration Wizard – Click Next > then select Standard Configuration and click Next > again. – Not necessary to install MySQL as a Windows service for our examples Uncheck Install as a Windows Service Check Include Bin Directory in Windows PATH – Click Next > then click Execute to perform the server configuration. – Click Finish to close the wizard.

 2005 Pearson Education, Inc. All rights reserved. 59 25.5 Instructions to Install MySQL and MySQL Connector/J Install MySQL Connector/J – Must install Connector/J JDBC driver from: dev.mysql.com/downloads/connector/j/ 5.0.html – Download mysql-connector-java-5.0.4.zip – Extract mysql-connector-java-5.0.4.zip to your hard disk into the folder mysql-connector-java-5.0.4 – Documentation for MySQL Connector/J is in connector-j.pdf in the docs subdirectory of mysql-connector-java-5.0.4 – Docs also online at dev.mysql.com/doc/connector/j/en/ connector-j.html

 2005 Pearson Education, Inc. All rights reserved. 60 25.6 Instructions on Setting MySQL User Account Set up a user account – Start database server mysqld-nt.exe on Windows – Start the MySQL monitor mysql –h localhost –u root – Select the built-in database mysql USE mysql; – Add the user account jhtp7 and specify privileges create user 'jhtp7'@'localhost' identified by 'jhtp7'; grant select, insert, update, delete, create, drop, references, execute on *.* to 'jhtp7'@'localhost'; – Exit the MySQL Monitor exit;

 2005 Pearson Education, Inc. All rights reserved. 61 25.7 Creating Database books in MySQL Create books database – Open Command Prompt and change to the directory containing the SQL script books.sql – Start the MySQL monitor mysql –h localhost –u jhtp7 –p – Execute the script source books.sql; – Exit the MySQL Monitor exit;

 2005 Pearson Education, Inc. All rights reserved. 63 25.8.1 Connecting to and Querying a Database DisplayAuthors – Retrieves the entire authors table – Displays the data in the standard output stream – Example illustrates Connect to the database Query the database Process the result

 2005 Pearson Education, Inc. All rights reserved. 64 25.8.1 Connecting to and Querying a Database JDBC – Java Database Connectivity – JDBC driver Enable Java applications to connect to database Enable programmers to manipulate databases using JDBC – Execute SQL statements – Retrieve results – Present data in a user frendly interface – Propagete changes back to database – JDBC API Classes and interfaces -

 2005 Pearson Education, Inc. All rights reserved. 65 25.8.1 Connecting to and Querying a Database JDBC API – Establishing connections with databases – Sending SQL statements to databases – Processing the results of the SQL statements – Obtaining database metadata Four key interfaces: – Driver, Connection, Statement, ResultSet – JDBC API define these interfaces – JDBC driver vendors provide implementations for them – Programmers use the interfaces

 2005 Pearson Education, Inc. All rights reserved. 66 25.8.1 Connecting to and Querying a Database Following steps – Loading drivers – Establishing connections – Creating statements – Executing statements – Obtain metadata – Processing resultSet

 2005 Pearson Education, Inc. All rights reserved. 67 Loading Drivers Appropriate driver must be loaded – Class.forName(String DriverClassName); – Drivers are concrete classes that imlement Java.sql.Driver – interface For Access databases Driver: sun.jdbc.odbc.JdbcOdbcDriver – in JDK After Jav a 6 automatically found and loaded

 2005 Pearson Education, Inc. All rights reserved. 68 Establishing connections To connected to the database use static method – getConnection(String databseuRL) – Of the DriverManager class Where databaseURL is the unique identiier of the database on the internet

 2005 Pearson Education, Inc. All rights reserved. 69 Establishing connections For Access databases databaseURL: – Jdbc:odbc:datasource – An ODBC datasource canbe created using ODBC Administrator of Windows Exaaple: Connection connection = DriverManager.getConnections(databaseURL,userName, passpard); Connection connection = DriverManager.getConnections(“jdbc:odbc:Personel”,””, ””);

