JNDI vs JDBC

JNDI is a protocol / mechanism used to lookup data / information, resources from a SPI that obeys the JNDI format. JNDI is available for manipulating naming services and directory services only. Examples include JNDI trees of EJB Containers, LDAP Directory Servers etc...

http://docs.oracle.com/javase/tutorial/jndi/overview/index.html

JDBC is a database specific protocol that Database vendors support for Java Data Access.

http://docs.oracle.com/javase/tutorial/jdbc/overview/index.html

JNDI is used when your are trying to advertise and lookup data from a naming service or directory service and JDBC is used when you are querying / updating data in a Database server.

Difference between JDBC and JNDI

Connection conn = null;
try {
Class.forName ("com.mysql.jdbc.Driver", true, Thread.currentThread (). GetContextClassLoader ());
conn = DriverManager.getConnection ("jdbc: mysql :/ / MyDBServer? user = *** & password = ****");
.....
conn.close ();
}
catch (...) {...} finally {
the if (conn! = null) {
try {
conn.close ();
}
catch (...) {...}
}
} 

Problems?
1, the database server name MyDBServer username and password may need to be modified, and consequent the JDBC URL repairs you want to modify;
2, the database may be the use of other products;
With the increase in the actual terminal, the original configuration of the connection pool parameters may need to be adjusted;

The solution database-level programmers do not have to care about things that only need to know how to refer to
The JNDI appear.
Define the data source, that is, JDBC reference parameters, set a name to the data source;
Data source name in the program by referencing the data source to access the database;

/ / Jndi connection

Context initCtx = new InitialContext ();
Context envCtx = (Context) initCtx.lookup ("java: comp / env");
DataSource ds = (DataSource) envCtx.lookup ("jdbc / webtest");
conn = ds.getConnection (); 

/ / Jdbc connection
Class.forName ("com.mysql.jdbc.Driver", true, Thread.currentThread (). GetContextClassLoader ());
conn = DriverManager.getConnection ("jdbc: mysql :/ / localhost / mismain? user = root & autoReconnect = true");

Programmers to develop, you know you want to develop the application to access the MySQL database, so a reference to the MySQL JDBC driver class is encoded by using the appropriate JDBC URL to connect to the database.

Just like the following code:

Connection conn = null;
try ... {
Class.forName ("com.mysql.jdbc.Driver", true, Thread.currentThread (). GetContextClassLoader ());
conn = DriverManager.getConnection ("jdbc: mysql :/ / MyDBServer? user = qingfeng & password = mingyue");
......
conn.close ();
} Catch (Exception e) {
e.printStackTrace ();
} Finally ... {
the if (conn! = null) ... {
try ... {
conn.close ();
} Catch (SQLException e) ... {}
}
}

This is the traditional approach, but also the previously common practice of non-Java programmers (such as Delphi, VB, etc.). This approach generally does not produce in the small-scale development process, as long as the programmers familiar with the Java language, understand the technology and MySQL JDBC can quickly develop the appropriate application.

No JNDI approach the problems: 1, database server name MYDBSERVER, user name and password may need to be changed, which led to the JDBC URL need to be modified; 2, the database may switch to other products, such as switching to DB2 or Oracle, triggered JDBC driver package and class names need to be modified; 3, with the increase of the actual use of the terminal, the original configuration of the connection pool parameters may need to be adjusted; ...

Solution: the programmer should not need to care about what specific database background? JDBC driver? What is JDBC URL format? What is the user name and password to access the database? "And so these problems, programmers write the program should no references to the JDBC driver, server name, user name or password - not even database pool or connection management. But these issues to the J2EE container to configure and manage, the programmer need only reference to these configuration and management.

Thus, there is a JNDI.

JNDI approach: First, configure JNDI parameters, define a data source in a J2EE container, which is the the JDBC reference parameter set a name to the data source; reference data source, the data source name in the program to access the back-end database.

The specific operation is as follows (in JBoss as an example):

1, configure the data source in JBoss D :/ jboss420GA/docs/examples/jca file folder, there are a lot of different databases referenced data source definition template. Copy the mysql-ds.xml file to the server you're using, such as D to :/ jboss420GA/server/default/deploy.
Mysql-ds.xml file to modify the content, so to through JDBC correct access your MySQL database,
As follows:

Connection conn = null;
try ... {
Class.forName ("com.mysql.jdbc.Driver", true, Thread.currentThread (). GetContextClassLoader ());
conn = DriverManager.getConnection ("jdbc: mysql :/ / MyDBServer? user = qingfeng & password = mingyue");
......
conn.close ();
} Catch (Exception e) {
e.printStackTrace ();
} Finally ... {
the if (conn! = null) ... {
try ... {
conn.close ();
} Catch (SQLException e) ... {}
}
}
<? Xml version = "1.0" encoding = "UTF-8"?>
<datasources>
<local-tx-datasource>
<jndi-name> MySqlDS </ jndi-name>
<connection-url> jdbc: mysql :/ / localhost: 3306/lw </ connection-url>
<driver-class> com.mysql.jdbc.Driver </ driver-class>
<user-name> root </ user-name>
<password> rootpassword </ password>
<exception-sorter-class-name> org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter </ exception-sorter-class-name>
<metadata>
<type-mapping> mySQL </ type-mapping>
</ Metadata>
</ Local-tx-datasource>
</ Datasources>

Defined a the named MySqlDS data source, parameters include the URL of the JDBC driver class name, user name and password.

2 references in the program data source:

Connection conn = null; try ... {
Context ctx = new InitialContext ();
Object datasourceRef = ctx.lookup ("java: MySqlDS"); / / the Citation data source DataSource ds = (DataSource) DataSourceRef; the conn = to the ds.getConnection ();
......
c.close ();
} Catch (Exception e) {
e.printStackTrace ();
} Finally ... {
the if (conn! = null) ... {
try ... {
conn.close ();
} Catch (SQLException e) ... {}
}
}

Using JDBC directly or referenced by JNDI data source programming code is almost the same, but now the program can not care about the specific JDBC parameters.

After the deployment of the system, if the relevant parameters of the database changes, you only need to reconfigure mysql-ds.xml modify the JDBC parameters, as long as the name of the data source is the same, there is no need to modify the source code.

Thus, JNDI to avoid the tight coupling between the program and database to make the application easier to configure, easy to deploy.