What is JDBC
JDBC is Java application programming interface that allows the Java programmers to access database management system from Java code. It was developed by JavaSoft, a subsidiary of Sun Microsystems.
Definition
Java Database Connectivity in short called as JDBC. It is a java API which enables the java programs to execute SQL statements. It is an application programming interface that defines how a java programmer can access the database in tabular format from Java code using a set of standard interfaces and classes written in the Java programming language.
JDBC has been developed under the Java Community Process that allows multiple implementations to exist and be used by the
same application. JDBC provides methods for querying and updating the data in Relational Database Management system such as SQL, Oracle etc.
The Java application programming interface provides a mechanism for dynamically loading the correct Java packages and drivers and registering them with the JDBC Driver Manager that is used as a connection factory for creating JDBC connections which supports creating and executing statements such as SQL INSERT, UPDATE and DELETE. Driver Manager is the backbone of the jdbc architecture.
Generally all Relational Database Management System supports SQL and we all know that Java is platform independent, so JDBC makes it possible to write a single database application that can run on different platforms and interact with different Database Management Systems.
Java Database Connectivity is similar to Open Database Connectivity (ODBC) which is used for accessing and managing database, but the difference is that JDBC is designed specifically for Java programs, whereas ODBC is not depended upon any language.
In short JDBC helps the programmers to write java applications that manage these three programming activities:
1. It helps us to connect to a data source, like a database.
2. It helps us in sending queries and updating statements to the database and
3. Retrieving and processing the results received from the database in terms of answering to your query.
Components of JDBC
JDBC has four Components:
1. The JDBC API.
2. The JDBC Driver Manager.
3. The JDBC Test Suite.
4. The JDBC-ODBC Bridge.
1. The JDBC API.
The JDBC application programming interface provides the facility for accessing the relational database from the Java programming language. The API technology provides the industrial standard for independently connecting Java programming language and a wide range of databases. The user not only execute the SQL statements, retrieve results, and update the data but can also access it anywhere within a network because of it's "Write Once, Run Anywhere" (WORA) capabilities.
Due to JDBC API technology, user can also access other tabular data sources like spreadsheets or flat files even in the a heterogeneous environment. JDBC application programmming interface is a part of the Java platform that have included Java Standard Edition (Java SE ) and the Java Enterprise Edition (Java EE) in itself.
The JDBC API has four main interface:
The latest version of JDBC 4.0 application programming interface is divided into two packages
i-) java.sql
ii-) javax.sql.
Java SE and Java EE platforms are included in both the packages.
2. The JDBC Driver Manager.
The JDBC Driver Manager is a very important class that defines objects which connect Java applications to a JDBC driver. Usually Driver Manager is the backbone of the JDBC architecture. It's very simple and small that is used to provide a means of managing the different types of JDBC database driver running on an application. The main responsibility of JDBC database driver is to load all the drivers found in the system properly as well as to select the most appropriate driver from opening a connection to a database. The Driver Manager also helps to select the most appropriate driver from the previously loaded drivers when a new open database is connected.
3. The JDBC Test Suite.
The function of JDBC driver test suite is to make ensure that the JDBC drivers will run user's program or not . The test suite of JDBC application program interface is very useful for testing a driver based on JDBC technology during testing period. It ensures the requirement of Java Platform Enterprise Edition (J2EE).
4. The JDBC-ODBC Bridge.
The JDBC-ODBC bridge, also known as JDBC type 1 driver is a database driver that utilize the ODBC driver to connect the database. This driver translates JDBC method calls into ODBC function calls. The Bridge implements Jdbc for any database for which an Odbc driver is available. The Bridge is always implemented as the sun.jdbc.odbc Java package and it contains a native library used to access ODBC.
Now we can conclude this topic: This first two component of JDBC, the JDBC API and the JDBC Driver Manager manages to connect to the database and then build a java program that utilizes SQL commands to communicate with any RDBMS. On the other hand, the last two components are used to communicate with ODBC or to test web application in the specialized environment.
Understanding JDBC Architecture
JDBC is an API specification developed by Sun Microsystems that defines a uniform interface for accessing various relational databases. JDBC is a core part of the Java platform and is included in the standard JDK distribution.