 2005 Pearson Education, Inc. All rights reserved. 70 Creating statements Once a connection object is created – in previous slide : connection Statement statement = connection.createStatement(); createStatement method of Connection class is invoked on the connection object Returns a Statement object on which queries can be executed

 2005 Pearson Education, Inc. All rights reserved. 71 Creating statements Executing queries: – Use executeQuery, execıte or executeUpdate – Methods of the Statement class on the statement object – ExecuteQuery returns a resultSet object – Methods of Statemet on a statement object Examples: – statement.executeQuery(“SELECT name from autors”); – On the statement object executeOuery method is inovked sending the SQL query as a String

 2005 Pearson Education, Inc. All rights reserved. 73 Example The first example queries a simple databes – An Access database – ODBC source name Personel – The database has an employee tabhle The employee table cansists of – EmployeeID and Name columns

 2005 Pearson Education, Inc. All rights reserved. 74 Example (cont.) // Import for the JDBC classes and interfaces from package java.sql import java.sql.*; public class DataBase { static final String DATASOURCE = “jdbc:odbc:Personel"; public static void main(String[] args) throws Exception { Connection connection; // Connection object Statement statement; // connection statement connection = DriverManager.getConnection( DATASOURCE,"",""); statement=connection.createStatement();

 2005 Pearson Education, Inc. All rights reserved. 75 Example (cont.) // insert a new employee String newInsert = "INSERT INTO employee (employeeID,name) VALUES (6,‘Ali')"; statement.execute(newInsert); // query database String query = "SELECT * FROM employee"; ResultSet results = statement..executeQuery(query);

 2005 Pearson Education, Inc. All rights reserved. 76 Example (cont.) // Position the ResultSet cursor to the first row in the ResultSet with method next while(results.next()) { // Extract the contents of one column in the current row System.out.print(results.getString(“EmloyeeID")); // System.out.print(results.getString(1)); System.out.print("\t"); System.out.print(results.getString(“Name")); // System.out.print(results.getString(2)); System.out.print("\t"); System.out.println(); } // end while loop

 2005 Pearson Education, Inc. All rights reserved. 77 Example (cont.) // Close the Statement and the database Connection. results.close(); statement.close(); connection.close(); } // end main } // end Database

 2005 Pearson Education, Inc. All rights reserved. 78 Example – different version // Imports for the JDBC classes and interfaces from package java.sql import java.sql.Connection; import java.sql.Statement; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; public class Database2 { static final String DATASOURCE = “jdc:odbc:Personel";

 2005 Pearson Education, Inc. All rights reserved. 79 Example – different version (cont.) public static void main(String[] args) throws SQLException, ClassNotFoundException { Connection connection; // Connection referance Statement statement; // connection statement connection = DriverManager.getConnection(, DATASOURCE,""); statement = connection.createStatement(); String query = "SELECT * FROM employee"; ResultSet results = statement.executeQuery(query); ResultSetMetaData metaData = results.getMetaData();

 2005 Pearson Education, Inc. All rights reserved. 80 Example – different version (cont.) int numberOfColunms = metaData.getColumnCount(); System.out.println(“Nuber of colluncs:"+numberOfCollunms); for(int i=1;i<=muberOfCollunms;i++) System.out.printf("%-12s\t", metaData.getColumnName(i)); System.out.println();

 2005 Pearson Education, Inc. All rights reserved. 81 Example – different version (cont.) // Position the ResultSet cursor to the first row in the ResultSet with method next while(results.next()) { // Extract the contents of one column in the current row for(int i = 1;i<=nuberOfCollumns;i++) System.out.printf("%- 12s\t",results.getObject(i)); System.out.println(); } // Close the Statement and the database Connection. results.close(); statement.close(); connection.close(); } // end main } // end Database

 2005 Pearson Education, Inc. All rights reserved. 82 Example – with exception handling // Import for the JDBC classes and interfaces from package java.sql import java.sql.*; public class Database3 { static final String DATASOURCE = “jdc:odbc:Personel"; public static void main(String[] args) throws SQLException, ClassNotFoundException { Connection connection; // Connection referance Statement statement; // connection statement

