Introduction to Programming with Java 1

Chapter 3 Database Programming 2

JDBC Introduction Java Data Base Connectivity(JDBC) is a set of Java APIs used for executing SQL statements. JDBC is much similar to Microsoft’s Open Database Connectivity(ODBC) interface to SQL (Structure Query Language). JDBC API is a set of interfaces and classes to be used for communicating with a database. These interfaces and classes are found in the java.sql package. JDBC allows developers to write client/server properties in Java. JDBC is an interface that stands between the specific database and the Java applications, applets and Servlets. Why JDBC is advantageous with Java? The reason behind that is programs developed with the java programming language and JDBC are platform independent.

Role of JDBC Establishes connection with the database. Sends SQL statements. Process the results Close the connection.

JDBC Characteristics It is call-level SQL interface for Java. It does not restrict the type of queries of passed to an underlying DBMS driver. JDBC mechanisms are simple to understand and use. It provides Java Interface that stays consistent with the rest of the Java system.

The Design of the JDBC At the initial, when the Sun team wants to built the database they extends the standard Java Library to deal with the SQL access to database. Because of this it is impossible task it didn’t take them very long to realize. Afterwards with the help of networking protocols Sun works on the pure java API for the SQL access. Then much of time later the API for the database access become the JDBC API, and the rules for writing drivers were encapsulated in the JDBC driver API.

The Design of the JDBC Simple Design JDBC consists of two layers: the top layer is the JDBC API and the bottom layer is the JDBC driver API Java Application JDBC Driver Manager JDBC/ODBC Bridge ODBC driver Vender supplied JDBC driver Data Base Server

The Design of the JDBC Simple Design The top layered API communicates with the JDBC manager driver API sending it the various SQL statements. Afterwards the manager communicates with the various third party drivers that actually connect to the database and return the information from the query or perform the action specified by the query. The Driver Manager also helps to select the most appropriate driver from the previously loaded drivers when a new open database is connected.

The Design of the JDBC Two – tier and Three – tier Models Two – tier Model Java applications/applets interact directly with the database. This model is referred to as client/server model where user is the client and the machine that has the database is called the server. First the is the JDBC API layer and second is the various third party drivers. Java Application JDBC DBMS Client Machine (GUI) DBMS proprietary protocol Database Server

The Design of the JDBC Two – tier and Three – tier Models A middle tier is introduced in this model. Uses of the middle tier: It collects the SQL statement from the client and hands it over to the database. Receives results from the database to the client. Controls accessing and updating of data. This three tier architecture introduces the Java API calls the middleware layer that in turn accesses the data. Java Applet or HTML browser Client Machine (GUI) HTTP, RMI or COBRA calls Remote Method Invocation Application Server(Java) Server machine (Business Logic) JDBC DBMS proprietary protocol DBMS Database Server eg. SQL Server Oracle

The Design of the JDBC Two – tier and Three – tier Models

JDBC Drivers The JDBC driver translates standard JDBC calls into a network or database protocol or into a database library API call that facilitates communication with the database. This translation layer provides JDBC application with database independence. If the back-end database changes, only the JDBC driver need to be replaced with few code modifications required.

Type 1: JDBC ODBC Bridge Driver Prepared by Allaudin “Hemat”

Type 1: JDBC ODBC Bridge Driver Type 1 drivers act as a “bridge” between JDBC and another database connectivity mechanism such as ODBC. Sun provided a JDBC-ODBC Bridge driver: sun.jdbc.odbc.JdbcOdbcDriver. In this driver the java statements are converted to jdbc statement. JDBC statements call the ODBC by using the JDBC-ODBC Bridge. And finally the query is executed by the database. This bridge is helpful for testing but it cannot recommend for the production used. Type 1 only runs on platforms where ODBC is available. This driver is native code and not Java i.e it is written in C or C++ language not in Java

Type 2: Native-API Driver

Type 2: Native-API Driver Type 2 driver converts JDBC API calls to the native C or C++ API calls. This driver converts the JDBC calls into a database specific call for databases such as SQL, ORACLE etc. This driver communicates directly with the database server. It require some native code to connect to the database. Type 2 drivers are usually faster than type 1 drivers.