The primary function of the JDBC API is to provide a means for the developer to issue SQL statements and process the results in a consistent, database-independent manner. JDBC provides rich, object-oriented access to databases by defining classes and interfaces that represent objects such as:
- Database connections
- SQL statements
- Result Set
- Database metadata
- Prepared statements
- Binary Large Objects (BLOBs)
- Character Large Objects (CLOBs)
- Callable statements
- Database drivers
- Driver manager
Layers of the JDBC Architecture
A 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 applications with database independence. If the back-end database changes, only the JDBC driver need be replaced with few code modifications required. There are four distinct types of JDBC drivers.
Type 1 JDBC-ODBC Bridge. Type 1 drivers act as a "bridge" between JDBC and another database connectivity mechanism such as ODBC. The JDBC- ODBC bridge provides JDBC access using most standard ODBC drivers. This driver is included in the Java 2 SDK within the sun.jdbc.odbc package. In this driver the java statements are converted to a jdbc statements. JDBC statements calls the ODBC by using the JDBC-ODBC Bridge. And finally the query is executed by the database. This driver has serious limitation for many applications. (See Figure 2.)
Type 1 JDBC Architecture
Type 2 Java to Native API. Type 2 drivers use the Java Native Interface (JNI) to make calls to a local database library API. 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 requires some native code to connect to the database. Type 2 drivers are usually faster than Type 1 drivers. Like Type 1 drivers, Type 2 drivers require native database client libraries to be installed and configured on the client machine. (See Figure 3.)
Type 2 JDBC Architecture
Type 3 Java to Network Protocol 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 calls. Type 3 drivers are the most flexible JDBC solution because they do not require native database libraries on the client and can connect to many different databases on the back end. Type 3 drivers can be deployed over the Internet without client installation. (See Figure 4.)
Java-------> JDBC statements------> SQL statements ------> databases.
Type 3 JDBC Architecture
Type 4 Java to Database Protocol. Type 4 drivers are pure Java drivers that implement a proprietary database protocol (like Oracle's SQL*Net) to communicate directly with the database. Like Type 3 drivers, they do not require native database libraries and can be deployed over the Internet without client installation. One drawback to Type 4 drivers is that they are database specific. Unlike Type 3 drivers, if your back-end database changes, you may save to purchase and deploy a new Type 4 driver (some Type 4 drivers are available free of charge from the database manufacturer). However, because Type drivers communicate directly with the database engine rather than through middleware or a native library, they are usually the fastest JDBC drivers available. This driver directly converts the java statements to SQL statements.
(See Figure 5.)
Type 4 JDBC Architecture
So, you may be asking yourself, "Which is the right type of driver for your application?" Well, that depends on the requirements of your particular project. If you do not have the opportunity or inclination to install and configure software on each client, you can rule out Type 1 and Type 2 drivers.
However, if the cost of Type 3 or Type 4 drivers is prohibitive, Type 1 and type 2 drivers may become more attractive because they are usually available free of charge. Price aside, the debate will often boil down to whether to use Type 3 or Type 4 driver for a particular application. In this case, you may need to weigh the benefits of flexibility and interoperability against performance. Type 3 drivers offer your application the ability to transparently access different types of databases, while Type 4 drivers usually exhibit better performance and, like Type 1 and Type 2 drivers, may be available free if charge from the database manufacturer.
JDBC Drivers and its type
JDBC Driver Manager
The JDBC DriverManager class defines objects which can connect Java applications to a JDBC driver. DriverManager has traditionally been the backbone of the JDBC architecture. It is quite small and simple.
This is a very important class. Its main purpose is to provide a means of managing the different types of JDBC database driver. On running an application, it is the DriverManager's responsibility to load all the drivers found in the system property jdbc. drivers. For example, this is where the driver for the Oracle database may be defined. This is not to say that a new driver cannot be explicitly stated in a program at runtime which is not included in jdbc.drivers. When opening a connection to a database it is the DriverManager' s role to choose the most appropriate driver from the previously loaded drivers.
The JDBC API defines the Java interfaces and classes that programmers use to connect to databases and send queries. A JDBC driver implements these interfaces and classes for a particular DBMS vendor.
A Java program that uses the JDBC API loads the specified driver for a particular DBMS before it actually connects to a database. The JDBC DriverManager class then sends all JDBC API calls to the loaded driver.
JDBC Driver
This topic defines the Java(TM) Database Connectivity (JDBC) driver types. Driver types are used to categorize the technology used to connect to the database. A JDBC driver vendor uses these types to describe how their product operates. Some JDBC driver types are better suited for some applications than others.
Types of JDBC drivers
This topic defines the Java(TM) Database Connectivity (JDBC) driver types. Driver types are used to categorize the technology used to connect to the database. A JDBC driver vendor uses these types to describe how their product operates. Some JDBC driver types are better suited for some applications than others.
