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  • Reiterate the concepts taught earlier by asking the given question.
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Jdbc session02 Jdbc session02 Presentation Transcript

  • JDBCObjectives In this session, you will learn to: Create applications using the PreparedStatement object Manage database transactions Perform batch updates Create and call stored procedures in JDBC Use metadata in JDBC Ver. 1.0 Session 2 Slide 1 of 39
  • JDBCCreate Applications 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. Ver. 1.0 Session 2 Slide 2 of 39
  • JDBCMethods of the PreparedStatement Interface • The PreparedStatement interface inherits the following methods to execute SQL statements from the Statement interface: – ResultSet executeQuery(): Executes a SELECT statement 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. Ver. 1.0 Session 2 Slide 3 of 39
  • JDBCMethods of the PreparedStatement Interface (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 = ?"); Ver. 1.0 Session 2 Slide 4 of 39
  • JDBCMethods of the PreparedStatement Interface (Contd.) 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,“a001"); ResultSet result=stat.executeQuery(); Ver. 1.0 Session 2 Slide 5 of 39
  • JDBCRetrieving Rows • The code snippet to retrieve books written by an author from the books table using the PreparedStatement object is: String str = "SELECT * FROM books WHERE au_id = ?"; PreparedStatement ps= con.prepareStatement(str); ps.setString(1, “a001"); ResultSet rs=ps.executeQuery(); Ver. 1.0 Session 2 Slide 6 of 39
  • JDBCInserting Rows The code snippet to create a PreparedStatement object that inserts a row into authors table by passing authors data at run time is: String str = "INSERT INTO Authors(au_id, au_name) VALUES (?, ?)"; PreparedStatement ps = con.prepareStatement(str); ps.setString(1, “a001"); ps.setString(2, "Abraham White"); int rt=ps.executeUpdate(); Ver. 1.0 Session 2 Slide 7 of 39
  • JDBCUpdating 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(); Ver. 1.0 Session 2 Slide 8 of 39
  • JDBCUpdating and Deleting Rows (Contd.) • The code snippet to delete a row from the Authors table where author’s name is Abraham White using the PreparedStatement object is: String str = "DELETE FROM Authors WHERE au_name= ? "; PreparedStatement ps = con.prepareStatement(str); ps.setString(1, "Abraham White"); int rt=ps.executeUpdate(); Ver. 1.0 Session 2 Slide 9 of 39
  • JDBCJust a minute Name the three methods of the PreparedStatement Interface. Answer: The three methods of the PreparedStatement Interface are: 1. ResultSet executeQuery() 2. int executeUpdate() 3. Boolean execute() Ver. 1.0 Session 2 Slide 10 of 39
  • JDBCDemonstration Problem Statement: The management of the City Library has decided to computerize the book inventory. You have been asked to create the Publisher Information application that has an interactive user interface. The application should allow the user to add the details of the new publishers to the publishers table. Ver. 1.0 Session 2 Slide 11 of 39
  • JDBCDemonstration (Contd.) A sample of the user interface is shown in the following fugure. Ver. 1.0 Session 2 Slide 12 of 39
  • JDBCDemonstration (Contd.) To insert information about a new publisher in the publishers table: 1. Specify the id for a publisher in the ID textbox and publishers details, such as name, phone, address, city, state, and zip in the respective text boxes. 2. Click the Insert button to insert information. 3. To exit from the application, click the Exit button. Ver. 1.0 Session 2 Slide 13 of 39
  • JDBCDemonstration (Contd.) Solution: To solve the problem, you need to perform the following tasks: 1. Code the application. 2. Compile and execute the application. Ver. 1.0 Session 2 Slide 14 of 39
  • JDBCManaging 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. Ver. 1.0 Session 2 Slide 15 of 39
  • JDBCManaging 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); Ver. 1.0 Session 2 Slide 16 of 39
  • JDBCCommitting 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. Ver. 1.0 Session 2 Slide 17 of 39
  • JDBCJust a minute How can you commit a transaction explicitly? Answer: You can commit a transaction explicitly by setting auto-commit mode to false. Ver. 1.0 Session 2 Slide 18 of 39
  • JDBCImplementing Batch Updates in JDBC 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. Ver. 1.0 Session 2 Slide 19 of 39
  • JDBCImplementing Batch Updates in JDBC (Contd.) • 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. Ver. 1.0 Session 2 Slide 20 of 39
  • JDBCImplementing Batch Updates in JDBC (Contd.) The code snippet to create a batch of SQL statements is: con.setAutoCommit(false); Statement stmt=con.createStatement(); stmt.addBatch("INSERT INTO Publishers (pub_id, pub_name) VALUES (‘p001’,‘Tate Publishing)"); stmt.addBatch("INSERT INTO Publishers (pub_id, pub_name) VALUES (‘p002’, ‘Publish America)"); 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=stmt.executeBatch(); Ver. 1.0 Session 2 Slide 21 of 39
  • JDBCException Handling in Batch Updates The batch update operations can throw two types of exceptions: SQLException BatchUpdateException – The BatchUpdateException class is derived from the SQLException class. Ver. 1.0 Session 2 Slide 22 of 39
  • JDBCException Handling in Batch Updates (Contd.) • 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. Ver. 1.0 Session 2 Slide 23 of 39
  • JDBCCreating 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. Ver. 1.0 Session 2 Slide 24 of 39
  • JDBCCreating Stored Procedures • Can be created using the CREATE PROCEDURE SQL statement in JDBC applications. • Are of two types: Parameterized Non-parameterized Ver. 1.0 Session 2 Slide 25 of 39
  • JDBCCreating Stored Procedures (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. Ver. 1.0 Session 2 Slide 26 of 39
  • JDBCCalling 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> }; Ver. 1.0 Session 2 Slide 27 of 39
  • JDBCCalling 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>]} Ver. 1.0 Session 2 Slide 28 of 39
  • JDBCCalling a Stored Procedure with Parameters (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>); Ver. 1.0 Session 2 Slide 29 of 39
  • JDBCCalling a Stored Procedure with Parameters (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) Ver. 1.0 Session 2 Slide 30 of 39
  • JDBCUsing 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 Ver. 1.0 Session 2 Slide 31 of 39
  • JDBCUsing the 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(); Ver. 1.0 Session 2 Slide 32 of 39
  • JDBCUsing the ResultMetadata 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(); Ver. 1.0 Session 2 Slide 33 of 39
  • JDBCJust a minute What are the metadata interfaces used to retrieve information about the database and result set? Answer: The metadata interfaces used to retrieve information about the database and result set are: 1. DatabaseMetaData interface 2. ResultSetMetaData interface Ver. 1.0 Session 2 Slide 34 of 39
  • JDBCDemonstration 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 run time. Ver. 1.0 Session 2 Slide 35 of 39
  • JDBCDemonstration (Contd.) Solution: To solve the Preceding problem, perform the following tasks: 1. Code the application. 2. Pass the command line argument. 3. Compile and execute the application. Ver. 1.0 Session 2 Slide 36 of 39
  • JDBCSummary In this session, you learned that: – The PreparedStatement object 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. Ver. 1.0 Session 2 Slide 37 of 39
  • JDBCSummary (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. 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. Ver. 1.0 Session 2 Slide 38 of 39
  • JDBCSummary (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. 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 Ver. 1.0 Session 2 Slide 39 of 39