 2005 Pearson Education, Inc. All rights reserved. 83 Example – with exception handling // connect to database Personel and query database try { // establish connection to database connection = DriverManager.getConnection(DATASOURCE, "", "" ); // create Statement for querying database statement = connection.createStatement(); // query database resultSet = statement.executeQuery(query);

 2005 Pearson Education, Inc. All rights reserved. 84 Example – with exception handling // process query results // Obtains the metadata for the ResultSet. ResultSetMetaData metaData = resultSet.getMetaData(); int numberOfColumns = metaData.getColumnCount(); System.out.println( "Authors Table of Books Database:\n" ); for ( int i = 1; i <= numberOfColumns; i++ ) System.out.printf( "%-8s\t", metaData.getColumnName( i ) ); System.out.println();

 2005 Pearson Education, Inc. All rights reserved. 85 Example – with exception handling // Position the ResultSet cursor to the first row in the ResultSet with method next while ( resultSet.next() ) { // Extract the contents of one column in the current row for ( int i = 1; i <= numberOfColumns; i++ ) System.out.printf( "%-8s\t", resultSet.getObject( i ) ); System.out.println(); } // end while } // end try // Catch SQLException, which is thrown if the query execution or ResultSet process fails catch ( SQLException sqle ) { sqle.printStackTrace(); } // end catch // ClassNotFoundException is thrown if the class loader cannot locate the driver class catch ( ClassNotFoundException cnf ) { cnf.printStackTrace(); } // end catch

 2005 Pearson Education, Inc. All rights reserved. 86 Example – with exception handling Finally { // ensure resultSet, statement and connection are closed // Close the Statement and the database Connection. try { resultSet.close(); statement.close(); connection.close(); } // end try catch ( Exception e ) { e.printStackTrace(); } // end catch } // end finally } // end main } // end class Database3

 2005 Pearson Education, Inc. All rights reserved. 87 Example – with exception handling // Initialize a Connection reference called connection. // Invokes Connection method createStatement to obtain an object that implements interface Statement. // Use the Statement object’s executeQuery method to execute a query that selects all the author information from table authors. // Obtains the metadata for the ResultSet. // Uses ResultSetMetaData method getColumnCount to retrieve the number of columns in the ResultSet. // Obtain column name using method getColumnName // Position the ResultSet cursor to the first row in the ResultSet with method next // Extract the contents of one column in the current row

 2005 Pearson Education, Inc. All rights reserved. 88 25.8.1 Connecting to and Querying a Database import java.sql.*; public class dbConnection { static final String DATASOURCE = “jdc:odbc:Personel"; public static void main(String[] args) throws Exception { Connection con = DriverManager.getConnection(DATASOURCE,"",""); Statement st = con.createStatement();

 2005 Pearson Education, Inc. All rights reserved. 89 25.8.1 Connecting to and Querying a Database PreparedStatement prSt = con.prepareStatement("insert into empluyee (EmployeeID,Name) values (?,?)"); prSt.setString(1, “7"); prSt.setString(2, “Mehmet"); prSt.executeUpdate(); st.close(); con.close() } // end main } // end dbConnection class

 2005 Pearson Education, Inc. All rights reserved. 90 Example: An update Query An example getting information from the user and by connecting to a database update the database Get a new employee: – Employee ID and Name from the user – from a GUI Insert the new employee to the Employee database

 2005 Pearson Education, Inc. All rights reserved. 91 Example: An update Query import javax.swing.*; import java.sql.*; import java.awt.event.*; import java.awt.*; public class DbConnection { public static void main(String[] args)throws Exception { Frame frame = new Frame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(300,300); frame.setVisible(true); } // end main } // end class DbConnection