There are four types of JDBC drivers known as:
- JDBC-ODBC bridge plus ODBC driver, also called Type 1.
- Native-API, partly Java driver, also called Type 2.
- JDBC-Net, pure Java driver, also called Type 3.
- Native-protocol, pure Java driver, also called Type 4.
The JDBC type 1 driver, also known as the JDBC-ODBC bridge is a database driver implementation that employs the ODBC driver to connect to the database. The driver converts JDBC method calls into ODBC function calls. The bridge is usually used when there is no pure-Java driver available for a particular database.
The driver is implemented in the sun.jdbc.odbc.JdbcOdbcDriver class and comes with the Java 2 SDK, Standard Edition. The driver is platform-dependent as it makes use of ODBC which in turn depends on native libraries of the operating system. Also, using this driver has got other dependencies such as ODBC must be installed on the computer having the driver and the database which is being connected to must support an ODBC driver. Hence the use of this driver is discouraged if the alternative of a pure-Java driver is available.
Type 1 is the simplest of all but platform specific i.e only to Microsoft platform.
A JDBC-ODBC bridge provides JDBC API access via one or more ODBC drivers. Note that some ODBC native code and in many cases native database client code must be loaded on each client machine that uses this type of driver. Hence, this kind of driver is generally most appropriate when automatic installation and downloading of a Java technology application is not important. For information on the JDBC-ODBC bridge driver provided by Sun, see JDBC-ODBC Bridge Driver.
Type 1 drivers are "bridge" drivers. They use another technology such as Open Database Connectivity (ODBC) to communicate with a database. This is an advantage because ODBC drivers exist for many Relational Database Management System (RDBMS) platforms. The Java Native Interface (JNI) is used to call ODBC functions from the JDBC driver.
A Type 1 driver needs to have the bridge driver installed and configured before JDBC can be used with it. This can be a serious drawback for a production application. Type 1 drivers cannot be used in an applet since applets cannot load native code.
Functions:
- Translates query obtained by JDBC into corresponding ODBC query, which is then handled by the ODBC driver.
- Sun provides a JDBC-ODBC Bridge driver. sun.jdbc.odbc.JdbcOdbcDriver. This driver is native code and not Java, and is closed
source. - Client -> JDBC Driver -> ODBC Driver -> Database
- There is some overhead associated with the translation work to go from JDBC to ODBC.
Almost any database for which ODBC driver is installed, can be accessed.
Disadvantages:
- Performance overhead since the calls have to go through the JDBC overhead bridge to the ODBC driver, then to the native database connectivity interface.
- The ODBC driver needs to be installed on the client machine.
- Considering the client-side software needed, this might not be suitable for applets.
The JDBC type 2 driver, also known as the Native-API driver is a database driver implementation that uses the client-side libraries of the database. The driver converts JDBC method calls into native calls of the database API.
The type 2 driver is not written entirely in Java as it interfaces with non-Java code that makes the final database calls.
The driver is compiled for use with the particular operating system. For platform interoperability, the Type 4 driver, being
a full-Java implementation, is preferred over this driver.
A native-API partly Java technology-enabled driver converts JDBC calls into calls on the client API for Oracle, Sybase, Informix, DB2, or other DBMS. Note that, like the bridge driver, this style of driver requires that some binary code be loaded on each client machine.
However the type 2 driver provides more functionality and performance than the type 1 driver as it does not have the overhead of the additional ODBC function calls.
Type 2 drivers use a native API to communicate with a database system. Java native methods are used to invoke the API functions that perform database operations. Type 2 drivers are generally faster than Type 1 drivers.
Type 2 drivers need native binary code installed and configured to work. A Type 2 driver also uses the JNI. You cannot use a Type 2 driver in an applet since applets cannot load native code. A Type 2 JDBC driver may require some Database Management System (DBMS) networking software to be installed.
The Developer Kit for Java JDBC driver is a Type 2 JDBC driver.
Functions:
- This type of driver converts JDBC calls into calls to the client API for that database.
- Client -> JDBC Driver -> Vendor Client DB Library -> Database
Better performance than Type 1 since no jdbc to odbc translation is needed.
Disadvantages
- The vendor client library needs to be installed on the client machine.
- Cannot be used in internet due the client side software needed.
- Not all databases give the client side library.
