Provides the API for accessing and processing data stored in a data source (usually a relational database) using the JavaTM programming language. This API includes a framework whereby different drivers can be installed dynamically to access different data sources. Although the JDBCTM API is mainly geared to passing SQL statements to a database, it provides for reading and writing data from any data source with a tabular format. The reader/writer facility, available through the `javax.sql.RowSet` group of interfaces, can be customized to use and update data from a spread sheet, flat file, or any other tabular data source.

## What the JDBCTM 4.0 API Includes

The JDBCTM 4.0 API includes both the `java.sql` package, referred to as the JDBC core API, and the `javax.sql` package, referred to as the JDBC Optional Package API. This complete JDBC API is included in the JavaTM Standard Edition (Java SETM), version 6. The `javax.sql` package extends the functionality of the JDBC API from a client-side API to a server-side API, and it is an essential part of the JavaTM Enterprise Edition (Java EETM) technology.

## Versions

The JDBC 4.0 API incorporates all of the previous JDBC API versions:

- The JDBC 3.0 API
- The JDBC 2.1 core API
- The JDBC 2.0 Optional Package API
  (Note that the JDBC 2.1 core API and the JDBC 2.0 Optional Package API together are referred to as the JDBC 2.0 API.)
- The JDBC 1.2 API
- The JDBC 1.0 API

Classes, interfaces, methods, fields, constructors, and exceptions have the following "since" tags that indicate when they were introduced into the Java platform. When these "since" tags are used in JavadocTM comments for the JDBC API, they indicate the following:

- Since 1.6 -- new in the JDBC 4.0 API and part of the Java SE platform, version 6
- Since 1.4 -- new in the JDBC 3.0 API and part of the J2SE platform, version 1.4
- Since 1.2 -- new in the JDBC 2.0 API and part of the J2SE platform, version 1.2
- Since 1.1 or no "since" tag -- in the original JDBC 1.0 API and part of the JDKTM, version 1.1

NOTE: Many of the new features are optional; consequently, there is some variation in drivers and the features they support. Always check your driver's documentation to see whether it supports a feature before you try to use it.

NOTE: The class `SQLPermission` was added in the JavaTM 2 SDK, Standard Edition, version 1.3 release. This class is used to prevent unauthorized access to the logging stream associated with the `DriverManager`, which may contain information such as table names, column data, and so on.

## What the `java.sql` Package Contains

The `java.sql` package contains API for the following:

- Making a connection with a database via the `DriverManager` facility
  - `DriverManager` class -- makes a connection with a driver
  - `SQLPermission` class -- provides permission when code running within a Security Manager, such as an applet, attempts to set up a logging stream through the `DriverManager`
  - `Driver` interface -- provides the API for registering and connecting drivers based on JDBC technology ("JDBC drivers"); generally used only by the `DriverManager` class
  - `DriverPropertyInfo` class -- provides properties for a JDBC driver; not used by the general user
- Sending SQL statements to a database
  - `Statement` -- used to send basic SQL statements
  - `PreparedStatement` -- used to send prepared statements or basic SQL statements (derived from `Statement`)
  - `CallableStatement` -- used to call database stored procedures (derived from `PreparedStatement`)
  - `Connection` interface -- provides methods for creating statements and managing connections and their properties
  - `Savepoint` -- provides savepoints in a transaction
- Retrieving and updating the results of a query
  - `ResultSet` interface
- Standard mappings for SQL types to classes and interfaces in the Java programming language
  - `Array` interface -- mapping for SQL `ARRAY`
  - `Blob` interface -- mapping for SQL `BLOB`
  - `Clob` interface -- mapping for SQL `CLOB`
  - `Date` class -- mapping for SQL `DATE`
  - `NClob` interface -- mapping for SQL `NCLOB`
  - `Ref` interface -- mapping for SQL `REF`
  - `RowId` interface -- mapping for SQL `ROWID`
  - `Struct` interface -- mapping for SQL `STRUCT`
  - `SQLXML` interface -- mapping for SQL `XML`
  - `Time` class -- mapping for SQL `TIME`
  - `Timestamp` class -- mapping for SQL `TIMESTAMP`
  - `Types` class -- provides constants for SQL types
- Custom mapping an SQL user-defined type (UDT) to a class in the Java programming language
  - `SQLData` interface -- specifies the mapping of a UDT to an instance of this class
  - `SQLInput` interface -- provides methods for reading UDT attributes from a stream
  - `SQLOutput` interface -- provides methods for writing UDT attributes back to a stream
- Metadata
  - `DatabaseMetaData` interface -- provides information about the database
  - `ResultSetMetaData` interface -- provides information about the columns of a `ResultSet` object
  - `ParameterMetaData` interface -- provides information about the parameters to `PreparedStatement` commands
- Exceptions
  - `SQLException` -- thrown by most methods when there is a problem accessing data and by some methods for other reasons
  - `SQLWarning` -- thrown to indicate a warning
  - `DataTruncation` -- thrown to indicate that data may have been truncated
  - `BatchUpdateException` -- thrown to indicate that not all commands in a batch update executed successfully

