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Pre-assessment Questions

Pre-assessment Questions ______________ layer signifies a Java application that uses the JDBC API to interact with the JDBC drivers. JDBC application layer JDBC driver layer JDBC driver manager layer JDBC API layer

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Pre-assessment Questions

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  1. Pre-assessment Questions • ______________ layer signifies a Java application that uses the JDBC API to interact with the JDBC drivers. • JDBC application layer • JDBC driver layer • JDBC driver manager layer • JDBC API layer • A JDBC __________ is a software that a Java application uses to access a database. • Driver manager • Driver • DSN • CLI JDBC and JavaBeans

  2. Pre-assessment Questions (Contd.) • Which JDBC driver works as an interface between the JDBC application and the ODBC driver ? • Native-API-Partly-Java driver • Native Protocol Pure-Java driver • JDBC-ODBC Bridge driver • JDBC-Net-Pure-Java driver • Which JDBC driver maps the JDBC calls to the native method calls, which are passed to the local native Call Level Interface(CLI)? • Native-API-Partly-Java driver • JDBC-ODBC Bridge driver • Native Protocol Pure-Java driver • JDBC-Net-Pure-Java driver JDBC and JavaBeans

  3. Pre-assessment Questions (Contd.) • Which interface enables you to establish a connection between a Java application and a database ? • Statement interface • ResultSet interface • DriverManager interface • Connection interface JDBC and JavaBeans

  4. Solutions to Pre-assessment Questions • a. Java application layer • b. Driver • c. JDBC-ODBC Bridge driver • a. Native-API-Partly-Java driver • d. Connection interface JDBC and JavaBeans

  5. Objectives • In this section, you will learn about: • Creating applications using the PreparedStatement object • Managing database transactions • Performing batch updates • Creating and calling stored procedures in JDBC • Using metadata in JDBC JDBC and JavaBeans

  6. Querying and Modifying Data Using the PreparedStatement Object • The PreparedStatement interface is derived from the Statement interface and is available in the java.sql package. • The PreparedStatement object: • Allows you to pass runtime parameters to the SQL statements to query and modify the data in a table. • Is compiled and prepared only once by JDBC. The future invocation of the PreparedStatement object does not recompile the SQL statements. • Helps in reducing the load on the database server and thus improving the performance of the application. JDBC and JavaBeans

  7. Querying and Modifying Data Using the PreparedStatement Object (Contd.) • Methods of the PreparedStatement Interface • The PreparedStatement interface inherits the following methods to execute SQL statements from the Statement interface: • ResultSet executeQuery(): Executes a SELECT statements and returns the result in a ResultSet object. • int executeUpdate(): Executes an SQL statement, INSERT, UPDATE, or DELETE and returns the count of the rows affected. • boolean execute(): Executes an SQL statement and returns a boolean value. JDBC and JavaBeans

  8. Querying and Modifying Data Using the PreparedStatement Object (Contd.) • The prepareStatement() method of the Connection object is used to submit parameterized query to a database. • The SQL statement can contain ‘?’ symbol as placeholders that can be replaced by input parameters at runtime. For example, • stat=con.prepareStatement("SELECT * FROM authors WHERE au_id = ?"); • The value of each ‘?’ parameter is set by calling an appropriate setXXX() method, where XXX is the data type of the parameter. For example, • stat.setString(1,"1001"); • ResultSet result=stat.executeQuery(); JDBC and JavaBeans

  9. Querying and Modifying Data Using the PreparedStatement Object (Contd.) • Retrieving Rows • The code snippet to retrieve books written by an author from the titles table using the PreparedStatement object is: • String str = "SELECT * FROM titles WHERE au_id = ?"; • PreparedStatement ps= con.prepareStatement(str); • ps.setString(1, "1001"); • ResultSet rs=ps.executeQuery(); JDBC and JavaBeans

