Transcript Java Database Connectivity (JDBC)
ADVANCED POGRAMMING (JAVA) COURSE
Topics:
Java Database Connectivity (JDBC) Graphics Programming with Java 2D and Java 3D Security Servlets Java Server Pages Java-Based Wireless Applications
Part I Java Database Connectivity
(
JDBC
)
Java Database Connectivity (
JDBC
)
A common programming interface
writing programs
that access information stored in databases, spreadsheets, and other data sources either directly or through middleware
JDBC cont’d
By using the JDBC interface, Java programmers can request a connection with a database, Send query statements using SQL Receive the results for processing. Java runs on many different hardware platforms and operating systems, Developers can use JDBC to write applications access data across incompatible database management systems running on varied platforms.
Internet Resources for JDBC
http://java.sun.com/docs/books/tutorial/jdbc/index.html
www.sql.org
industry.java.sun.com/products/jdbc/drivers http://servlet.java.sun.com/products/jdbc/drivers java.sun.com/products/jdbc/faq.html
http://java.sun.com/products/jdbc/articles/package2.html
http://java.sun.com/developer/Books/JDBCTutorial/chapter5.html
www.jguru.com/jguru/faq/faqpage.jsp?name=JDBC
What is the JDBC API?
A set of classes and interfaces written in the Java a standard API for tool/database developers & makes possible to write database applications using an Java API. Obtaining a variety of different data sources is possible for Java applications Makes possible to publish a web page containing an applet that uses information obtained from a remote data source.
For example
: To connect all employees (even if they are using Windows, Macintosh, and UNIX machines) is possible as one or more internal databases via an intranet
The JDBC 3.0 API
Includes two packages:
java.sql
package
javax.sql
package (adds server-side capabilities) While downloading the Java 2 Platform Standard Edition, Version 1.4 (J2SE), we can automatically get both packages The JDBC-ODBC Bridge provides a limited subset of the JDBC 3.0 API.
Summary of new features has to be read at http://www-106.ibm.com/developerworks/java/library/j-jdbcnew/ .
The java.sql Package
The java.sql Package
Contains the entire JDBC API that sends SQL statements to relational databases and retrieves the results of executing those SQL statements. The Driver interface represents a specific JDBC implementation for a particular database system. Connection represents a connection to a database. The Statement, PreparedStatement, and CallableStatement interfaces support the execution of various kinds of SQL statements.
ResultSet is a set of results returned by the database in response to a SQL query. The ResultSetMetaData result set interface provides metadata about a DatabaseMetaData whole. provides metadata about the database as a
Array
Provides an interface to SQL ARRAY objects.
getArray() method returns a standard Java array of objects of the type returned by getBaseType().
The contents of the array can also be returned as a ResultSet using the various getResultSet() methods.
public abstract interface Array
{
// Public Instance Methods
public abstract Object
getArray
() throws SQLException; public abstract int
getBaseType
() throws SQLException public abstract String
getBaseTypeName
() throws SQLException; public abstract ResultSet
getResultSet
() throws SQLException; }
import java.sql. Connection ; import java.sql. DriverManager ; import java.sql. SQLException ; public class JdbcExam { public static void main (String args[]) {
Connection con = null
; try {
Class.forName ("com.mysql.jdbc.Driver"). newInstance(); con =DriverManager. getConnection ("jdbc:mysql:///test", "root", "secret"); if (!con.isClosed()) System.out.println ("Successfully connected to MySQL server using TCP/IP...");
} catch(Exception e) { System.err.println ("Exception: " + e.getMessage()); } finally {
try { if(con != null) con.close(); } catch (SQLException e) {}
} } }
import java.sql. Connection ; import java.sql. DriverManager ; import java.sql. SQLException ;
we imported 3 classes from java.sql package. Connection represents a connection to a database DriverManager manages JDBC drivers used to create connections to databases SQLException is an exception class which gets thrown in case any error occurs in the program
We declare a local variable to hold our java.sql. Connection object that we'll retrieve from java.sql. DriverManager later on.
Connection con = null;
We encapsulate our JDBC code in a try/catch/finally block. This is to ensure that if any runtime error gets thrown we catch it and display it to the user.
try { ... … } catch(Exception e) { System.err.println("Exception: " + e.getMessage()); } finally { ... ….