 2005 Pearson Education, Inc. All rights reserved. 92 Example: An update Query Frame class extends from JFrame – Two labels and two textFields and a button – When the user enters new emloyee ID and name Presses the Send button An action event is generated The actionPerformed method – gets the values of the two textFields – Creates a specific connection object that accept these two strings as arguments – Call the connectTo method of over the object to connect to the database

 2005 Pearson Education, Inc. All rights reserved. 93 Example: An update Query class Frame extends JFrame{ private JLabel label1; private JLabel label2; private JTextField textField1; private JTextField textField2; private JButton button1; public Frame() { label1=new JLabel("New Employee ID"); label2=new JLabel("New Name"); button1 = new JButton("Send"); textField1 = new JTextField(); textField2 = new JTextField();

 2005 Pearson Education, Inc. All rights reserved. 94 Example: An update Query setLayout(new GridLayout(3,2)); add(label1); add(textField1); add(label2); add(textField2); add(button1); ButonHandler handler = new ButonHandler(); button1.addActionListener(handler); } // end of constructor

 2005 Pearson Education, Inc. All rights reserved. 95 Example: An update Query private class ButonHandler implements ActionListener { public void actionPerformed(ActionEvent e) { String s1 = textField1.getText(); String s2 = textField2.getText(); MyConnection myCon = new MyConnection(s1,s2); myCon.connectTo(); } // end method actionPerformed } // end class ButtonHandler } // end class Frame

 2005 Pearson Education, Inc. All rights reserved. 96 Example: An update Query class MyConnection { private String str1; private String str2; public MyConnection(String s1, String s2) { str1 = s1; str2 = s2; } // end constructor

 2005 Pearson Education, Inc. All rights reserved. 97 Example: An update Query public void connectTo() { // make the odbc within java String c onnectionStr = "jdbc:odbc: Personel "; try { Connection con = DriverManager.getConnection( c onnectionStr,"",""); PreparedStatement prSt = con.prepareStatement("insert into employee values (?,?)");

 2005 Pearson Education, Inc. All rights reserved. 98 Example: An update Query prSt.setString(1, str1); prSt.setString(2, str2); prSt.executeUpdate(); } // end try catch (Eexception e) { e.getStackTrace(); } // end catch Finally { prSt.close(); con.close(); } // end finally } // end method connectTo } // end class MyConnection

 2005 Pearson Education, Inc. All rights reserved. 99 Another Desing Option Frame class – Get data from the user – to insert a new employee – Send the information to an object of MyConnection MyConnect class – Having the values of two Strings – Prepare a SQL query statement – Call a generic Connection class Connection class – A generic Connectin class written for geeral purpases – Accept Driver Name, dataSource,query Returns a ResultSet reference

 2005 Pearson Education, Inc. All rights reserved. 100 Another Desing Option Frame and MyConnection classes are the same But MyConnection’s connectTo method: creates an object from a generic connection class sending drivename,url,username,pasward.and query returns a resultset or for update or insert queries sending drivename,url,username,pasward.and query and parameters

 2005 Pearson Education, Inc. All rights reserved. 101 Another Desing Option class MyConnection { private String str1; private String str2; private String Driver = …; private String url =…; private ResultSet myResults; private String query = "insert into employee ( employeeID, Name) values ( “+str1+”, ”+str2+” )"

 2005 Pearson Education, Inc. All rights reserved. 102 Another Desing Option public MyConnection(String s1, String s2) { str1 = s1; str2 = s2; prepareQuery(); sendQuery(); } // end constructor public void prepareQuery() { // prepare query here } public void sendQuery() { ConnectClass conClass = new ConnectClass(Driver,url,query); myResults = conClass.execute(); } // process results here // other methods } // end class

 2005 Pearson Education, Inc. All rights reserved. 103 Another Desing Option class ConnectClass { private String driver; private String url; private String query; private String userName; private String passward; public ConnectClass(String sdrv, String surl, Srring squery) { driver = sdrv; url = surl; query = squery; }