  10. Querying and Modifying Data Using the PreparedStatement Object (Contd.) • Inserting Rows • The code snippet to create a PreparedStatement object that inserts a row into authors table by passing authors data at runtime is: • String str = "INSERT INTO authors (au_id, au_fname, au_lname) VALUES (?, ?, ?)"; • PreparedStatement ps = con.prepareStatement(str); • ps.setString(1, "1001"); • ps.setString(2, "Abraham"); • ps.setString(3, "White"); • int rt=ps.executeUpdate(); JDBC and JavaBeans

  11. Querying and Modifying Data Using the PreparedStatement Object (Contd.) • Updating and Deleting Rows • The code snippet to modify the state to CA where city is Oakland in the authors table using the PreparedStatement object is: • String str = "UPDATE authors SET state= ? WHERE city= ? "; • PreparedStatement ps = con.prepareStatement(str); • ps.setString(1, "CA"); • ps.setString(2, "Oakland"); • int rt=ps.executeUpdate(); JDBC and JavaBeans

  12. Querying and Modifying Data Using the PreparedStatement Object (Contd.) • The code snippet to delete a row from the authors table where author’s first name is Abraham using the PreparedStatement object is: • String str = "DELETE FROM authors WHERE au_fname= ? "; • PreparedStatement ps = con.prepareStatement(str); • ps.setString(1, "Abraham"); • int rt=ps.executeUpdate(); JDBC and JavaBeans

  13. Demonstration- Creating an Application that Uses PreparedStatement Object • Problem Statement • The management of a departmental store has decided to computerize the inventory. You have been asked to create the Product Information application that has an interactive user interface. The application should allow the user to add, update, and delete product information from the product table. JDBC and JavaBeans

  14. Demonstration- Creating an Application that Uses PreparedStatement Object (Contd.) • Problem Statement (Contd.) • The user interface of the application should be as shown in the following figure: JDBC and JavaBeans

  15. Demonstration- Creating an Application that Uses PreparedStatement Object (Contd.) • Solution • The GUI for the application is created using the java.swing package. The database operations are performed using the PreparedStatement object. • To solve the above problem, perform the following tasks: • Code the application. • Compile and execute the application. JDBC and JavaBeans

  16. Managing Database Transactions • A transaction: • Is a set of one or more SQL statements that are executed as a single unit. • Is complete only when all the SQL statements in a transaction execute successfully. • Maintains consistency of data in a database. JDBC and JavaBeans

  17. Managing Database Transactions • (Contd.) • JDBC API provides support for transaction management. • The database transactions can be committed in two ways in the JDBC applications: • Implicit: The Connection object uses the auto-commit mode to execute the SQL statements implicitly. • Explicit: The auto-commit mode is set to false to commit the transaction statement explicitly. The method call to set the auto-commit mode to false is: • con.setAutoCommit(false); JDBC and JavaBeans

  18. Managing Database Transactions • (Contd.) • Committing a Transaction • The commit() method is used to reflect the changes made by the transactions in a database. • The rollback() method is used to undo the changes made in the database after the last commit operation. • You need to explicitly invoke commit() and rollback() methods. JDBC and JavaBeans

  19. Performing Batch Updates • A batch: • Is a group of update statements that are sent to a database to be executed as a single unit. • Reduces network calls between the application and the database. • Is a more efficient way as compared to the processing of a single SQL statement. JDBC and JavaBeans

  20. Performing Batch Updates (Contd.) • Implementing Batch Updates in JDBC • The Statement or PreparedStatement interface provides the following methods to create and execute a batch of SQL statements: • void addBatch(): Adds an SQL statement to a batch. • int executeBatch(): Sends a batch of SQL statements to a database for processing and returns the total number of the rows updated. • void clearBatch(): Removes the SQL statements from the batch. JDBC and JavaBeans