}
We take the first step in establishing a connection to our MySQL database by loading the driver explicitly using Class.forName() method Class.forName("com.mysql.jdbc.Driver").newInstance(); Once the JDBC driver has been loaded in the JVM, we retrieve a connection to our MySQL database running on the local system using DriverManager.getConnection() method .The first argument to this method is complete database URL, next parameter is the user name and last parameter is the password.
con=DriverManager.getConnection("jdbc:mysql:/// test", "root", "secret");
After these steps are completed, it is required to obtain a connection to the MySQL database .
We check to make sure we are properly connected and display a success message if we are.
if(!con.isClosed()) System.out.println("Successfully connected to " + "MySQL server using TCP/IP...");
To close the connection, we execute the Connection.close() method in the finally block of our try/catch/finally statement.
try { if(con != null)
con.close(); } catch (SQLException e) {}
The Connection.close() method can also throw SQLException so that is why we encapsulate this close() method in a separate try/catch block.
http://www.mysql.com/get/Downloads/MySQL 4.0/mysql-4.0.18-win.zip/from/pick#mirrors is the website which you can download the mysql http://www.mysql.com/doc/en/Windows_installatio n.html
is the website which you can install the mysql
javax.sql
package
The
javax.sql
package
Contains the JDBC 2.0 Standard Extension API. The classes and interfaces in this package provide new functionality, connection pooling, that do not fall under the scope of the original JDBC API and can therefore be safely packaged separately. The DataSource interface serves as a factory for Connection objects; DataSource objects can be registered with a JNDI (
Java Naming and Directory Interface
)server, making it possible to get the name of a database from a name service. PooledConnection supports connection pooling, which allows an application to handle multiple database connections in a fairly transparent manner. RowSet extends the ResultSet interface to a JavaBeans component that can be manipulated at design time and used with non-SQL data sources
What Is the JDBC-ODBC Bridge?
A JDBC driver implements JDBC operations which translate them into ODBC operations.
ODBC acts as a normal application program.
The bridge implements JDBC for any database for which an ODBC driver is available. contains a native library used to access ODBC. The Bridge is installed automatically with the Java 2 SDK, Standard Edition, as package sun.jdbc.odbc
.
A Base for Other APIs
Java APIs are implemented as Java classes. The following are just a few of the available APIs except JDBC Java Real Time Java Foundation Classes (JFC) Swing —user interface Remote Method Invocation (RMI) Java for XML (JAXP) Java for XML Messaging (JAXM) Java Sound Java Media Framework Java 2D and 3D graphics Java Naming and Directory Interface (JNDI) http://www.alumni.caltech.edu/~croft/research/java/snapshot/
What Does the JDBC API Do?
Establish a connection with a data source Send queries and update statements to the data source Process the results Connection con = DriverManager.getConnection( "jdbc:myDriver:wombat", "myLogin", "myPassword"); Statement stmt = con.createStatement(); ResultSet rs = stmt.
executeQuery ("SELECT a, b, c FROM Table1"); while (rs. next()) { int x = rs.getInt ("a") String s = rs.getString ("b"); float f = rs.getFloat ("c"); }
Why not Use ODBC from Java?
Before the development of the JDBC API The most widely used programming interface Microsoft's ODBC (Open DataBase Connectivity) API To access relational databases ODBC can be used with Java, but The best application is JDBC API Applied as the form of the JDBC-ODBC Bridge ODBC is not appropriate for direct use from the Java programming language Uses C interface. Occurs a number of drawbacks in the security, implementation, robustness, automatic portability during the calls from Java to native C code QUESTION: What are other important differences between JDBC API and ODBC API?
Once ODBC (as native code) is called, Java programming language can't guarantee that a security violation won't occur (untrusted).
The Bridge ’s usage
A JDBC connection is opened using a URL with the odbc subprotocol. Loading is done as follows:
Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver");
Before any connection, the bridge driver class, sun.jdbc.odbc.JdbcOdbcDriver
added to the java.lang.System property named jdbc.drivers
OR explicitly loaded using the Java class loader.
After loaded, the ODBC driver creates an instance of itself and registers this with the JDBC driver manager.
What Is the JDBC URL Supported by the Bridge?
uses the odbc subprotocol jdbc:odbc:
JDBC Drivers
Provides JDBC access via one or more Open Database Connectivity (ODBC) drivers.
