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What is JDBC?
Java Database Connectivity (JDBC) is a standard Java API to interact with relational databases form Java. JDBC has set of classes and interfaces which can use from Java application and talk to database without learning RDBMS details and using Database Specific JDBC Drivers.
What is JDBC Driver ?
The JDBC Driver provides vendor-specific implementations of the abstract classes provided by the JDBC API. This driver is used to connect to the database.
What is DriverManager ?
DriverManager is a class in java.sql package. It is the basic service for managing a set of JDBC drivers.
A JDBC application can be logically divided into two layers:
1. Driver layer
2. Application layer
>Driver layer consists of DriverManager class and the available JDBC drivers.
>The application begins with requesting the DriverManager for the connection.
>An appropriate driver is choosen and is used for establishing the connection. This connection is given to the application which falls under the application layer.
>The application uses this connection to create Statement kind of objects, through which SQL commands are sent to backend and obtain the results.
What are the main components of JDBC ?
The life cycle of a servlet consists of the following phases:
DriverManager: Manages a list of database drivers. Matches connection requests from the java application with the proper database driver using communication subprotocol. The first driver that recognizes a certain subprotocol under JDBC will be used to establish a database Connection.
Driver: The database communications link, handling all communication with the database. Normally, once the driver is loaded, the developer need not call it explicitly.
Connection : Interface with all methods for contacting a database.The connection object represents communication context, i.e., all communication with database is through connection object only.
Statement : Encapsulates an SQL statement which is passed to the database to be parsed, compiled, planned and executed.
ResultSet: The ResultSet represents set of rows retrieved due to query execution.
What are the steps required to execute a query in JDBC?
First we need to create an instance of a JDBC driver or load JDBC drivers, then we need to register this driver with DriverManager class. Then we can open a connection. By using this connection , we can create a statement object and this object will help us to execute the query.
What are the different types of Statements?
1.Statement (use createStatement method) 2. Prepared Statement (Use prepareStatement method) and 3. Callable Statement (Use prepareCall)
How do I load a database driver with JDBC 4.0 / Java 6?
Provided the JAR file
containing the driver is properly configured, just place the JAR file in the classpath. Java developers NO longer need to explicitly load JDBC drivers using code like Class.forName() to register a JDBC driver.The DriverManager class takes care of this by automatically locating a suitable driver when the DriverManager.getConnection() method is called. This feature is backward-compatible, so no changes are needed to the existing JDBC code.
What are types of JDBC drivers?
There are four types of drivers defined by JDBC as follows:
Type 1: JDBC/ODBC—These require an ODBC (Open Database Connectivity) driver for the database to be installed. This type of driver works by translating the submitted queries into equivalent ODBC queries and forwards them via native API calls directly to the ODBC driver. It provides no host redirection capability.
Type2: Native API (partly-Java driver)—This type of driver uses a vendor-specific driver or database API to interact with the database. An example of such an API is Oracle OCI (Oracle Call Interface). It also provides no host redirection.
Type 3: Open Protocol-Net—This is not vendor specific and works by forwarding database requests to a remote database source using a net server component. How the net server component accesses the database is transparent to the client. The client driver communicates with the net server
using a database-independent protocol and the net server translates this protocol into database calls. This type of driver can access any database.
Type 4: Proprietary Protocol-Net(pure Java driver)—This has a same configuration as a type 3 driver but uses a wire protocol specific to a particular vendor and hence can access only that vendor's database. Again this is all transparent to the client.
What is the fastest type of JDBC driver?
Type 4 (JDBC Net pure Java Driver) is the fastest JDBC driver. Type 1 and Type 3 drivers will be slower than Type 2 drivers (the database calls are make at least three translations versus two), and Type 4 drivers are the fastest (only one translation).
What is Connection?
Connection class represents a connection (session) with a specific database. SQL statements are executed and results are returned within the context of a connection.
A Connection object's database is able to provide information describing its tables, its supported SQL grammar, its stored procedures, the capabilities of this connection, and so on. This information is obtained with the getMetaData method.
What is a ResultSet ?
A table of data representing a database result set, which is usually generated by executing a statement that queries the database.
A ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row. The next method moves the cursor to the next row, and because it returns false when there are no more rows in the ResultSet object, it can be used in a while loop to iterate through the result set.
xplain Basic Steps in writing a Java program using JDBC?
JDBC makes the interaction with RDBMS simple and intuitive. When a Java application needs to access database :
>Load the RDBMS specific JDBC driver because this driver actually communicates with the database (Incase of JDBC 4.0 this is automatically loaded).
>Open the connection to database which is then used to send SQL statements and get results back.
>Create JDBC Statement object. This object contains SQL query.
>Execute statement which returns resultset(s). ResultSet contains the tuples of database table as a result of SQL query.
>Process the result set.
>Close the connection.
What is connection pooling? what is the main advantage of using connection pooling?
A connection pool is a mechanism to reuse connections created. Connection pooling can increase performance dramatically by reusing connections rather than creating a new physical connection each time a connection is requested.
Which type of JDBC driver is the fastest one?
JDBC Net pure Java driver(Type IV) is the fastest driver because it converts the JDBC calls into vendor specific protocol calls and it directly interacts with the database.
Does the JDBC-ODBC Bridge support multiple concurrent open statements per connection?
No. You can open only one Statement object per connection when you are using the JDBC-ODBC Bridge.
What are the different types of RowSet ?
There are two types of RowSet are there. They are:
Connected - A connected RowSet object connects to the database once and remains connected until the application terminates.
Disconnected - A disconnected RowSet object connects to the database, executes a query to retrieve the data from the database and then closes the connection. A program may change the data in a disconnected RowSet while it is disconnected. Modified data can be updated in the database after a disconnected RowSet reestablishes the connection with the database.How can you use PreparedStatement?
This special type of statement is derived from the more general class, Statement.If you want to execute a Statement object many times, it will normally reduce execution time to use a PreparedStatement object instead.
The advantage to this is that in most cases, this SQL statement will be sent to the DBMS right away, where it will be compiled. As a result, the PreparedStatement object contains not just an SQL statement, but an SQL statement that has been precompiled. This means that when the PreparedStatement is executed, the DBMS can just run the PreparedStatement 's SQL statement without having to compile it first.
Eg. PreparedStatement updateSales = con.prepareStatement("UPDATE TEST SET SALES = ? WHERE COM_NAME LIKE ?");
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