  21. Performing Batch Updates (Contd.) • When a Statement object is created to perform batch updates, an empty array is associated with the object. • Multiple SQL statements can be added to the empty array to execute them as a batch. • You also need to disable the auto-commit mode using setAutoCommit(false) while working with batch updates in JDBC. • The executeBatch() method returns an integer array that stores the values of the update count. • The update count is the total number of rows affected when an SQL statement in a batch is processed. JDBC and JavaBeans

  22. Performing Batch Updates (Contd.) • The code snippet to create a batch of SQL statements is: • con.setAutoCommit(false); • Statement stmt=con.createStatement(); • stmt.addBatch("INSERT INTO product (p_id, p_desc) VALUES (1001, 'Printer')"); • stmt.addBatch("INSERT INTO product (p_id, p_desc) VALUES (1002, 'Scanner')"); • The SQL statements in a batch are processed in the order in which the statements appear in a batch. • The method call to execute a batch of SQL statements is: • int[] updcount=state.executeBatch(); JDBC and JavaBeans

  23. Performing Batch Updates (Contd.) • Exception Handling in Batch Updates • The batch update operations can throw two types of exceptions: • SQLException • BatchUpdateException • The BatchUpdateException class is derived from SQLException class. JDBC and JavaBeans

  24. Performing Batch Updates (Contd.) • The the SQLException is thrown by the JDBC API methods, addBatch() or executeBatch(), when problem occurs while accessing a database. • The BatchUpdateException exception is thrown when the SQL statements in the batch cannot be executed due to: • Presence of illegal arguments in the SQL statement. • Absence of the database table from which you need to retrieve data. • The BatchUpdateException uses an array of the update count to identify the SQL statement that throws the exception. JDBC and JavaBeans

  25. Creating and Calling Stored Procedures in JDBC • The java.sql package provides the CallableStatement interface that contains various methods to enable you to call the stored procedures from a database. • The CallableStatement interface is derived from the PreparedStatement interface. JDBC and JavaBeans

  26. Creating and Calling Stored Procedures in JDBC (Contd.) • Creating Stored Procedure • Stored Procedures: • Can be created using the CREATE PROCEDURE SQL statement in JDBC applications. • Are of two types: • Parameterized • Non-parameterized JDBC and JavaBeans

  27. Creating and Calling Stored Procedures in JDBC (Contd.) • A parameterized stored procedure can accept one or multiple parameters. • A parameter of a stored procedure can take any of these forms: • IN: Refers to the argument that you pass to a stored procedure. • OUT: Refers to the return value of a stored procedure. • INOUT: Combines the functionality of the IN and OUT parameters. The INOUT parameter enables you to pass an argument to a stored procedure. The same parameter can also be used to store a return value of a stored procedure. JDBC and JavaBeans

  28. Creating and Calling Stored Procedures in JDBC (Contd.) • Calling a Stored Procedure without Parameters • The Connection interface provides the prepareCall() method that is used to create the CallableStatement object to call a stored procedure. • The prepareCall() has the following three forms: • CallableStatement prepareCall(String str) • CallableStatement prepareCall(String str, int resSetType, int resSetConcurrency) • CallableStatement prepareCall(String str, int resSetType, int resSetConcurrency, int resSetHoldability) • The syntax to call a stored procedure without parameters is: • { call <procedure_name> }; JDBC and JavaBeans

  29. Creating and Calling Stored Procedures in JDBC (Contd.) • Calling a Stored Procedure with Parameters • The SQL escape syntax is a standard way to call a stored procedure from a Relational Database Management System (RDBMS) and is independent of the RDBMS. • There are two forms of the SQL escape syntax, one that contains result parameter and one that does not. • The syntax of the SQL escape syntax is: • {[? =] call <procedure_name> [<parameter1>,<parameter2>, ..., <parameterN>]} JDBC and JavaBeans