ODBC, which predates JDBC, is widely used by developers to connect to databases in a non-Java environment. JDBC supports four categories of drivers:
JDBC- to ODBC driver (Type 1)
Native-API, partly driver (Type 2)
JDBC- Net pure driver (Part 3)
Native-Protocol pure Java driver (Type 4)
JDBC- to ODBC driver (Type 1)
A good approach for learning JDBC.
May be useful for companies that already have ODBC drivers installed on each client machine The case for Windows-based machines running productivity applications.
May be the only way to gain access to some low-end desktop databases. Not for large-scale applications . Performance suffers because there's some overhead associated with the translation work to go from JDBC to ODBC. Doesn't support all the features of Java. User is limited by the functionality of the underlying ODBC driver
Native-API, partly driver (Type 2)
Converts the calls that a developer writes to the JDBC application programming interface into calls that connect to the client machine's application programming interface for a specific database, such as IBM, Informix, Oracle or Sybase. Performance is better than that of Type 1 operating system. , in part because the Type 2 driver contains compiled code that's optimized for the back-end database server's User needs to make sure the JDBC driver of the database vendor is loaded onto each client machine. Must have compiled code for every operating system that the application will run on. Best use is for controlled environments, such as an intranet.
JDBC- Net pure driver
(
Type 3)
Pure Java driver for database middleware, which provides connectivity to many different databases.
Translates JDBC calls into the middleware vendor's protocol, which is then converted to a database-specific protocol by the middleware server software.
Better performance than Types 1 and 2.
multiple databases and wants to use a single JDBC driver to connect to all of them.
Can be used when a company has Server-based , so no need for JDBC driver code on client machine .
For performance reasons, the back-end server component is optimized for the operating system that the database is running on.
Needs some effective.
database-specific code on the middleware server.
If the middleware must run on different platforms, a Type 4 driver might be more
Native-Protocol pure (all) Java driver (Type 4 )
Written entirely in Java Converts JDBC calls into packets that are sent over the network in the proprietary format used by the specific database. Allows a direct call from the client machine to the database. Better performance than Types 1 and 2. No need to install special software on client or server. Can be downloaded dynamically. .
Type 4 Java Driver cont’d
Not optimized for server operating system, so the driver can't take advantage of operating system features.
The driver is optimized for the database and can take advantage of the database vendor's functionality.
User needs a different driver for each different database These drivers are also well suited for applet programming, provided that the Java security manager allows TCP/IP connections to the database server.
Driver Types Results
Type 1 and Type 2 drivers were provided primarily to allow Java programmers to create data-driven solutions before database vendors created pure java drivers Type 3 and Type 4 drivers are preferred, because they are pure Java solutions The cloudscape driver COM.cloudscape.core. RMiJdbcDriver is a Type 4 driver
New APIs from Microsoft
OLE (Object Linking and Embedding) DB ADO (ActiveX Data Objects) RDS (Remote Data Service) UDA (Universal Data Access) an umbrella term that covers OLE DB, ADO, RDS, and ODBC The JDBC 2.0 API contains all of the important functionality of UDA plus features not found in UDA, such as SQL3 support.
OLE DB
Microsoft's strategic low-level application program interface for access to different data sources. Includes the SQL capabilities of the Microsoft sponsored standard data interface Open Database Connectivity Includes access to data other than SQL data.
As a design from Microsoft's Component Object Model (COM), OLE DB is a set of methods, for reading and writing data. The objects in OLE DB consist mainly of a data source object, a session object, a command object, and a row set object. :
An application using OLE DB
Initialize OLE Connect to a data source Issue a command Process the results Release the data source object Uninitialize OLE
As a result:
A general-purpose set of interfaces designed to let developers build data access tools as components using the Component Object Model (COM). OLE DB enables applications to have uniform access to data stored in DBMS and non-DBMS information containers OLE DB takes advantage of the benefits of database technology without having to transfer data from its place of origin to a DBMS
ActiveX Data Objects (ADO)
A language-independent object model Expose data by an OLE DB Provider. The most commonly used OLE DB Provider the OLE DB Provider for ODBC Drivers, Exposes ODBC Data sources to ADO. ADO is newer and more like the JDBC API it is not pure Java http://msdn.microsoft.com/library/default.asp?url=/downl oads/list/dataaccess.asp
Remote Data Service (RDS)
The part of Microsoft's ActiveX Data Objects (ADO) programming model designed for remote data access in internet client/server applications .