The JDBC type 3 driver, also known as the network-protocol driver is a database driver implementation which makes use of a middle-tier between the calling program and the database. The middle-tier (application server) converts JDBC calls directly or indirectly into the vendor-specific database protocol.
This differs from the type 4 driver in that the protocol conversion logic resides not at the client, but in the middle-tier. However, like type 4 drivers, the type 3 driver is written entirely in Java.
The same driver can be used for multiple databases. It depends on the number of databases the middleware has been configured to support. The type 3 driver is platform-independent as the platform-related differences are taken care by the middleware. Also, making use of the middleware provides additional advantages of security and firewall access.
A net-protocol fully Java technology-enabled driver translates JDBC API calls into a DBMS-independent net protocol which is then translated to a DBMS protocol by a server. This net server middleware is able to connect all of its Java technology-based clients to many different databases. The specific protocol used depends on the vendor. In general, this is the most flexible JDBC API alternative. It is likely that all vendors of this solution will provide products suitable for Intranet use. In order for these products to also support Internet access they must handle the additional requirements for security, access through firewalls, etc., that the Web imposes. Several vendors are adding JDBC technology-based drivers to their existing database middleware products.
These drivers use a networking protocol and middleware to communicate with a server. The server then translates the protocol to DBMS function calls specific to DBMS.
Type 3 JDBC drivers are the most flexible JDBC solution because they do not require any native binary code on the client. A Type 3 driver does not need any client installation.
Functions:
- Follows a three tier communication approach.
- Can interface to multiple databases - Not vendor specific.
- The JDBC Client driver written in java, communicates with a middleware-net-server using a database independent protocol, and then this net server translates this request into database commands for that database.
- Thus the client driver to middleware communication is database independent.
- Client -> JDBC Driver -> Middleware-Net Server -> Any Database
- Since the communication between client and the middleware server is database independent, there is no need for the vendor db library on the client machine. Also the client to middleware need'nt be changed for a new database.
- The Middleware Server (Can be a full fledged J2EE Application server) can provide typical middleware services like caching (connections, query results, and so on), load balancing, logging, auditing etc..
- eg. for the above include jdbc driver features in Weblogic.
- Can be used in internet since there is no client side software needed.
- At client side a single driver can handle any database.(It works provided the middlware supports that database!!)
- Requires database-specific coding to be done in the middle tier.
- An extra layer added may result in a time-bottleneck. But typically this is overcome by providing efficient middleware
services described above.
The JDBC type 4 driver, also known as the native-protocol driver is a database driver implementation that converts JDBC calls directly into the vendor-specific database protocol.
The type 4 driver is written completely in Java and is hence platform independent. It is installed inside the Java Virtual Machine of the client. It provides better performance over the type 1 and 2 drivers as it does not have the overhead of conversion of calls into ODBC or database API calls. Unlike the type 1 and 2 drivers, it does not need associated software to work.
A native-protocol fully Java technology-enabled driver converts JDBC technology calls into the network protocol used by DBMSs directly. This allows a direct call from the client machine to the DBMS server and is a practical solution for Intranet access. Since many of these protocols are proprietary the database vendors themselves will be the primary source for this style of driver. Several database vendors have these in progress.
As the database protocol is vendor-specific, separate drivers, usually vendor-supplied, need to be used to connect to the database.
A Type 4 driver uses Java to implement a DBMS vendor networking protocol. Since the protocols are usually proprietary, DBMS vendors are generally the only companies providing a Type 4 JDBC driver.
Type 4 drivers are all Java drivers. This means that there is no client installation or configuration. However, a Type 4 driver may not be suitable for some applications if the underlying protocol does not handle issues such as security and network connectivity well.
The IBM Toolbox for Java JDBC driver is a Type 4 JDBC driver, indicating that the API is a pure Java networking protocol driver.
Functions
- Type 4 drivers are entirely written in Java that communicate directly with a vendor's database through socket connections. No translation or middleware layers, are required, improving performance.
- The driver converts JDBC calls into the vendor-specific database protocol so that client applications can communicate directly with the database server.
- Completely implemented in Java to achieve platform independence.
- e.g include the widely used Oracle thin driver - oracle.jdbc.driver. OracleDriver which connect to jdbc:oracle:thin URL format.
- Client Machine -> Native protocol JDBC Driver -> Database server
These drivers don't translate the requests into db request to ODBC or pass it to client api for the db, nor do they need a middleware layer for request indirection. Thus the performance is considerably improved.
Disadvantage
At client side, a separate driver is needed for each database.