 2005 Pearson Education, Inc. All rights reserved. 104 Another Desing Option // a generic method for exeuting a general query and // returning its results as a Resultset reference public ResultSet execute() throws Exception { Class.forName( driver ); Connection con = DriverManager.getConnection( url, userName,passward ); Statement statement = con.createStatement(); return statement..executeQuery(query); } // end method // other methods for get set … } end class

 1992-2007 Pearson Education, Inc. All rights reserved. 105 Outline DisplayAuthors.java (1 of 3 ) Imports for the JDBC classes and interfaces from package java.sql Declare a String constant that specifies the JDBC driver’s class name Loads the class definition for the database driver. Declare a String constant that specifies the database URL

 1992-2007 Pearson Education, Inc. All rights reserved. 106 Outline DisplayAuthors.java (2 of 3 ) Invokes Connection method createStatement to obtain an object that implements interface Statement. Use the Statement object’s executeQuery method to execute a query that selects all the author information from table authors. Obtains the metadata for the ResultSet. Uses ResultSetMetaData method getColumnCount to retrieve the number of columns in the ResultSet. Obtain column name using method getColumnName Position the ResultSet cursor to the first row in the ResultSet with method next Extract the contents of one column in the current row Initialize a Connection reference called connection.

 1992-2007 Pearson Education, Inc. All rights reserved. 107 Outline DisplayAuthors.java (3 of 3 ) Catch SQLException, which is thrown if the query execution or ResultSet process fails ClassNotFoundException is thrown if the class loader cannot locate the driver class Close the Statement and the database Connection.

 1992-2007 Pearson Education, Inc. All rights reserved. 108 Software Engineering Observation 25.4 Most major database vendors provide their own JDBC database drivers, and many third-party vendors provide JDBC drivers as well. For more information on JDBC drivers, visit the Sun Microsystems JDBC Web site, servlet.java.sun.com/products/ jdbc/drivers.

 1992-2007 Pearson Education, Inc. All rights reserved. 109 Software Engineering Observation 25.5 Most database management systems require the user to log in before accessing the database contents. DriverManager method getConnection is overloaded with versions that enable the program to supply the user name and password to gain access.

 1992-2007 Pearson Education, Inc. All rights reserved. 111 Software Engineering Observation 25.6 Metadata enables programs to process ResultSet contents dynamically when detailed information about the ResultSet is not known in advance.

 1992-2007 Pearson Education, Inc. All rights reserved. 112 Common Programming Error 25.8 Initially, a ResultSet cursor is positioned before the first row. Attempting to access a ResultSet ’s contents before positioning the ResultSet cursor to the first row with method next causes a SQLException.

 1992-2007 Pearson Education, Inc. All rights reserved. 113 Performance Tip 25.1 If a query specifies the exact columns to select from the database, the ResultSet contains the columns in the specified order. In this case, using the column number to obtain the column’s value is more efficient than using the column name. The column number provides direct access to the specified column. Using the column name requires a search of the column names to locate the appropriate column.

 1992-2007 Pearson Education, Inc. All rights reserved. 115 Common Programming Error 25.10 Attempting to manipulate a ResultSet after closing the Statement that created the ResultSet causes a SQLException. The program discards the ResultSet when the corresponding Statement is closed.

 1992-2007 Pearson Education, Inc. All rights reserved. 116 Software Engineering Observation 25.7 Each Statement object can open only one ResultSet object at a time. When a Statement returns a new ResultSet, the Statement closes the prior ResultSet. To use multiple ResultSet s in parallel, separate Statement objects must return the ResultSet s.

 1992-2007 Pearson Education, Inc. All rights reserved. 118 Outline ResultSetTable Model.java (1 of 7 ) Class ResultSetTableModel extends class AbstractTableModel, which implements interface TableModel. Instance variable keeps track of database connection status

 1992-2007 Pearson Education, Inc. All rights reserved. 119 Outline ResultSetTable Model.java (2 of 7 ) Establishes a connection to the database. Invokes Connection method createStatement to create a Statement object. Constructor accepts five String arguments—the driver class name, the database URL, the username, the password and the default query to perform Indicate that connect to database is successful Invokes ResultSetTableModel method setQuery to perform the default query.