Type 3: Network Protocol Driver

Type 3: Network Protocol Driver Or All-Java Driver Type 3 drivers are pure Java drivers that use a proprietary network protocol to communicate with JDBC middleware on the server. The middleware then translates the network protocol to database-specific function call. Type 3 drivers can be deployed over the Internet without client installation. Java----> JDBC statements-----> SQL statements -- --->databases.

Type 4: Database Protocol Driver

Type 4: Database Protocol Driver The JDBC type 4 driver, also known as the Direct to Database Pure Java Driver, is a database driver implementation that converts JDBC calls directly into a vendor- specific database protocol. Written completely in Java, type 4 drivers are thus platform independent. They install inside the Java Virtual Machine of the client.

JDBC API Interfaces in java.sql package Interfaces Methods Array getArray(), getBaseType, getResultSet Blob getBinaryStream, getBytes, length, position CallableStatement registerOutParameter, wasNull Clob getAsciiStream, getCharacterStrea, getSubString, length, position Connection commit, createStatement, isClosed, isReadOnly, rollback DatabaseMetadata getColumns, getConnection, ResultSet absolute, afterLast, beforeFirst, close, next, previous, deleteRow, insertRow Statement cancel, close, executeUpdate, getConnection, getMaxRows Prepared by Allaudin “Hemat”

JDBC API Classes in java.sql package Classes Methods Date getHours, getMinutes, setTime, toString, valueOf DriverManager getConnection, println, registerDriver, getDriver Time getDate, getYear, getMonth, setTime, setYear Prepared by Allaudin “Hemat”

Essential JDBC progam Import the java.sql package import java.sql.*; Steps for using JDBC to access Database Import the java.sql package import java.sql.*; Load a JDBC driver All drivers are required to register themselves at load time. try { Class.forName("com.mysql.jdbc.Driver"); } catch(Exception e) System.out.println("Unable to load the driver..."); Prepared by Allaudin “Hemat”

Essential JDBC progam Connect to the database Steps for using JDBC to access Database Connect to the database The JDBC DriverManager Class defines objects which can connect java applications to a JDBC driver, which is backbone of JDBC architecture. getConnection() method used to establish connection. Connection con = DriverManager.getConnection("jdbc:mysql://localhost/db_hms","root",""); Create a statement To execute SQL statements, we need to initiate a statement object form our connection object by using createstatement() method. con.createstatement(); Prepared by Allaudin “Hemat”

Essential JDBC progam Steps for using JDBC to access Database There are 3 types of statement Statement: Simple SQL queries without parameters. Prepared Statement: Executed precompiled SQL queries with or without parameters. PrepareStatement objects are precompile SQL statement. Callable Statement: Execute a call to a database stored procedure. CallableStatement objects are SQL stored procedure call statements Execute the statement stmt.exeuteUpdate(String str); To exeute query executeQuery() methods comes in picture. The executeQuery() method takes SQL query as a parameter and returns the result of the query as the ResultSet Object.

Essential JDBC progam Retrieve the result Steps for using JDBC to access Database Result rs1=stmt.executeQuery("Select id, name,salary from teacher where department="Computer" "); Retrieve the result while(rs1.next()) { int x=rs1.getInt(1); String s=rs1.getString("b"); } The above is just an example where rs1 is a ResutlSet object. The results of the SQL statements are stored in a ResultSet object. To retrieve the data from this object, we use the getXXX methods. To move to the next row, we make use of rs1.next() method.

Essential JDBC progam Close the statement and the connection: Steps for using JDBC to access Database Close the statement and the connection: stmt.close(); con.close(); con.commit(); Prepared by Allaudin “Hemat”

Essential JDBC progam Steps for using JDBC to access Database Write JDBC program to accept employee information from database and update first tuple and display after updating. Write JDBC program that insert the following details to a teacher table having the following structure. teacher_name, department, salary