implementation

关系型数据库 Postgresql 6.5.2

This short document is provided to help programmers through the internals of
the PostgreSQL JDBC driver.

Makefile
--------

All compilation must be done by using Make. This is because there are two
versions of the driver, one for JDBC1 (for JDK 1.1.x) and the other for JDBC2
(for JDK 1.2 or later). The makefile determines which version to compile by
using a helper class makeVersion. This class is only used by make, and is not
stored in the Jar file.

Note:	It is not sufficient to simply call javac on postgresql/Driver.java as
	some classes are dynamically loaded, so javac will not compile them.

postgresql.jar
--------------

This jar file is produced by make, and contains the driver for your JDK
platform.

Note:	It is possible to compile the driver under say JDK1.1.7, then under
	JDK 1.2. Because make doesn't remove the old classes before compiling,
	jar will simply package both sets together. When the driver is loaded,
	the postgresql.Driver class will sort out which set of classes to use.

Importing packages
------------------

In user code, you may have to import one or more packages, if and only if you
are using the non jdbc extensions (like FastPath, or LargeObject).

DO NOT import the postgresql, postgresql.jdbc1 or postgresql.jdbc2 packages!

Internally, some classes will import the packages when there is a link between
them and the other packages. However, the above rule still applies. It's there
because Javac becomes confused between the different places that similar class
names are present.

However, there are places where they need to refer to classes in the postgresql
package. In this case, import the individual classes, and not the entire
package.

ie:	import postgresql.Field

    NOT	import postgresql.*

Package Layout
--------------

The driver is split into several packages:

postgresql			core classes, common to both JDBC 1 & 2
postgresql.jdbc1		classes used only in implementing JDBC 1
postgresql.jdbc2		classes used only in implementing JDBC 2
postgresql.fastpath		FastPath to backend functions
postgresql.geometric		2D Geometric types mapped to Java Objects
postgresql.largeobject		Low level Large Object access
postgresql.util			Utility classes


Package postgresql
------------------

This package holds the core classes.

Driver		registers the driver when it's loaded, and determines which
		Connection class (in jdbc1 or jdbc2 packages) to use when
		connecting to a database.

Field		Used internally to represent a Field
PG_Stream	Used internally to manage the network stream.

	These classes contains common code that is not dependent to the
	two JDBC specifications.

Connection	Common code used in Connections, mainly Network Protocol stuff.
ResultSet	Common code used in ResultSet's

Package postgresql.fastpath
---------------------------

Fastpath	Handles executing a function on the PostgreSQL Backend
FastpathArg	Defines an argument for a function call

Package postgresql.geometric
----------------------------

PGbox		Maps to postgresql type box
PGcircle	Maps to postgresql type circle
PGline		Maps to postgresql type line
PGlseg		Maps to postgresql type lseg
PGpath		Maps to postgresql type path
PGpoint		Maps to postgresql type point
PGpolygon	Maps to postgresql type polygon

Package postgresql.jdbc1
------------------------

The classes in this package handle the JDBC 1 Specification, for JDK 1.1.x
All interfaces in the java.sql package are present here.

Package postgresql.jdbc2
------------------------

The classes in this package handle the JDBC 2 Specification, for JDK 1.2
All interfaces in the java.sql, and javax.sql packages are present here.

Package postgresql.largeobject
------------------------------

LargeObject		Represents an open LargeObject
LargeObjectManager	Handles the opening and deleting of LargeObjects

Package postgresql.util
-----------------------

PGmoney		Maps to postgresql type money
PGobject	Used to represent postgresql types that have no Java equivalent
PGtokenizer	Helper class for the geometric types
Serialize	Used to serialise Java objects into tabes, rather than Blobs
UnixCrypt	Used to handle crypt authentication