 1992-2007 Pearson Education, Inc. All rights reserved. 120 Outline ResultSetTable Model.java (3 of 7 ) Override method getColumnClass to obtain a Class object that represents the superclass of all objects in a particular column Verify database connection status Loads the class definition for the class and returns the corresponding Class object. Returns the default type. Obtains the fully qualified class name for the specified column. Override method getColumnCount to obtain the number of columns in the model’s underlying ResultSet

 1992-2007 Pearson Education, Inc. All rights reserved. 121 Outline ResultSetTable Model.java (4 of 7 ) Obtains the number of columns in the ResultSet. Override method getColumnName to obtain the name of the column in the model’s underlying ResultSet Obtains the column name from the ResultSet.

 1992-2007 Pearson Education, Inc. All rights reserved. 122 Outline ResultSetTable Model.java (5 of 7 ) Override method getColumnCount to obtain the number of rows in the model’s underlying ResultSet Uses ResultSet method absolute to position the ResultSet cursor at a specific row. Override method getValueAt to obtain the Object in a particular row and column of the model’s underlying ResultSet Uses ResultSet method getObject to obtain the Object in a specific column of the current row.

 1992-2007 Pearson Education, Inc. All rights reserved. 123 Outline ResultSetTable Model.java (6 of 7 ) Executes the query to obtain a new ResultSet. Uses ResultSet method last to position the ResultSet cursor at the last row in the ResultSet. Uses ResultSet method getRow to obtain the row number for the current row in the ResultSet. Invokes method fireTableAStructureChanged to notify any JTable using this ResultSetTableModel object as its model that the structure of the model has changed.

 1992-2007 Pearson Education, Inc. All rights reserved. 124 Outline ResultSetTable Model.java (7 of 7 ) Method disconnectFromDatabase implement an appropriate termination method for class ResultSetTableModel Verify whether the connection is already terminated Close the Statement and Connection if a ResultSetTableModel object is garbage collected. Set connectedToDatabase to false to ensure that clients do not use an instance of ResultSetTableModel after that instance has already been terminated

 1992-2007 Pearson Education, Inc. All rights reserved. 126 Portability Tip 25.3 Some JDBC drivers do not support scrollable ResultSet s. In such cases, the driver typically returns a ResultSet in which the cursor can move only forward. For more information, see your database driver documentation.

 1992-2007 Pearson Education, Inc. All rights reserved. 127 Portability Tip 25.4 Some JDBC drivers do not support updatable ResultSet s. In such cases, the driver typically returns a read-only ResultSet. For more information, see your database driver documentation.

 1992-2007 Pearson Education, Inc. All rights reserved. 128 Common Programming Error 25.11 Attempting to update a ResultSet when the database driver does not support updatable ResultSet s causes SQLFeatureNotSupportedException s.

 1992-2007 Pearson Education, Inc. All rights reserved. 129 Common Programming Error 25.12 Attempting to move the cursor backward through a ResultSet when the database driver does not support backward scrolling causes a SQLException.

 1992-2007 Pearson Education, Inc. All rights reserved. 131 Outline DisplayQuery Results.java (1 of 8 ) Declare the database driver class name, database URL, username and password for accessing the database

 1992-2007 Pearson Education, Inc. All rights reserved. 132 Outline DisplayQuery Results.java (2 of 8 ) Declare the default queryDeclare tableModel to be a reference to ResultSetTableModel Create TableModel for results of default query “SELECT * FROM authors”

 1992-2007 Pearson Education, Inc. All rights reserved. 134 Outline DisplayQuery Results.java (4 of 8 ) Register an event handler for the submitButton that the user clicks to submit a query to the database Invoke ResultSetTableModel method setQuery to execute the new query

 1992-2007 Pearson Education, Inc. All rights reserved. 137 Outline DisplayQuery Results.java (7 of 8 ) Ensure that the database connection is closed Ensure that the database connection is closed when window is closed