  30. Creating and Calling Stored Procedures in JDBC (Contd.) • The placeholders are used to represent the IN, OUT, and INOUT parameters of a stored procedure in the procedure call. • The syntax to call a stored procedure with parameters is: • { call <procedure_name>(?) }; • You need to set the value of the IN parameters using the set methods before the CallableStatement object is executed. • The syntax to set the value of the IN parameter is: • <CallableStatement_object>.setInt(<value>); JDBC and JavaBeans

  31. Creating and Calling Stored Procedures in JDBC (Contd.) • If the stored procedure contains OUT and INOUT parameters, these parameters should be registered with the corresponding JDBC types. • The registerOut() method is used to register the parameters. • The prototypes of the registerOut() method are: • registerOut(int index, int stype) • registerOut(int index, int stype, int scale) JDBC and JavaBeans

  32. Using Metadata in JDBC • Metadata is the information about data, such as structure and properties of table. • The metadata of the employee table includes following information: • Names of the columns. • Data type of each column. • Constraints to enter data values in the table columns. • JDBC API provides the following two metadata interfaces to retrieve the information about the database and result set: • DatabaseMetaData interface • ResultSetMetaData interface JDBC and JavaBeans

  33. Using Metadata in JDBC (Contd.) • Using DatabaseMetaData Interface • The DatabaseMetaData interface provides the methods that enable you to determine the properties of a database or RDBMS. • An object of DatabaseMetaData is created using the getMetaData() method of the Connection interface. • The method call to create an object of the DatabaseMetaData interface is: • DatabaseMetaData dm=con.getMetaData(); JDBC and JavaBeans

  34. Method Description ResultSet getColumns(String catalog, String schema, String table_name, String column_name) Retrieves the information about a column of a database table that is available in the specified catalog. Connection getConnection() Retrieves the database connection that creates the DatabaseMetaData object. String getDriverName() Retrieves the name of the JDBC driver for the DatabaseMetaData object. String getDriverVersion() Retrieves the version of the JDBC driver. • Using Metadata in JDBC (Contd.) • The following table lists the commonly used methods of the DatabaseMetaData interface: JDBC and JavaBeans

  35. Method Description ResultSet getPrimaryKeys(String catalog, String schema, String table) Retrieves the information about the primary keys of the database tables. String getURL() Retrieves the URL of the database. boolean isReadOnly() Returns a boolean value that indicates whether the database is a read only database. boolean supportsSavepoints() Returns a boolean value that indicates whether the database supports savepoints. • Using Metadata in JDBC (Contd.) • The methods of the DatabaseMetaData interface: (Contd.) JDBC and JavaBeans

  36. Using Metadata in JDBC (Contd.) • Using the ReultSetMetaData Interface • The ReultSetMetaData Interface contains various methods that enable you to retrieve information about the data in a result set. • The ResultSet interface provides the getMetaData() method to create an object of the ResultSetMetaData interface. • The method call to create an object of the ResultSetMetaData interface: • ResultSetMetaData rm=rs.getMetaData(); JDBC and JavaBeans

  37. Method Description int getColumnCount() Returns an integer indicating the total number of columns in a ResultSet object. String getColumnLabel(int column_index) Retrieves the title of the table column corresponding to the index passed as a parameter to this method. String getColumnName(int column_index) Retrieves the name of the table column corresponding to the index passed as a parameter to this method. int getColumnType(int column_index) Retrieves the SQL data type of the table column corresponding to the index passed as a parameter. • Using Metadata in JDBC (Contd.) • The following table lists the commonly used methods of the ResultSetMetaData interface: JDBC and JavaBeans

  38. Method Description String getTableName(int column_index) Retrieves the name of the database table that contains the column corresponding to the index passed as a parameter. boolean isAutoIncrement(int column_index) Returns a boolean value that indicates whether the table column corresponding to the index passed as a parameter increments automatically. boolean isCaseSensitive(int column_index) Returns a boolean value that indicates whether the table column corresponding to the index passed as a parameter is case sensitive. • Using Metadata in JDBC (Contd.) • The methods of the ResultSetMetaData interface: (Contd.) JDBC and JavaBeans