### `java.sql` and `javax.sql` Features Introduced in the JDBC 4.0 API

- auto java.sql.Driver discovery -- no longer need to load a `java.sql.Driver` class via `Class.forName`
- National Character Set support added
- Support added for the SQL:2003 XML data type
- SQLException enhancements -- Added support for cause chaining; New SQLExceptions added for common SQLState class value codes
- Enhanced Blob/Clob functionality -- Support provided to create and free a Blob/Clob instance as well as additional methods added to improve accessiblity
- Support added for accessing a SQL ROWID
- Support added to allow a JDBC application to access an instance of a JDBC resource that has been wrapped by a vendor, usually in an application server or connection pooling environment.
- Availability to be notfied when a `PreparedStatement` that is associated with a `PooledConnection` has been closed or the driver determines is invalid

### `java.sql` and `javax.sql` Features Introduced in the JDBC 3.0 API

- Pooled statements -- reuse of statements associated with a pooled connection
- Savepoints -- allow a transaction to be rolled back to a designated savepoint
- Properties defined for `ConnectionPoolDataSource` -- specify how connections are to be pooled
- Metadata for parameters of a `PreparedStatement` object
- Ability to retrieve values from automatically generated columns
- Ability to have multiple `ResultSet` objects returned from `CallableStatement` objects open at the same time
- Ability to identify parameters to `CallableStatement` objects by name as well as by index
- `ResultSet` holdability -- ability to specify whether cursors should be held open or closed at the end of a transaction
- Ability to retrieve and update the SQL structured type instance that a `Ref` object references
- Ability to programmatically update `BLOB`, `CLOB`, `ARRAY`, and `REF` values.
- Addition of the `java.sql.Types.DATALINK` data type -- allows JDBC drivers access to objects stored outside a data source
- Addition of metadata for retrieving SQL type hierarchies

### `java.sql` Features Introduced in the JDBC 2.1 Core API

- Scrollable result sets--using new methods in the `ResultSet` interface that allow the cursor to be moved to a particular row or to a position relative to its current position
- Batch updates
- Programmatic updates--using `ResultSet` updater methods
- New data types--interfaces mapping the SQL3 data types
- Custom mapping of user-defined types (UDTs)
- Miscellaneous features, including performance hints, the use of character streams, full precision for `java.math.BigDecimal` values, additional security, and support for time zones in date, time, and timestamp values.

### `javax.sql` Features Introduced in the JDBC 2.0 Optional Package API

- The `DataSource` interface as a means of making a connection. The Java Naming and Directory InterfaceTM (JNDI) is used for registering a `DataSource` object with a naming service and also for retrieving it.
- Pooled connections -- allowing connections to be used and reused
- Distributed transactions -- allowing a transaction to span diverse DBMS servers
- `RowSet` technology -- providing a convenient means of handling and passing data

### Custom Mapping of UDTs

A user-defined type (UDT) defined in SQL can be mapped to a class in the Java programming language. An SQL structured type or an SQL `DISTINCT` type are the UDTs that may be custom mapped. The following three steps set up a custom mapping:

1. Defining the SQL structured type or `DISTINCT` type in SQL
2. Defining the class in the Java programming language to which the SQL UDT will be mapped. This class must implement the `SQLData` interface.
3. Making an entry in a `Connection` object's type map that contains two things:
   - the fully-qualified SQL name of the UDT
   - the `Class` object for the class that implements the `SQLData` interface

When these are in place for a UDT, calling the methods `ResultSet.getObject` or `CallableStatement.getObject` on that UDT will automatically retrieve the custom mapping for it. Also, the `PreparedStatement.setObject` method will automatically map the object back to its SQL type to store it in the data source.

## Package Specification

- Specification of the JDBC 4.0 API

## Related Documentation

- Getting Started--overviews of the major interfaces

- Chapters on the JDBC API--from the online version of The Java Tutorial Continued

- JDBCTMAPI Tutorial and Reference, Third Edition-- a complete reference and tutorial for the JDBC 3.0 API

@since 1.1