 2005 Pearson Education, Inc. All rights reserved. 139 25.10 RowSet Interface Interface RowSet – Configures the database connection automatically – Prepares query statements automatically – Provides set methods to specify the properties needed to establish a connection – Part of the javax.sql package Two types of RowSet – Connected RowSet Connects to database once and remain connected – Disconnected RowSet Connects to database, executes a query and then closes connection

 2005 Pearson Education, Inc. All rights reserved. 140 25.10 RowSet Interface (Cont.) Package javax.sql.rowset – JdbcRowSet Connected RowSet Wrapper around a ResultSet Scrollable and updatable by default – CachedRowSet Disconnected RowSet Cache the data of ResultSet in memory Scrollable and updatable by default Serializable – Can be passed between Java application Limitation – Amount of data that can be stored in memory is limited

 1992-2007 Pearson Education, Inc. All rights reserved. 143 Outline JdbcRowSetTest.java (2 of 3 ) Use Sun’s reference implementation of JdbcRowSet interface ( JdbcRowSetImpl ) to create a JdbcRowSet object Invoke JdbcRowSet method setUrl to specify the database URL Invoke JdbcRowSet method setUsername to specify the username Invoke JdbcRowSet method setUsername to specify the password Invoke JdbcRowSet method setCommand to specify the query Invoke JdbcRowSet method execute to execute the query

 2005 Pearson Education, Inc. All rights reserved. 145 25.11 Java DB/Apache Derby As of JDK 6, Sun Microsystems now bundles the open-source, pure Java database Java DB (the Sun branded version of Apache Derby) with the JDK We use the embedded version of Java DB There is also a network version that executes similarly to the MySQL DBMS introduced earlier in the chapter

 2005 Pearson Education, Inc. All rights reserved. 146 25.11 Java DB/Apache Derby Java DB comes with several batch files to configure and run it First set the environment variable JAVA_HOME to refer to the JDK’s C:\Program Files\Java\jdk1.6.0 installation directory Open the batch file setEmbeddedCP.bat (located in C:\Program Files\Java\jdk1.6.0\db\frameworks\embedded\bin ) in a text editor such as Notepad Locate the line rem set DERBY_INSTALL= and change it to set DERBY_INSTALL=C:\Program Files\Java\jdk1.6.0\db Also, comment out the line @FOR %X in ("%DERBY_HOME%") DO SET DERBY_HOME=%~sX by preceding it with REM Save your changes and close this file

 2005 Pearson Education, Inc. All rights reserved. 147 25.11 Java DB/Apache Derby Change directories to C:\Program Files\Java\ jdk1.6.0\db\frameworks\embedded\bin\. Then, type setEmbeddedCP.bat and press Enter to set the environment variables required by Java DB. Embedded Java DB database must reside in the same location as the application that manipulates the database – Change to the directory that contains the code for Figs. 25.30– 25.32 Execute the command "C:\Program Files\Java\jdk1.6.0\db\frameworks\embedded\bin\ij" to start the command-line tool for interacting with Java DB. The double quotes are necessary because the path contains a space.

 2005 Pearson Education, Inc. All rights reserved. 148 25.11 Java DB/Apache Derby At the ij> prompt type connect 'jdbc:derby:AddressBook;create=true; user=jhtp7;password=jhtp7'; to create the AddressBook database in the current directory. This command also creates the user jhtp7 with the password jhtp7 for accessing the database. To create the database table and insert sample data in the database type run 'address.sql'; To terminate the Java DB command-line tool, type exit;

 2005 Pearson Education, Inc. All rights reserved. 150 25.12 PreparedStatements PreparedStatement to locate all book titles for an author with a specific last name and first name, and to execute that query for several authors: – PreparedStatement authorBooks = connection.prepareStatement( "SELECT lastName, firstName, title " + "FROM authors INNER JOIN authorISBN " + "ON authors.authorID=authorISBN.authorID " + "INNER JOIN titles " + "ON authorISBN.isbn=titles.isbn " + "WHERE lastName = ? AND firstName = ?" ); Question marks (?) are placeholders for values that will be passed as part of the query to the database