  39. Method Description boolean isReadOnly(int column_index) Returns a boolean value that indicates whether the column in a ResultSet corresponding to the index passed as a parameter is read only. boolean isWritable(int column_index) Returns a boolean value that indicates whether ResultSet column corresponding to the index passed as a parameter is updatable. • Using Metadata in JDBC (Contd.) • The methods of the ResultSetMetaData interface: (Contd.) JDBC and JavaBeans

  40. Demonstration- Creating an Application to Retrieve the Information of Database Tables • Problem Statement • The Manager of New Publishers publishing company, sometimes require the information about the tables of the database used by the company. He is not familiar with the SQL statements, therefore, he has asked you to create an application to determine the total number of columns and the data types of the columns of a given table. The table name has to be specified at the runtime. JDBC and JavaBeans

  41. Demonstration- Creating an Application to Retrieve the Information of Database Tables (Contd.) • Solution • The getColumnName(), getColumnCount(), and getColumnTypeName() methods of the ResultSetMetaData interface are used to develop the above application. To solve the above problem, perform the following tasks: • Code the application. • Compile and execute the application. JDBC and JavaBeans

  42. Summary • In this lesson, you learned: • The PreparedStatement object of the Connection interface allows you to pass runtime parameters to the SQL statements using the placeholders. • There can be multiple placeholders in a single SQL statement. An index value is associated with each placeholder depending upon the position of the placeholder in the SQL statement. • The placeholder stores the value assigned to it until the value is explicitly changed. • A transaction is a set of one or more SQL statements that are executed as a single unit. A transaction is complete only when all the SQL statements in a transaction are successfully executed. • If the setAutoCommit() method is set to true the database operations performed by the SQL statements are automatically committed in the database. JDBC and JavaBeans

  43. Summary (Contd.) • The commit() method reflects the changes made by the SQL statements permanently in the database. • The rollback() method is used to undo the effect of all the SQL operations performed after the last commit operation. • A batch is a group of update statements that are sent to a database to be executed as a single unit. You send the batch to a database as a single request using the same Connection object. • The executeBatch() method returns an integer array that stores the update count for all the SQL statements that are executed successfully in a batch. The update count is the number of database rows affected by the database operation performed by each SQL statement. • Batch update operations can throw two types of exceptions, SQLException and BatchUpdateException. • The SQLException is thrown when the database access problem occurs. The SQLException is also thrown when a SELECT statement that returns a ResultSet object is executed in a batch. JDBC and JavaBeans

  44. Summary (Contd.) • The BatchUpdateException is thrown when the SQL statement in the batch cannot be executed due to the problem in accessing the specified table or presence of illegal arguments in the SQL statement. • The CallableStatement interface contains various methods that enable you to call the stored procedures from a database. • The parameters of a stored procedure can take any of these three forms: • IN: Refers to the argument that you pass to a stored procedure. • OUT: Refers to the return value of a stored procedure. • INOUT: Enables you pass an argument to a stored procedure. The same parameters can also be used to pass a return value of a stored procedure. • Metadata is the information about data, such as structure and properties of table. • JDBC API provides two metadata interfaces to retrieve the information about the database and result set, DatabaseMetaData and ResultSetMetaData. JDBC and JavaBeans

  45. Summary (Contd.) • The DatabaseMetaData interface declares methods that enable you to determine the properties of a database or RDBMS. • The ResultSetMetaData interface declares methods that enable you to determine information about data in a result set. • The getMetaData() method of the Connection interface enables you to declare the objects of the DatabaseMetaData interface. The methods in the DatabaseMetaData interface retrieve information only about the database to which a Java application is connected. • The getMetaData() method of the ResultSet interface enables you to create the instance of the ResultSetMetaData interface. JDBC and JavaBeans

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