On both client and server computers it depends upon the installation of the Microsoft Data Access Components (MDAC).
RDS has three core objects that are used to r etrieve , manipulate, and update data in applications.
Remote Data Service (RDS ) con’t
The
RDS.DataControl
and
RDS.DataSpace
objects installed on client computers and are directly accessed within applications to retrieve data from servers The
RDSServer.DataFactory
server component object, a can be accessed directly to communicate with data sources operates behind the scenes with the other RDS objects in handling database maintenance
Cloudscape
• Cloudscape is a DBMS, a database management system, accessed by applications through the JDBC API.
IBM Cloudscape provides developers a small footprint, standards- based Java database that can be tightly embedded into any Java based solution. Supports complex SQL, transactions and JDBC so that your applications can be migrated to DB2 UDB when they need to grow. Supports data encryption on disk via JCE for secure operation in hostile environments. http://www.deitel.com/books/advjHTP1/advjHTP1_CloudscapeInst allation.html
Cloudscape con’t
Some standard Java tools and utilities that make it easier to use Cloudscape and to develop Cloudscape applications ij is Cloudscape's interactive JDBC scripting tool a simple utility for running scripts against a . It is Cloudscape database. You can also use it interactively to run ad hoc queries. ij provides several commands for ease in accessing a variety of JDBC features. ij can be used in an embedded or a client/server environment. Cloudview is a graphical user interface for creating and managing Cloudscape databases. It can be used in an embedded or a client/server environment.
Cloudscape Database
Consists of platform-independent files stored in a directory that has the same name as the database. Most of the Cloudscape tools are JDBC applications.
A JDBC application is one that uses the classes in the
java.sql
package to interact with a DBMS. When we work with JDBC applications, we need to know about the following two JDBC concepts Drivers Database connection URLs
Drivers
Before a JDBC application interacts with a database, it must cause the appropriate JDBC driver to be loaded in the Java session. Cloudscape provides three JDBC drivers for use with the Cloudscape database engine. When you use the Cloudscape tools that are JDBC applications, you will need to know which driver to load.
COM.cloudscape.core.JDBCDriver
For embedded environments, when Cloudscape runs in the same JVM as the application
COM.cloudscape.core.WebLogicDriver
For client/server environments in which Cloudscape runs in the Cloudconnector framework and applications connect via the network
COM.cloudscape.core.RmiJdbcDriver
For client/server environments in which Cloudscape runs in the RmiJdbc Server framework and applications connect via the network
Run as two different frameworks
• Embedded The simplest Cloudscape environment. Enables Cloudscape as part of a Java application Database accession as only one application at a time No network access Starting of an Cloudscape instance within the current JVM and shutting down before completing • Client/Server The connection to Cloudscape over the network. Running embedded in a connectivity or server framework allows multiple network connections.
The RmiJdbc framework enables the Cloudscape to execute as a stand-alone database server (a lightweight JDBC server and client) Each frame work directory has a bin subdirectory containing batch files
A JDBC URL
Provides a way of identifying a database so that the appropriate driver recognizes it and connects to it. . After the driver is loaded, an application must specify the correct database connection URL to connect to a specific database. The Cloudscape database connection URL allows us to accomplish more tasks than simply connecting.
Some of them:
jdbc:cloudscape:
databaseName
; For embedded environments jdbc:cloudscape:weblogic:
CloudscapeURLAttributes CloudscapeURLAttributes databaseName
; For connecting to Cloudscape running inside the Cloudconnector framework, when the server is running on the default host
localhost
is using the default port number
7001
and
RmiJdbc Framework
Change directories to bin directory in RmiJdbc Set the environment variables for the server Execution of the batch file
setServerCloudscapeCP
Launch the Cloudspace database server Execution of the batch file
startCS
Shut down the server Executiong
stopCS
Cloudview
Graphical user interface for creating and managing Cloudscape databases.
Connecting to a Server
You can use Cloudview as a client application that interacts with Cloudscape running in a server framework. To do that, simply load the appropriate driver and use the appropriate protocol for the server framework, either RmiJdbc or Cloudconnector.
CLOUDSPACE
ORDBMS
• A Java and SQL based object-relational database management system
Description:
Founded in 1996, cloudspace is an Internet services company specializing in open-source Website and online software development for the entertainment, technology and professional services industries.
Url:
http://www.cloudspace.com