 2005 Pearson Education, Inc. All rights reserved. 151 25.12 PreparedStatements Program must specify the parameter values by using the PreparedStatement interface’s set methods. For the preceding query, both parameters are strings that can be set with PreparedStatement method setString as follows: authorBooks.setString( 1, "Deitel" ); authorBooks.setString( 2, "Paul" ); setString automatically escapes String parameter values as necessary (e.g., the quote in the name O’Brien) More info at java.sun.com/javase/6/docs/api/ java/sql/PreparedStatement.html

 1992-2007 Pearson Education, Inc. All rights reserved. 152 Performance Tip 25.2 PreparedStatement s are more efficient than Statement s when executing SQL statements multiple times and with different parameter values.

 1992-2007 Pearson Education, Inc. All rights reserved. 153 Error-Prevention Tip 25.1 Use PreparedStatement s with parameters for queries that receive String values as arguments to ensure that the String s are quoted properly in the SQL statement.

 1992-2007 Pearson Education, Inc. All rights reserved. 157 Outline PersonQueries.java (1 of 7 ) All program to use PreparedStatement s Declare PreparedStatement s Note that we do not load the Java DB driver first. JDBC 4’s automatic driver discovery is used here.

 1992-2007 Pearson Education, Inc. All rights reserved. 160 Outline PersonQueries.java (4 of 7 ) Specify the parameter to PreparedStatement selectPeopleByLastName. Executes the query in PreparedStatement selectPeopleByLastName.

 1992-2007 Pearson Education, Inc. All rights reserved. 162 Outline PersonQueries.java (6 of 7 ) Specify the parameters to PreparedStatement insertNewPerson. Executes the insert operation in PreparedStatement insertNewPerson.

 2005 Pearson Education, Inc. All rights reserved. 178 25.12 Stored Procedures Stored procedures – Store SQL statements in a database – Invoke SQL statements by programs accessing the database Interface CallableStatement – Receive arguments – Output parameters

 1992-2007 Pearson Education, Inc. All rights reserved. 179 Portability Tip 25.6 Although the syntax for creating stored procedures differs across database management systems, the interface CallableStatement provides a uniform interface for specifying input and output parameters for stored procedures and for invoking stored procedures.

 1992-2007 Pearson Education, Inc. All rights reserved. 180 Portability Tip 25.7 According to the Java API documentation for interface CallableStatement, for maximum portability between database systems, programs should process the update counts or ResultSet s returned from a CallableStatement before obtaining the values of any output parameters.

 2005 Pearson Education, Inc. All rights reserved. 181 25.13 Transaction Processing Many applications require guarantees that a series of database insertions, updates and deletions executes properly before the applications continue processing the next database operation Enables a program that interacts with a database to treat a database operation (or set of operations) as a single operation – Known as an atomic operation or a transaction – At the end of a transaction, decide to commit or roll back

 2005 Pearson Education, Inc. All rights reserved. 182 25.13 Transaction Processing Committing a transaction finalizes the database operation(s); all insertions, updates and deletions performed as part of the transaction cannot be reversed without performing a new database operation Rolling back a transaction leaves the database in its state prior to the database operation

 2005 Pearson Education, Inc. All rights reserved. 183 25.13 Transaction Processing Methods of interface Connection – setAutoCommit specifies whether each SQL statement commits after it completes (a true argument) or if several SQL statements should be grouped as a transaction (a false argument) If the argument to setAutoCommit is false, the program must follow the last SQL statement in the transaction with a call to Connection method commit or rollback – getAutoCommit determines the autocommit state for the Connection.

 1992-2007 Pearson Education, Inc. All rights reserved. 1 25 Accessing Databases with JDBC.

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 1992-2007 Pearson Education, Inc. All rights reserved. 1 25 Accessing Databases with JDBC.

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